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. 2025 Jul 26;151(7):222.
doi: 10.1007/s00432-025-06268-w.

The risk of mortality from multiple primary cancers in colorectal cancer survivors: analysis of data from the South Australian Cancer Registry

Mulugeta Melku  1   2 , Oliver G Best  3 , Jean M Winter  3 , Lauren A Thurgood  3 , Ganessan Kichenadasse  3   4 , Molla M Wassie  3 , Muktar Ahmed  3 , Erin L Symonds  3   5
Affiliations

The risk of mortality from multiple primary cancers in colorectal cancer survivors: analysis of data from the South Australian Cancer Registry

Mulugeta Melku et al. J Cancer Res Clin Oncol. .

Abstract

Purpose: Colorectal cancer (CRC) survivors face an increased risk of multiple primary cancers (MPCs), but evidence on MPC-related mortality is limited.

Methods: Using data from the South Australian Cancer Registry (1982-2017), this retrospective study analysed CRC survivors diagnosed with MPCs, defined as distinct primary cancers arising ≥ 2 months after CRC diagnosis. Causes of death were categorised as index CRC, MPC, or non-cancer related. Poisson regression estimated cancer-specific mortality risk compared to the general population. Propensity score weighting was applied to balance covariate distribution between CRC survivors with and without MPC groups. A hazard ratio (HR) for all-cause mortality was estimated using a weighted dataset to assess the impact of MPC on overall survival.

Results: Among 26,093 CRC survivors (181,877 person-years follow-up), the age-standardised MPC-related mortality rate was 240 per 100,000 population. Gastrointestinal, lung, haematological, and urinary tract cancers were the most common MPC-related causes of death. CRC survivors had a 45% higher risk of dying from MPCs than the general population (standardised mortality ratio = 1.45, 95%CI 1.38-1.52). Adjusted analyses showed a 58% increase in all-cause mortality among CRC survivors with MPCs (HR = 1.58, 95%CI 1.51-1.65).

Conclusions: CRC survivors with MPC face significantly worse survival compared to those with a single primary CRC. Early detection and management of MPCs are essential for improving long-term survival in individuals diagnosed with CRC.

Keywords: Colorectal cancer; Hazard ratio; Mortality; Multiple primary cancer; Standardised mortality ratio.

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Conflict of interest statement

Declarations. Conflict of interest: The authors declare no competing interests. Ethical approval: The study was approved by the South Australian Department for Health and Wellbeing Human Research Ethics Committee (Ref: 2022/HRE00169) and was conducted in accordance with the principles, regulations, and ethical conduct of research prescribed by the Australian Government and its regulatory authorities.

Figures

Fig. 1
Fig. 1
Vital status and cause of death among CRC survivors by December 31, 2019
See this image and copyright information in PMC

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