586P - Clinical and molecular characteristics of colorectal adenosquamous carcinoma: A multicenter retrospective study

Background

Colorectal adenosquamous carcinoma (CRASC) is a rare and heterogeneous disease characterized by components of both adenocarcinoma (ACC) and squamous cell carcinoma (SCC). Due to its low incidence, understanding of the epidemiology, clinicopathology, molecular features, genomic profile, clinical management, and survival outcomes of CRASC remains limited.

Methods

CRC patients treated between December 2011 and December 2022 at the Sixth Affiliated Hospital of Sun Yat-sen University, Sun Yat-sen University Cancer Center, Fudan University Cancer Center, Yunnan Cancer Hospital, and Cancer Hospital of Chinese Academy of Medical Science were retrospectively enrolled. Clinical characteristics, pathogenic variations, epidemiological features and prognosis of CRASC were evaluated. Follow-up data were collected until April 30, 2024.

Results

A total of 171213 CRC patients were enrolled, 44 (0.026%) patients were diagnosed with CRASC, with a median age of 59(27-83) years and 59.1% (26/44) were male. The clinical stages including: IV (47.7%, 21/44), III (36.4%, 16/44), II (11.4%, 5/44) and I (4.5%, 2/44). dMMR)/MSI-H status was observed in 9.1% (4/44) of patients. The most common site of CRASC was the rectum (36.4%, 16/44), followed by the right-sided colon (31.8%, 14/44). ACC and SCC components in CRASC were similar (P=0.676). ACC was predominantly moderately differentiated (63.6%, 28/44), while SCC was mainly well-differentiated (45.5%, 20/44). ACC was present in 62.2% (23/37), SCC in 27.0% (10/37) and both ACC and SCC in 10.8% (4/37) of patients with metastatic lymph nodes. Notably, one patient received immunotherapy after multiple chemotherapy regimens and showed significant tumor regression. The median follow-up was 8.9 (1.3-146.2) months. The PFS rates at 1, 2 and 3 years were 36.2%, 24.1% and 14.1%, while the OS rates at 1, 2, and 3 years were 44.9%, 39.8% and 14.7%, respectively.

Conclusions

This study represents the largest multicenter retrospective analysis of CRASC to date. CRASC is associated with poor prognosis, highlighting the need for further investigation into its clinical staging. Combination chemotherapy with immunotherapy shows promise for the treatment of CRASC and warrants further exploration.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.