Pathologic complete response to standard preoperative chemoradiation in patients with locally advanced rectal cancer.
686 Background: Pathologic complete response (pCR) is associated with lower rates of recurrences and longer disease-free survival rates in locally advanced rectal cancer (LARC) patients. The purpose of this study was to evaluate clinical outcomes of neoadjuvant chemoradiation and pCR among these patients. Methods: A retrospective chart review was performed for all patients treated for LARC between August 2005 and May 2011 at St. Michael's Hospital, Toronto. Patients were stratified into pCR and no-pCR groups and compared with respect to tumor size, nodal status, and treatment characteristics. Descriptive statistics were calculated for all variables of interest. Chi-square and t-tests were conducted to test for associations between categorical and continuous variables respectively. Disease free survival was calculated as the time between diagnosis and recurrence date, censored at last follow up. Results: A total of 92 patient charts were reviewed; 21 patients had metastatic carcinoma and were excluded from analysis. 63.4% (45/71) were male, with a mean age of 61.2 years and median follow up of 15 months. 12.7% (9/71) of patients achieved a pCR, while the remaining 87.35% (62/71) were no-pCR. All pCR patients received and completed standard pre-operative chemotherapy-radiotherapy. 73.4% (52/71) of the patients had complications from chemoradiotherapy. Furthermore, there was a significant association between having a significant response to treatment and achieving a pCR; where 78% (7/9) of pCR patients had a significant response to treatment. Overall, 4/71 patients had a local recurrence, 22.2% (2/9) pCR and 3.2% (2/62) no-pCR. Those with no-pCR had a recurrence at 1 and 2.2 years post diagnosis, while those with pCR had a recurrence at 3.7 years. Conclusions: This study suggests that patients undergoing standard pre-operative chemoradiotherapy are likely to have a significant response and achieve a pCR. Based on this study, although a pCR does not prevent the risk of recurrence, it delays the onset of local recurrence. Longer follow-up is required to determine if these results are robust and to develop future studies to improve efficacy of treatment delivery in LARC patients.