Biomedical subjects

M Schlienger

Publications and source records attributed to M Schlienger.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Surgical removal of radio-induced lesions after radiosurgery of cerebral arteriovenous malformations].

Radioinduced lesions after radiosurgery of cerebral arteriovenous malformations may be associated with an increased signal on T2-weighted and gadolinium enhancement on T1-weighted MR images. They do not have necessarily a poor prognosis. These lesions are mostly asymptomatic. But in a few cases they can be associated with severe clinical symptoms which can become corticodependant or corticoresistant. We present the 5 cases of such cerebral arteriovenous malformations treated by radiosurgery, out of our series of 705 patients. The removal was easier than that of untreated cerebral arteriovenous malformations, and led to a complete recovery of symptoms and progressive decrease of imaging abnormalities. Such surgery should be proposed in case of symptomatic radioinduced lesions which fail to respond to steroids.

Adult↗

PubMed2001

[Re-irradiation of cerebral arteriovenous malformations. Experience of the Sainte-Anne-Tenon Group].

BACKGROUND AND PURPOSE: Between 20 to 50% of cerebral arteriovenous malformations treated with radiosurgery (RS) fail to obliterate 2 to 5 years after irradiation. Patients are not protected against the risks leading to treatment. Two therapeutic options can be used to eradicate the persisting nidus: micro-surgery and a second irradiation. Our group has reirradiated 39 such patients. MATERIAL: From 1989 to 2000, 39 patients have been reirradiated (14 females and 25 males; median age 31 years). There were more left lesions: 59% than right (35%) and 5% on midline. The most frequent locations were: temporal 12 cases; parietal 8 cases; frontal 7 cases; thalamus 7 cases. The predominant first symptoms were hemorrhage (68.5%) and seizure (15.8%). Prior RS, 21/39 patients had embolization (53.8%) and 3 surgery. Method. Treatment has been performed with the same system for the first and the second radiosurgery for 37 patients. Planification and dosimetry improved during that period. The level of dose was similar for the 2 RS. MRI has been used as a non invasive follow-up tool. RESULTS: Only 28 patients were evaluable because 7/39 patients had the second radiosurgery in 1999 or in 2000 and data were lacking at the time of writing for 4 patients. Obliteration rate was 17/28 (60.7%). Nine patients bled between the two radiosurgery procedures. COMPLICATIONS: 4 new regressive deficits occurred after the second radiosurgery. The rate of parenchymal changes were higher, after the second radiosurgery. Except one patient who died of a non-related affection 2 years after obliteration of his cerebral arteriovenous malformation, thus 38/39 patients were alive. CONCLUSION: This series was small compared to the potential number of candidates suffering from failure of the first radiosurgery, but the results are promising.

Adolescent↗

PubMed2001

[Second treatment of cAVMs after radiosurgery].

Risks of bleeding from partially or unobliterated cerebral arteriovenous malformations remain unchanged. A complementary treatment should be indicated after radiosurgery. In this brief review the following data are discussed: the reasons of second treatment, imaging follow-up of cerebral arteriovenous malformations after radiosurgery, types of cerebral arteriovenous malformations to be treated, timing and therapeutic modalities.

Case Management↗

PubMed2001

[Hemorrhage after radiosurgery of cerebral arteriovenous malformations].

