Radiation Effect on Growth Plates in Children
Dear OncoLink "Ask The Experts,"
My son has ARMS (alveolar rhabdomyosarcoma), stage IV. The primary site is his calf, with metastases to lung and lymph nodes in the knee and hip. Chemotherapy has been able to dissolve the tumor after 2 treatments so that it is undetectable after MRI scan. We are concerned about radiation. Is there any way to protect the growth plates in the femur and tibia? Is there any drug that could be given? Could the femur be [intentionally] dislocated so that it is removed from the radiation field? What are our options? He is only 3 years old. He has a lot of growing to do.
Amit Maity, MD, PhD, Assistant Professor of Radiation Oncology at the Hospital of the University of Pennsylvania, responds:
If the lymph nodes in the knee are involved (popliteal nodes) and if they are encompassed within the radiation field (which would be prudent), the growth plates of both the upper tibia and the lower femur will be irradiated. Likewise, if the nodes in the hip region (inguinal nodes) are involved and included, there is really no way of protecting
that upper femur growth plate. Unfortunately, there is no drug that can be given to protect these areas.
For the lower leg, it is possible to surgically ablate the growth plate in the unaffected tibia several years down the line in order to make both tibias non-functional, thereby minimizing leg growth discrepancy. This issue of irradiation of growth plates is a real problem in a 3-year-old, which is why we are very hesitant to irradiate such young kids to high doses.