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Biomedical subjects

E G Shaw

Publications and source records attributed to E G Shaw.

At least 37 records · Page 2Linked to original sources

Survival of patients with extensive small-cell lung cancer who have only brain metastases at initial diagnosis.

To study the therapeutic outcome of patients with extensive small-cell lung cancer (SCLC) with the brain as the single site of metastases at initial diagnosis, we retrospectively reviewed the outcome of 30 such patients (23 men and seven women; median age, 59 years; range, 36-74 years). Medical histories were taken, and physical examination, complete blood cell count, chemistry profile, chest radiography, radionuclide bone scan, computed tomography (CT) scan of the abdomen or radionuclide liver scan, and CT scan of the head were performed as the staging workup for each patient. Bone marrow biopsies were performed in 19 patients. All patients initially received cisplatin-based chemotherapy and concomitant whole-brain radiation therapy consisting of 3,600-4,800 cGy. Subsequently, 22 patients also received thoracic radiation therapy (17 patients as part of the protocol treatment and five patients at the time of disease progression). Thirteen patients had a complete response, 11 had a partial response, three had regression, and three had stable disease. Median survival of the entire group was 14 months (range, 1.4-70.7 months). Twenty-four patients eventually had progression of disease, with a median time to progression of 10 months (range, 2.3-48.5 months). Only one patient had disease progression in the brain (12.6 months after diagnosis). Twenty-two patients eventually died of the disease. The results of our study suggest that the therapeutic outcome in SCLC with the brain as the single site of metastases at initial diagnosis is similar to that of limited-stage SCLC.

Adult↗

Gamma knife for glioma: selection factors and survival.

PURPOSE: To determine factors associated with survival differences in patients treated with radiosurgery for glioma. METHODS AND MATERIALS: We analyzed 189 patients treated with Gamma Knife radiosurgery for primary or recurrent glioma World Health Organization (WHO) Grades 1-4. RESULTS CONCLUSION: The median minimum tumor dose was 16 Gy (8-30 Gy) and the median tumor volume was 5.9 cc (1.3-52 cc). Brachytherapy selection criteria were satisfied in 65% of patients. Median follow-up of all surviving patients was 65 weeks after radiosurgery. For primary glioblastoma patients, median survival from the date of pathologic diagnosis was 86 weeks if brachytherapy criteria were satisfied and 40 weeks if they were not (p = 0.01), indicating that selection factors strongly influence survival. Multivariate analysis showed that increased survival was associated with five variables: lower pathologic grade, younger age, increased Karnofsky performance status (KPS), smaller tumor volume, and unifocal tumor. Survival was not found to be significantly related to radiosurgical technical parameters (dose, number of isocenters, prescription isodose percent, inhomogeneity) or extent of preradiosurgery surgery. We developed a hazard ratio model that is independent of the technical details of radiosurgery and applied it to reported radiosurgery and brachytherapy series, demonstrating a significant correlation between survival and hazard ratio. CONCLUSIONS: Survival after radiosurgery for glioma is strongly related to five selection variables. Much of the variation in survival reported in previous series can be attributed to differences in distributions of these variables. These variables should be considered in selecting patients for radiosurgery and in the design of future studies.

Adolescent↗

Analysis of outcome in patients reirradiated for brain metastases.

PURPOSE: Patients with newly diagnosed brain metastases generally benefit from whole brain radiation therapy (WBRT). However, the role of reirradiation for patients who develop progressive brain metastases has been controversial. This retrospective study examines our experience with reirradiation of patients for progressive brain metastases after an initial+ course of WBRT. METHODS AND MATERIALS: From 1975-1993, 2658 patients received WBRT for brain metastases at our institution. Eighty-six patients were subsequently reirradiated for progressive brain metastases. The median age of these patients was 58 (range: 31-81). The most common primary sites were breast and lung. Fifty patients had metastatic disease at other sites. Most patients had an Eastern Cooperative Oncology Group (ECOG) performance status of 2 (40 patients) or 3 (38 patients). The median dose of the first course of irradiation was 30 Gy (range: 1.5-50.6 Gy). The median dose of the second course of irradiation was 20 Gy (range: 8.0-30.6 Gy). RESULTS: Twenty-three patients (27%) had resolution of neurologic symptoms, 37 patients (43%) had partial improvement of neurologic symptoms, and 25 patients (29%) had either no change or worsened after reirradiation. The median survival following reirradiation was 4 months (range: 0.25-72 months). The majority of patients had no significant toxicity secondary to reirradiation. Five patients had radiographic abnormalities of their brain consistent with radiation-related changes. One patient had symptoms of dementia that was thought to be caused by radiotherapy. Various potential prognostic factors were evaluated for possible associations with survival, including age, sex, primary site, ECOG performance status, RTOG neurologic functional class, absence of extracranial metastases, and dose of irradiation. Absence of extracranial metastasis, solitary brain metastasis, and retreatment dose > 20 Gy were associated with improved survival in univariate analysis (p=0.025, 0.033, and 0.061, respectively). The absence of extracranial disease was the only significant factor in multivariate analysis (p=0.05). CONCLUSION: The majority of patients in our series had favorable symptomatic responses. Clinically significant complications were minimal. Reirradiation should be offered to patients who develop progressive brain metastases.

