Early radiologic tumour volume response in non-metastatic rhabdomyosarcoma is not predictive for survival

Background: There is an urgent need for early radiological markers predicting survival in paediatric rhabdomyosarcoma patients. Objective: To analyse the predictive value of early radiological tumour volume response to chemotherapy in non-metastatic rhabdomyosarcoma patients. Methods: The European paediatric Soft tissue sarcoma Study Group (EpSSG) RMS 2005 study prospectively included non-metastatic rhabdomyosarcoma patients. Patients with Intergroup Rhabdomyosarcoma Studies (IRS) postsurgical Group III (i.e. measurable disease) at diagnosis, with three tumour diameters available at diagnosis and following three cycles of chemotherapy, were included. Tumour response was categorized as complete response, partial response, minor partial response, stable disease, or progressive disease. Patients with progressive disease were excluded from analyses. Failure-free survival and overall survival were estimated with Kaplan-Meier using a landmark analysis. Prognostic factors were assessed using Cox proportional hazards analyses. Results: Of 1,674 patients aged < 18 years at diagnosis included in the EpSSG RMS 2005 study, 613 patients (median age 4.2 years, interquartile range 2.2–8.0, 346 males) were eligible for analysis. After three cycles of chemotherapy, 48 patients reached complete response, 371 partial response, 139 minor partial response, 48 stable disease, and seven patients progressive disease. Univariate Cox proportional hazards model showed no significant difference between response groups for failure-free survival or overall survival. In multivariate Cox regression analysis, tumour volume response was not an independent prognostic factor for failure-free survival or overall survival. Conclusion: Early radiological tumour volume response after the third cycle of neoadjuvant chemotherapy, with exclusion of progressive disease, does not predict survival in paediatric rhabdomyosarcoma patients.