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R Pötter

Publications and source records attributed to R Pötter.

At least 19 recordsLinked to original sources
PubMed2005

[Partial breast irradiation for early breast cancer with favorable prognostic factors: 3-year results of the German-Austrian phase II-trial].

PURPOSE: To evaluate perioperative morbidity, toxicity and cosmetic outcome in patients treated with interstitial brachytherapy to the tumor bed as the sole radiation modality after breast conserving surgery. MATERIALS AND METHODS: From 11/2000 to 11/2004, 240 women with early stage breast cancer participated in a protocol of tumor bed irradiation alone using pulsed dose rate (PDR) or high dose rate (HDR) interstitial multi-catheter implants (partial breast irradiation). Perioperative morbidity, acute and late toxicity as well as cosmetic outcome were assessed. Of the first 51 patients treated in this multicenter trial, we present interim findings after a median follow-up of 36 months. RESULTS: Perioperative Morbidity: Bacterial infection of the implant: 2 % (1/51). Acute toxicity: radiodermatitis Grade 1: 4 % (2/51). Late toxicity: breast pain Grade 1: 8 % (4/51), Grade 2: 2 % (1/51); dyspigmentation Grade 1: 8 % (4/51); fibrosis Grade 1: 4 % (2/51), Grade 2: 8 % (4/51); telangiectasia Grade 1: 10 % (5/51), Grade 2: 4 % (2/51). Cosmetic results: Excellent and good in 94 % (48/51) of the patients. CONCLUSION: This analysis indicates that accelerated partial breast irradiation with 192-iridium interstitial multicatheter PDR-/HDR-implants (partial breast irradiation) is feasible with low perioperative morbidity, low acute and mild late toxicity at a median follow-up of 36 months. The cosmetic result is not significantly affected.

Adult↗
PubMed2004

Hyperfractionated accelerated radiochemotherapy (HFA-RCT) with mitomycin C for advanced head and neck cancer.

To investigate efficacy and feasibility of hyperfractionated accelerated radiotherapy combined with mitomycin C, patients with locally advanced unresectable squamous cell carcinomas of the head and neck region were administered 64-66 Gy in four weeks and mitomycin C (20 mg/m(2)) on day five. Twenty-one consecutive patients were included between November 1997 and June 1999 (median age: 57 years). All tumours were stage T3-4 and 18/21 were N2-3. Eighteen patients experienced grade 3 and three patients grade 2 mucosal toxicity. With median follow up for surviving patients of 42 months, loco-regional control was 55% at three years, overall survival was 33% at three years. This treatment is at the edge of local tolerability, but there is a good curative chance even for very advanced localised tumours, provided a complete remission is induced at primary treatment.

Adult↗
PubMed2004

Diffuse large B-cell lymphomas with plasmablastic/plasmacytoid features are associated with TP53 deletions and poor clinical outcome.

To define reproducible criteria for subgroups of diffuse large B-cell lymphomas (DLBCL), including lymphomas with plasmablastic/plasmacytoid features (PB/PC-Fs), we investigated 66 DLBCL; the samples were categorized as either centroblastic (CB), immunoblastic (IB) or PB/PC-F applying standardized morphologic criteria. Blinded specimens were reviewed by three independent pathologists. The final consensus classification included 44 CB (67%), seven IB (10%) and 15 PB/PC-F (23%). The interobserver agreement between two centers (Vienna, Würzburg) was 93.5%. Most PB/PC-F were CD20+, cIgM+, MUM-1+, CD138+/-, bcl-6-, corresponding to an activated B-cell phenotype. Immunoglobulin-V(H) gene mutation analysis was consistent with a germinal or postgerminal center-cell origin. By fluorescence in situ hybridization analysis, 11/13 (85%) PB/PC-F had a monoallelic TP53 deletion. The pretreatment characteristics of patients with PB/PC-F included a tendency for more B symptoms, extranodal disease and a higher IPI. Importantly, PB/PC-F were resistant to standard chemotherapy (complete remission rate 47%, relapse rate 71%) and even autologous stem-cell transplantation. The median overall survival (OS) (14 months, P<0.002) and disease-free survival (6 months, P=0.02) were significantly shorter compared to patients with CB and IB. The OS difference was pronounced within the low and low-intermediate IPI risk group (P<0.001). Our data indicate a strong association of plasmablastic/plasmacytoid morphology with TP53 deletions, poor response to chemotherapy and short survival.

