Risk of Second Primary Neoplasms Among Cancer Survivors: A Population-Based, Cohort Study in Golestan Province, Northern Iran, 2004-2019.

BACKGROUND

Recent reports of the Golestan population-based cancer registry (GPCR) suggested increasing trends in the incidence and survival rates of cancers in Golestan, Northern Iran. We investigated the risk of developing second primary neoplasms (SPNs) among cancer survivors in Golestan.

METHODS

The GPCR cases for whom a first primary cancer was diagnosed between 2004 and 2019 were included as cohort participants. The cohort members were followed by the end of 2020, and the occurrence of a second primary neoplasm (SPN) was considered as the study outcome event. The standardized incidence ratios (SIRs) and the Absolute excess risks (AERs), with corresponding 95% confidence intervals (95% CI) were calculated to evaluate the risk of SPNs.

RESULTS

Of the total 32,980 cases with first primary cancer, with a median follow-up of 3.4 years, 772 (2.3%) SPNs were registered. Our findings suggested a significantly higher risk of occurring new neoplasms among cancer survivors, with a SIR of 4.6 (95% CI: 4.3-4.9) and an AER of 41.8 per 10,000 person-years (95% CI: 37.6-46.0). Rural residents had a higher risk of SPN (SIR = 5.48) than urban dwellers (SIR = 3.99). Patients with first primary cancers of the ovary (SIR = 6.83) and prostate (SIR = 6.72) had the highest risk of any SPNs. The highest risk of site-specific SPNs was observed for the SPNs of the ovary (SIR = 8.11) and NHL (SIR = 7.07).

CONCLUSIONS

Our results suggest that cancer patients are at significantly higher risk of getting a new neoplasm than the general population. These findings highlight the need for designing and implementing efficient surveillance programs for cancer survivors.