Genitourinary embryonal rhabdomyosarcoma clinicopathologic determinants of clinical outcomes: Analysis of a pooled database.

Abstract

e23536 Background: Embryonal rhabdomyosarcoma (ERS) refers to malignant soft tissue tumors with phenotypical, histological features of primitive skeletal muscle. ERS commonly involves the head and neck region and genitourinary system. Genitourinary embryonal rhabdomyosarcoma (GUERS) is considered an entity similar to other ERS based on Intergroup Rhabdomyosarcoma Study Group (IRSG) with non-prostate GUERS considered low risk. This study seeks to define other high-risk subtypes in this population. Methods: To study the demographic and molecular characteristics, therapeutic interventions, survival, and prognostic factors, we compiled a pooled database of 137 cases of GUERS. Kaplan-Meier survival curves, Cox proportional-hazards model and Log-rank tests were used to assess the influence of demographic and clinicopathologic factors on overall survival (OS) and disease-free survival (DFS). Results: 137 patients with confirmed GUERS were identified: median age was 16 and F:M ratio of 1.6. Female reproductive organs (49%), renal and urinary tract (24%), male reproductive organs (23%), and abdomino-pelvis (4%) were involved. Lymph node involvement and metastasis occurred in 11% and 13%, respectively. Staging consisted of stage I (65%), stage II (15%), stage III (8%), and stage IV (12%). Rhabdomyosarcoma clinical groups were mostly IA (41%), IIIA (31%) and IV (13%). Risk groups consisted of low (71%), intermediate (17%), and high (13%). Median OS and DFS were 96 and 42 months, respectively. The primary site of involvement impacted OS, with urinary tract organ involvement having the best median OS, compared to female reproductive organs, male reproductive organs, and abdomino-pelvis involvement (p = 0.01). While primary pelvic disease (p = 0.03), prostate (p = 0.008), and lymph node involvement (p = 0.001) were associated with worse OS, cervix/vaginal involvement tended to have better OS (p = 0.06). Constitutional symptoms (p = 0.0007), obstruction (p = 0.047) and metastases (p = 0.02) were associated with worse OS. Clinical staging system (p = 0.0008), risk groupings (p = 0.06) correlated with OS, but not clinical groupings (p = 0.26). GUERS with vimentin+, CD99- and SMA+ had worse survival (only the latter was statistically significant). Compared to no treatment, RT, CT+/-RT, S+CT+RT were superior with mOS of 2, 6, NR, 96 months, respectively (p < 0.0001). Achieving CR had superior OS (p < 0.0001). OS was not impacted by age, sex, or extent of surgery. Conclusions: Genitourinary embryonal rhabdomyosarcoma is a distinct clinical entity with outcomes worse than other forms of ERS defined by the Clinical Groups of IRSG. Prostate, primary pelvic and obstructive symptoms have worse OS compared to bladder and cervical involvement and we propose their inclusion in the current Clinical Group. This study presents updated clinicopathologic data from a pooled cohort of patients with GUERS.