Adult↗
PubMed2003

Endovascular brachytherapy in peripheral arteries.

Increasing knowledge about the pathophysiology of the process leading to restenosis has given the rationale to investigate the potential role of radiation in the prevention of restenosis. Compared to the rapidly increasing experience in the coronary circulation, there is until now only a limited number of studies concerning the use of brachytherapy (BT) in the peripheral circulation. The-Vienna 2-Trial was the first randomized study to demonstrate the efficacy of endovascular BT for prophylaxis of restenosis after femoropopliteal percutaneous transluminal angioplasty. The cumulative patency rates at 12 months of follow-up were 63.6% in the PTA + BT-group and 35.3% in the PTA-group (p < 0.005), and the significant improvement in patency was also maintained after two years. The results of two ongoing randomized, double-blinded multicenter trials (PARIS; Vienna 3) have to be awaited before definitive recommendations can be given. The rather high incidence of late thrombotic occlusion after long-segment femoropopliteal stenting and endovascular BT requires optimization of the antithrombotic regimen.

Angioplasty, Balloon↗
PubMed2001

Radiation therapy in the treatment of endometrial stromal sarcoma.

OBJECTIVE: The efficacy of radiation therapy in the treatment of endometrial stromal sarcoma (ESS) is still not clear. We report our results over an 18-year period in comparison to data from literature concerning adjuvant radiation therapy and other treatment modalities. PATIENTS AND METHODS: During 1981-1998, 21 patients with ESS were treated at General Hospital Vienna. The age of the patients ranged between 44-76 years (median: 65 yr). The 1989 FIGO classification for endometrial carcinoma was used in this study retrospectively. Eleven patients presented in Stage I, 1 in Stage II and 5 in Stage III. Four patients had Stage IV tumors or recurrences. The majority of patients (66.7%) had a Grade 3 tumor. Seventeen patients were treated in a curative intent. Fifteen patients were referred for postoperative radiotherapy after hysterectomy. Thirteen of them received a combined radiotherapy. Two patients were referred for primary radiotherapy. They received a combined radiotherapy. Four patients were referred for radiotherapy with a palliative intent. Twenty patients received external beam therapy (EBT) in daily fractions of 1.6-2.0 Gy up to a total dose of 27-57 Gy to the pelvis. Seventeen patients received brachytherapy. RESULTS: Follow-up was 8 to 170 months (mean: 70.3 months, median: 64 months). Eleven patients are still alive, 10 without tumor and 1 with tumor. Ten patients are dead, 6 due to ESS, 1 due to breast cancer, and 3 due to intercurrent diseases. After adjuvant radiotherapy, 3 patients had tumor recurrences. All had distant metastases, and 1 had local failure additionally. Two patients with primary treatment died due to intercurrent disease without tumor. The overall actuarial survival and the disease-specific survival rates were 63.4% and 80.9% after 5 years and 52.8% and 80.9% after 10 years. The overall local control rate was 93.8% after 5 years. Four patients treated with a palliative intent showed partial response. Three patients died rapidly due to tumor. One patient with a Grade 1 tumor is still alive 12 months after treatment. CONCLUSION: In our experience, surgery and adjuvant radiation therapy are most effective treatments for patients with ESS due to the excellent local control in all stages and the good disease-specific survival in early stages.

Adult↗
PubMed2001

Combined radiochemotherapy of locally advanced unresectable pancreatic adenocarcinoma with mitomycin C plus 24-hour continuous infusional gemcitabine.

