Essentially all forms of cancer therapy, including surgery, chemotherapy, and radiation therapy, can affect the musculoskeletal system of a growing child or adolescent. The following outcomes affecting the musculoskeletal system are discussed: bone and joint late effects (abnormal bone and muscle growth, amputation/limb-sparing surgery, joint contracture, osteoporosis/fractures, osteonecrosis) and changes in body composition (obesity and body fatness). While these late effects are discussed individually, it is important to remember that all of the components within the musculoskeletal system are interrelated. For example, hypoplasia to a muscle group can negatively affect the function of the long bones and the resultant dysfunction can subsequently lead to disuse and osteoporosis.
Bone and Joint
Abnormal bone growth
In an age- and dose-dependent fashion, radiation can inhibit normal bone and muscle maturation and development. Radiation to the head (e.g., cranial, orbital, infratemporal, or nasopharyngeal radiation therapy) can cause craniofacial abnormalities, particularly in children treated before age 5 years or with radiation doses of 20 Gy or more.[1,2,3,4,5] Soft tissue sarcomas, such as orbital rhabdomyosarcoma and retinoblastoma are two of the more common cancer groups with these radiation fields. Often, in addition to the cosmetic impact of the craniofacial abnormalities, there can be related dental and sinus problems.
Radiation therapy can also directly affect the growth of the spine and long bones (and associated muscle groups) and can cause premature closure of the epiphyses, leading to short stature, scoliosis/kyphosis, or limb-length discrepancy.[6,7,8,9,10,11,12] Orthovoltage, commonly used before 1970, delivered higher doses of radiation to the bone and was commonly related to abnormalities in bone growth. However, even with contemporary radiation therapy, if the location of the solid tumor is near an epiphysis or the spine, alterations in normal bone development can be difficult to avoid.
The effects of radiation administered to the spine on stature in survivors of Wilms tumor were assessed in the National Wilms Tumor Study (NWTS), studies 1 through 4. Stature loss in 2,778 children treated on NWTS 1 to 4 was evaluated. Repeated height measurements were collected during long-term follow-up. The effects of radiation dosage, age at treatment, and chemotherapy on stature were analyzed using statistical models that accounted for the normal variation in height with gender and advancing age. Predictions from the model were validated by descriptive analysis of heights measured at ages 17 to 18 years for 205 patients. For those younger than 12 months at diagnosis who received more than 10 Gy, the estimated adult-height deficit was 7.7 cm when contrasted with the nonradiation group. For those who received 10 Gy, the estimated trunk shortening was 2.8 cm or less. Among those whose height measurements in the teenage years were available, patients who received more than 15 Gy of radiation therapy were 4 to 7 cm shorter on average than their nonirradiated counterparts, with a dose-response relationship evident. Chemotherapy did not confer additional risk. The effects of radiation on the development of scoliosis have also been re-evaluated. In a group of 42 children treated for Wilms tumor from 1968 to 1994, scoliosis was seen in 18 patients, with only one patient needing orthopedic intervention. Median time to development of scoliosis was 102 months (range 16-146 months). A clear dose-response relationship was seen, with children treated with lower dosages (<24 Gy) of radiation having a significantly lower incidence of scoliosis than those who received more than 24 Gy of radiation. There was also a suggestion that the incidence was lower in patients who received 10 to 12 Gy, the dosages currently used for Wilms tumor, although the sample size was small.