Clinico-biological Study/Characterization of Rhabdomyosarcoma in Adolescents and Young Adults, 15-25-year-old Patients

Rhabdomyosarcoma (RMS) is a rare tumor, with an incidence rate estimated at 4.5-6.9/1,000,000 in paediatric and, adolescent and young adult (AYA, 15 -25 years old) populations. RMS stands for the most frequent soft tissue sarcoma in children and adolescents, accounting for approximately half of the whole soft tissue sarcomas in these populations. Conversely, RMS represents a very small proportion of the soft tissue sarcomas in adults (3%), that is less than 1% of the solid cancers of the adult. To date, previous studies undertaken among the paediatric population have pointed out several prognostic factors such as tumor localisation, tumor invasiveness at diagnosis, tumor size, histological subset, and treatment plans. Age at diagnosis remains an independent prognostic factor. MYOD1 gene expression profile, more common in AYA, also seems to impair the prognosis.

RMS management is consensual in Europe for paediatric population, essentially based on the protocol RMS 2005 within the framework of the European Paediatric Soft tissue sarcoma Study Group (EpSSG). Care in AYAs remain heterogeneous and are either achieved in paediatric department, according to EpSSG guidelines, or in oncology department, known as "adult unit", depending on ESMO (European Society for Medical Oncology), which are non-specific recommendations for the management of rhabdomyosarcoma.

No consensus has been published yet for RMS in AYA despite the growing interest in cancers in AYA population - topic.supported by the French National Cancer Institute (INCa) - and the increasing network between paediatricians and adult-oncologists. Thus management of RMS in AYA remains patchy/unequal depending on the type of care unit.

Principal study

• To evaluate the prognostic value in terms of Progression Free Survival (PFS), in AYA patients with RMS, of clinical factors known as prognostic in children, and of biological factors (MYOD1 mutation in non-alveolar tumor; FOXO1).
• To describe clinical, histological and biological characteristics of RMS in AYA.
• To describe the therapeutic strategy according to the type of department (pediatric, AYA or adults):
• To evaluate the impact on PFS of treatment strategy
• To estimate the Overall Survival (OS) in AYA with RMS
• To estimate the OS curve after relapse for patients who achieved complete remission during first line of treatment

Exploratory study Molecular profiling of RMS with the following subtypes: with fusiform cells (Embryonal RMS with fusiform cells vs adult RMS with fusiform cells or sclerosing) or pleomorphic (Embryonal RMS with anaplasia vs adult pleomorphic RMS) by RNAseq, and by CGH for ambiguous cases.

Methodology Clinical data from the different databases will be merged using a standardized format.

A pathology review of the slides is planned as well as a molecular characterization in borderline cases and unusual subtypes. MYOD1 mutations and molecular profile will be investigated for embryonal RMS.

Patient and treatment characteristics will be described with median, range, mean and standard deviation for continuous variables and in terms of frequency and percent of each modality for categorical variables.

PFS will be estimated using Kaplan-Meier method from diagnosis until relapse, progression or death from any cause. Patients alive without progression will be censored at the date of last news.

OS will be estimated using Kaplan-Meier method from diagnosis until death from any cause.

OS after relapse will be estimated using Kaplan-Meier method from the date of first relapse until the death whatever the cause. Patients alive will be censored at the date of last news.

Prognostic factors of PFS will be analyzed using Cox models after check of the proportional hazard assumption. The following factors will be evaluated:

• age: continuous or 15-18 vs 18-25
• tumor size: ≤ 5cm vs > 5cm
• primary tumor site according to the EPSSG classification: favorable (orbit, head and non parameningeal neck, paratesticular, vagina, uterus) vs unfavorable (head and parameningeal, vesico -prostatic, limb, other)
• IRS stage for primary tumor
• nodal and metastatic involvement at diagnostic
• histology (alveolar vs embryonic vs pleomorphic vs other)
• PAX3-FOXO1 and PAX7-FOXO1 fusion gene status, MYOD1 mutation The impact of treatment intervention on PFS will be evaluated using a Cox model stratified or adjusted over prognostic factors identified at the previous step.