BACKGROUND AND PURPOSE: Obliteration is progressive after radiosurgery of cerebral arteriovenous malformations. Thus the hemorrhage risk still remains until obliteration. Purposes of this study are to appreciate severity of post-radiosurgery hemorrhages, actuarial risk of hemorrhage and parameters associated with it. PATIENTS: and method. Over 705 patients treated, 46 (6.5%) had one or several hemorrhages. Clinical, anatomic, dosimetric parameters and obliteration rates before hemorrhage were studied. Then, actuarial risks per patient and per hemorrhage were calculated. Correlations between parameters and risk were searched by uni and multivariate analysis by drawing hemorrhage-free survival curves (limit-product Kaplan-Meier) and Cox model. RESULTS: Except one pure ventricular hemorrhage causing death of one patient, only parenchymal hemorrhages were associated with morbidity (80% of cases with 45% of permanent deficits). Overall mortality rate by hemorrhage was 6.5%. Overall morbidity rate was 34.8% and 13.6% for permanent deficit. Mean obliteration rate before hemorrhage was 25%. Actuarial hemorrhage rate were 2.98% per patient and 3.24% per hemorrhage. Actuarial rate per patient increased from 1.46% first year to 5.95% 4(th) year after radiosurgery. Parameters correlated with hemorrhage risk were in univariate analysis size (p=0.01), Spetzler and Martin's grade (p<0.001), dose to reference isodose (p=0.03), Dmin (p=0.08), intra or paranidal aneurysms (p<0.001), and recoverage (p<0.001). After multivariate analysis, only intra or paranidal aneurysms, recovering and Dmin were significantly associated with hemorrhage-free survival after RS. CONCLUSIONS: Post-radiosurgery hemorrhages are often sum of hemorrhage risk factors of the cerebral arteriovenous malformation and factors predicting low rate of obliteration. They can be in some cases foreseen but rarely avoided.

Adolescent↗

PubMed2001

[Parenchymal changes after radiosurgery of cerebral arteriovenous malformations. Clinical and MRI data].

BACKGROUND AND PURPOSE: Purposes of this study are to describe different parenchymal changes seen after radiosurgery of cerebral arteriovenous malformations and the clinical symptoms which can be associated, and risk factors correlated with them. PATIENTS: and method. From the whole population of 705 patients with a cerebral arteriovenous malformations treated by radiosurgery between 1984 and 1998, clinical from 615 patients and post radiosurgery MRI data from 367 patients were reviewed. Neurological deficit occurred in 5.37% of cases and was still persistant in 1.46% of cases. Delay of occurrence of deficits ranged from 6 to 83 months (mean: 27 months, median: 15 months). Parenchymal changes seen in MRI were classified in 4 grades: 1 without parenchymal changes, 2 hypersignal in sp T2, 3=2 with homogenous enhancement with gadolinium, 4 with hyposignal in spT1 and annular irregular enhancement. Several parameters (size, volume, angioarchitecture of the cerebral arteriovenous malformation, dosimetric parameters) were studied and correlations were searched by uni and multivariate analysis with occurrence and delay of occurrence of deficits or parenchymal changes. RESULTS: In multivariate analysis, only size was significantly correlated with occurrence of parenchymal changes (p=0.0016); only size of the malformation was significantly correlated with delay of occurrence of parenchymal changes (p=0.0082); only grade 4 was correlated with occurrence of neurological deficit (p<0.00001). However, when only "a priori" parameters (known before radiosurgery) are introducted in logistic model, size taille (p=0.02) and hypoplasy of a sinus (p=0.0049) are significantly correlated with occurrence of neurological deficit. Only parenchymal changes grade 4 was significantly correlated with delay of occurrence of a neurological deficit (p<0.00001). However, when only a priori parameters (known before radiosurgery) are introducted in logistic model, only arterial steal (p=0.054) was significantly correlated with delay of occurrence of a neurological deficit. CONCLUSION: Parenchymal changes are various in expression, signification and clinical symptoms associated with them. They must be known and recognized for better prevention and symptomatic treatment as well.

Adolescent↗

PubMed2001

[Treatment of cerebral arteriovenous malformations: decision making strategy].

We have evaluated our therapeutic strategy through the results of modalities used alone or in association. Should the place of each modality be modified? What could be the influence of the first consulting physician? We feel at the present time that small cerebral arteriovenous malformations could be treated by radiosurgery, surgery and embolization according to their characteristics and location. For middle size and some large cerebral arteriovenous malformations, we consider that embolization and/or surgery are adjuvant modalities, specifically when the cerebral arteriovenous malformation is located in an eloquent area.

