Clinical characteristics and prognostic factors of male yolk sac tumor: a Surveillance, Epidemiology, and End Results program study.

INTRODUCTION Yolk sac tumor (YST) is a rare malignant germ cell tumor, which usually affects young males. Because of the low incidence, few studies on YST have been published. In our study, we aim to investigate the clinical characteristics, survival and risk factors of male YST patients based on the Surveillance, Epidemiology, and End Results (SEER) program. METHODS We identified 569 male YST patients from the SEER-18 database with additional treatment fields. Clinical characteristics, survival and prognostic factors were described in the study. Chi-square tests were applied to analyze categorical and continuous variables between different groups. Univariate and multivariate Cox proportional hazard model were performed to assess the relative impacts of risk factors on cancer-specific survival (CSS) in YST patients. Kaplan-Meier method and the log-rank test were used to analyze differences in survival that were significant. RESULTS The major primary sites of YST were testis (74.69%), mediastinum (15.47%), retroperitoneum (2.64%) and central nervous system (1.24%). The 3-year and 5-year CSS was 70.0%, 56.5% vs. 97.2%, 96.0% for the mediastinal and testicular YST patients, respectively (p < 0.001). Primary site of mediastinum, distant SEER Summary stage were independent factors of poor prognosis (hazard ratio (HR) = 2.010 (1.094-3.695), p = 0.025; HR = 6.501 (2.294-18.424), p < 0.001, respectively). Receiving surgery was a good prognosis factor for all patients (HR = 0.495 (0.260-0.940), p = 0.032) and for the mediastinal group (p = 0.0019). Being treated with chemotherapy indicated poor outcome in all patients (HR = 3.624 (1.050-12.507), p = 0.042) and in the localized testicular YST patients (p = 0.0077). CONCLUSION For the first time, our study revealed the primary site distribution of male YST, and summarized the clinical characteristics, survival and prognostic factors based on the SEER database, which provided important epidemiological evidence for clinical practice.