Rate of pathologic complete response with increased interval between preoperative combined modality therapy and...

Recent data suggest a favorable prognosis for rectal cancer patients with a pathologic complete response to preoperative combined modality therapy. Prolongation of the interval between preoperative combined modality therapy and surgery (RT-surgery interval) as a means of increasing pathologic complete response rate has not been fully examined.

One hundred and fifty-five rectal cancer patients undergoing preoperative pelvic external beam radiation therapy and 5-fluorouracil-based chemotherapy followed by rectal resection were identified. All patients had endorectal ultrasound prior to combined modality therapy. Final pathology reports were reviewed for ypT and ypN stage and margin status. Medical records were reviewed for sphincter preservation, operative time, estimated blood loss, hospital stay, and morbidity (overall, anastomotic, and perineal).

A pathologic complete response (ypT0N0) occurred in 24 patients (15 percent). Median RT-surgery interval was 44 (range, 15-206) days. A pathologic complete response occurred in 19 percent of patients with an interval >44 days, vs. 12 percent in those with an interval < or =44 days ( P = 0.27). Downstaging by three stages occurred more frequently in the long-interval group (15 percent vs. 6 percent, P = 0.11). The rates of sphincter preservation, positive margins, estimated blood loss, and operative time were not significantly different. Overall morbidity was similar between groups.

Our results demonstrate a trend toward increased pathologic complete response rate and downstaging with increased RT-surgery interval. However, sphincter preservation is not increased. Until prospective analyses are conducted assessing the impact of prolonged RT-surgery interval on long-term outcome, the benefit of a prolonged interval between the completion of preoperative combined modality therapy and surgery remains unclear.