The women are skipping radiation therapy despite guidelines from four organizations that recommend the treatment for this type of patient. The treatment decreases recurrence and boosts survival, says study researcher Ben Smith, MD, assistant professor of radiation oncology at the University of Texas M.D. Anderson Cancer Center in Houston.
"Even if you have adequate surgery, there is a chance of hidden cancer cells after the surgery," he tells WebMD. If women with advanced cancer do not have the radiation after the mastectomy, he says, "up to 30 or 40% will have a recurrence."
Smith tracked more than 38,000 women ages 66 and above. All had mastectomies for invasive beast cancer between 1992 and 2005. He calculated how many had high-risk invasive cancer and which of them had the recommended radiation treatment.
Even though radiation therapy after mastectomy is known to improve survival for high-risk patients, some previous research has suggested it is underused.
Smith and colleagues evaluated information from a data base known as SEER-Medicare (Surveillance, Epidemiology, and End Results).
The researchers divided patients into low risk, intermediate risk, and high risk, depending on such factors as tumor size and lymph node involvement. The guidelines suggest the high-risk women benefit from the radiation after mastectomy. Whether to give it to intermediate-risk women is debated, Smith says.
From 1996 to 1998, high-risk patients who got radiation therapy increased from 36.5% to 57.7%. That increase followed published studies showing the value of the therapy, Smith says.
However, no further increase was seen from 1999 to 2005. During this period, only 54.8% of high-risk patients got radiation therapy after mastectomy.
Four organizations had issued guidelines about the value of radiation after mastectomy from 1999 to 2001: the American Society for Therapeutic Radiology and Oncology, the American Society of Clinical Oncology, the National Institutes of Health, and the National Comprehensive Cancer Network.