Case Management↗

PubMed2001

[Endometrial adenocarcinoma treated with combined radiotherapy and surgery: 437 cases].

PURPOSE: To identify prognostic factors and treatment toxicity in a series of operable endometrial adenocarcinomas. PATIENTS AND METHODS: Between November 1971 and October 1992, 437 patients (pts) with endometrial carcinoma, staged according to the 1988 FIGO staging system, underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy without (n = 140) or with (n = 297) pelvic lymph node dissection. The chronology of RT was not randomized and depended on the usual practices of the surgical teams. Group I: 79 pts received preoperative uterovaginal brachytherapy (mean total dose [MD]: 57 Gy). Group II: 358 pts received postoperative RT (196 pts received vaginal brachytherapy alone [MD: 50 Gy], 158 pts had external beam pelvis RT [EPRT] [MD: 46 Gy over 5 weeks] followed by vaginal brachytherapy [MD: 17 Gy], and 4 pts had EPRT alone [MD: 46 Gy over 5 weeks]). The mean follow-up was 128 months. RESULTS: The 10-year disease-free survival rate was 86%. From 57 recurrences, 12 were isolated locoregionally. Multivariate analysis showed that independent factors decreasing the probability of disease-free survival were: histologic type (clear cell carcinoma, p = 0.038), largest histologic tumor diameter > 3 cm (p = 0.015), histologic grade (p = 0.008), myometrial invasion > 1/2 (p = 0.0055), and 1988 FIGO staging system (p = 9.10(-8)). In group II, the addition of EPRT did not seem to improve locoregional control. The postoperative complication rate was 7%. The independent factors increasing the risk of postoperative complications were FIGO stage (p = 0.02) and pelvic lymph node dissection (p = 0.011). The 10-year rate for grade 3 and 4 late radiation complications according to the LENT-SOMA scoring system was 3.1%. EPRT independently increased the 10-year rate for grade 3 and 4 late radiation complications (R.R.: 5.6, p = 0.0096). CONCLUSION: EPRT increases the risk of late radiation complications. After surgical and histopathologic staging with pelvic lymph node dissection, in a subgroup of intermediate risk patients (stage IA grade 3, IB-C and II), postoperative vaginal brachytherapy alone is probably sufficient to obtain a good therapeutic index. Results for patients with stage III tumor are not satisfactory.

Adenocarcinoma↗

PubMed2000

Linac radiosurgery for cerebral arteriovenous malformations: results in 169 patients.

PURPOSE: To present the SALT group results using Linac radiosurgery (RS) for AVM in 169 evaluable patients treated from January 1990 thru December 1993. METHODS AND MATERIALS: Median age was 33 years (range 6-68 years). Irradiation was the only treatment in 55% patients. Other treatment modalities had been used prior to RS in 45%: one or more embolizations in 36%, surgery in 6%, and embolization and surgery in 3% patients. Nidus were supratentorial in 94% patients, infratentorial in 6% patients. Circular 15 MV x-ray minibeams (6-20 mm) were delivered in coronal arcs by a GE-CGR Saturne 43 Linac. Patient set-up included a Betti arm-chair, a Talairach frame. Prescribed peripheral dose was 25 Gy on the 60%-70% isodose (max dose 100%). Arteriographic results were reassessed in December 1997 at 48 to 96 months follow-up. RESULTS: The overall obliteration rate (OR) was 64% (108/169). AVM volumes ranged from 280 to 19,920 mm(3), median 2460 mm(3). OR was 70% for AVM </= 4200 mm(3) 4200 mm(3) (p 25 mm (p = 0.04). OR was 71%, in the absence of embolization, vs. 54% for previously embolized nidus (p = 0.03). OR was 71% for monocentric RS vs. 54% for multi-isocenters (p 28 Gy vs. 55% for values </= 28 Gy (p 79% vs. 57% for lower values (p 17 Gy, vs. 59% for mLd </= 16 Gy (p 40%, vs. 54% for mLi </= 40% (p 85% vs. 60% for CR </= 84% (NS). For patients treated according to our protocol, i.e., 24-26 Gy on the 60%-70% isodoses, OR was higher (68%) than for other patients (47%) (p = 0.02). After multivariate analysis, absence of previous embolization and mono isocentric-irradiation were independent factors predicting obliteration. Complications were: recurrent hemorrhage, 4 patients (1 patient died); brain necrosis on MRI, 2 patients; subsequent epilepsy, 4 patients; other subsequent neurologic deficits, 3 patients. CONCLUSION: Overall OR was 64% (48-96 months follow-up). After monovariate analysis higher ORs were associated with smaller volumes </= 4200 mm(3), smaller nidus size </= 25 mm, absence of prior embolization, monoisocentric RS, higher values for mean and minimum lesion doses and compliance to our protocol. Higher values for the peripheral dose and isodose tended to give better results. Multivariate analysis showed that the absence of prior embolization and monoisocentric irradiation were independent factors predicting successful irradiation.

