Purpose: The purpose of this study was to analyze the influence of variations in clinical practice regarding the timing of surgery with short-course chemoradiotherapy with delayed surgery (SCRT-delay) for lower rectal cancer.
Methods: A total of 171 patients with T3 N0-2 lower rectal cancer treated with SCRT-delay (25 Gy/10 fractions/5 days (S-1); days 1-10) were retrospectively evaluated. The median waiting period of 30 days was used as a discriminator (group A: waiting period, ≤30 days; group B: waiting period, ≥31 days). Preoperative treatment responses and oncological outcomes were analyzed.
Results: The mean waiting periods for groups A and B were 24.4 ± 5.3 and 41.4 ± 12.3 days, respectively. There were no statistically significant differences between the two groups in any of the clinical variables. The clinicopathological outcomes were as follows: T downstaging (43.5 vs 37.2 %; p = 0.400), negative yp N (67.1 vs 75.6 %; p = 0.218), pCR (7.1 vs 1.2 %; p = 0.119). The 5-year local recurrence-free survival (89.3 vs 87.6 %; p = 0.956), the recurrence-free survival (82.2 vs 78.8 %; p = 0.662), and the overall survival (88.5 vs 84.4 %; p = 0.741), all of which were similar between the two groups.
Conclusions: The longer waiting period did not increase the tumor downstaging and not improve the oncological outcomes for T3 lower rectal cancer treated with SCRT-delay. In addition, considering that the impaired leukocyte response occurred during the sub-acute period, any time after the sub-acute period (day 12) up to 30 days after radiotherapy would be a suitable waiting period.