e15177 Background: Treatment of locally advanced rectal cancer is based on chemoradiation associated with surgery. This treatment has high potential for curability. Tumor regression grade appears to be a prognostic factor and be influenced by the timing of surgery. Methods: A retrospective database was formed. We included patients submitted to neoadjuvant chemoradiotherapy and rectal surgery, treated at the Hospital de Clínicas, Porto Alegre. We analyzed outcomes, pathologic and treatment toxicity data. TRG was mensurated by the modified Ryan method, as the AJCC. We sought to analyze the better timing for surgery after chemotherapy, comparing the weeks after surgery with the rate of pCR. Statistical analysis was done with Kaplan Meier, Pearson's Chi-square and the Cox regression method. Results: We accrued 156 patients between 2006 and 2018. The rate of PFS at 3 and 5 years were 75% and 70%, respectively. The 5-year overall survival was 91%. The rate of pCR was 12.8%. TRG was an important prognostic factor. The absence of a pathological response (TRG 3) was associated with an increase in mortality, HR 3,148 (95% CI 1.6-12.2 P 0.003) and a decrease in PFS, HR 3,148 (95% CI 1, 7-5.8 P 0.0001). The 5-years PFS with TRG 0,1, 2 and 3 were 95%, 87%, 73.3% and 48%, respectively. Comparing the time between neoadjuvant treatment and surgery of less than 8 weeks versus 8 and 12 weeks versus above 12 weeks, the rates of pCR were 4.3%, 18.6% and 7.1% and the rates of TRG 3 were 32,6%, 18,6% and 57,1% (P 0.016). The chemotherapy regimens included 5FU bolus (75.1%) and capecitabine (19.1%). Doses of radiotherapy above 45 Gy were received by 80.5% of patients. Adjuvant treatment was not performed in 30.6% and 16.6% of these cases had positive pathological lymph nodes. The grade 3/4 adverse event rate was 21.6%. Conclusions: The outcomes found are favorable. The pathological tumor regression grade is an important prognostic factor. New strategies such as total neoadjuvant may play a role considering the rate of patients who cannot perform adjuvant chemotherapy. The time after neoadjuvant treatment seems to influence the tumor regression rate, especially between 8 and 12 weeks.
Impact of tumor regression grade as a major prognostic factor in pathological stage II and III rectal cancer after neoadjuvant chemoradiotherapy