Adolescent↗

PubMed2000

Parenchymal pineal tumors: a clinicopathological study of 76 cases.

PURPOSE: The aim of this study was to identify factors that could lead to optimization of the management of pineal parenchymal tumors (PPT) which remains equivocal and controversial. METHODS AND MATERIALS: In order to determine factors that influence PPT prognosis, a series of 76 consecutive patients from 12 European centers with histologically proven tumors was retrospectively reviewed. The clinical records and material for histologic review were available in all cases. Follow-up was achieved in 90% of cases. RESULTS: According to WHO classification, there were 19 pineocytomas, 28 intermediate and mixed PPT, and 29 pineoblastomas. According to a four-grade institutional classification, there were 11 Grade 1, 27 Grade 2, 20 Grade 3, and 18 Grade 4. Surgical resection was attempted in 44 patients, whereas 30 had biopsy only. In one case, diagnosis was made at autopsy and in another on spinal deposits. Forty-four patients were irradiated following surgery, 15 patients received chemotherapy. Forty-one patients were alive (median follow-up: 85 months); 9 patients died perioperatively; 26 patients relapsed. Univariate analysis showed a good outcome correlated with age above 20 years, tumor diameter less than 25 mm, and low-grade histology. Multivariate analysis confirmed histology and tumor volume to be significant independent prognostic factors. The extent of surgery and radiotherapy had no clear influence on survival. CONCLUSIONS: This review highlights the prognostic features of PPT and may help to determine treatment strategies based on radiologic and pathologic characteristics.

Adolescent↗

PubMed2000

Dose-volume analysis of different stereotactic radiotherapy mono-isocentric techniques.

Several stereotactic irradiation techniques, using Linacs with the patient in lying and sitting position and a Gamma Knife Unit, were compared with regard to mono-isocentric three-dimensional dose distributions. Three types of target volumes, a sphere and two ellipsoids, were used for the comparisons. All three targets were centered on a real head, reconstructed from transversal CT scans. The ARTEMIS 3D Treatment Planning System, developed by the Tenon Hospital, Paris, was used for the dosimetry and the dose-volume histogram (DVH) calculation. For the comparative study, several quantitative parameters were used, derived from the dose-volume histogram calculation. Differential DVHs were plotted for each target volume and beam arrangement. Irradiation techniques were compared by deriving quantitative parameters from the DVHs such as mean and integral dose delivered to the target and normal tissue irradiated, as well as by the relative volume of the examined areas. All techniques used in this study produced very similar dose distributions. The small differences confirm the capability of the studied techniques to produce the same irradiation effects. By changing from the spherical target shape to a more elliptical shape, more of the normal tissue was irradiated with higher doses. For elliptical cases we therefore identified a need for more conformal stereotactic planning.

Brain Neoplasms↗

PubMed1999

Local recurrences and distant metastases after breast-conserving surgery and radiation therapy for early breast cancer.

