Shorter time from rectal cancer diagnosis to NCRT tied to pathologic complete response

The time elapsed between diagnosis of rectal cancer and initiation of neoadjuvant chemoradiation (NCRT) shows a significant association with pathologic complete response (pCR), and shortening this time may improve the likelihood of achieving pCR, suggests a recent study.

This single-centre retrospective study was conducted from 2011 to 2020 and included patients with stage II to III rectal cancer who had received NCRT. The standard radiotherapy was 45 Gy to the pelvis, with a simultaneous integrated 50 Gy boost to the primary tumour. Continuous 5-Fluorouracil or oral capecitabine was administered concomitantly, while surgery was preplanned within 6 to 8 weeks.

The investigators performed multinomial logistic regression to assess clinical factors, Kaplan-Meier method to evaluate disease-free survival (DFS), and receiver operating characteristic analysis to determine the optimal timeframe.

Seventy-two of the 279 patients (25.8 percent) achieved pCR. In 207 patients, 137 (66.2 percent) obtained pTis-4N-negative, six (2.9 percent) pT0N-positive, and 64 (30.9 percent) pTis-4N-positive.

Patients in the pCR group had shorter diagnosis-to-NCRT time (p<0.01) and on-treatment time (p=0.05). DFS was longer for pCR and partial responders with clinical stage II and III (p<0.0001). A different diagnosis‒NCRT time was noted between pCR and non-pCR groups.

In receiver operating characteristic analysis, a diagnosis-to-NCRT time of <4.5 weeks was predictive of pCR, with a sensitivity of 88 percent and specificity of 81 percent (p<0.01).

“In rectal cancer, NCRT is preferred because of toxicity profile, improved resectability, and sphincter preservation, although with no impact on overall survival,” the investigators said. “PCR to NCRT has been linked with longer DFS.”