Epidemiology, Pattern, and Survival of Multiple Primary Malignant Neoplasms in Southeast Iran: Results of Kerman Population-Based Cancer Registry 2014-2020.

Purpose: Cancer survivors may experience a subsequent primary cancer that affects their survival and quality of life. This study aimed to investigate the epidemiology of multiple primary malignant neoplasms (MPMNs) in Kerman province, southeast Iran during 2014-2020.

Materials And Methods: In this retrospective cohort study, all patients who had been diagnosed with primary cancers and registered with the Kerman Cancer Registry Program (KPBCR) during 2014-2020 were included. MPMNs were defined as primary malignant tumors arising in different sites and/or were of different histological or morphological origins. If the second malignancy was diagnosed within the first six months from the diagnosis of the first tumor it was considered synchronous, and if after six months it was defined as metachronous. Logistic regression was used to analyze the relationship between age, sex, and primary cancer site with incidence and survival of secondary in the entire population.

Results: Of 26,315 patients registered with a primary cancer diagnosis, 492 (1.86%) developed subsequent primary cancers. The most common type of secondary cancer was skin and mucosa (n=131, 26.63%) followed by urogenital (n=115, 23.37%), followed by, gastrointestinal (n=62, 14.45%), and breast neoplasms (n=57, 11.59%). Most patients had metachronous tumors (n=350, 71.13%). The primary cancer site (Skin and mucosa, urogenital, and breast) was significantly associated with developing subsequent cancer among cancer survivors. The overall 5-year survival of MPMNs cases was over 50%. Older age at diagnosis (HR= 1.02) and having synchronous tumors (HR=1.41) were negatively associated with the survival time of patients with MPMNs.

Conclusion: Both patients and physicians should be taught about the importance of prevention and the provision of care and screening services among cancer survivors. Studying the epidemiology, susceptibility, and risk factors of MPMNs among cancer survivors will open windows to a better understanding of this phenomenon and policy making.