According to recent results published in The New England Journal of Medicine, children diagnosed with acute lymphoblastic leukemia (ALL) who receive treatment including radiation therapy to the brain are at an increased risk of suffering long-term side effects.
Acute lymphoblastic leukemia (ALL) is a cancer of the bone marrow and lymph system. The bone marrow produces early blood-forming cells, called stem cells, which grow and mature into the three blood cell types: white blood cells, which fight infection; red blood cells, which carry oxygen to tissue; and platelets, which help blood to clot. ALL is characterized by uncontrolled production of immature lymphocytes (white blood cells), of which there are two types: B and T cells. These immature lymphocytes never mature enough to perform their specific function of fighting infection. In addition, these rapidly dividing cells crowd out and suppress the formation of other important blood cells, such as red blood cells, platelets and other white blood cells. ALL is an aggressive cancer that must be treated aggressively for optimal chances of a cure.
The central nervous system (CNS), including the brain and spinal column, is a common site for cancer to recur in patients with ALL. Historically, patients were treated with radiation to the brain alone or brain and spinal column to reduce the risk of a recurrence in the CNS. Due to known long-term side effects that can be caused by irradiation to the CNS, present treatment for the prevention of a recurrence in the CNS is chemotherapy delivered systemically (full-body) or intrathecally (spinal column).
Researchers from St. Jude Children’s Research Hospital have recently compared long-term side effects of patients who had received or not received radiation to the brain for treatment of childhood ALL. This study involved 856 patients who had survived at least 10 years following treatment for ALL; 597 of whom received radiation therapy and 259 who had not. The risk of developing a second cancer was 21% in patients who received radiation therapy, compared with less than 1% in patients who did not receive radiation. Survival at approximately 30 years following treatment was 95.3% in the group of patients treated with radiation therapy, compared with 98.3% in patients not treated with radiation, which is the approximate survival rate of the general population. Furthermore, patients treated with radiation therapy had significantly higher than average rates of unemployment and women in this group were less likely to be married.
The researchers concluded that brain and spinal radiation therapy in childhood patients diagnosed with ALL can lead to long-term consequences, including an increased risk of developing a second cancer. Since the vast majority of pediatric patients treated for ALL achieve long-term survival, it is important for both patients and physicians to be aware of long-term sequelae of CNS radiation. Patients who are survivors of childhood ALL and received CNS radiation should discuss risks associated with this therapeutic regimen with their physician.
Reference: Pui C-H, Cheng C, Leung W, et al. Extended follow-up of long-term survivors of childhood acute lymphoblastic leukemia.
The New England Journal of Medicine. 2003;349:640-649.