126P - From tumor height (TH) to tumor regression grade (TRG) in locally advanced rectal cancers (LARC) during total neadjuvant therapy (TNT): A retrospective analysis

Background

Treatment of LARC has the main goal to achieve a tumor pathological complete response (pCR) that is strongly related to better disease-free survival (DFS) and overall survival (OS). However, it occurs only in 10-30% of LARC patients with neoadjuvant chemoradiotherapy (nCRT) with a high rate of distant metastasis (DM). TNT can improve patient’s outcomes by delivering systemic chemotherapy and nCRT prior to surgery. Multiple randomized trials (RAPIDO, PRODIGE 23, OPRA, CAO/ARO/AIO-12) evaluated different TNT strategies in terms of CRT sequencing, chemotherapy intensity, and radiotherapy. Overall, as a result from those trials, emerges that TNT increased pCR rate compared with standard nCRT (28,4% vs 14,3% RAPIDO and 27,5% vs 11,7% PRODIGE 23 and 28% vs 14% OPRA). However, there is lack of data about any difference in pathological response according to primary TH from anal verge and TNT.

Methods

This is a retrospective, multicentric, observational study whose aim is to evaluate the impact of TH from anal verge on pathological response (pR) to TNT in LARC through Ryan modified TRG score. Data were collected from 48 LARC patients (cT4N+), treated with induction mFOLFOX followed by long course nCRT and total mesorectal excision (TME). The secondary endpoint was ORR.

Results

The median age was 65 (± 8), 75% were male. All patients had clinical stage III. TH from anal verge were as follows 21% proximal (>10 cm), 46% middle (5-10 cm), and 33% (<5 cm) distal side. After TNT proximal cancers (PC) showed worst TRGs: TRG-4 (3 patients), TRG-3 (5 patients), and TRG-2 (2 patients). Middle cancers (MC) cancer showed: TRG-3 (1 patient), TRG-2 (11 patients), TRG1-0 (10 patients). Distal cancers (DC) showed: TRG2 (2 patients), TRG1-0 (13 patients). ORR was also different according to the TH: 30% PC, 77% for MC, and 80% for DC.

Conclusions

The results of our study show a correlation between rectal TH and responses to TNT. DCs seem to have a poorer pR to TNT. This data is consistent with recent literature about the actual usefulness of radiotherapy (RT) in patients with DCs and could help to a better selection of patients more suitable for TNT with or without RT.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

A. Pretta: Financial Interests, Personal, Speaker, Consultant, Advisor: Merck. All other authors have declared no conflicts of interest.