Abstract 140P
Background
The incidence of bowel cancer in patients (pts) under 50 years old has been increasing over the past 2 decades. Recent evidence shows that early-onset proficient Mismatch Repair (pMMR) bowel cancer has different characteristics than late onset pMMR bowel cancer but the reasons are poorly understood and more research is needed.
Methods
This was a retrospective single tertiary cancer centre study of adult pts newly diagnosed with pMMR bowel cancer under 50 years old reviewed between 1st January 2022, and 31st December 2023 at University College London Hospital (UCLH). Pts were analysed for clinico-pathological characteristics, treatments and survival. The survival analysis cut-off date was 31st March 2024.
Results
Of the 136 pts diagnosed with pMMR bowel cancer; 98% (133 /136) had large bowel cancer (4 appendix, 129 colorectal) and 2% (3) had small bowel cancer. Demographics of the early-onset colorectal cancer (EOCRC) pts are shown in the table. Of the pts with early--stage CRC (M0), 97% (57/59) underwent curative surgery. 30% were pT4 tumours and 58 % had involved lymph nodes. At median follow-up of 26.6 months (IQR 10.2-54.3) 25/59 (42%) of them relapsed and 13/59 had died. Median relapse free survival (RFS) and median overall survival (OS) were 25.4 (95% CI 16.3-49) and 87.7 months (95% CI 32.4-NR) respectively. All metastatic (M1) pts received first-line systemic chemotherapy; 77% of them underwent curative or palliative surgery. At median follow up of 45.8 months (IQR 18.9-76.5) 40/70 patients have died. Median progression free survival was 11.4 months (95% CI 8.0-14.9) and median OS was 35.4 months (95% CI 23.2-40). Table: 140P
| Total (N=129) | |
| Age at diagnosis, median (range) | 40 (13-50) |
| N (%) | |
| Female | 65 (50.4) |
| Male | 64 (49.6) |
| Stage at diagnosis | |
| I | 7 (5.4) |
| IIA | 14 (10.8) |
| IIB | 3 (2.3) |
| IIIA | 3 (2.3) |
| IIIB | 19 (14.7) |
| IIIC | 13 (10.07) |
| IV | 70 (54) |
| Primary location | |
| Caecum | 16 (12) |
| Ascending to transverse colon | 32 (25) |
| Splenic flexure to rectosigmoid colon | 51 (39.5) |
| Rectum | 30 (23.2) |
| Mutation status | |
| BRAF, KRAS, NRAS wild type | 41 (31.8) |
| KRAS or NRAS mutant | 44 (32.5) |
| BRAF mutant | 21 (16.2) |
| Could not be evaluated | 23(17.8) |
Conclusions
This retrospective study shows that EOCRC pts present with high risk clinicopathological disease in early and late stage, as well as poor clinical outcomes. It is crucial to do more research in collaboration with other cancer centres to better understand the underlying biology, improving treatment strategies and outcomes for pts living with EOCRC.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.