Clinical outcomes and prognostic factors of parameningeal rhabdomyosarcoma in children and adolescents: results of two consecutive protocols.

Background: Parameningeal rhabdomyosarcoma (PM-RMS) accounts for about 20% of all rhabdomyosarcoma (RMS) cases. At present, most research on PM-RMS has been conducted in Europe and the United States of America, and research in China has been very limited. This study sought to analyze the clinical outcomes and prognostic factors of PM-RMS in children and adolescents from two consecutive protocols at Beijing Children's Hospital (BCH).

Methods: A total of 80 patients aged up to 18 years with previously untreated PM-RMS who had received treatment under two consecutive protocols [i.e., either the BCH-RMS-2006 protocol or the Chinese Children Cancer Group (CCCG)-RMS-2016 protocol] were included in the statistical analysis. The Kaplan-Meier method was used for the survival analysis, and Cox regression was used for the univariate and multivariate analyses.

Results: Of the 80 patients enrolled in the study, 69 (86.2%) had meningeal invasion (MI). Of these 69 MI patients, 18 (22.5%) had cranial nerve palsy (CNP), 64 (80.0%) had cranial base bone erosion (CBBE), 25 (31.3%) had intracranial extension (ICE), and 2 (2.5%) had positive cerebrospinal fluid (CSF) tumor cells. The median follow-up time was 20.5 months (range, 5-100 months). The 5-year overall survival (OS) and progression-free survival (PFS) rates for the entire cohort were 51.7% and 45.6%, respectively. The 5-year OS rates of the patients who received the BCH-RMS-2006 protocol (18/80, 22.5%) and the CCCG-RMS-2016 protocol (62/80, 77.5%) were 33.3% and 57.0%, respectively (P<0.05), while the PFS rates of these patients were 22.2% and 53.6%, respectively (P<0.05). In relation to the PM-RMS patients with MI, the 5-year OS rates were 21.4% and 52.7%, and the 5-year PFS rates were 14.3% and 51.1% for the patients who received the old and new regimens, respectively (P<0.05). The extent of surgical resection had no significant effect on survival. The multivariate analysis showed that the coexistence of CBBE and ICE, no radiotherapy, a poor response to induction chemotherapy, and the BCH-RMS-2006 protocol were risk factors affecting PFS and OS.

Conclusions: Of the patients examined in this study, those with PM-RMS with CBBE accompanied by ICE had the worst prognosis. The patients with MI benefited from intensive chemotherapy combined with radiation therapy, but the effect of surgery was very limited.