BACKGROUND: In locally advanced pancreatic cancer, the combination of chemotherapy with radiotherapy is gaining increasing importance; although, in view of the reported long-term results of several contemporary trials, further improvements are certainly warranted. The aim of the present study was to evaluate the effectiveness and safety of a combined-treatment modality consisting of systemic chemotherapy with 24-h continuous infusional gemcitabine and mitomycin C, plus external beam radiotherapy in patients with localized unresectable adenocarcinoma of the pancreas. METHODS AND MATERIALS: Systemic chemotherapy consisted of mitomycin C 8 mg/m2 given as i.v. bolus injection on day 1 and gemcitabine administered as a 24-h continous infusion once weekly for 3 of 4 weeks. The starting dose of gemcitabine was 100 mg/m2 and dose levels were escalated in consecutive cohorts of 3-6 patients to 130 and 160 mg/m2, utilizing an escalating-dose Phase I trial design. Radiation therapy using megavolt irradiation (total dose, 45 Gy, 1.8 Gy/day) of 6 MV photons or greater with a 3- or 4-field technique was delivered concurrently for 5-6 weeks. RESULTS: Between January 1997 and August 1998, a total of 15 patients were enrolled in this trial, all of whom were assessable for toxicity, response, and survival. The dose-limiting toxicities at the 160 mg/m2 gemcitabine level were myelosuppression, specifically neutropenia +/- thrombocytopenia, and gastrointestinal symptoms, including stomatitis, vomiting, and diarrhea. Only 1 partial response was observed (7%), and disease was stabilized in 10 additional patients (67%). The median time to progression was 5.5 months (range, 2-12 months). Whereas all patients developed distant metastases, locoregional failure occurred in only 3. The median survival time was 8.3 months (range, 2.5 to 22.0+ months), and the 1-year survival rate was 13.3%. CONCLUSION: The MTD of gemcitabine when given as prolonged infusion in combination with mitomycin C and radiation therapy was 130 mg/m2/week. Therapeutic results suggest that combined chemoradiation with this regimen is feasible and effective for local control of pancreatic cancer, but essentially ineffective in counteracting metastatic tumor growth.

Adenocarcinoma↗
PubMed2001

High-dose versus low-dose rate brachytherapy in definitive radiotherapy of cervical cancer.

BACKGROUND: To retrospectively compare the clinical outcome in cervical cancer patients treated by external irradiation and intracavitary high-dose rate (HDR) brachytherapy with iridium 192 versus low-dose rate (LDR) brachytherapy with radium 226 or caesium 139. METHODS: 450 LDR patients were treated from 1982 to 1986 and compared with 189 HDR patients treated from 1993 to 1999. Cobalt (CO) 60 treatment was replaced in the HDR group by modern megavoltage photon radiotherapy (Linac 25 MV). Brachytherapy was given in either 2 or 3 LDR radium 226 implants for the earlier patient cohort, and 3-6 HDR iridium 192 implants for the latter cohort. The primary endpoint assessed was the 3-year overall survival. RESULTS: The median duration of follow-up was 70 months (range, 2-108 months) in the LDR group and 34 months (range, 4-69 months) in the HDR group. Actuarial overall 3-year survival after conventional LDR brachytherapy was 51.3%, versus 58.2% after HDR brachytherapy. No difference in 3-year survivors was seen in the small groups of stage I (68.3% vs. 84.6%) and stage IV (23.1% vs. 37.5%) patients. In stage II and III and in the overall group there were statistically significantly more 3-year survivors in the HDR group (58.1% vs. 78.9%, p < 0.001 in stage II; 37.3% vs. 53.8%, p < 0.01 in stage III; and 46.7% vs. 67.2%, p < 0.001 in the total group). Retrospectively assessed complication rates in the former LDR group were 3.8% for irreversible side effects, and 13.3% for chronic radiation damage. In the HDR group the actuarial late complication rates for grades 3 and 4 were 2.9% for the bladder, 4.0% for the bowel, and 6.1% for the rectum. CONCLUSION: In our preliminary experience, HDR brachytherapy combined with external beam radiation produced similar and even better survival rates compared with the LDR series. HDR brachytherapy combined with external beam radiation is an efficient method for the treatment of cervical cancer and adverse side effects are comparable.

Brachytherapy↗
PubMed2001

Aspects of MR image distortions in radiotherapy treatment planning.

