BACKGROUND
The number of cancer survivors who develop subsequent primary cancers (SPCs) is expected to increase.
OBJECTIVE
We evaluate the overall and cancer type-specific risks of SPCs among adult-onset cancer survivors by first primary cancer (FPC) types considering sex and age.
METHODS
A retrospective cohort study using the Health Insurance Review and Assessment database of South Korea including 5-year cancer survivors diagnosed with FPC from 2009-2010, followed up until December 31, 2019. We measured the incidence of SPCs per 10,000 person-years and the standardized incidence ratio (SIR) compared to those expected in the general population.
RESULTS
Among 266,241 survivors (mean age at FPC, 55.7 years; 56.1% women), we observed 7,348 SPCs during 1,003,008 person-years of follow-up (median, 4.3 years). The risk of developing any type of SPC differed by age; the risk was 28% higher in young (< 40 years) cancer survivors (SIR, 1.28 [95% CI, 1.16-1.42]; incidence, 30 per 10,000 person-years), while 27% lower in middle-aged and older (≥ 40 years) cancer survivors (SIR, 0.73 [95% CI, 0.71-0.74]; incidence, 80 per 10,000 person-years) compared with risks in the age-corresponding general population. Strong positive associations among smoking-related cancers were observed, including laryngeal, head & neck, and esophageal cancers in men, and laryngeal and lung cancers in women. Substantial variation existed in the associations of specific types of FPC with specific types of SPC risk, which may be linked to hereditary cancer syndrome; breast cancer survivors for ovarian cancer and colo-rectal cancer survivors for uterus cancers in women, and kidney cancer survivors for pancreas cancer in men.
CONCLUSIONS
The risk of developing SPC among adult-onset cancer survivors in South Korea varies depending on their age compared with the general population. Cancers related to smoking pose a significant risk for developing subsequent smoking-related cancers. The risk of SPCs varies by the patient’s age, sex, and the type of FPC. This highlights the need for ongoing efforts and tailored prevention and screening programs for cancer survivors, which may include genetic testing.