Childhood cancers: rhabdomyosarcoma

Characteristics and prognosis of rhabdomyosarcoma

The origin of this cancer is the mesenchymal stem cells, which form the embryo support tissues that produce a variety of tissues in adults; this explains why it can be found in any part of the body.

The prognosis depends on the age of the child, the extent of the primary tumor, its location and size, its operability and the morphological type. Rhabdomyosarcoma is classified into two sub-types – alveolar or embryonic – according to its morphological characteristics. Alveolar rhabdomyosarcoma is more common in adolescents and is more likely to be located in the extremities.

“Tried and tested” treatments adapted to the various forms

Treatment for rhabdomyosarcoma combines chemotherapy, surgery and, most often, radiotherapy. Surgery is offered as a first line of treatment when tumors are small and easy to access. Otherwise, neoadjuvant chemotherapy is used to reduce the size of the tumor. Several molecules, alone or combined, may be administered, taking care to use combinations that will affect boys’ fertility as minimally as possible.

Radiotherapy usually follows surgery, to eliminate any tumor cells still present.

In tumors of the jaw and face and the urogenital system, radiotherapy may take the form of proton therapy. This ultra-precise form of radiotherapy restricts the radiation of healthy tissues and thus limits after-effects.

Since alveolar forms are more aggressive than others, their treatment is a lot more complex and requires more intensive radiotherapy and chemotherapy. This therapeutic strategy has helped considerably to improve the prognosis for alveolar rhabdomyosarcoma. 

The role of genetics in diagnosing rhabdomyosarcoma

Intensive treatments may have long-term consequences, especially in young children (secondary cancers, infertility, etc.). It is therefore crucial that they be administered only to children with very aggressive forms of rhabdomyosarcoma. In recent years, molecular knowledge on rhabdomyosarcoma has made great progress. A genetic alteration that helps distinguish cases of rhabdomyosarcoma with a positive prognosis from those with a poor prognosis appears to have been identified and seems to be more significant than the morphological characteristics for distinguishing them.

This new classification helps to avoid aggressive treatments and their consequences for children with tumors until now defined as high risk, and which, in light of this new study, appear to have a standard level of risk. Conversely, it allows intensification of treatment for patients classified as high risk.