Parameningeal rhabdomyosarcoma- clinical profile, outcomes and prognostic factors in children treated at a single center over a decade

1 Background Parameningeal Rhabdomyosarcomas (PM-RMS) in children are challenging to treat. While ten-year Event Free Survival (EFS) of 62% have been reported from High-Middle Income Countries (HMICs) for localized disease, data is limited from Low-Middle Income Countries (LMICs). We studied the clinical profile, outcomes, and prognostic factors in PM-RMS. 2 Materials and Methods Children≤15 years with PM-RMS treated on a uniform chemotherapy protocol from January 2013-December 2021 were retrospectively analysed. Local therapy at 10-12weeks of induction was radiotherapy (RT)+/-surgery where possible with early RT for intracranial extension (ICE). 3 Results Seventy-six patients with a median age of 6.7years (range,3.2-15years), male to female ratio of 1.8:1 formed the study cohort. Eleven patients (14.5%) had metastasis (lungs-8, bone-2, bone marrow-1) and ICE seen in 46.1%(n=35). Twenty-five patients (49.0%) had alveolar histology with PAX3/7 positive in 17/59 (28.8%). Median tumor size(t ) at baseline was 5.2cm(range,1.2-12.8cm). Seventy-one patients received RT, 5 also underwent surgery. At a median follow-up of 65months (range,53-76months) 4year EFS, OS of the whole cohort were 47.3%(95%CI:34.8%-58.8%), 51.7%(95%CI:38.0%-64.0%) respectively. Four-year EFS, OS of localized and metastatic cohort were 54.7%(95%CI:41.3%-68.1%), 56.0%(95%CI:42.0%-70.0%) and 9.1%(95%CI:0%-26.5%), 18.2%(95%CI:0%-47.8%) respectively. Metastases (HR-3.38,95%CI:1.57-7.26,p=0.002), t (HR-1.17,95%CI:1.02-1.34,p=0.026) were prognostic for survival on multivariate analysis. 4 Conclusions Survival of children with localized PM-RMS in our study is relatively fair compared to the reported literature probably due to application of RT in all despite higher proportion of larger tumors, unfavorable sites of primary and intracranial extension. Identification of high-risk subsets and optimizing current treatment strategies, both systemic and local therapy may partly improve outcomes.