Adult↗

Etoposide-cisplatin and thoracic radiation therapy salvage of incomplete responders to a noncisplatin induction regimen for limited and extensive small-cell carcinoma of the lung.

Our purpose was to determine the ability of an etoposide-cisplatin (EP )-based regimen to salvage patients with limited and extensive small-cell lung cancer who are incomplete responders to cyclophosphamide-Adriamycin-vincristine-etoposide (CAVE) chemotherapy, and to determine the ability of thoracic radiation therapy (TRT) to salvage CAVE and EP incomplete responders. Fifty-eight patients with small-cell lung cancer (33, limited disease; 25, extensive disease) were entered on this Phase II study between November 1984 and December 1987. Patients received three cycles of CAVE chemotherapy, followed by two cycles of CEPi (cyclophosphamide-etoposide-cisplatin (infusional) and two cycles of CE (cyclophosphamide-etoposide) in conjunction with TRT and prophylactic cranial irradiation (PCI). The overall response rate to CAVE was 62% [5% complete response (CR), 57% partial response (PR) + regression (REGR)]. Of the patients who failed to achieve a CR with CAVE, 81% responded to CEPi (44% CR, 36% PR). Of the patients who did not achieve a CR with either CAVE or CEPi, 89% responded to TRT (65% CR, 24% PR + REGR). For the 33 patients with limited disease, the median survival time and 2-year survival rate were 16.1 months and 24%, respectively. The corresponding figures for the 25 patients with extensive disease were 9.8 months and 4%, respectively. Eleven of these 25 patients were "downstaged" to "limited disease" with CAVE + CEPi and then received TRT + PCI + CE. Their median survival time and 2-year survival rate were 12.6 months and 9%, respectively. The EP-based regimen CEPi and TRT were able to convert 44 to 65% of patients to a complete response who had failed to do so with non-EP induction chemotherapy. This study supports the use of an EP regimen with TRT as initial therapy for newly diagnosed small-cell lung cancer.

Adult↗

Infusion cisplatin chemotherapy and hyperfractionated thoracic radiotherapy for small-cell lung cancer.

Sixty patients, 29 with limited disease and 31 with extensive disease, received an infusion cisplatin-based chemotherapy regimen and, where applicable, subsequent hyperfractionated thoracic radiation therapy (HTRT). Of the patients with limited disease, the response rate was 100% (76% complete response); median survival 26.5 months; 1- and 2-year survival 90 and 55%, respectively. Of those with extensive disease,96% responded (36% complete response) with median survival 12.0 months and 1- and 2-year survival 48 and 29%, respectively. Thirty-five percent of extensive disease patients were downstaged to a "limited" status. with a median survival of 20.3 months. Grade IV leukopenia and thrombocytopenia were seen in 25 and 7% of patients, respectively, with one patient dying of radiation pneumonitis. Within the constraints of the study, infusion cisplatin-based chemotherapy and HTRT appear to be a safe and effective program for the treatment of small-cell lung cancer.

Antineoplastic Agents↗

Randomized double-blind placebo-controlled trial of cisplatin and etoposide plus megestrol acetate/placebo in extensive-stage small-cell lung cancer: a North Central Cancer Treatment Group study.

