Pediatric cancer survivors face reduced risk for subsequent neoplasms
medwireNews: The risk of developing subsequent neoplasms is lower for survivors of childhood cancer diagnosed in the 1990s than in earlier decades, a decrease largely attributed to the reduction in therapeutic radiation doses, say researchers.
They analyzed data from 23,603 participants of the Childhood Cancer Survivor Study, which comprises US and Canadian pediatric cancer patients who survive for at least 5 years beyond diagnosis.
Over the course of an average follow-up of 20.5 years, 1639 survivors experienced 3115 subsequent neoplasms, including malignancy, benign meningioma, and nonmelanoma skin cancer, with breast and thyroid cancer the most common subsequent malignant neoplasms reported.
Lucie Turcotte (University of Minnesota Medical School, Minneapolis, USA) and colleagues found that the 15-year cumulative incidence of subsequent neoplasms was significantly lower among individuals who received their primary diagnosis in the 1990s than the 1980s or 1970s, at 1.5% versus 2.4% and 2.9%, respectively.
The findings were similar for subsequent malignant neoplasms, with corresponding rates of 1.3%, 1.7%, and 2.1%, they report in JAMA.
Furthermore, among individuals who survived until their 20s and 30s, the standardized incidence ratios for subsequent malignancies were significantly lower for those initially diagnosed in the 1990s than in the 1980s or 1970s.
After adjusting for gender, age at diagnosis, and attained age, the relative rate (RR) for subsequent neoplasms declined significantly (RR=0.81) with every 5-year increment of treatment era, as did the RRs for malignancy, meningioma, and nonmelanoma skin cancer, at 0.87, 0.85, and 0.75, respectively.
Mediation analysis enabled the assessment of the effect of variations in treatment over time, such as changes in chemotherapy and radiation doses. This showed that the era-associated decline in the rate of subsequent neoplasms was largely explained by the reduction in therapeutic radiation doses, from a median of 30 Gy in the 1970s to 26 Gy in the 1990s.
The researchers summarize: “Ongoing efforts to reduce long-term therapeutic toxicity were associated with decreasing subsequent neoplasms among 5-year survivors of childhood cancer.”
However, continued follow-up is needed to determine the change in risk over time, they add, “particularly given the long latency from primary diagnosis to many subsequent malignant neoplasms.”
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