Use of adjuvant chemotherapy may need to be rethought for patients who experience a pathologic complete response (pCR) or with ypT3-4 residual tumor after neoadjuvant chemoradiation (CRT) for rectal cancer, according to a new analysis presented at the 2011 Gastrointestinal Cancers Symposium (Abstract 361).
By pooling data from multiple studies that evaluated different degrees of response to CRT, researchers sought to evaluate if the response level affected the disease-free survival (DFS) benefit received from adjuvant chemotherapy in rectal cancer. Patients were stratified into three subgroups: pCR(ypT0N0), ypT1-2 tumor, and ypT3-4 tumor after CRT.
Of 2724 patients, 811 had pCR, 863 had ypT1-2, and 1050 had ypT3-4. With a median follow-up of 50 months (0-277), 41% of patients had received adjuvant chemotherapy, most of which were 5-flouruoracil based. Researchers found less benefit from adjuvant chemotherapy after CRT in patients with pCR (hazard ratio [HR], 0.94; 95% confidence interval [CI], 0.50-1.78) as well as in those with ypT3-4 tumors (HR, 0.97; 95% CI, 0.75-1.25). Patients with ypT1-2 tumors received benefit from adjuvant treatment (HR, 0.61; 95% CI, 0.40-0.92), of which those with ypT1-2N0 tumors received the most benefit (HR, 0.45; 95% CI, 0.27-0.75).
The researchers noted that the lack of benefit in patients with pCR may be due to their already good prognosis and in patients with ypT3-4 residual tumor may be due to their lack of response to 5-flouruoracil-based chemotherapy.