PURPOSE: To identify predicting factors for local failure and increased risk of distant metastases by statistical analysis of the data after breast-conserving treatment for early breast cancer. METHODS AND MATERIALS: Between January 1976 and December 1993, 528 patients with nonmetastatic T1 (tumors < or = 1 cm [n = 197], >1 cm [n = 220]) or T2 (tumors < or = 3 cm [n = 111]) carcinoma of the breast underwent wide excision (n = 435) or quadrantectomy (n = 93) with axillary dissection (negative nodal status [n-]: 396; 1-3 involved nodes: 100; >3 involved nodes: 32). Radiotherapy consisted of 45 Gy to the entire breast via tangential fields. Patients with positive axillary lymph nodes received 45 Gy to the axillary and supraclavicular area. Patients with positive axillary nodes and/or inner or central tumor locations received 50 Gy to the internal mammary lymph node area. A boost dose was delivered to the primary site by iridium 192 Implant in 298 patients (mean total dose: 15.2+/-0.07 Gy, range: 15-25 Gy) or by electrons in 225 patients (mean total dose: 14.8+/-0.09 Gy, range: 5-20 Gy). The mean age was 52.5+/-0.5 years (range: 26-86 years) and 267 patient were postmenopausal. Histologic types were as follows: 463 infiltrating ductal carcinomas, 39 infiltrating lobular carcinomas, and 26 other histotypes. Grade distribution according to the Scarff, Bloom, and Richardson (SBR) classification was as follows: 149 grade 1, 271 grade 2, 73 grade 3, and 35 nonclassified. The mean tumor size was 1.6+/-0.3 cm (range: 0.3-3 cm). The intraductal component of the primary tumor was extensive (EIC = IC > or = 25%) in 39 patients. Tumors were microscopically bifocal in 33 cases. Margins were assessed in the majority of cases by inking of the resection margins and were classified as positive in 13 cases, close (< or = 2 mm) in 21, negative (>2 mm tumor-free margin) in 417, and indeterminate in 77. Peritumoral vascular invasion was observed in 40 patients. Tamoxifen was administered for at least 2 years in 176 patients. At least six cycles of adjuvant systemic chemotherapy were administered in 116 patients. The mean follow-up period from the beginning of the treatment was 84.5+/-1.7 months. RESULTS: First events included 44 isolated local recurrences, 8 isolated axillary node recurrences, 44 isolated distant metastases, 1 local recurrence with synchronous axillary node recurrence, 7 local recurrences with synchronous metastases, and 2 local recurrences with synchronous axillary node recurrences and distant metastases. Of 39 pathologically evaluable local recurrences, 33 were classified as true local recurrences and 6 as ipsilateral new primary carcinomas. Seventy patients died (47 of breast carcinoma, 4 of other neoplastic diseases, 10 of other diseases and 9 of unknown causes). The 5- and 10-year rates were, respectively: specific survival 93% and 86%, disease-free survival 85% and 75%, distant metastasis 8.5% and 14%, and local recurrence 7% and 14%. Mean intervals from the beginning of treatment for local recurrence or distant metastases were, respectively, 60+/-6 months (median: 47 months, range: 6-217 months) and 49.5+/-5.4 months (median: 33 months, range: 6-217 months). After local recurrence, salvage mastectomy was performed in 46 patients (85%) and systemic hormonal therapy and/or chemotherapy was administered to 43 patients. The 5-year specific survival rate after treatment for local recurrence was 78+/-8.2%. Multivariate analysis (multivariate generalization of the proportional hazards model) showed that the probability of local control was decreased by the following four independent factors: young age (< or = 40 yr vs. >40 yr; relative risk [RR]: 3.15, 95% confidence interval [CI]: 1.7-5.8, p = 0.0002), premenopausal status (pre vs. post; RR: 2.9, 95% CI: 1.4-6, p = 0.0048), bifocality (uni- vs. bifocal; RR: 2.7, 95% CI: 2.6-2.8,p = 0.018), and extensive intraductal component (IC <25% vs. IC > or = 25%; RR: 2.6, 95% CI: 13-5.2, p = 0

Adult↗

PubMed1999

Small intestine protection from radiation by means of a removable adapted prosthesis.

