Investigation of multiple primary cancers in patients with bone and soft tissue primary malignancies: A retrospective, institution-based study.

In the aging society in Japan, the occurrence of multiple primary cancers has recently increased due to an increase in life expectancy and increased development in cancer diagnostic technology and improvement in treatment outcomes. However, few reports have focused on multiple primary cancers in patients with bone and soft tissue tumors. The present study aimed to analyze the clinical characteristics of patients with multiple malignancies of the bone and soft tissue. Between April 2008 and April 2017, among 973 patients treated at the Department of Orthopedic Surgery, Osaka City University Hospital, those with multiple primary cancers involving bone and soft tissue were identified. The number of cases with multiple cancers in the present study was 30/973 (3.08%), including 21 males and 9 females. The median age at diagnosis of patients with bone and soft tissue sarcoma was 73.5 years (range, 7-83 years). There were 22 patients with double cancers, and 5, 2 and 1 patients with triple, quadruple and quintuple cancers, respectively. Colorectal cancer was the most common primary cancer (n=9). In total, 28.6% of patients had simultaneous cancer, while 71.4% of patients had heterochronous cancer. The overall 5-year survival for all patients was 75.6%. The prognosis of patients with double cancer of bone and soft tissue sarcoma was not necessarily poor. However, it is necessary to pay attention to the possibility of secondary malignancy. Therefore, it is essential to be careful and well organized when selecting treatment modalities and to adopt a logistical approach for the care of patients with ongoing multiple malignancies.