Therapeutic radiation has
been strongly associated with development of subsequent tumors; however,
links have also been identified between specific chemotherapeutic
agents and the development of tumors. With this information, childhood
cancer treatment has been modified over time with the hope of reducing
subsequent tumor risk, while maintaining or improving five-year survival.
Although the risk of subsequent malignancies for survivors of
childhood cancer diagnosed in the 1990s remains increased, the risk is
lower compared with those diagnosed in the 1970s, a decrease that is
associated with a reduction in therapeutic radiation dose, according to a
study appearing in the JAMA
‘Modifications of primary cancer therapy were associated with reduced risk of subsequent malignancies among childhood cancer survivors treated in more recent treatment eras.’
The Childhood Cancer Survivor Study and other groups of childhood
cancer survivors have reported extensively on the incidence of and risk
factors for subsequent neoplasms (tumors).
Lucie M. Turcotte of the University of
Minnesota Medical School, Minneapolis, and colleagues conducted a study
that included 23,603 five-year cancer survivors (average age at
diagnosis, 7.7 years) from pediatric hospitals in the United States and
Canada between 1970-1999, with follow-up through December 2015.
1,639 survivors experienced 3,115 subsequent neoplasms, during an average follow-up of 20.5 years. The most common subsequent
malignancies were breast and thyroid cancers. Proportions of individuals
receiving radiation decreased (77% for 1970s vs 33% for
1990s), as did median dose.
A 15-year cumulative incidence of
subsequent malignancies decreased by decade of diagnosis (2.1%
for 1970s, 1.7% for 1980s, 1.3% for 1990s). Relative rates
declined with each five-year increment for subsequent malignancies.
Radiation dose changes were associated with reduced risk for
subsequent malignancies, meningiomas (a tumor that arises from the
membranes that surround the brain and spinal cord), and nonmelanoma skin
"The current analysis, including more than 23,000 survivors of
childhood cancer treated over three decades, demonstrated that the
cumulative incidence rates of subsequent neoplasms, subsequent malignant
neoplasms, meningiomas, and nonmelanoma skin cancers were lower among
survivors treated in more recent treatment eras and that modifications
of primary cancer therapy were associated with these declines," the