Discussion
Herein we presented two pediatric patients with findings of secondary EWS of the rib within 5 years of treatment completion for primary leukemia. Literature has suggested that ESFT are rare as a secondary neoplasm.2 According to the CCSS, incidence of EWS after ALL was 1/49 (2%) and AML was 2/49 (4%) in 5-year survivors. Childhood cancer survivors have a nine-fold increased risk of developing secondary sarcoma compared to rates of sarcoma in the general population.4 Spunt et al found that 4 of their 6 secondary ESFT developed in the bone, most commonly the rib.2 Risk factors for subsequent bone sarcomas include younger age at time of cancer diagnosis (<4 years), radiation therapy, and exposure to both anthracyclines and alkylating agents.4, 5 Both patients in our series were older at time of diagnosis and did not receive radiation therapy. Patient 2 did receive >300 mg/m2 cumulative anthracycline dosage during treatment of AML – a level that has been associated with increased risk of secondary sarcomas.3There were common environmental factors in this case series to consider. Two months prior to diagnosis, Patient 1 was at the 92nd percentile for body mass index (BMI); and patient 2 was at the 93rd percentile for BMI. Limited literature exists regarding obesity and the risk of developing a second malignant neoplasm; Moke et al found a significantly increased risk among patients who were obese both at the time of diagnosis and at the end of treatment.6 Both patients resided in Northeast Pennsylvania, where there is an abundance of hydraulic fracturing (or “fracking”) wells that have been linked to the release of carcinogens.7 Others have reported locally increased incidence of rare EWS.8 Further investigation is warranted to evaluate environmental factors that may increase the risk of EWS. This case series emphasizes the importance of continued surveillance and regular cancer screening for childhood cancer survivors.