Induction chemotherapy plus concomitant oxaliplatin-based chemoradiotherapy for locally advanced rectal cancer: A real world experience at San Raffaele Hospital.

Abstract

144 Background: The standard treatment of locally advanced rectal cancer (LARC) consists of giving preoperative chemoradiation therapy (CT/RT) followed by surgery. Recently, total neoadjuvant therapy (TNT) has shown greater efficacy in terms of increasing the rate of complete pathological response (pCR) and reducing local and systemic relapse. However, based on the proposed therapy scheme, the risk of overtreatment and side effects is not negligible. The objective of this study was to evaluate the efficacy and safety of neoadjuvant doublet with oxaliplatin-based CT and concomitant RT. Methods: Patients with clinically staged II-III rectal cancer were treated with preoperative CT/RT using up to 3 cycles of oxaliplatin and fluoropyrimidine plus pelvic radiation daily, for a total dose of 46.2 Gy in 18 fractions. The first cycle of mXELOX (oxaliplatin 85 mg/m2 D1 Q14 plus capecitabine 825 mg/m2 BID) was administrated before RT (as induction CT); the other 2 cycles of mXELOX were administrated concurrent with RT, with capecitabine continued until the end of RT. Radical resection was performed within median 11 weeks of the last dose of RT. Adjuvant CT with FOLFOX or XELOX was administered according to pathological report. Results: Between 2007 and 2022, a total of 186 patients were enrolled, mean age was 61 years. 19 (10.2%) patients were clinically stage II and 167 (89.8%) were clinically stage III. Any grade most common toxicities during neoadjuvant CT/RT included diarrhea (53.2%), proctitis (51.2%) and neutropenia (14.5%). The most common grade 3/4 toxicity was diarrhea (9.1%). A total of 146 (78.5%) patients achieved a downstaging after CT/RT and 174 (93.5%) patients underwent surgery with R0 resection. Clinical meaningful surgical morbidities included infections (10.7%), anastomotic fistula (10.2%) and anastomotic leakage (7.5%). The pathological complete response (pCR) rate was 25.3%. Adjuvant CT was administered in 122 (65.6%) patients. Local recurrences and distant metastases were confirmed in 6 (3.2%) and 54 (29%) cases respectively. Median observation time, calculated with reverse Kaplan-Meier estimator, was 84 months and median overall survival (OS) was not reached. The estimated probability of OS (Kaplan-Meier method) at 3-5 years were 92.8% and 85.5% respectively. The median disease-free survival (DFS) was not reached and the estimated probability of DFS at 3-5 years were 74.7% and 69% respectively. Conclusions: Considering the low rate of toxicities and the comparable efficacy in terms of downstaging, pCR, probability of DFS and OS to other TNT regimens proposed in recent studies, our schedule of neoadjuvant CT/RT may represent a potential alternative to standard CT/RT in selected patients with LARC.