Stereotactic Body Radiation Therapy (SBRT) and Image Guided Accelerated Hypofractionated Radiation Therapy (IGAHRT) for the Treatment of Oligometastatic Cancers

Abstract

Data in support of aggressive treatment of oligometastatic cancers is still relatively modest in scope. We report our experience treating single or multiple sites, as well as outcomes for patients receiving sequential treatment during the course of their disease. Patients treated between 2009 and 2011 with stereotactic body radiation therapy [SBRT] or image-guided accelerated hypofractionated radiation therapy [IGAHRT] for metastatic cancer were screened and included. Patients were treated using an SBRT technique, with a stereotactic body-fixation device and abdominal compression for immobilization during non-spine treatment. SBRT was defined as 1 to 5 fractions (fxs) with a minimum of 9 Gy/fxs. IGAHRT was defined as 6 to 10 fxs and minimum 5 Gy/fxs. 4D CT was used to define an ITV with a 5 mm PTV expansion. Toxicities were recorded per NCI CTCAE v4.0. Kaplan Meier estimates were performed for local control (LC) and overall survival (OS). A Wilcoxon log-rank test was used for comparison. Fifty-seven patients (pts) were treated for oligometastatic cancer (AJCC 7th ed), 2009-2011. Represented histologies included lung (15 pts), GI (16 pts), sarcoma (6 pts), breast (4 pts), head and neck (H&N) (10 pts), and renal (6 pts). Initial metastatic sites treated included lung (36 pts), liver (8 pts), spine (6 pts), adrenal gland (5 pts), lung/liver (1 pt), and lung/adrenal (1 pt). SBRT/IGAHRT dose by site are as follows: lung 26-54 Gy, 1-10 fxs; liver 45-54 Gy, 3-10 fxs; spine 24-50 Gy, 1-10 fxs; adrenal 50 Gy, 10 fxs. The most common IGAHRT dose was 50 Gy/10 fxs. Median follow-up was 19 months (range, 1-43 months) from treatment. 43 pts received chemotherapy prior to SBRT/IGAHRT. 29/57 pts were treated to multiple lesions during a single course. 12/57 pts were treated with several single courses over 36 m, with a maximum of 3 courses. Two yrs LC was 86% (95% CI 70-95%). Median and 2 year OS from diagnosis of metastatic disease were 55 m and 75% respectively. Median OS from first SBRT/IGAHRT was 35 m for all pts, 35 m for lung cancer pts, 29 m GI, 23 m for breast, 13 m for sarcoma, and was not reached in H&N/renal pts. Median OS for lung site vs all other sites was not reached vs 13.5 months (p = 0.01). Two-yr OS for lung site vs all others: 74% vs 43%. Median OS for single vs multi-target: not reached vs 27 months (p = 0.06); Median OS for single SBRT vs multiple courses: 29 m vs 39 m (p = 0.21). No grade 4 or 5 toxicity noted. In these highly selected patients with oligometastatic cancers, multiple courses of SBRT/IGAHRT were used with durable local control. Prolonged survival from original metastatic diagnosis suggests favorable selection bias. Patients with metastasis to lung had superior outcomes when compared to other sites. Patients with multiple lesions during single course tended to fair worse. Additional prospective study is warranted.