BACKGROUND: Registration of computed tomography (CT) and magnetic resonance (MR) images are commonly performed to define the different target regions used in radiotherapy treatment planning (RTTP). The accuracy of target definition will then depend on the spatial accuracy of the CT and MR data, and on the technique used to register the images. CT images are usually regarded as geometrically correct, while MR images are known to suffer from geometric distortion. The aim of this paper is to discuss the possible impact of MR image distortions in the radiotherapy treatment planning process. METHODS: The origin, magnitude, and relative impact of the different sources of geometric distortions that affect the MR image data at different magnetic fields and for different acquisition settings are described. Techniques for distortion correction are reviewed, and their limitations are outlined. The sensitivity of image registration techniques to the presence of geometric distortions in the MR data is discussed. Finally, an overview of image registration techniques used and results obtained in clinical radiotherapy treatment planning applications is given. RESULTS: Spatial distortions in MR images vary with field strength and with the image acquisition protocol. The spatial accuracy generally decreases with distance from the magnet isocenter. Distortion correction techniques based on phantom evaluations cannot adequately model patient-induced distortions. CONCLUSION: Image protocols with high gradient bandwidths should be used to reduce the spatial distortions in MR images. Correction techniques based only on phantom measurements could be sufficient at low magnetic fields, while at higher fields additional corrections of patient-related distortions might be needed. Registration techniques based on matching of Landmark points located far from the magnet isocenter are especially prone to MR distortions.

Abdominal Neoplasms↗
PubMed2001

[Mediastinal Hodgkin lymphomas in computerized tomography. Comparison of exact CT-assisted volumetry and volume assessment using simple geometric models].

BACKGROUND: The importance of the size of the primary tumor in lymphomas and its size after treatment is still uncertain. Assuming a prognostic relevance, an assessment of tumor volume before and after induction of chemotherapy has been performed in the pediatric Hodgkin's disease study (HD-90). Since an exact CT-scan-based volumetric tumor assessment is time-consuming and in some centers not possible, the tumor volume is often estimated based on simple geometric approximations. Aim of this study was the development of an easy to apply and nearly exact model of volume estimation compared to CT-scan-based tumor volume measurements. MATERIAL AND METHODS: Thirty computed tomographies (CT) of mediastinal Hodgkin lymphomas of children aged 5 to 16 years have been examined. The CT scans were digitalized using a CCD camera combined with a frame grabber. Applying the Global Lab image software, the true tumor volume was determined excluding local organs, which did not belong to the lymphoma. Subsequently, volumes were assessed using simple geometric models (block, ellipsoid, octaeder) by using the maximum diameters of the tumor. The differences between the volume of the geometric models and the true volume, based on the CT scan evaluation, were compared. RESULTS: The maximum diameters of a tumor can be used to calculate its volume based on simple geometric models. The model "block" overestimates the volume by 89 to 268%. The model "ellipsoid" overestimates the volume on average by 29%. The model "octaeder" underestimates the volume on average by 18%. A division of the block volume by 2.3 approximated the geometric closest to the true volume: the average volume was overestimated by 2% in tumors with a volume larger than 20 ml. No model was sufficient to approximate tumors with a volume of less than 20 ml. CONCLUSIONS: For the estimation of tumor volumes in mediastinal Hodgkin lymphomas exceeding 20 ml, the formula "block/2.3" results in the closest approximation compared to the true volume. In the course of clinical studies it might be helpful to apply this formula to determine the prognostic relevance of the tumor size and its development under therapy.

Adolescent↗
PubMed2001

[MRI-assisted brachytherapy of nonresectable liver metastases. Preliminary technical and clinical experiences].

PURPOSE: To evaluate the feasibility and efficacy of MR-guided interstitial brachytherapy of non-resectable liver metastasis. METHODS: Liver metastases (0.8-5.2 cm in diameter) were treated during a prospective phase I/II study using an open 0.2 Tesla MR system (Magnetom Open Viva, Siemens, Erlangen). MR-compatible brachytherapy applicators were placed percutaneously under MR-guidance in an open 0.2 Tesla MR system (Magnetom Open Viva, Siemens, Erlangen) using fast T1-weighted sequences. Pretreatment and follow-up studies were performed using a 1.5 Tesla MR system. RESULTS: Preliminary results of an unpublished prospective study are discussed exemplary on 2 selected patients. The median procedure time was 4.9 h. No major complications were observed and late effects were acceptable. In large symptomatic metastases only a temporary relief of pain was achieved. In smaller metastases (DM 3 cm) a tumor control was observed. CONCLUSION: MR-guided brachytherapy is feasible and has the potential to ablate liver metastases with diameter of less than 3 cm. Further developments are necessary.

