Distal spread and tumor regression patterns following preoperative chemoradiotherapy in rectal cancer patients

This study aimed to evaluate the regression pattern with the distal intramural spread (DIS) of rectum cancer after preoperative chemoradiation.

Specimens from 56 patients who underwent radical resection after preoperative chemoradiation for rectal cancer were examined. The regression pattern (total, fragmented) of the tumor was recorded. DIS status was evaluated by creating sections 0.2 to 0.3 cm thick.

A single macroscopic residual area was detected in all specimens. In 10 patients (17.8 %), pathologically complete responses were identified, and DIS was detected in 33 patients (58.9%). The average DIS distance was 0.56± 0.3 cm (range 0.2 – 1.8 cm); the spread was < 1 cm in 87.9% of the patients (29/33). The overall survival rates for 5 and 7 years were 76.8% and 73.2%, respectively. The survival rates between patients with and without DIS were not statistically different (94.6± 5.5 vs. 75.1 ± 10.2 months, respectively). In all of the patients, tumor regression pattern was total shrinkage of the tumor.

A sufficient distal resection margin for rectal cancer after preoperative chemoradiation is 1 cm in the vast majority of cases. However, DIS may exceed 1 cm in a small proportion of patients.