BACKGROUND: A prosthesis has been designed to protect intestinal loops from radiation when postsurgical radiotherapy is necessary in cancer treatment. It is a silicone balloon that allows the small bowel to be pushed back away from the radiation field, and it is easily removed at the conclusion of radiotherapy. METHODS: The device was used in 22 patients: 5 retroperitoneal tumors and 17 pelvic cancers. After surgical resection of the tumor, the device is placed either in the retroperitoneal area or in the pelvic cavity. A polyglactine 910 mesh is placed between the spacer and the bowel to prevent incarceration of the loops. The prosthesis can be filled or emptied between each radiation course and finally removed by means of a short incision under local or locoregional anesthesia. RESULTS: The tolerance of the small intestine to radiation therapy has been satisfactory in each case, with a mean follow-up of 24.5 months (range 10 to 73). No modification of biological parameters was observed during the pelvic radiation therapy at 30, 45, and 65 Gy. CONCLUSION: This device should appears to efficient for prevention of bowel injury during postsurgical radiation in successful treatment of abdominal, pelvic, or retroperitoneal tumors when indicated.

Abdominal Neoplasms↗

PubMed1999

Study of ill-conditioning of Linac stereotactic irradiation subspaces using singular values decomposition analysis.

A Linac stereotactic irradiation space is characterized by different angular separations of beams because of the geometry of the stereotactic irradiation. The regions of the stereotactic space characterized by low angular separations are one of the causes of ill-conditioning of the stereotactic irradiation inverse problem. The singular value decomposition (SVD) is a powerful mathematical analysis that permits the measurement of the ill-conditioning of the stereotactic irradiation problem. This study examines the ill-conditioning of the stereotactic irradiation space, provoked by the different angular separations of beams, using the SVD analysis. We subdivided the maximum irradiation space (MIS: (AA)AP x (AA)RL = 180 degrees x 180 degrees) into irradiation subspaces (ISSs), each characterized by its own angular separation. We studied the influence of ISSs on the SVD analysis and the evolution of the reconstruction quality of well defined three-dimensional dose matrices in each configuration. The more the ISS is characterized by low angular separation the more the condition number and the reconstruction inaccuracy are increased. Based on the above results we created two reduced irradiation spaces (RIS: (AA)AP x (AA)RL = 180 degrees x 140 degrees and (AA)AP x (AA)RL = 180 degrees x 120 degrees) and compared the reconstruction quality of the RISs with respect to the MIS. The more an irradiation space is free of low angular separations the more the irradiation space contains useful singular components.

Humans↗

PubMed1999

A computerized dosimetric database for conformal stereotactic irradiations.

An innovative computerized dosimetric database (DDB) is proposed to enable the analysis of the stereotactic radiosurgical dose distributions; it contains relationships between the irradiation parameters and the dose-volume data. Dose-volume data provide guidance to the physicist-physician team by facilitating the initialization of the irradiation parameters and the treatment planning. The presented DDB contains dose-volume data such as the 70% isodose widths and the 70%-30% isodose penumbra along the right-left, anterior-posterior, and superior-inferior directions as a function of the irradiation parameters defined by the user. In order to demonstrate the usefulness of the DDB, the effects of the collimator diameter, the number of arcs, and their length on the shape of the prescription isodose surface are shown and are related to practical considerations for the treatment plan. However, the presented DDB is one example that can be generated by the DDB system. The planner can define as many different DDBs as he/she wishes, which can then be used for different investigations. This type of DDB enables us to investigate the irradiation technique used, to compare different irradiation techniques, to inspect the feasibility of planning different lesion types, or to define some dosimetric rules. The DDB provides useful interactive guidelines for the treatment planning process and replaces the voluminous dosimetric atlas. It has now been in clinical use for a year in a conformal procedure which automatically proposes collimator diameters, arc positions, and lengths allowing rapid conformal planning.