Adenocarcinoma↗
PubMed2001

Dose-volume histograms based on serial intravascular ultrasound: a calculation model for radioactive stents.

BACKGROUND AND PURPOSE: Radioactive stents are under investigation for reduction of coronary restenosis. However, the actual dose delivered to specific parts of the coronary artery wall based on the individual vessel anatomy has not been determined so far. Dose-volume histograms (DVHs) permit an estimation of the actual dose absorbed by the target volume. We present a method to calculate DVHs based on intravascular ultrasound (IVUS) measurements to determine the dose distribution within the vessel wall. MATERIALS AND METHODS: Ten patients were studied by intravascular ultrasound after radioactive stenting (BX Stent, P-32, 15-mm length) to obtain tomographic cross-sections of the treated segments. We developed a computer algorithm using the actual dose distribution of the stent to calculate differential and cumulative DVHs. The minimal target dose, the mean target dose, the minimal doses delivered to 10 and 90% of the adventitia (DV10, DV90), and the percentage of volume receiving a reference dose at 0.5 mm from the stent surface cumulated over 28 days were derived from the DVH plots. Results were expressed as mean+/-SD. RESULTS: The mean activity of the stents was 438+/-140 kBq at implantation. The mean reference dose was 111+/-35 Gy, whereas the calculated mean target dose within the adventitia along the stent was 68+/-20 Gy. On average, DV90 and DV10 were 33+/-9 Gy and 117+/-41 Gy, respectively. Expanding the target volume to include 2.5-mm-long segments at the proximal and distal ends of the stent, the calculated mean target dose decreased to 55+/-17 Gy, and DV 90 and DV 10 were 6.4+/-2.4 Gy and 107+/-36 Gy, respectively. CONCLUSIONS: The assessment of DVHs seems in principle to be a valuable tool for both prospective and retrospective analysis of dose-distribution of radioactive stents. It may provide the basis to adapt treatment planning in coronary brachytherapy to the common standards of radiotherapy.

Aged↗
PubMed2001

Survey of the use of the ICRU 38 in recording and reporting cervical cancer brachytherapy.

BACKGROUND: A survey on the practice of reporting intracavitary cervix cancer brachytherapy (LDR and HDR) in clinical practice (CP) and in literature (LIT) was performed on the occasion of a workshop, 'ICRU 38: The Basis for a Revision', which took place at the Annual GEC ESTRO meeting in Naples in 1998. MATERIALS AND METHODS: The answers (n=85) to a specific questionnaire which had been sent to all ESTRO members (n=1600), were evaluated. In parallel, a systematic survey on the literature reporting cervix cancer brachytherapy since 1985 was performed using the MEDLINE database. The main recommendations for reporting as given in the ICRU 38 were addressed for both surveys: technique; total reference air kerma (TRAK); dose specification to the target volume '60 Gy reference volume', to organs at risk 'ICRU rectum and bladder point' and other reference points and time-dose pattern. In addition, some other items were investigated such as mg h, Point A, B, and in vivo dosimetry in bladder and rectum. RESULTS: Issues related to technique (source, machine and applicator type) and to time-dose pattern are reported in the majority of patients in CP and LIT. The same applies for the following parameters: Point A is indicated in 76% (LDR) to 89% (HDR) in CP, in 60% (LDR) to 96% (HDR) in LIT. Rectum and bladder ICRU points are recorded in 55% (HDR) to 90% (LDR) and 58% (HDR) to 84% (LDR), respectively, in CP. On the other hand, TRAK is given in 14% (HDR) to 43% (LDR) in CP, in 0% (HDR) to 10% (LDR) in LIT. '60 Gy reference volume' is recorded in 18% (HDR) to 51% (LDR) in CP, in 0% (HDR) to 17% (LDR) in LIT. Rectum and bladder ICRU points are reported in 18% (LDR) to 28% (HDR) and 14% (HDR) to 29% (LDR), respectively, in LIT. Other reference points and in vivo dosimetry measurements are given in a low percentage. Dose rate and overall treatment time is reported in 10-44%. CONCLUSION: Recording and reporting in CP and in LIT meets the recommendations as given in ICRU 38 to different degrees. Specific items such as TRAK and the 'Reference volume' have only limited penetration into CP and LIT, which applies in particular to centers using HDR brachytherapy. The discrepancies between CP and LIT may be due to the well-known delay between change in CP and its translation into LIT. In order to arrive at a more common language for the better exchange of clinical results, it seems to be necessary to adapt some terms and recommendations. In particular, comprehensive concepts are needed for reporting dose to points and volumes in the target and in critical organs, according to the new potential from imaging and computer technology and from modern radiobiological insights, bridging the gap between LDR and HDR brachytherapy.

