ESTRO 2024 - Abstract Book

S1569

Clinical - Lower GI

ESTRO 2024

1 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Diagnostic Imaging, Radiation Oncology and Haematology Department, Rome, Italy. 2 Catholic University of Sacred Heart, Diagnostic Imaging, Radiation Oncology and Haematology Department, Rome, Italy

Purpose/Objective:

It is well known that neoadjuvant chemoradiotherapy (nCRT) is the standard of care for locally advanced rectal cancer (LARC) and has a role to play in reducing the incidence of local and distant recurrence.

Folfox is known to reduce the risk of distant metastases and has shown promising results in the preoperative setting. The recent multicenter randomised PROSPECT trial aimed to evaluate and compare the outcomes associated with the use of at least five cycles of neoadjuvant Folfox versus nCRT, consisting of 50.4 Gy delivered in 28 fractions with concomitant fluoropyrimidine-based chemotherapy (fCHT).

The aim of our study is to compare PROSPECT data with Real-World Data (RWD) from a single institution of patients with the same inclusion criteria undergoing nCRT.

Material/Methods:

The PROSPECT trial included Eastern Cooperative Oncology Group (ECOG) performance status 0-2 patients with clinical T2 N-positive and T3 N-negative and N-positive rectal cancer who were candidates for organ-preserving surgery. Excluded from the trial were patients with clinical T4 disease with extensive lymph nodes, presence of tumour deposits, previous pelvic irradiation or abnormal laboratory tests. The patients in our study were matched in terms of clinical stage and selected within the same time frame as those in the PROSPECT trial, with the exception that some of them were referred for conservative approaches when deemed appropriate. The nCRT regimen prescribed consisted of delivering 55 Gy to the primary tumour and associated mesorectum and 45 Gy to the lymphatic drainage chains, administered in 25 fractions using the concomitant boost approach, with concurrent fCHT.

Surgery was performed at least 6-8 weeks after the completion of fCRT.

Pathological complete response (pCR) was defined as the absence of tumor cells in the rectum and mesorectal lymph nodes when examined in the surgical specimen.

To assess the outcomes, we calculated the five-year survival (OS), disease-free survival (DFS), and local recurrence (LR), including any regrowth following conservative treatment, starting from the initiation of neoadjuvant chemoradiotherapy. Acute and post-operative toxicities were evaluated and graded according to the Common Terminology Criteria for Adverse Events (CTCAE) 4.0 scale.

We conducted a comparative analysis of response rates in terms of pCR and survival outcomes between the PROSPECT cohort and our cohort based on RWD.

Results:

249 rectal cancer patients treated between 2012 and 2018 met the inclusion criteria.