Survival outcomes of primary mediastinal germ cell malignancies based on clinicopathological characteristics: A SEER database analysis.

Abstract

e17055 Background: Primary mediastinal germ cell malignancies (PMGCM) account for up to 5% of all germ cell tumors. Different clinical and epidemiological factors have been known to have important prognostic implications as they contribute to a wide range of long term survival in individuals with PMGCM. Methods: We obtained data from the Surveillance, Epidemiology and End Results (SEER) database from years 1975-2016 to include cases with confirmed primary mediastinal germ cell tumors. After complete gathering of selected data, a total of 1,328 number of cohorts were obtained which were stratified by age, sex, race, type of malignancy, size of primary tumor, site, grade etc. and were analyzed by Cox regression using proportional hazard model. Kaplan Meier curves were also obtained to visualize all cause survival and stratified survival according to the types of malignancy. Results: In our study, we found the incidence of PMGCM to be 0.18 per 1,000 people with malignant cancer with a median age at diagnosis of 28 years, the age range being 21-50 years. 92.9% patients were males and 7.1% were females with more common occurrence in White patients (54.5%). Most common type of PMGCM was found to be Seminoma (23.4%) and 56.32% were poorly differentiated (Grade III), excluding unknown cases. About half (52%) of all was found to arise from the anterior mediastinum. 36% of all cases died from primary cancer. 42.7% underwent surgery, however there was no data for chemotherapy or radiotherapy. Mean survival time among all PMGCM was 37.5 months (p <0.05). A significant negative correlation was observed between survival time & age at diagnosis with Rp of 0.12 (p < 0.001). On survival analysis, age was a significant factor for decreased survival time with patients more than 50 years having a HR of 2 (p<0.001). Similarly, choriocarcinoma was associated with decreased survival time with HR 1.71 (p=0.03). Germinoma and seminoma were found to have higher survival time (HR 0.65 & 0.18; p=0.03 and <0.001 respectively). Patients with grade IV PMGCM had significantly lower survival time (HR 1.74, p<0.001). Patients who had undergone surgery had a better survival time compared to those who didn’t get surgery. There was no significant association of sex, race, tumor size or site with the survival time. Conclusions: Our study concludes that among PMGCM, seminomatous tumors have a favorable prognosis compared to non-seminomatous tumors with higher survival time. Age was found to be a significant contributing factor with ages over 50 having lower survival time. Surgical intervention was found to be associated with increased survival time, although it is important to recognize the lack of chemo-radiotherapeutics data.