Clinical Features of Multiple Primary Malignant Tumors: A Retrospective Clinical Analysis of 213 Chinese Patients at Two Centers

Background: The definition of multiple primary malignant tumors (MPMT) is two or more cancers without any correlation occur in an individual. Aim: This study is to delineate clinical characteristics of patients with MPMT and explore the treatment strategies for these patients. Methods: This retrospective study analyzed the information of MPMT patients collected from two databases from January 2017 to September 2020. R tool and SPSS were used for statistical analysis. Results: The cohort consisted of a total of 213 patients (male:female ratio 1.17:1) with MPMT. Among them, 159 patients had metachronous multiple primary malignant tumors (mMPMT), and 54 had synchronous multiple primary malignant tumors (sMPMT). The age at the time of diagnosis for most of them was 61-70 years. For mMPMT, the most common primary cancers were of digestive, breast, and lung origins, while the secondary ones were of digestive, lung, and urinary origins. For sMPMT patients, the most occurrences were digestive cancers in different organs of the digestive system. The most common pathological type of both primary and secondary cancers was adenocarcinoma. In this study, 54.92% of MPMT patients experienced treatments in addition to the surgical treatment, including targeted therapy and anti-PD-1 immunotherapy. The median survival time was 234.97 months, and the 5-year survival rate was 79% of all patients. The classification of MPMT and the age when the first primary cancer was diagnosed were independent factors affecting the prognosis of MPMT. Conclusion: Clinical characteristics of patients with sMPMT and mMPMT were different. Patients with cancer need primary cancer surveillance and screening of other cancers.