Introduction Multiple primary malignancies (MPMs) are seen in ~5% of all tumors. The aim of this study was to determine the quantitative impact on overall survival (OS) and treatment choices in patients with MPMs. Methods A retrospective analysis to determine patients with MPMs was conducted over a six-year period. Patients were defined as simultaneous MPMs if the second malignancy was discovered within 60 days of the first, and as sequential MPMs if discovered after 60 days of the first. Results Fifty-six patients with MPMs as defined above were identified, 38 (68%) simultaneous and 18 (32%) sequential. Development of second malignancy did not affect treatment in 47 (84%) of patients. Median OS after diagnosis of first malignancy was 13.0 months (95% confidence interval (CI) 10.3-15.8 months), compared to 10.6 months (95% CI 7.1-13.9 months) after the diagnosis of second malignancy. Median OS for the simultaneous MPM group was 13.5 months (95% CI 7.1-19.9 months), compared to 3.2 months (95% CI 0.0-9.8 months) for the sequential MPM group. Conclusions The development of a second malignancy impacts OS and treatment decisions. Patients who developed sequential MPM performed poorer than those who developed simultaneous MPM. This was likely in part due to effects of existing treatment on performance status as well as treatment preferences when second MPM is diagnosed (as many patients opted for supportive care after second MPM). Further analysis with larger patient cohorts is necessary to ascertain the aforementioned effects of OS and treatment options with respect to tumor pathology, stage, and performance status.
Keywords: multiple primary cancers; multiple primary malignancies; multiple primary malignancy; multiple primary malignant neoplasms.