Soft-tissue sarcoma in Japan: National Cancer Registry-based analysis from 2016 to 2019.

Background: No previous reports have characterized national profiles of soft-tissue sarcoma overall. We examined the nationwide statistics for soft-tissue sarcoma in Japan using data from the population-based National Cancer Registry.

Methods: We identified 23 522 soft-tissue-sarcoma patients who were entered in the National Cancer Registry during 2016-19 using International Classification of Diseases-Oncology, Third Edition codes for cancer topography and morphology. We extracted data on patient demographics, tumor details (reason for diagnosis, tumor location, histology, extent of disease), hospital volume/type, treatment, and prognosis for each patient.

Results: Soft-tissue sarcoma showed a slight male preponderance. Approximately 5500-6000 new cases were diagnosed as soft-tissue sarcoma per year, with the age-adjusted incidence of soft-tissue sarcoma being 3.22/100000/year. The age distribution showed a single peak in the 70-79 age range, and sex-stratified data showed it was higher in men. The most common histologic subtype was liposarcoma. The most frequent tumor locations were the soft tissue and skin, followed by the retroperitoneum. Extent of disease was categorized as: "localized" (31.3%), "regional" (38.9%), or "distant" (10.5%). We found significant associations between overall survival and sex, age, tumor location, facility type, hospital volume, reason for diagnosis, extent of disease, and surgical treatment.

Conclusions: This is the first study to outline the epidemiology, clinical features, treatment, prognosis, and significant factors affecting prognosis of soft-tissue sarcoma in Japan using the National Cancer Registry. Documenting our data regarding elderly patients' outcomes is essential so other countries showing similar population-aging trends can learn from our experiences.

Level of evidence: Prognostic studies, Level III.