580P - Prognosis in stage II colorectal cancer: The effect of the primary tumor location and biomarkers

Background

Primary tumor location (PTL) is a well-established prognostic factor in stage III and IV colorectal cancer (CRC), with right-sided CRC (RSCC) showing a worse prognosis compared to left-sided CRC (LSCC). However, the impact of PTL on stage II CRC remains uncertain. One explanation for these inconsistencies is the potential confounding effect of molecular biomarkers, such as MMR status. Therefore, there is a need to elucidate the prognostic value of PTL, as well as the role of biomarkers in this effect.

Methods

This study utilized observational data from a retrospective cohort obtained from the Belgian Cancer Registry (BCR). The study population comprised all patients diagnosed with pathologically confirmed stage II CRC in Belgium from January 1st, 2015, to December 31st, 2016 (n= 3,278). Information on PTL, demographics, pathologic T category (pT category), and molecular biomarkers (including MMR status, BRAF and KRAS mutations) was collected from the registry, along with vital status to calculate overall survival (OS). The primary aim of this study was to investigate the independent prognostic value of PTL in stage II CRC. Additionally, we assessed whether potential confounding factors, such as biomarkers and demographics, influenced the prognostic effect of PTL.

Results

In the univariate analysis, patients with stage II RSCC had a significantly worse OS compared to those with LSCC (including rectal cancer; p-value=0.0055 and excluding rectal cancer; p-value=0.0035). Higher age and pT4 were also significantly associated with worse OS. However, in the multivariable analysis, only gender, age, and pathologic T-stage were found to be significant predictors of OS. PTL was not a significant factor in multivariable analysis. Furthermore, biomarkers such as MMR-status, BRAF-, and KRAS mutations did not show a significant effect on OS in either analysis.

Conclusions

Our analysis led us to the conclusion that PTL is not an independent prognostic factor in stage II. Notably, we observed confounding effects between patient characteristics and the prognostic impact of PTL, such as older age at diagnosis and shorter OS in patients with RSCC. Furthermore, molecular biomarkers did not have a statistically significant effect on OS in stage II CRC.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

University of Antwerp.

Funding

Antwerp University Hospital.

Disclosure

All authors have declared no conflicts of interest.