Radiation therapy after mastectomy is not always necessary for women with low-risk breast cancer, but it is frequently recommended for high-risk breast cancers. For intermediate breast cancers, use of radiation therapy after surgery remains controversial. Following the publication of three landmark trials in the mid- 1990s showing that post-mastectomy radiation therapy decreases locoregional recurrence and improves survival in patients with high-risk breast cancer, rates of this type of radiation increased from 36.5% to 57.7% from 1996 to 1998 (Table 1). In the late 1990s, several major associations released treatment guidelines endorsing the use of post-mastectomy radiation therapy in this population, most notably the American Society of Clinical Oncology and the National Comprehensive Cancer Care Network.
A New Analysis of Post-Mastectomy Radiation
In the October 15, 2011 issue of Cancer, investigators sought to determine if the use of post-mastectomy radiation has increased since national guidelines have recommended this approach for high-risk breast cancer patients. Researchers analyzed data from the SEER-Medicare database on 38,332 women aged 66 or older who underwent mastectomy for invasive breast cancer between 1992 and 2005. “Our study found that about 55% of women with high-risk breast cancer were receiving post-mastectomy radiation therapy,” says Benjamin D. Smith, MD, lead author of the analysis. “That is substantially lower than what we had anticipated.”
“About 55% of women with high-risk breast cancer were receiving post-mastectomy radiation therapy. That is substantially lower than what we had anticipated.”
Dr. Smith says that the rate of radiation therapy when indicated following lumpectomy is about 90%. “It’s paradoxical,” he adds. “Although radiation after lumpectomy has been shown to lower risk of cancer recurrence in the breast, it has not been shown to improve overall survival in older patients. To the contrary, there is compelling data demonstrating that radiation improves survival after mastectomy. It’s probably more important to give radiation after mastectomy for high-risk breast cancer than after lumpectomy for low-risk breast cancer, yet we’re falling behind in our treatment of high-risk patients.”
Why the Disparity in Post-Mastectomy Care?
In their study in Cancer, Dr. Smith and colleagues found that the following factors were associated with a lower likelihood of receiving post-mastectomy radiation:
Falling on the lower spectrum of high risk (fewer positive nodes or smaller tumors).
Age 80 or older.
Having ductal rather than lobular breast cancer.
Having larger tumors not growing into the chest wall or skin vs T4 tumors.
Having not received chemotherapy.
Dr. Smith offers a few hypotheses as to why rates are better following lumpectomy than mastectomy. “Physicians have a clear understanding that radiation therapy is required after lumpectomy,” he says. “Surgeons are also adept at explaining to patients that if they choose lumpectomy, they will need to follow it with radiation. On the other hand, providers may not be fully cognizant of guideline recommendations for post-mastectomy radiation therapy when they discuss this treatment option with patients. Furthermore, patients sometimes view mastectomy as a means to avoid radiation therapy.”
Beyond the patient and provider factors that affect post-mastectomy radiation therapy and practice (Table 2), Dr. Smith says that post-mastectomy radiation was not thought to improve outcomes significantly until the mid-to-late 90s. “We may still be in the phase of trying to engrain the importance of this change within the prevailing medical culture.” In addition, patients may have high-risk breast cancer because they neglected it to a certain extent or were unable to access screening, which could suggest that they may not be able to access radiation therapy.
Some patients may also be too ill to receive radiation therapy. “However, when we looked at a healthier population of women aged 66 to 69 with relatively few or no comorbid illnesses, 35% were not receiving post-mastectomy radiation therapy,” explains Dr. Smith. “I’m not sure comorbid illness can account for the entire phenomenon. There is a chance that some providers still have a bias against radiation therapy, or they may be unaware that it has been shown to be effective in high-risk patients.”
Making Improvements in Post-Mastectomy Therapy
Unlike with lumpectomy, no comparable quality metric exists for the use of radiation therapy for high-risk breast cancer patients. “A quality metric stating that radiation therapy be given after mastectomy for women with stage III breast cancer needs to be added by organizations that study quality of care,” says Dr. Smith. “Compliance with this metric should then be tracked. The hope is that this metric would become part of an institution’s accreditation process. It’s likely that there will be financial incentives to comply with quality metrics. It seems clear from the data and the fact that this is a guideline recommendation that this would be a quality metric worth promoting. If it were to become a quality metric, it’s certainly plausible that compliance with guideline recommendations for post-mastectomy radiation would improve.”
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