Pediatric non-rhabdomyosarcoma soft tissue sarcomas

Abstract

Keywords Pediatric .Softtissuesarcoma .Non-rhabdomyosarcoma .RadiotherapyBackgroundSofttissuesarcomasencompassadiversegroupofmesenchy-mal tumors, some of which have unique biology and epide-miologywithinthepediatricagegroup.Rhabdomyosarcomasare the best characterized and studied with relatively goodsensitivity to both chemotherapy and radiotherapy. To distin-guish the other broad category of pediatric tumors derivedfrom connective tissue, the cumbersome term, non-rhabdomyosarcoma soft tissue sarcomas (NRSTS), has beencoined. Many, but not all NRSTS, share characteristics withadult-type soft tissue sarcomas (STS) leading to a wealth oftreatment principles that cross the age spectrum. But becauseof developmental toxicities especially from radiotherapy,there are considerable modifications in treatment philosophywiththemanagementofNRSTS.Unlikerhabdomyosarcoma,where well conducted randomized trials have progressivelyrefined the dose, fractionation, and volume of radiotherapy ina risk adapted manner, the evidence for optimal managementof NRSTS is still evolving. Relative to the adult managementof STS, the oncologist needs to be more mindful of the lateeffects of treatment, which include concerns for normalgrowth, fertility, and risk for secondary malignancy. But atwhat age should STS be treated more aggressively with ra-diotherapyisdifficulttoknowasNRSTSclinicaltrialsextendeligibility to young adults. This review will provide an over-view of evolving knowledge regarding NRSTS while focus-ing on the radiotherapeutic aspects.EpidemiologySoft tissue sarcomas represent 6–7 % of all pediatric cancers(defined as those occurring before age 20 years). Of these,40 % are rhabdomyosarcoma and 60 % are NRSTS [1–3].The USA’s Surveillance, Epidemiology, and End Results(SEER) program provides some of the most comprehensivecancer epidemiologic data available [4]. Of the EuropeanTumor Registries, only data published from Germany havesufficient detail to distinguish rhabdomyosarcoma fromNRSTS [5]. Overall, NRSTS comprise approximately 3–3.5 % of all pediatric cancers with 550 to 600 new casesdiagnosed each year in the USA. The incidence rate overtime has remained steady in the range of six to eight casesper million population. In Germany, the incidence rate isslightly less at five cases per million persons. Data fromSEER based on the time period 1975–1995 suggest thatNRSTS has had a propensity to dominate in older pediatricage groups (10–14 years and 15–19 years, specifically) aspart of the incidence curves for STS leading into adulthood.In fact, clinical features for soft tissue sarcomas are similarbetween children and adults, except that survival rates di-minish for patients over age 50 years [6]. See Fig. 1, depict-ing the distributionof STS subtypes, location of disease, andstaging by 10-year age intervals.The survival of patients with NRSTS is dependent on thehistologic subtype to a certain degree. Figure 2 depicts the