Structure of residual metastases in patients with advanced testicular non-seminomatous germ cell tumors and incomplete serological and radiological response to chemotherapy
Authors: Volkova M. I. , Arakelyan G. A. , Klimov A. V. , Fainstein I. A. , Sergeev Yu. S. , Fedyanin M. Yu. , Rumyantsev A. A. , Tryakin A. A. , Tyulyandin A. S. , Matveev V. B. , Stilidi I. S. 
Published: May 2022

Objective: to analyze histological structure and identify predictors of detecting malignant non-seminoma in residual tumor masses obtained from patients with testicular non-seminomatous germ cell tumors (TNSGCTs) who had not achieved complete serological and radiological response to chemotherapy (CT).Materials and methods. This study included 96 out of 703 patients with TNSGCTs (13.7 %) operated on in N.N. Blokhin National Medical Research Center of Oncology. The inclusion criteria were as follows: verified advanced TNSGCT, elevated levels of alpha-fetoprotein and/or chorionic gonadotropin at the moment of CT initiation, at least 3 completed courses of first-line or second-line platinum-based CT, residual tumor foci after CT visualized with radiological methods, alpha-fetoprotein >7.29 IU/mL or chorionic gonadotropin >5 mIU/mL 3 weeks after the initiation of the last CT course, and surgery after CT. Histological examination of the primary tumors demonstrated that they contained elements of seminoma (n = 14; 14.6 %), teratoma (n = 29; 30.2 %), choriocarcinoma in (n = 23; 23.9 %), embryonal carcinoma (n = 45; 46.9 %), and yolk sac (n = 18; 18.8 %). All study participants received first-line CT; 58 of them (60.4 %) also received second-line CT. All patients underwent surgery after CT, including retroperitoneal lymph node dissection (RPLND) (n = 96; 100 %) and excision of extra-retroperitoneal lesions (n = 8; 8.3 %).Results. Histological examination of excised retroperitoneal masses showed that they contained areas of necrosis and fibrosis (n = 25; 26.0 %), teratoma (n = 29; 30.2 %), and viable malignant non-seminoma (n = 42; 43.8 %). There was a strong positive correlation between the existence of residual malignant non-seminomatous components in retroperitoneal masses and presence of choriocarcinoma (r = 0.300; р = 0.004), as well as the absence of embryonal carcinoma in the primary tumor (r = –0.300; р = 0.004), invasion of retroperitoneal metastases into major vessels and/or adjacent organs (r = 0.243; р = 0.017), and second-line CT prior to RPLND (r = 0.413; р <0.0001). Patients having ≥3 risk factors were significantly more likely to have residual malignant non-seminoma in retroperitoneal masses than patients who had 0–2 risk factors (73.5 % vs 27.3 %; р <0.0001). Excised residual extra-retroperitoneal masses contained areas of necrosis and fibrosis (n = 3; 37.5 %), teratoma (n = 1; 12.5 %), and malignant non-seminoma (n = 4; 62.5 %). Concordant structure of retroperitoneal and extra-retroperitoneal lesions was observed in 4 patients (50.0 %).Conclusion. Malignant non-seminomas were detected in 43.8 % of retroperitoneal and 62.5 % of extra-retroperitoneal residual tumorsremoved after CT in patients with advanced TNSGCTs and incomplete serological and radiological response. Discordant structure of metastases at different locations was observed in 50 % of patients. Our finding can be used to select candidates for surgical excision of residual tumors among these patients.