A Case Series of Multiple Primary Malignancies Among Patients With Advanced Melanoma

Multiple primary malignancies (MPM) are described as two or more primary tumors within the same individual. The impact of MPM on the tumor microenvironment among patients with melanoma is poorly understood. Here, we describe this unique group of patients who have both advanced melanoma and at least one other primary malignancy and report their survival outcomes. In this study, patients with advanced melanoma and a second primary malignancy were identified. Medical records were reviewed for cancer treatment history. Kaplan-Meier methods were used to derive survival curves and estimate overall survival (OS), and log-rank tests were used to compare OS. Among 11 MPM patients, the most common non-melanoma cancers were breast (n = 3) and thyroid (n = 3). Median OS was 153.5 months for all patients. Median OS for synchronous MPM (sMPM) and metachronous MPM (mMPM) were 83.1 and 196.7 months, respectively (p= 0.10). Median OS was not reached when melanoma was diagnosed first, and 153.5 months when diagnosed second (p= 0.45). For six patients receiving immunotherapy for melanoma, there was a 100% complete response rate. In conclusion, patients with melanoma are at risk of secondary malignancies, including breast and thyroid cancer. The timing of secondary malignancies may impact prognosis. Further study of the impact of immunotherapy on MPM is warranted.