Prognostic factors associated with malignant somatic transformation (MST) of germ cell tumors (GCT) in a Mexican cohort: The experience of the Instituto Nacional de Cancerología, Mexico (NCIM).

Abstract

427 Background: MST is a rare entity defined as the development of somatic non-germ cell malignancies within GCT, its incidence varies between 2.7% and 8.6% of GCT’s. Previously reported favorable prognostic factors include synchronous diagnosis of MST and GCT, absence of non-pulmonary visceral metastases (NPVM) and presence of rhabdomyosarcoma. Methods: Retrospective study to describe prognostic factors of MST in GCT in a Hispanic population. Patients (pts) with diagnosis of MST from 2006 to 2019 were identified from the GCT database of the NCIM. Pts’ characteristics and outcomes were collected from clinical charts and recorded. Overall survival (OS) was performed with the Kaplan Meier (KM) method in the whole cohort and in patients with advanced disease (AD) (stage II and III). Comparisons were calculated with the log-rank test for KM and Chi squared test for categorical factors. Results: Seventy-one pts with MST were included in the overall population (OP). Non-seminoma 95.8%; testicular primary 97.2%; clinical stage (CS) I 32.4%, II 16.3%, III 49.3%; S2-S3 42.3%, 39.6% poor IGCCCG prognosis, 11.3% NPVM. Type of MST: 56.3% rhabdomyosarcoma (RMS), 21.1% spindle cell sarcoma, 12.7% PNET, 9.9% adenocarcinoma. 18.3% more than 1 MST histology. Median follow-up: 43.8 months (m). For the OP, mOS 71.1m (95% CI 80.0 – 119.2). OS for CS I have not been reached (NR). Forty-seven pts with AD were included, mOS 37m (95% CI 9.69 – 64.36). Characteristics associated with prognosis for OS for the OP and the AD cohorts are summarized in table. Pts with AD and RMS had more frequently a synchronous tumor (87.5% vs 58.3%, p=0.02) and absence of surgery for MST (70.8% vs 37.5%, p=.02). Conclusions: As far as we know, this is the largest cohort of hispanic pts with MST. Prognostic factors differed between OP and AD cohorts. Pts with MST and AD have a poor prognosis. Synchronous diagnosis of MST and presence of rhabdomyosarcoma are adverse prognostic factors for AD pts. Further study with a larger population is needed to verify these findings. Univariate analysis for OS.[Table: see text]