Total neoadjuvant therapy (TNT) for locally advanced rectal cancer (LARC): Real-world experience from a tertiary Asian cancer center.

Abstract

39 Background: Multiple studies of TNT for LARC have shown improved pathological complete response (pCR) rate and disease-free survival (DFS). However, real-world data in Asia is limited. Methods: Patients (pts) diagnosed with LARC at National University Cancer Institute, Singapore were discussed at a multidisciplinary tumor board. Patients were eligible for TNT if they had cT2/3N+ or cT4Nany, threatened circumferential resection margin (CRM) and adequate organ function. TNT protocol was systemic chemotherapy with 5-6 cycles of mFOLFOX6 (5-fluorouracil, leucovorin, oxaliplatin) or 3-4 cycles of XELOX (capecitabine, oxaliplatin) followed by short- or long-course chemoradiation (CRT), then 3 cycles of mFOLFOX6 or 2 cycles of XELOX. Clinical outcomes included rates of clinical complete response (cCR), pCR, surgery type, R0 resection and DFS. Baseline pt demographics, laboratory results and tumor characteristics were analyzed against these outcomes. Results: 173/205 pts who were diagnosed with rectal cancer between February 2020 and November 2022 had LARC and 47 received TNT. Median age was 65 (range: 33-79), 68.1% male, 78.7% were Chinese, 19.2% had cT4 tumors, 87.2% node positive and 80.9% had CRM involvement. Median tumor distance from anal verge was 6cm (range: 1-15cm) on colonoscopy and 5cm (range: 2-12cm) on magnetic resonance imaging. 95.7% received XELOX, 87.0% had long-course CRT and 83.0% completed all cycles of systemic chemotherapy and CRT. 44.7% had dose reduction of systemic therapy and 4.3% required emergent surgery due to local complications during TNT. After TNT completion, 7 pts did not pursue surgery – 3 achieved cCR (6.4%) and adopted a watch-and-wait approach, 2 had disease progression (PD), and 2 declined. Of those who underwent surgery, 75.0% had sphincter-preserving surgery and 85.0% achieved R0 resection. 2.1% (n =1) achieved pCR. Rates of tumour regression grade (TRG) 0, 1, 2, 3 were 7.5%, 15.0%, 67.5% and 10.0%, respectively. After a median follow up of 21.7 months (range: 9.3 – 41.6 months), 21.3% (n = 10) had disease recurrence and 14.9% (n=7; 5 from PD, 1 from surgery-related complication, 1 unrelated to treatment) passed away. 1-year DFS rate was 88.7% (95% CI 75.0% - 95.2%). Conclusions: This is the first Asian study reporting real-world data of TNT for LARC since its wide-scale adoption. pCR rates appear lower than reported studies. Understanding the limitation of retrospective studies, further analysis is ongoing to determine if factors other than sequence of modality can contribute to the observed findings.