Most cancer patients die from recurrence or metastasis of their original cancer. Second primary cancers are another factor, in addition to recurrence and metastasis of the original cancer, that contributes to mortality among cancer survivors. A paper recently published in The Lancet Oncology delves into that question: Cumulative incidence of second primary cancers in a large nationwide cohort of Danish cancer survivors a population-based retrospective cohort study – PubMed
The study titled "Cumulative incidence of second primary cancers in a large nationwide cohort of Danish cancer survivors: a population-based retrospective cohort study" delves into the incidence of secondary primary cancers among Danish cancer survivors. It particularly focuses on the absolute and relative incidence of these cancers and examines associations between first and second primary cancers across various etiologies such as alcohol, smoking, virus, and hormone-related factors.
Key Findings and Methods:
Methods: The study is a retrospective cohort study including 457,334 Danish adults diagnosed with cancer from 1997 to 2014 and alive a year after diagnosis. They were followed up to 24 years till the end of 2020. The study used the Danish Cancer Registry for identification and information on second primary cancers and employed cumulative incidence functions and Cox proportional hazard regression models to estimate the incidence of second primary cancers and related hazards, adjusting for factors like age, sex, cohabitation status, income, and comorbidity.
Findings: Over the follow-up period, the cumulative incidence of second primary cancer increased from 6.3% at 5 years to 13.5% at 15 years post-diagnosis. Specifically, the highest incidences at 10 years were observed in survivors of larynx, oropharynx, oral cavity, and bladder and urinary tract cancers. The study also found that survivors with alcohol, smoking, diet (high in red or processed meat), or virus-related cancers were at increased risk of developing a second cancer of the same etiology. Conversely, those with hormone-related first cancers had a lower risk of subsequent hormone-related cancers.
Interpretation: The findings underscore the importance of optimizing prevention efforts and targeting modifiable risk factors to reduce the risk of developing a second primary cancer. The clear delineation of risk based on cancer type and etiology can guide more personalized surveillance and intervention strategies.
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