Outcomes following stereotactic body radiotherapy (SBRT) in locally recurrent rectal cancer (LRRC) in a previously irradiated pelvis.

Abstract

640 Background: Management of LRRC is challenging. There is no consensus regarding the best approach for patients not suitable for exenteration. Hyperfractionated re-irradiation is associated with > 10% grade 3 toxicity and it is demanding for patients and department. Here we report initial outcomes of an inoperable cohort treated with SBRT. Methods: A prospective nationally maintained database for SBRT re-irradiation was interrogated. Eligibility criteria were pelvic recurrence in a previously irradiated colorectal cancer, not eligible for exenteration, > 6 mo disease free survival, > 6mo from previous RT, ≤ 3 metastases, PS 0-1. SBRT dose of 30Gy in 5 fractions in < 10 days was specified. Every 3 mo toxicity was assessed using the CTCAE v4.0, QoL using the EQ5D, respectively and imaging was undertaken. Median progression free survival (PFS) and overall survival (OS) were calculated using the Kaplan-Meier method. Results: 28 patients with 33 separate pelvic lesions were treated between Oct 2015-June 2018. The median age was 64 years (range 36-84). 27/28 had received 45-50.4Gy in 25-28F with concurrent Capecitabine, 1/28 received 25Gy/5F, all followed by surgery. Combining SBRT, the cumulated effective dose received was >100Gy10. The median GTV volume was 14.9cc (range 0.47-121.73cc). All completed the SBRT. There were minimal symptoms at baseline pain = 7, urinary = 3, GI = 3, nerve = 1. 48% grade 1 or grade 2 acute toxicity was reported at 6 weeks, with 25% grade 1 or grade 2 late toxicity, but no grade 3 toxicities reported with a median follow up of 10 months (range 2-30). There was an 81% local control rate with a median PFS of 12.2 months (95% CI 4.0-20.5) and a 2-year OS of 70.4% (95% CI 49.0-100). 28% (8/28) solely progressed out of field. Conclusions: Acute toxicity is minimal in this cohort of patients with initial excellent local control. Follow-up is continued. SBRT appears effective and convenient for patients who are non-surgical candidates with pelvic recurrence and offers the opportunity for local and symptom control, whilst deferring systemic treatment.