PURPOSE: Megestrol acetate has been reported to improve appetite and quality of life and to decrease nausea and vomiting in patients with cancer anorexia/cachexia. The present trial was formulated to evaluate the impact of megestrol acetate on quality of life, toxicity, response, and survival in individuals with extensive-stage small-cell lung cancer who received concomitant chemotherapy. PATIENTS AND METHODS: Patients were randomized to receive megestrol acetate 800 mg/d orally or placebo. In addition, all patients were scheduled to receive a maximum of four cycles of cisplatin and etoposide chemotherapy. Quality of life was self-assessed at entry onto study, with every cycle of chemotherapy, and 4 months thereafter with a linear visual analog scale. Toxicity was evaluated by patient questionnaire and investigator reports. RESULTS: A total of 243 eligible patients were randomized. Those who received megestrol acetate had increased nonfluid weight gain (P = .004) and significantly less nausea (P = .0002) and vomiting (P = .02). Significant thromboembolic phenomena occurred more often in patients who received megestrol acetate versus placebo (9% v 2%, P = .01). Patients who received megestrol acetate had more edema (30% v 20%, P = .002), an inferior response rate to chemotherapy (68% v 80%, P = .03), and a trend for inferior survival duration (median, 8.2 v 10.0 months, P = .49). These findings may have been influenced by a poorer quality of life of the megestrol acetate group at study initiation. There were no significant changes in quality of life scores over time between either of the study arms. CONCLUSION: Megestrol acetate cannot be routinely recommended for all patients with small-cell lung cancer at the time of chemotherapy initiation. Rather, its therapeutic ratio may be more favorable for patients with problematic cancer anorexia/cachexia.

Anorexia↗

Supratentorial low-grade glioma: is there a role for radiation therapy?

The supratentorial low-grade gliomas are a heterogeneous group of central nervous system tumours. Knowledge of their biology, primarily based on histologic subtype and patient age, is helpful in determining prognosis and guiding therapeutic recommendations. The pilocytic tumours usually occur in younger patients and carry a favourable prognosis. Recurrence following gross total excision is rare, and approximately 80% of patients undergoing subtotal removal with or without postoperative radiation therapy (RT) will survive 10 years or longer. In contrast, non-pilocytic, supratentorial low-grade tumours (including the diffuse fibrillary, protoplasmic and gemistocytic subtypes), as well as mixed oligoastrocytomas and oligodendrogliomas are infrequently cured, even with gross total excision. Survival benefit with postoperative RT has been suggested by several retrospective studies. When RT is prescribed, localized treatment fields are suggested for total doses of 4500 to 6500 cGy. Ongoing prospective, randomized studies hopefully will clarify the role of RT in these neoplasms, as well as the optimal dose.

Age Factors↗

Genetic analysis of second primary lung cancers in patients surviving small cell lung cancer.

We performed genetic analysis on 12 second primary non-small cell lung cancers in patients surviving small cell lung cancer to assess the potential contribution of smoking to the development of these tumors. Mutations of TP53 were found in three (25%) tumors, KRAS2 in three (25%) tumors, and CDKN2 in two (18%) tumors. Four (50%) mutations (one each in TP53 and CDKN2 and two in KRAS2) were G:C to T:A transversions on the coding strand, a mutation accounting for approximately one-third of mutations in smoking-related tumors but uncommonly found in lung cancers not associated with smoking. The genetic changes in these second lung cancers are more representative of smoking-associated malignancies than lung cancers arising in patients occupationally exposed to irradiation and atomic bomb survivors.

Carcinoma, Small Cell↗

Long term results of a phase I/II study of aggressive chemotherapy and sequential upper and lower hemibody radiation for patients with extensive stage small cell lung cancer.

BACKGROUND: A Phase I/II study of an aggressive six-drug chemotherapy regimen followed by the use of sequential hemibody radiation therapy as a possible non-cross-resistant systemic treatment was undertaken for patients with extensive stage small cell lung cancer. METHODS: The 20 enrolled patients received 7 cycles of cyclophosphamide-based chemotherapy. The first cycle consisted of cyclophosphamide, doxorubicin, etoposide, vincristine, and lomustine. Subsequent cycles used a regimen of doxorubicin alternating with cisplatin. Thoracic radiation was delivered in a split-course fashion during the first week of chemotherapy cycles 5 and 6 (2000 cGy in five fractions during each week). Prophylactic cranial radiation was delivered in a split-course fashion during the first week of chemotherapy cycles 2 and 3 (1700 cGy in 5 fractions during each week). After the 7 cycles, patients received 600 cGy upper hemibody radiation followed by 800 cGy lower hemibody radiation. RESULTS: Nineteen of 20 patients were evaluable for toxicity and response to treatment. Hematologic toxicity accounted for treatment delays or decreased doses in 16 of 19 patients. Thirteen patients completed the initial 7 cycles; progressive disease was the only reason for discontinuing treatment. Two patients had fatal hematologic complications after lower hemibody radiation. Three patients had severe or greater peripheral neurologic toxicity, two had severe central neurologic toxicity, and one had severe cardiac toxicity. Of 19 patients, 9 achieved a complete response; median survival was 11.5 months. Five-year progression free survival and 5-year overall survival were 27% and 16%, respectively. CONCLUSIONS: This aggressive regimen is feasible for patients with extensive stage small cell lung cancer; however, hematologic-related mortality after lower hemibody radiation suggests that future investigations should be initiated at lower initial doses of lower hemibody radiation. Long term survival of the patients suggests that sequential hemibody radiation treatment warrants further investigation.

