“These findings suggest that surveillance of at-risk childhood cancer survivors should begin at a younger age than that recommended for the general population,” the authors advise.
Dr. Tara O. Henderson, at the University of Chicago, Illinois, and colleagues point out that a subsequent malignant neoplasm (SMN) occurs in up to 15% of survivors of childhood cancer some 20 to 30 years after the diagnosis of their first cancer. Factors associated with the occurrence of gastrointestinal cancers in this setting are unclear.
To determine the risk and associated risk factors for GI SMNs in childhood cancer survivors, the team collected data on outcomes in 14,358 patients diagnosed when they were younger than 21 years of age who survived for 5 or more years.
During a median follow-up of 22.8 years in this cohort, 45 GI cancers occurred — more than half in the colon, rectum or anus. The standardized incidence ratio of GI cancers in childhood cancer survivors compared to the general population was 4.6, the investigators report.
The 30-year cumulative incidence rates were highest among survivors of Hodgkin lymphoma at 2.08% and Wilms tumor at 1.20%, they found, and abdominal radiation was associated with a cumulative incidence of 1.16%.
Even so, the risk was still significantly increased in survivors not exposed to radiation. High-dose procarbazine and platinum drugs were independent risk factors for GI SMNs.
Given the priority for curing childhood cancer, Dr. Henderson and colleagues do not suggest that treatment protocols should be modified to reduce the long-term risk of secondary GI malignancies.
However, they conclude, “Our observations should enable researchers and clinicians to better identify survivors at highest risk for gastrointestinal SMNs, potentially facilitating the implementation of better surveillance in clinical practice.”