Adjuvant Chemotherapy Key to Improving OS in Rectal Cancer

A retrospective study shows 30 patients need to be treated with adjuvant therapy to prevent 1 death at 3 years.

Undergoing adjuvant chemotherapy for rectal cancer with pathologic complete response (pCR) after resection was associated with a better overall survival (OS) compared with no adjuvant therapy, according to the results of a retrospective study published recently in JAMA Oncology. The improvement in OS was particularly strong in patients with pretreatment node-positive disease.

“While previous studies have suggested withholding adoptive cellular therapy (ACT) in patients who achieve pCR, our findings suggest that the use of ACT may confer a survival benefit in this population,” wrote Fahima Dossa, MD, University of Toronto, and colleagues. “Ideally, a prospective randomized controlled trial would be used to evaluate the role of ACT among patients with pCR. However, given the difficulty in accruing the number of patients that such a study would require, observational studies remain the best evidence to guide management.”

The retrospective study looked at 2,455 patients with locally advanced rectal cancer from the National Cancer Database from 2006 to 2012. Patients had nonmetastatic disease and achieved pCR after undergoing neoadjuvant chemoradiation therapy and resection of disease. Patients who received adjuvant chemotherapy were matched 1:1 with those who did not.

With a median follow-up of about 3 years, patients who received adjuvant therapy had a significantly better OS than those who did not (hazard ratio [HR], 0.44; 95% CI: 0.28-0.70). The 3-year OS was 97.6% for patients given adjuvant chemotherapy and 94.0% for those who did not receive adjuvant chemotherapy. The number of patients needed to treat with adjuvant therapy to prevent 1 death at 3 years was 30.

When stratified according to nodal status, those patients with pretreatment node-positive disease had improved OS after undergoing adjuvant chemotherapy (HR, 0.24; 95% CI: 0.10-0.58). Three-year OS for node negative patients was 97.1% when treated with adjuvant therapy and 95.2% for patients who did not receive adjuvant therapy. In node-positive patients it was 98.3% and 93.1%, respectively.

In an editorial, George J. Chang, MD, of The University of Texas MD Anderson Cancer Center, said that the results of this study should be interpreted with caution and cautioned not to overlook the underlying limitation of the methods used.

“Although a trial in which patients are randomized based on their pathologic stage may yield definitive evidence, large sample size requirements and strong clinician bias may preclude its completion,” he wrote. “If there is a true benefit associated with adjuvant chemotherapy, it is likely to be small and the estimates of number needed to treat may be markedly underestimated. Given the favorable prognosis of ypT0N0 status following nCRT, the potential harms of adjuvant therapy, including risk for long-term neuropathy, cannot be ignored and alternative strategies for analysis that are less subject to unmeasured confounding should be pursued.”