Algorithms↗

PubMed1999

Radiosurgery of cerebral arteriovenous malformations: is an early angiogram needed?

BACKGROUND AND PURPOSE: Radiosurgical treatment of arteriovenous malformations (AVMs) has slow and progressive vasoocclusive effects. We sought to determine if early posttherapeutic angiography provides relevant information for the management of radiosurgically treated AVMs. METHODS: Between 1990 and 1993, the progress of 138 of 197 cerebral AVMs treated by linear accelerator (Linac) was regularly followed by angiographic study. On each posttherapeutic angiogram ("early," 6-18-month follow-up; "intermediate," 19-29-month-follow-up; and "late," > 30-month follow-up), the degree of reduction across the greatest diameter of the nidus and hemodynamic modifications were analyzed. Each cerebral AVM was qualitatively classified into one of the following categories after early angiographic study: 0%-reduced, 25%-reduced, 50%-reduced, 75%-reduced, and 100%-reduced or "complete obliteration." Vasoocclusive progress for each category was then studied over time. RESULTS: Three (10%) of the 30 0-25%-reduced, eight (38%) of 21 50%-reduced, and 27 (84%) of 32 75%-reduced cerebral AVMs showed complete obliteration after further follow-up. The three 0-25%-reduced AVMS that went on to complete obliteration underwent very early angiography (6-7 months). Fifty-five cerebral AVMs showed complete obliteration on early angiograms (40%). In this group, more follow-up, when performed, confirmed complete obliteration in all cases (n = 17). CONCLUSION: An early angiogram is needed to predict the effectiveness of radiosurgery. Important AVM changes seen on early angiograms are highly correlated with treatment success. Moreover, no or minor changes seen on early angiograms are highly predictive of radiosurgical failure. For these patients, further treatment should be discussed promptly.

Adolescent↗

PubMed1998

Single-fraction stereotactic radiotherapy: a dose-response analysis of arteriovenous malformation obliteration.

PURPOSE: Stereotactic radiotherapy delivered in a high-dose single fraction is an effective technique to obliterate intracranial arteriovenous malformations (AVM). To attempt to analyze the relationships between dose, volume, and obliteration rates, we studied a group of patients treated using single-isocenter treatment plans. METHODS AND MATERIALS: From May 1986 to December 1989, 100 consecutive patients with angiographically proven AVM had stereotactic radiotherapy delivered as a high-dose single fraction using a single-isocenter technique. Distribution according to Spetzler-Martin grade was as follows: 79 grade 1-3, three grade 4, 0 grade 5, and 18 grade 6. The target volume was spheroid in 74 cases, ellipsoid in 11, and large and irregular in 15. The targeted volume of the nidus was estimated using two-dimensional stereotactic angiographic data and, calculated as an ovoid-shaped lesion, was 1900 +/- 230 mm3 (median 968 mm3; range 62-11, 250 mm3). The mean minimum target dose (Dmin) was 19 +/- 0.6 Gy (median 20 Gy; range: 3-31.5). The mean volume within the isodose which corresponded to the minimum target dose was 2500 +/- 300 mm3 (median 1200 mm3; range 75-14 900 mm3). The mean maximum dose (Dmax) was 34.5 +/- 0.5 Gy (median 35 Gy; range 15-45). The mean angiographic follow-up was 42 +/- 2.3 months (median 37.5; range 7-117). RESULTS: The absolute obliteration rate was 51%. The 5-year actuarial obliteration rate was 62.5 +/- 7%. After univariate analysis, AVM obliteration was influenced by previous surgery (p = 0.0007), Dmin by steps of 5 Gy (p = 0.005), targeted volume of the nidus (< or = 968 mm3 vs. >968 mm3; p = 0.015), and grade according to Spetzler-Martin (grade 1-3 vs. grade 4-6; p = 0.011). After multivariate analysis, the independent factors influencing AVM obliteration were the Dmin [relative risk (RR) 1.9; 95% confidence interval (CI) 1.4-2.5; p < 0.0001] and grade distribution according to Spetzler-Martin (RR 1.4; 95% CI 1.1-1.7; p = 0.010). Delayed complications were observed in eight patients. The 5-year actuarial rate of delayed complications was 7.4%. CONCLUSION: After stereotactic radiotherapy delivered in a single high dose using a single-isocenter technique, the success rate for complete obliteration is independently correlated to Dmin but does not seem to be influenced by Dmax and the targeted volume of the nidus.

