Stereotactic body radiotherapy (SBRT) in difficult-to-treat areas (para-aortic lymphadenoapthy and pelvic recurrence) in oligometastatic colorectal carcinoma.

Abstract

733 Background: Oligometastatic (OM) colorectal carcinoma (defined as three or fewer sites of isolated metastatic disease) may occur in potentially difficult to treat areas (including para-aortic lymphadenopathy and pelvic recurrence). Proximity of critical structures and previous irradiation may prove treatment of OM disease challenging. The aim of this study was to identify local control, overall survival (OS), and progression free survival (PFS) of patients receiving SBRT for difficult to treat oligometastatic disease (para-aortic lymphadenopathy and pelvic recurrence). Methods: Data were prospectively collected for patients receiving SBRT between 1/9/10-31/3/14, including demographic details, SBRT date, date of local/distant progression, toxicity, and date of death. Data was collected until 1/6/14. All patients were discussed within a specialist SBRT MDT and planned for treatment utilizing the Cyberknife (Accurray) treatment system. Treatment doses included 24 Gy/3F (22.7%), 27 Gy/3F (27.3%), 30 Gy/3F (13.6%), 30 Gy/5F (4.5%), 33 Gy/3F (22.7%), 36 Gy/3F (9.1%). Total dose was determined by surrounding normal tissue toxicities. Results: 9 received SBRT for para-aortic lymphadenopathy and 13 for pelvic recurrence. Median age was 58 (38-81) years. 14 were male. Median follow-up was 8.0 (0.5-28.0) months. 59.1% patients were treated within a prior radiotherapy treatment volume. 31.8% patients were disease free after SBRT. 63.6% had distant relapse and 4.5% had local and distant relapse. Local control was 95%. Median time to relapse was 4.5 (1.2-37.2) months. OS was 72% at 1 year and 46% at 2 years. PFS was 36% at 1 year and 27% at 2 years. Significant toxicities included 1 patient with duodenal ulcer formation following para-aortic node SBRT. Conclusions: Our prospective series confirms excellent local control (95%) with SBRT for OM colorectal carcinoma in areas considered to be difficult to treat, and with limited toxicity.