Abstract

PURPOSE/OBJECTIVE(S): Patients with locally recurrent colorectal cancer represent a particular clinical challenge as these patients often present with unresectable disease and a history of prior pelvic radiotherapy. While options are therefore limited, radiation is usually the only local therapy available. The purpose of this study was to analyze the efficacy and outcomes associated with treating recurrent colorectal cancer using stereotactic body radiation therapy (SBRT) in patients who have been previously irradiated to the pelvis.MATERIALS/METHODS: We identified 23 patients with recurrent rectal (n?=?20, 87%) or colon (n?=?3, 13%) adenocarcinoma who were treated with SBRT in the Department of Radiation Oncology at Stanford University from June 2009 to November 2019. In total, 11 males and 12 females were included in this study with a median age of 53 years old (range: 25-76). All 23 patients had a history of surgical resection and at least one course of radiation therapy to disease in the pelvis before SBRT treatment to the pelvis for recurrent cancer, of which 8 patients (35%) received two prior radiotherapy courses and 1 patient (4%) received three prior courses. Data collection included tumor staging and grading, radiation treatment details, and follow up information to determine toxicities and survival outcomes. Time to events were calculated from the completion of SBRT. Toxicities were graded using the Common Terminology Criteria for Adverse Events (CTCAE) v.5.0.RESULTS: Median time to follow up was 91 months (range: 36-237). Median GTV and PTV volumes for tumor treated using SBRT were 79.9 and 136.5 cm3, respectively. Median SBRT dose was 40 Gy (range: 30 - 50). Median PTV mean dose was 41.8Gy. The median cumulative biological effective dose (BED) was 145 Gy (range: 72.0-254.4). Overall, 22 patients received 5 fractions of treatment and one patient received 4 of the 5 planned fractions due to deteriorating condition related to disease. Median time to overall survival (OS) was 125 months (range: 61-194) and median progression free survival (PFS) was 82 months (range: 57-142). The 3- and 5-year rate of local failure was 4.4% and 17.4%, respectively. Of the 23 patients in this cohort, there were 6 patients (26%) with grade 2 acute toxicities, including 3 patients (13%) with increased pain, and 6 patients (26%) with late grade 2 or 3 toxicities, including 3 patients (13%) with grade 3 neuropathy. There was no grade 3 or 4 acute, or grade 4 late toxicities reported. On univariate analysis, no factors were significantly predictive of OS, PFS, or toxicity.CONCLUSION: SBRT to previously irradiated areas of the pelvis was effective in controlling unresectable pelvic recurrences of colorectal cancer following previous radiation. While treatment was generally well-tolerated, pelvic pain was the most common acute toxicity, and neuropathy was the most common late toxicity. Further investigation is needed to improve the toxicity profile and optimize the therapeutic ratio.

View details for DOI 10.1016/j.ijrobp.2021.07.405

View details for PubMedID 34701819