Brachytherapy↗
PubMed2001

Quality control in interstitial brachytherapy of the breast using pulsed dose rate: treatment planning and dose delivery with an Ir-192 afterloading system.

BACKGROUND AND PURPOSE: In the Radiotherapy Department of Leuven, about 20% of all breast cancer patients treated with breast conserving surgery and external radiotherapy receive an additional boost with pulsed dose rate (PDR) Ir-192 brachytherapy. An investigation was performed to assess the accuracy of the delivered PDR brachytherapy treatment. Secondly, the feasibility of in vivo measurements during PDR dose delivery was investigated. MATERIALS AND METHODS: Two phantoms are manufactured to mimic a breast, one for thermoluminescent dosimetry (TLD) measurements, and one for dosimetry using radiochromic films. The TLD phantom allows measurements at 34 dose points in three planes including the basal dose points. The film phantom is designed in such a way that films can be positioned in a plane parallel and orthogonal to the needles. RESULTS: The dose distributions calculated with the TPS are in good agreement with both TLD and radiochromic film measurements (average deviations of point doses <+/-5%). However, close to the interface tissue-air the dose is overestimated by the TPS since it neglects the finite size of a breast and the associated lack of backscatter (average deviations of point doses -14%). CONCLUSION: Most deviations between measured and calculated doses, are in the order of magnitude of the uncertainty associated with the source strength specification, except for the point doses measured close to the skin. In vivo dosimetry during PDR brachytherapy treatment was found to be a valuable procedure to detect large errors, e.g. errors caused by an incorrect data transfer.

Brachytherapy↗
PubMed2001

Comparison of radiography- and computed tomography-based treatment planning in cervix cancer in brachytherapy with specific attention to some quality assurance aspects.

INTRODUCTION: A modern approach in treatment planning for cervix carcinoma is based on a series of computed tomography (CT) sections and 3D dose computation. When these techniques were not yet available, dose evaluation was based on orthogonal radiographs. The CT based planning provides information on target and organ volumes and dose-volume histograms. The radiography based planning provides only dimensions and doses at selected points. The aim of the presented study is to correlate the information obtained with the two approaches for high dose-rate (HDR) brachytherapy of cervix carcinoma. METHODS: For the study 28 patients with 35 applications receiving HDR treatment with Ir-192 were investigated. The planning system PLATO (Nucletron) was used. The different aspects of available data, results and inaccuracies regarding quality assurance were looked at. RESULTS: From the CT based planning, the volume, location and dose-volume histograms were calculated for the CTV, rectum and bladder. From the radiography-based planning, the dose to point A (prescription), point B, rectum and bladder ICRU reference points [14], points related to the bony structures could be evaluated as well as volumes receiving different dose levels. These two sets of information were compared and following mean values derived. For a dose prescription of 7 Gy at point A, as an average, 83% (44 cm(3)) of the clinical target volume (CTV) receives at least 7 Gy. The mean dose at the rectum ICRU reference point is 4.3 Gy, and 12% (9 cm(3)) of the rectum is encompassed by the 4.3 Gy isodose. The mean dose at the bladder ICRU reference point is 5.8 Gy, and 8% (16 cm(3)) of the bladder is encompassed by the 5.8 Gy isodose. The maximum dose to the rectum is 1.5 times higher than the dose at the ICRU reference point, and for the bladder 1.4 times higher. Uncertainties caused by the reconstruction of the applicator and merging of isodoses could be evaluated. DISCUSSION: The subdivision of different approaches and the transfer from point doses to volumes in treatment planning is possible and practical for the treatment of cervix carcinoma in brachytherapy.

Brachytherapy↗