Inclusion Criteria:

          -  Participants must have a new histologic diagnosis of rhabdomyosarcoma

          -  Participants must have FISH, PCR or other molecular confirmation of PAX/FOXO1 fusion
             per institutional standards

          -  Participants must have sufficient tissue (up to 10 unstained FFPE) for correlative
             testing

          -  All participants must have distant metastatic disease; either biopsy positive or PET
             avid extranodal lesions determined by the investigator to be metastatic disease.
             Patients with a single distant metastatic site that has been excised prior to study
             entry are eligible

          -  No prior systemic chemotherapy

          -  Participants enrolled to Arm B, maintenance, must be able to take oral
             cyclophosphamide. Note: enteral administration of cyclophosphamide is allowable.

          -  Pregnancy or Breast Feeding: Pregnant or breast-feeding women will not be entered on
             this study, because there is no available information regarding human fetal or
             teratogenic toxicities. Females of childbearing potential must have a negative serum
             or urine pregnancy test within 24 hours of starting protocol therapy.

          -  Males and females of reproductive potential may not participate unless they have
             agreed to the use of, at minimum, two methods of contraception during and after
             treatment.

          -  Women of childbearing potential should adhere to contraception for a period of 4
             months after completion of systematic chemotherapy administration

          -  Men who are sexually active with women of child bearing potential should adhere to
             contraception for a period of 4 months after completion of systematic chemotherapy
             administration

          -  All patients and/or their parents or legal guardians must have the ability to
             understand and the willingness to sign a written informed consent or assent document.

        Exclusion Criteria:

          -  Participants with regional lymph nodes as the only site of disease are not eligible.
             Distant nodal sites alone would be eligible

          -  Participants who are receiving any other investigational agents for rhabdomyosarcoma
             are ineligible

          -  Participants must not be receiving any additional medicines being given for the
             specific purpose of treating cancer. Alternative medications including, but not
             limited to cannabis based products would not be a reason for exclusion

          -  Participants are ineligible if they have uncontrolled intercurrent illness including,
             but not limited to:

               -  ongoing or active infection not expected to resolve with current antibiotic plan

               -  cardiac arrhythmia

               -  psychiatric illness/social situations that would limit compliance with study
                  requirements

          -  Participants who are considered unable to comply with the safety monitoring
             requirements of the study are not eligible