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March 20, 2012

Report highlights understudied, unwelcome side of cancer treatment

The number of cancer survivors in the United States has tripled since 1971, and yet gains in survival have come at the price of second malignancies and cardiovascular disease, according to a report by a national scientific committee chaired by the Medical Center’s Lois Travis.

The Journal of the National Cancer Institute published a detailed summary of the report this month. The expert scientific committee, convened by the National Council on Radiation Protection and Measurements (NCRP), deliberated intensely for five years as they considered some of the most important repercussions of radiation treatments and made several important conclusions and recommendations. The comprehensive, 425-page report will be made available in the spring.

“For many survivors the successes of treatment have been offset by the late effects of cancer and its therapy,” says Travis, professor in the Department of Radiation Oncology and director of the Rubin Center for Cancer Survivorship at the Wilmot Cancer Center. “Although many complex factors influence the risk of second malignancies and other health issues after cancer treatment—including lifestyle choices such as diet, exercise, alcohol and tobacco use, as well as genetics, age, and immune system function—it is vital that we develop the best possible long-term risk estimates and prediction models, and that we establish research priorities and identify concrete ways to prevent serious additional health problems among cancer survivors.”

The committee’s focus was on the consequences of radiation therapy, which is a cornerstone of cancer treatment and used in approximately 50 percent of all cancer cases. (Chemotherapy is addressed to a lesser degree, when it is used in combination with radiation.)

Louis Constine, professor and vice chair of the Department of Radiation Oncology, was a member of the NCRP scientific committee and echoes Travis’s sentiments. He adds that although radiation can be a lifesaving therapy, it is critical that physicians and patients be alert to long-term side effects and plan appropriately for follow-up. As clinical director of the Wilmot Cancer Center’s Survivorship division, he is working with others to develop a program that will provide patients with a comprehensive plan for their post-cancer care.

Among the NCRP’s key findings:

Newer radiotherapy treatment methods and techniques result in a different distribution of the radiation to organs and tissue from older treatment regimens. However, the current models used to assess risk of second malignancies and cardiovascular disease are often based on older treatment regimens. Newer risk-prediction models should be based on the dose absorbed by the organ and the type of radiation prescribed.

A few studies have gone on to describe survival after the diagnosis of the second malignancies after a patient develops a second primary cancer.

Establishing a research infrastructure that can be used by the many disciplines involved in the care of survivors is important.

Specifically, follow-up studies of cancer survivors should evaluate populations treated with modern radiotherapy methods such as tomotherapy, cyberknife, etc., and at reduced field sizes and lower dosages.

More studies are needed to analyze all aspects of the relationship between radiation dose and risk of second malignancies and heart disease.

Long-term, large-scale studies are needed to follow cancer survivors of all ages, but particularly those who are adolescents and young adults, and characterize their risks as they age.

Studies are needed to understand the molecular and genetic underpinnings of radiotherapy-associated late health effects, with a particular focus on patients who develop two or more primary cancers after radiation treatment.

Modern radiation techniques and lower doses result in a much smaller risk of cardiovascular problems for patients. However, an important noncancer cause of death for some survivors is radiation-related heart disease, including pericardial disease, coronary artery disease, valvular dysfunction, conduction abnormalities, and stroke. More research and analysis is needed to predict the high complication rates in certain populations of cancer patients.

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