Background: An increasing number of cancer survivors have developed multiple primaries. This study aims to describe the incidence and risk patterns of metachronous second primary cancers (SPCs) in Osaka, Japan.
Methods: Data were obtained from the Osaka Cancer Registry, a population-based database of all cancers diagnosed in Osaka. The study subjects were individuals who were first diagnosed with invasive cancers in 16 major cancer sites during 2000-2014, aged 15-79 years, survived at least 3 months, and were followed up for 10 years. We measured incidence rates, cumulative risks, and standardized incidence ratios (SIRs: with the Osaka general population as the referent) of developing SPCs during 3 months to 10 years after the first diagnosis.
Results: During 2000-2015, among 418,791 cancer survivors, 24,368 (5.8%) developed SPCs within 10 years of first diagnosis. Males had higher incidence rates than females except among young-onset survivors (aged 15-39 years). 10-year cumulative risks among survivors aged 70-79 years (the most dominant age group) were 24.0% (male) and 11.8% (female). 10-year SIRs were 1.38 (95% CI, 1.36-1.40; male) and 1.44 (95% CI, 1.41-1.48; female) with higher estimates among younger survivors in both sexes. Strong bidirectional associations were observed between oral/pharyngeal, esophageal, and laryngeal cancers. Survivors of any smoking-related cancers had elevated SIRs of developing smoking-related SPCs. Similar results were observed for alcohol-related cancers.
Conclusions: Cancer survivors are at excess risk of developing SPCs compared to the general population. Continued surveillance is warranted to inform survivorship care through risk-based long-term care planning and lifestyle-changing efforts to prevent new cancers.
Keywords: alcohol-related cancer; cumulative risk; epidemiology; incidence rate; multiple primary cancers; smoking-related cancer; standardized incidence ratio.
© 2021 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.