BACKGROUND: Rhabdomyosarcoma (RMS) is a rare, highly malignant childhood cancer with an annual incidence of four cases per million and approximately 350 new cases are diagnosed in the U.S. annually. Due to its rarity, relatively little is known about the etiology of this childhood malignancy. Early immunologic challenges such as immunizations and infections have been hypothesized to be protective in certain malignancies. To our knowledge, these associations have not been studied in relation to childhood RMS risk. The purpose of our study was to better characterize the association between childhood immunizations and infections and RMS risk using data from the largest case-control study of RMS to date.
MATERIALS AND METHODS: Cases (n=322) were previously enrolled in the Intergroup Rhabdomyosarcoma Study, which became a part of the Children’s Oncology Group in 2000. Controls (n=322) were selected by random-digit telephone dialing and pair-matched to cases on race, sex, and age. We evaluated RMS risk based on whether parents reported that their child was up-to-date on immunizations and had completed their DPT (diphtheria, pertussis and tetanus), oral polio, and MMR (measles, mumps and rubella) series. In addition, we evaluated whether the child ever had previous infections including mumps, pneumonia, rubella, rubeola, pertussis, tuberculosis, meningitis, scarlet fever, and chickenpox. Conditional logistic regression models were used to calculate an adjusted odds ratio (aOR) and 95% confidence interval (CI) for each exposure, adjusted for age, race, and sex.
RESULTS: Having up-to-date immunizations had a protective effect on childhood RMS (aOR=0.22, 95% CI: 0.11-0.44). More specifically, children who did not receive the complete vaccination series of DPT (aOR=1.70 95% CI: 1.18-2.50) or did not receive the MMR vaccine (aOR=1.59, 95% CI: 1.04-2.44) had an increased risk of being diagnosed with childhood RMS. Most infectious conditions examined were negatively associated with childhood RMS; however, these findings were not statistically significant (p>0.05).
CONCLUSIONS: This is the first study of its kind to provide evidence that receiving childhood immunizations may be protective against RMS risk. Although the effect estimates suggested a possible protective role of childhood infections against RMS risk, these findings were not statistically significant. Future studies will be needed to further evaluate the role of immunizations and childhood infections in the development of this tumor.