Adult↗

Prophylactic cranial irradiation in limited-stage small cell lung cancer.

BACKGROUND: The role of prophylactic cranial irradiation (PCI) for patients with limited-stage small cell lung cancer (LSSCLC) remains a controversial issue. This study evaluated PCI in patients with LSSCLC who achieved a complete response to initial chemotherapy. METHODS: A retrospective case study of all nonprotocol patients with LSSCLC examined at our institution from 1982 to 1990 was performed. Of the 67 nonprotocol patients who were treated with combination chemotherapy (cyclophosphamide-based) and thoracic radiotherapy during those years, 43 achieved a complete response. Twenty-four patients received prophylactic cranial irradiation (PCI+) (25-36 Gy in 10-16 fractions), and 19 did not (PCI-) at the physician's or patient's discretion. RESULTS: The distribution of prognostic factors between the PCI+ and PCI- groups was well balanced. Of the PCI+ patients, the 2-year actuarial freedom from relapse in the central nervous system was 93% versus 47% for the PCI- patients (log rank analysis, P = 0.001). An initial central nervous system relapse developed in 2 of the 24 PCI+ patients as the only site of failure versus 7 of 19 PCI- patients (P = 0.003). The 2-year actuarial overall survival was 50% for the PCI+ patients versus 21% for the PCI- patients (P = 0.01). The addition of prophylactic cranial irradiation was the only significant factor contributing to an improvement in time to central nervous system relapse and survival for the PCI+ patients. There were five patients alive at the time of this report, and all received prophylactic cranial irradiation. None had cognitive or neurologic impairment. CONCLUSIONS: Prophylactic cranial irradiation may contribute to improved survival in patients with LSSCLC who achieve a complete response after chemotherapy and thoracic radiation therapy.

Antineoplastic Combined Chemotherapy Protocols↗

Pilot study of human recombinant interferon gamma and accelerated hyperfractionated thoracic radiation therapy in patients with unresectable stage IIIA/B nonsmall cell lung cancer.

PURPOSE: Gamma interferon has a wide range of properties, including the ability to sensitize solid tumor cells to the effects of ionizing radiation. The North Central Cancer Treatment Group has previously completed pilot studies of accelerated hyperfractionated thoracic radiation therapy (AHTRT) in patients with unresectable Stage IIIA/B nonsmall cell lung cancer (NSCLC). This Phase I study was designed to assess the toxicity of concomitant gamma interferon and AHTRT in a similar patient population. METHODS AND MATERIALS: Between December 1991 and May 1992, 18 patients with unresectable Stage IIIA/B NSCLC were treated with daily gamma interferon (0.2 mg subcutaneously) concomitant with AHTRT (60 Gy given in 1.5 Gy twice daily fractions). All patients had an Eastern Cooperative Oncology Group performance status of 0 or 1 with weight loss < 5%. Eight patients had Stage IIIA and 10 had Stage IIIB disease. RESULTS: Nine patients (50%) experienced severe, life-threatening, or fatal toxicities. Eight of the patients (44%) developed significant radiation pneumonitis, which was severe in six patients and fatal in two patients (11% treatment-related mortality). Two patients (11%) developed severe radiation esophagitis. With follow-up of 15-21 months, 2 patients are alive, and 16 have died. The median survival time and 1-year survival rate is 7.8 months and 38%, respectively. CONCLUSION: Gamma interferon appeared to sensitize normal lung tissue to the effects of radiation, as demonstrated by the high incidence of severe or fatal radiation pneumonitis. We do not recommend pursuing gamma interferon as a radiosensitizer in this setting.

Adult↗

Outcome after spinal reirradiation for malignant epidural spinal cord compression.

