Discussion
Rhabdomyosarcoma (RMS) is a malignancy of mesenchyme cells that have varying degrees of differentiation towards skeletal muscle cells1. The most common affected sites are head and neck (28%), extremities (24%), with genitourinary tract only comprising 18%2. Rhabdomyosarcoma is generally a disease of children, and is exceedingly rare in adults3.
Prostate RMS accounts for <1% of all prostate malignancies in adult life4. It is described only in case reports. Clinical presentation includes dysuria, urinary and rectal obstruction. PSA levels are usually normal. Main sites of metastasis include the lungs, liver and skeleton. Having a cancer predisposition syndrome, such as Neurofibromatosis, Noonan, Li Fraumeni, is the strongest risk factor for developing RMS5.
RMS is histologically divided into embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. Each harbor characteristic genetic aberrations6 with implications for prognostication. Due to high discordance among pathologists, genetic testing is used for confirmation.
For early stage RMS, surgical management aims for complete tumor resection. For unrestable cases, the mainstay of treatment remains to be chemotherapy. Vincristine sulfate, dactinomycin (actinomycin-D), and cyclophosphamide (VAC) regimen remains the backbone of Pediatric RMS chemotherapy8. Due to the rarity of the disease in adults, there is a lack of standardized treatment in this age group, but retrospective studies have shown that concordance with pediatric protocols have better survival9. Hence our patient was managed with VAC. Since VAC has been associated with high risk of gonadal dysfunction, sperm cryopreservation was performed prior to initiation.
Compared to children, adult RMS has significantly worse outcome. Five-year overall survival in children was 61% compared to 27% in adults (7). The reason for poor survival has been found to be due to higher IRS stage, unusual histology and metastatic disease at the time of diagnosis. Additional studies have shown other factors that contribute to poor survival, including lack of compliance to the regimen, delays in diagnosis and the lack of RCTs for the adult groups11.
The advent of gene testing has implications for prognostication, enabling identification of the specific genetic aberrations driving the tumors. This area of research may help find potential therapeutic targets in the future12.