Adolescent↗

PubMed1998

Use of a general inverse technique for the conformational stereotactic treatment of complex intracranial lesions.

PURPOSE: The stereotactic irradiation of intracranial lesions constitutes an excellent example of conformational therapy whose purpose is to adapt the dose envelope to the target volume with great precision and at the same time to deliver as low a dose as possible to the healthy tissues. We propose the mathematical analysis of the singular values decomposition (SVD) as an inverse planning process to find the optimal minibeam weightings that permit the calculation of the most conformational dose distribution. METHODS: For the radiosurgical treatment of complex lesions, we realize a division of the lesion into several elliptic volumes using the "Associated Target Methodology." This division allows the definition of an irradiation configuration: the number of isocenters, the position of the isocenters, and the diameter of each collimator. For this defined irradiation configuration, we use SVD to find the optimal minibeam weightings. This analysis enables us to understand better the ill-conditioning of the multi-isocentric irradiation and the influence of irradiation parameters on the process of reconstruction minibeam weightings. RESULTS: In this paper, the SVD analysis and the reconstruction technique have been evaluated for the first time on practical cases. We present, as an example, a complex lesion compartmentalized into 3 subvolumes according to our Associated Target Methodology. This analysis allows us to study the ill-conditioning of the example and proposes a large number of solutions from among which we have to choose the most conformational physical solution. This choice is based on the dose-volume histograms. CONCLUSION: We use the SVD procedure as a computer-aided planning system and obtain good solutions, i.e., healthy tissue protection and lesion coverage similar to or better than an experimented planner solution.

Brain Neoplasms↗

PubMed1998

Failure in radiosurgery treatment of cerebral arteriovenous malformations.

OBJECTIVE: The aim of this study was to retrospectively analyze the reasons for the failure of radiosurgical treatment of cerebral arteriovenous malformations (AVMs). METHODS: Seventeen cases of noncured AVMs were reviewed 3 years after radiosurgical treatment. Follow-up ranged from 33 to 54 months (mean, 44.3 mo). Lesion dimensions varied from 9 to 55 mm (mean, 29.2 mm). The lesions were located in critical or near-critical brain regions. Angiography was performed under Talairach's stereotactic conditions. Two large AVMs bled 36 and 39 months after receiving irradiation, respectively. These two AVMs had been incompletely irradiated. RESULTS: Retrospectively, in four cases (23.5%) we observed errors in determining AVM target shape and size because of inaccurate definition of the nidus and/or because of stereoangiographic incompleteness (absence of external carotid artery injections). In five large and/or irregularly shaped AVMs (29.4%), a strategy of partial volume irradiation had been used. In one patient (5.8%), we observed the recanalization of previously embolized AVMs. In another case (5.8%), the target had been partially missed. The AVMs in one case (5.8%) had been treated with an ineffective peripheral dose. In one (5.8%), the failure occurred because of the lesion angio-architecture. In four cases (23.5%), no evident reasons for failure were determined. CONCLUSION: The results of this study suggest the necessity of complete irradiation of the nidus. The strategy of partial volume irradiation might be avoided, even if it necessitates lowering the doses to treat large AVMs. Accuracy in the target determination is required, and complete stereoangiography is necessary.

Adult↗