Radiotherapy is effective for most cases of spinal cord compression. Although recurrent spinal cord compression is a common problem, little is known about whether reirradiation preserves neurologic function and what risk of radiation myelopathy it carries. To investigate this question, we reviewed patients at the Mayo Clinic between 1975 and 1992 undergoing two or more courses of radiotherapy to the same segment of the spinal column with radiographically documented epidural disease at the time of reirradiation to determine outcome as measured by the ability to walk and by survival. Fifty-four patients met the study criteria. Radiation doses for the first course ranged from 2,250 to 5,400 cGy (median, 3,000 cGy), and total dose for all courses to the reirradiated spinal segment ranged from 3,650 to 8,089 cGy (median, 5,425 cGy). All patients were ambulatory following the first course of radiation, 40 (74%) were ambulatory at the onset of reirradiation, and 42 (78%) were ambulatory at the end of reirradiation. Thirty-seven patients (69%) remained ambulatory at their last follow-up 6 days to 80 months following reirradiation (median, 4.7 months). Five patients eventually became nonambulatory 6.5 to 35 months following reirradiation. Median survival for all patients following reirradiation was 4.2 months. We conclude that for cancer patients with progressive epidural disease following radiotherapy, reirradiation frequently preserves ambulation and carries minimal risk of radiation myelopathy during the patients' lifetime.

Adult↗

Lung cancer complicating pregnancy: case report and review of literature.

Lung cancer during pregnancy is rare. Herein we describe a case of metastatic cancer of the lung in a 36-year-old pregnant patient whose initial complaint was pain in the left thigh. Management of this neoplasm during pregnancy depends on the gestational age of the fetus and the potential operability of the tumor. Surgical, chemotherapeutic, and radiation management considerations are discussed.

Adenocarcinoma↗

Radiation necrosis or glioma recurrence: is computer-assisted stereotactic biopsy useful?

Fifty-one patients with supratentorial glioma treated with external beam radiotherapy (median dose 59.5 Gy) who then demonstrated clinical or radiographic evidence of disease progression underwent stereotactic biopsy to differentiate tumor recurrence from radiation necrosis. The original tumor histological type was diffuse or fibrillary astrocytoma in 21 patients (41%), oligodendroglioma in 13 (26%), and oligoastrocytoma in 17 (33%); 40 tumors (78%) were low-grade (Kernohan Grade 1 or 2). The median time to suspected disease progression was 28 months. Stereotactic biopsy showed tumor recurrence in 30 patients (59%), radiation necrosis in three (6%), and a mixture of both in 17 (33%); one patient (2%) had a parenchymal radiation-induced chondroblastic osteosarcoma. The tumor type at stereotactic biopsy was similar to the original tumor type and was astrocytoma in 24 patients (47%), oligodendroglioma in eight (16%), oligoastrocytoma in 16 (31%), unclassifiable in two (4%), and chondroblastic osteosarcoma in one patient (2%). At biopsy, however, only 19 tumors (37%) were low grade (Kernohan Grade 1 or 2). Subsequent surgery confirmed the stereotactic biopsy histological findings in eight patients. Follow-up examination showed 14 patients alive with a median survival of 1 year for the entire group. Median survival times after biopsy were 0.83 year for patients with tumor recurrence and 1.86 years for patients with both tumor recurrence and radionecrosis; these findings were significantly different (p = 0.008, log-rank test). No patient with radiation necrosis alone died. Other factors associated with reduced survival were a high proportion of residual tumor (p = 0.024), a low proportion of radionecrosis (p < 0.001), and a Kernohan Grade of 3 or 4 (p = 0.005). In conclusion, in patients with previously irradiated supratentorial gliomas in whom radionecrosis or tumor recurrence was clinically or radiographically suspected, results of stereotactic biopsy could be used to differentiate tumor recurrence, radiation necrosis, a mixture of both lesions, or radiation-induced neoplasm. In addition, biopsy results could predict survival rates.

Adult↗

Papillary craniopharyngioma: a clinicopathological study of 48 cases.

