부산대학교 도서관

Purpose: The treatment of relapses of already irradiated primary brain tumors and metastases is difficult, given the limited effectiveness of systemic therapy and the risks of surgery or re-irradiation. Here we present the results of salvage Stereotactic Radiotherapy (SRT) for the treatment of recurrent primary brain tumors and metastases (mts) after previous radiotherapy (RT). Material/methods: From January 2018 to October 2021, 137 intracranial lesions (33 patients) were re-irradiated with robotic SRT. Primary histology was: NSCLC (n=10), breast cancer (n=9), glioblastoma (n=4), meningioma (n=2), oligodendroglioma (n=2), hemangiopericytoma (n=2), pituitary adenoma (n=2), prostate cancer (n=1), and melanoma (1). Previous RT on the same volume were performed with: GammaKnife (n=11), CyberKnife (n=8), Whole-Brain RT (n=8), post-operative IMRT/ Helical IMRT (n=8), VMAT-SRT (n=5), post-operative 3D-CRT (n=3). Eight patients had multiple previous treatments. Median time from the previous radiotherapy was 13 (3-377) months. Gross Tumor Volume (GTV) was delineated on computed tomography and contrast-enhanced T1 magnetic resonance. Median GTV was 5.24 (0.22-78.32) cc. Planning Target Volume (PTV) was obtained adding an expansion to GTV of 1 mm (for brain metastases), or 3 mm (for glioblastoma). Median PTV was 10.19 (0.43-136.9) cc. Median prescribed dose was 30 (24-37.5) Gy in 1-5 fractions (median number of fractions was 5), at a median isodose of 76% (67-80%). The patients were followed up with contrast-enhanced MRI performed every three months. Results: SRT was delivered on a median number of 2 (1-24) lesions; 7 patients were treated on ≥ 5 lesions simultaneously (from 5 to 24 lesions). Acute toxicity was G2 headache in three patients (GTV>1cc or >3 lesions), controlled by increasing the dose of steroids. Median follow-up after re-irradiation in 20 evaluable patients was 9 (1-37) months. Radionecrosis occurred in only one patient (GTV>1cc). He underwent two previous VMAT SRT (prescribed dose 30 Gy in 5 fractions and 21 Gy in 3 fractions) and presented seizures. He was treated with steroids and levetiracetam. Six-, 12-, 18-month overall survival (OS) was 79.2%, 51.7%, 37.7% respectively. Six-, 12-, 18-month local relapse free survival was 70.7%, 64.8%, 48.6% respectively (see Figure 1). Conclusions: SRT for re-irradiation is feasible, with only one case of radionecrosis registered. The treatment is effective with 12-month local control registered in 65% of pts. An accurate patient selection is warranted in order to avoid toxicity and a longer follow-up is needed to confirm the low radionecrosis rate. [ABSTRACT FROM AUTHOR]