Stereotactic radiosurgery for treatment of brain metastases. A report of the DEGRO Working Group on Stereotactic Radiotherapy.

BACKGROUND: This report from the Working Group on Stereotaktische Radiotherapie of the German Society of Radiation Oncology (Deutsche Gesellschaft für Radioonkologie, DEGRO) provides recommendations for the use of stereotactic radiosurgery (SRS) on patients with brain metastases. It considers existing international guidelines and details them where appropriate. RESULTS AND DISCUSSION: The main recommendations are: Patients with solid tumors except germ cell tumors and small-cell lung cancer with a life expectancy of more than 3 months suffering from a single brain metastasis of less than 3 cm in diameter should be considered for SRS. Especially when metastases are not amenable to surgery, are located in the brain stem, and have no mass effect, SRS should be offered to the patient. For multiple (two to four) metastases--all less than 2.5 cm in diameter--in patients with a life expectancy of more than 3 months, SRS should be used rather than whole-brain radiotherapy (WBRT). Adjuvant WBRT after SRS for both single and multiple (two to four) metastases increases local control and reduces the frequency of distant brain metastases, but does not prolong survival when compared with SRS and salvage treatment. As WBRT carries the risk of inducing neurocognitive damage, it seems reasonable to withhold WBRT for as long as possible. CONCLUSION: A single (marginal) dose of 20 Gy is a reasonable choice that balances the effect on the treated lesion (local control, partial remission) against the risk of late side effects (radionecrosis). Higher doses (22-25 Gy) may be used for smaller (< 1 cm) lesions, while a dose reduction to 18 Gy may be necessary for lesions greater than 2.5-3 cm. As the infiltration zone of the brain metastases is usually small, the GTV-CTV (gross tumor volume-clinical target volume) margin should be in the range of 0-1 mm. The CTV-PTV (planning target volume) margin depends on the treatment technique and should lie in the range of 0-2 mm. Distant brain recurrences fulfilling the aforementioned criteria can be treated with SRS irrespective of previous WBRT.

Changes of dose delivery distribution within the first month after permanent interstitial brachytherapy for prostate cancer.

PURPOSE: To evaluate changes of dose distribution for both the prostate and the surrounding tissues after permanent brachytherapy as monotherapy for prostate cancer. PATIENTS AND METHODS: In 35 patients, CT scans were performed before, 1 day after (day 1) and 1 month after the implantation (day 30). Changes of prostate volume, dosimetric parameters, and distances between posterior prostate contour and rectal wall as well as prostate contour and prescription isodose were analyzed. RESULTS: Prostate volume increased from 37+/-11 cm3 (mean+/-standard deviation) to 49+/-12 cm3 on day 1 and dropped to 40+/-9 cm3 on day 30. Prostate V100 increased from 87+/-7% to 90+/-7%, prostate D90 from 138+/-21 Gy to 151+/-30 Gy. Mean rectal volume covered by the prescription isodose rose from 0.4 cm3 to 1.0 cm3; a changing distance between the prostate and rectal wall was excluded as a reason. Prostate D90 (day 1) and rectum V100 (day 30) proved to be significantly higher for larger prostate sizes. The distance between the prescription isodose and the prostate contour increased particularly at the posterior and inferior borders: 1.9 mm and 2.5 mm on average (0.1 mm and -0.7 mm at opposite borders, respectively). CONCLUSION: With a decreasing edema of the prostate, an increasing dose both to the prostate and the anterior rectal wall resulted--the postimplant interval is essential for the dosimetry report. Due to a larger edema, a higher prescription dose might be needed for optimal cancer control in smaller prostates. Compared to day 1, the dose to the surrounding tissues increased on day 30, particularly at the posterior and inferior prostate borders.