Impact on Loco-regional Control of Radiochemotherapeutic Sequence and Time to Initiation of Adjuvant Treatment in Stage II/III Rectal Cancer Patients Treated with Postoperative Concurrent Radiochemotherapy

PURPOSE This study was designed to evaluate the impact of radiochemotherapeutic sequence and time to initiation of adjuvant treatment on loco-regional control for resected stage II and III rectal cancer. MATERIALS AND METHODS Treatment outcomes for rectal cancer patients from two hospitals with different sequencing strategies regarding adjuvant concurrent radiochemotherapy (CRCT) were compared retrospectively. Pelvic radiotherapy was administered concurrently on the first (early CRCT, n=180) or the third cycle of chemotherapy (late CRCT, n=180). During radiotherapy, two cycles of fluorouracil were provided to patients in both groups. In the early CRCT group, median six cycles of fluorouracil and leucovorin were prescribed during the post-CRCT period. In the late CRCT group, two cycles of fluorouracil were administered in the pre- and post-CRCT periods. RESULTS No significant differences in the 5-year loco-regional recurrence-free survival (LRRFS) (92.5% vs. 95.6%, p=0.43) or overall survival and disease-free survival were observed between groups. Patients who began receiving adjuvant treatment later than five weeks after surgery had lower LRRFS than patients who received adjuvant treatment within five weeks following surgery (79% vs. 91%, p<0.01). The risk of loco-regional recurrence increased as the time to initiation of adjuvant treatment was delayed. CONCLUSION In the current study, treatment outcomes were not significantly influenced by the sequence of adjuvant treatment but by the delay of adjuvant treatment for more than five weeks. Timely administration of adjuvant treatment is deemed important in achieving loco-regional tumor control for stage II/III rectal cancer patients.