Watchful Waiting After Complete Clinical Response Following Concurrent Chemoradiation for Rectal Adenocarcinoma

Abstract

The standard of care for patients with locally advanced rectal cancer is neoadjuvant chemoradiation followed by surgery. However, some patients achieve a complete clinical response to neoadjuvant therapy. Increasing evidence has shown that such patients may be able to avoid surgery while achieving excellent functional and oncological outcomes 1. We retrospectively reviewed patients with rectal adenocarcinoma treated at Kaiser Permanente Los Angeles Medical Center from 2015 to 2016 who underwent neoadjuvant chemoradiation. Patients who achieved a complete clinical response based on strict criteria and who declined surgery were followed with watchful waiting. A complete clinical response on clinical exam was defined as the absence of mass or ulceration, and presence of flat mucosa or scar only. In addition, magnetic resonance imaging (MRI) showed no evidence of residual mass. Patients on watchful waiting were followed with MRI every 3-6 months for 2 years then every 6 months after for 5 years. Exam with rigid proctoscopy was performed every 3 months for 2 years and every 6 months up to 5 years. Local, regional, and distant recurrences were calculated using the Kaplan-Meier method, and statistical analysis was performed with R version 3.3.1. 238 patients were treated with neoadjuvant chemoradiation. Of these, 28 patients, including 2 patients treated prior to 2015, were followed with watchful waiting after achieving a complete clinical response by strict criteria (median age 67. 11% Stage I, 43% stage IIA, 4% stage IIIA, 36% stage IIIB, 7% stage IIIC). 13 patients on watchful waiting had negative repeat biopsy and 3 had local excisions negative for residual tumor. 16 patients (55%) received adjuvant chemotherapy. At a median follow up of 12 months, 3 patients developed local recurrence and were salvaged with surgery. The 12-month Kaplan-Meier rate of local control was 92%. No patients developed regional or distant recurrences. We observed a high rate of local, regional, and distant control among patients who achieved a complete clinical response to neoadjuvant chemoradiation and who were managed non-operatively with watchful waiting. Longer follow up will be needed to confirm our findings. Bibliography: 1. Appelt AL, Ploen J, Harling H, et al. High-dose chemoradiotherapy and watchful waiting for distal rectal cancer: a prospective observational study. The Lancet Oncology. 2015;16(8):919-927.