Two distinct clinicopathological variants of craniopharyngioma exist: the classic adamantinomatous type and a recently described papillary form that predominates in adults and reportedly behaves in a less aggressive manner. The present study describes the clinicopathological features of 48 patients with papillary craniopharyngioma treated at the Mayo Clinic between 1910 and 1994. An additional four tumors were found to have histological features of both adamantinomatous and papillary craniopharyngioma. Whereas adamantinomatous tumors typically occur in adolescent patients, the mean age of the 48 patients (23 males and 25 females) with papillary craniopharyngioma was 44.7 years (range 10 to 74 years). Presenting clinical features included visual impairment (84%), headache (68%), and pituitary insufficiency (anterior 42%; posterior 27%). Preoperative computerized tomography (CT) and magnetic resonance (MR) imaging in 17 patients typically revealed a noncalcified, partially cystic mass that enhanced peripherally and contained mural nodules (67%). Many (41%) of the lesions involved or extended into the third ventricle on imaging. At first surgery, gross total tumor removal was achieved in 17 patients (36%) and subtotal resection in 30 patients (64%) in whom tumor resection was attempted. Tumor recurrence was noted in two patients who underwent gross total removal. Tumor-free survival rates of 100% and 78% were obtained in patients who underwent gross total and subtotal resection at initial surgery, respectively. Postoperative radiation therapy was beneficial to patients having undergone a subtotal resection, with an increase in tumor-free survival from 26% to 86%. Aside from well-documented morphological distinctions, papillary craniopharyngiomas differ from adamantinomatous tumors in several important respects. These include the almost exclusive occurrence of papillary tumors in adulthood and their more uniform appearance on both CT and MR imaging. However, a preliminary analysis of our data suggests there are no significant differences between the two lesions with respect to resectability, efficacy of radiation therapy, and overall survival.

Adolescent↗

Spinal cord astrocytoma: pathological and treatment considerations.

Seventy-nine patients underwent surgery, with or without radiation therapy, for astrocytoma of the spinal cord. There were 43 tumors (54%) classified as pilocytic astrocytoma and 25 (32%) as diffuse fibrillary astrocytoma. Eleven tumors (14%) could not be classified other than as astrocytoma, "type not otherwise specified." The 10-year overall survival rate for all 79 patients was 50% but significantly differed by histological type: 81% for patients with pilocytic astrocytoma compared to 15% for those with diffuse fibrillary astrocytoma. Tumor grade by the Kernohan, et al., or St. Anne-Mayo methods was also a significant predictor of survival in patients with diffuse fibrillary astrocytoma. The extent of surgical resection (biopsy vs. subtotal resection vs. gross total resection) did not significantly impact survival among patients with pilocytic or nonpilocytic astrocytomas of the spinal cord, although there was a trend toward poorer survival in patients undergoing some degree of resection as opposed to biopsy. Postoperative radiation therapy improved survival but did so more for diffuse fibrillary astrocytoma than pilocytic astrocytoma. In this series, histological type was the most significant predictor of survival in patients with astrocytoma of the spinal cord. The survival rate was highest in patients who underwent biopsy followed by postoperative radiation therapy.

Adult↗

Interim report on the radiosurgical treatment of cerebral arteriovenous malformations. The influence of size, dose, time, and technical factors on obliteration rate.

During the authors' initial 4-year experience with radiosurgery using the Leksell cobalt-60 gamma unit, they treated 121 patients with cerebral arteriovenous malformations (AVMs). The radiosurgical dose to the margin of the nidus was 20 Gy for lesions less than 2.0 cm in diameter (volume < or = 4.2 cm3); 18 Gy for malformations 2.1 to 3.0 cm in diameter (volume 4.2-14.1 cm3); and 16 Gy for malformations greater than 3.0 cm (volume > 14.1 cm3). Fifty-one patients underwent follow-up angiography between 1 and 3 years after treatment, and complete obliteration of the nidus was confirmed in 38 (74.5%) of these patients. Thirty-two (74.4%) of 43 AVMs with volumes of 10 cm3 or less and six (75%) of eight larger AVMs (volume 11-30 cm3) showed complete obliteration. Analysis of the time course of AVM nidus shrinkage and obliteration showed that most of the radiosurgically induced effect had occurred by 36 months after treatment. Retrospective analysis of the dose plans for 10 AVMs that were not obliterated by 36 months after gamma knife radiosurgery at the authors' institution (eight cases) or elsewhere (two cases) revealed that six AVMs had not been covered completely by the prescribed isodose. Six (5%) of the 121 patients developed neurological deficits as a direct result of radiosurgical treatment. The authors infer from these data that malformations up to 30 cm3 in volume (approximately 4.0 cm in average diameter) can be treated effectively with an acceptably low complication rate using a radiosurgical dose of 16 Gy to the margin of the nidus. The obliteration rate for the larger malformations that were treated with a dose of 16 to 18 Gy appears to be similar to that for smaller ones treated with 18 to 20 Gy. As more experience accrues using radiosurgery to treat AVMs, patient selection criteria and the variables associated with successful obliteration of the nidus should become more clearly defined.

Adolescent↗