# Impact of Primary Tumor Location on Demographics, Resectability, Outcomes, and Quality of Life in Finnish Metastatic Colorectal Cancer Patients (Subgroup Analysis of the RAXO Study)

## TL;DR

This study shows that where a colorectal cancer starts in the colon or rectum affects how the disease progresses, treatment options, and patients' quality of life.

## Contribution

The study provides new insights into how specific primary tumor locations (right colon, left colon, rectum) influence metastasis patterns, resectability, survival, and quality of life in metastatic colorectal cancer patients.

## Key findings

- Right colon tumors had the lowest resectability and shortest survival compared to left colon and rectal tumors.
- Primary tumor location was linked to differences in metastatic sites and symptom patterns affecting quality of life.
- Overall survival was significantly shorter for right colon tumors (median 21 months) compared to left colon or rectal tumors (median 35-36 months).

## Abstract

The location of the primary tumor in the right colon, left colon, or rectum affects the efficacy of biological drugs used in the treatment of metastatic colorectal cancer, but how? We examined how the primary tumor location affects disease characteristics, treatability, quality of life, and outcome in a real-life study population of 1080 Finnish patients in the RAXO study. The primary tumor location correlates with the location of metastases, the frequency of gene mutations, how often metastases can be operated upon, long-term survival after curative surgery or palliative chemotherapy, and the quality of life during the disease trajectory. The primary tumor location is a helpful surrogate for clinicians working with metastatic colorectal cancer patients in estimating the clinical course of the disease. This study cannot identify the reasons for the associations, i.e., whether it is the primary location per se, the different mutations, or other reasons.

The primary tumor location (PTL) is associated with the phenotype, metastatic sites, mutations, and outcomes of metastatic colorectal cancer (mCRC) patients, but this has mostly been studied according to sidedness (right vs. left sided). We studied right colon vs. left colon vs. rectal PTL in a real-life study population (n = 1080). Health-related quality of life (HRQoL) was assessed multi-cross-sectionally with QLQ-C30, QLQ-CR29, EQ-5D, and 15D. A chi-square, Kaplan–Meier, and Cox regression were used to compare the groups. The PTL was in the right colon in 310 patients (29%), the left colon in 396 patients (37%), and the rectum in 375 patients (35%). The PTL was associated with distinct differences in metastatic sites during the disease trajectory. The resectability, conversion, and resection rates were lowest in the right colon, followed by the rectum, and were highest in the left colon. Overall survival was shortest for right colon compared with left colon or rectal PTL (median 21 vs. 35 vs. 36 months), with the same trends after metastasectomy or systemic therapy only. PTL also remained statistically significant in a multivariable model. The distribution of symptoms varied according to PTL, especially between the right colon (with general symptoms of metastases) and rectal PTL (with sexual- and bowel-related symptoms). mCRC, according to PTL, behaves differently regarding metastatic sites, resectability of the metastases, outcomes of treatment, and HRQoL.