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.