Post operative stereotactic radiosurgery for positive or close margins after preoperative chemoradiation and surgery for rectal cancer.

Background: The incidence of positive margins after neoadjuvant chemoradiation and adequate surgery is very low. However, when patients do present with positive or close margins, they are at a risk of local failure and local therapy options are limited. We evaluated the role of stereotactic body radiotherapy (SBRT) in patients with positive or close margins after induction chemoradiation and total mesorectal excision.

Methods: This is a retrospective evaluation of patients treated with SBRT after induction chemoradiation and surgery for positive or close margins. Seven evaluable patients were included. Fiducial seeds were place at surgery. The Cyberknife(TM) system was used for planning and treatment. Patients were followed 1 month after treatment and 3-6 months thereafter. Descriptive statistics and Kaplan-Meir method was used to repot the findings.

Results: Seven patients (3 men and 4 women) were included in the study with a median follow-up of 23.5 months. The median initial radiation dose was 5,040 cGy (in 28 fractions) and the median SBRT dose was 2,500 cGy (in 5 fractions). The local control at 2 years was 100%. The overall survival at 1 and 2 years was 100% and 71% respectively. There was no Grade III or IV toxicity.

Conclusions: SBRT reirradiation is an effective and safe method to address positive or close margins after neoadjuvant chemoradiation and surgery for rectal cancer.