TUESDAY, March 29 (HealthDay News) -- The odds a second cancer will develop after radiation treatment for a first cancer are relatively low, U.S. National Cancer Institute researchers report.
In a long-term study of more than 600,000 cancer survivors, an estimated 8 percent of second cancers were attributable to radiation treatment for the original cancer, according to the study.
The results suggest that other factors, such as lifestyle risks and genetics, cause the majority of second cancers, the researchers say.
"The findings can be used by physicians to really put the risks into perspective when they are talking treatment options with their patients," said lead researcher Amy Berrington de Gonzalez, an investigator in the NCI's radiation epidemiology branch.
Patients should feel reassured, she added. "In general, the risks [of radiation therapy] are smaller than the benefits," she said.
The study, published online March 30 in The Lancet Oncology, is the first to quantify the cancer risks posed by radiation treatment for different malignancies.
Berrington de Gonzalez and colleagues collected data on 647,672 adult cancer survivors included in the U.S. Surveillance, Epidemiology and End Results cancer registries. All had survived five years or longer after cancer treatment, and follow-up ran from 1978 to 2007.
The researchers looked at outcomes for 15 different types of cancer for which radiation treatment is routine, including cancers of the rectum, larynx, lung, breast, cervix, testicles, prostate, eye and orbit, brain and thyroid.
Over the 30 years of follow-up, 9 percent of these participants developed a second cancer. Of these, about 3,300 (8 percent) might have been the result of radiation treatment, the study authors said.
Second cancers related to earlier radiation therapy varied by type, the researchers noted.
All rights reserved