Shorter Course of Radiation Might Be Just as Effective with Early Breast Cancer
Key Words
Breast cancer, radiation therapy. (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary.)
Summary
Women with low-risk, early stage breast cancer who received a shorter, more intense course of radiation therapy after lumpectomy (breast-conserving surgery) had the same risk of disease recurrence in the breast and equivalent cosmetic outcomes as women who received a longer, more standard course of radiation therapy.
Source
Journal of the National Cancer Institute, Aug. 7 2002 (see the journal abstract)
(J Natl Cancer Inst. 2002 Aug 7;94(15):1143-50)
Updated results were presented at the American Society for Therapeutic Radiation and Oncology (ASTRO) annual meeting in Boston, September 22, 2008.
Background
While radiation therapy after lumpectomy (also known as breast-conserving surgery) has been shown to significantly decrease the likelihood of a local recurrence (cancer returning in the same breast) and increase survival, the amount of radiation that is given and the number of days of treatment have not been standardized across hospitals.
One radiation therapy schedule that has been used widely in clinical trials and adopted by many doctors in the United States is a ‘long’ course of 50 Gray (Gy: a measurement of radiation exposure) broken up into 25 fractions to the whole breast, which are delivered five days a week over seven weeks. However, some hospitals in the United Kingdom and Canada use a shorter, more intensive treatment schedule based on the hypothesis that this would be equally effective and more convenient for patients, who would not have to return for as many treatment sessions.
To compare whether longer and shorter courses of radiation therapy are equally effective at preventing local recurrence and to learn whether they provide comparable cosmetic results (whether the treated breast looks similar to the untreated breast), a group of Canadian investigators designed a randomized clinical trial testing 50 Gy in 25 fractions over 35 days against 42.5 Gy in 16 fractions over 22 days.
The study’s lead author is Timothy J. Whelan B.M., B.Ch., M.Sc., of the Juravinski Cancer Centre and McMaster University in Hamilton, Ontario, Canada.
The Study
The study, conducted at 10 cancer centers in Canada, involved 1,234 women who were randomly assigned to receive either the standard 25-session course of radiation therapy or the shorter 16-session course. Women assigned to the shorter course received a larger dose of radiation per treatment session than those on the standard course. All of the women had been diagnosed with breast cancer that had not spread to the lymph nodes and had had a lumpectomy (surgery to remove the cancer but preserve the breast).
Some women also received chemotherapy or hormone therapy according to the treatment guidelines of the cancer center at which they were treated. After completing their assigned course of radiation therapy, all women returned for follow-up visits every six months for the first five years, then once a year thereafter. The researchers performed mammograms of both breasts six months after the end of radiation therapy, then once a year after the first follow-up visit.
The cosmetic appearance of the breast that received radiation was assessed before treatment, and at three and five years after enrollment in the trial, by a nurse specially trained in a specific breast-appearance rating system.
Results from the trial were presented at the 2000 annual meeting of the American Society of Clinical Oncology, and subsequently published in the Aug. 7, 2002, Journal of the National Cancer Institute. The updated results described here were presented at the 2008 annual meeting of the American Society for Therapeutic Radiation and Oncology.
Results
After five years, rates of survival without local recurrence were almost identical in the two groups (96.8 percent for women receiving the standard course versus 97.2 percent for women receiving the short course). After ten years, the risk of local recurrence remained approximately the same between the two groups: 6.7 percent for women receiving the standard course versus 6.2 percent of women receiving the short course.
In addition, after five years, similar numbers of women in both treatment groups (77.4 percent of those receiving the standard course and 76.8 percent of those who received the short course) had excellent or good cosmetic outcomes, avoiding these adverse affects. No difference between the groups was observed even after 10 years -- 71 percent of women receiving the standard course had excellent or good cosmetic outcomes compared with 70 percent of women receiving the short course.
A small number of women in both groups had late radiation damage to the skin or underlying tissue after ten years of follow-up. In the group receiving the standard course, 3 percent had late damage to the skin compared to 6 percent in the group receiving the short course. In the group receiving the standard course, 4 percent had late damage to the underlying tissue compared to 8 percent in the group receiving the short course. These differences were not statistically significant (that is, they could be due to chance).
Limitations
Most of the patients enrolled in the study had a low risk of disease recurrence, which means a shorter course might not be best for women with higher-risk breast cancer. For example, the study excluded patients whose cancer was not entirely removed by lumpectomy. Only 11 percent of patients in the study received adjuvant (additional) chemotherapy as well as radiation therapy.
Also excluded were patients with large breasts, who are more likely to experience adverse cosmetic effects of radiation therapy such as swelling, scarring, and thickening of the breast tissue.
Doctors should not apply the results of this study to patients with higher-risk disease, explains Kevin Camphausen, M.D., chief of the National Cancer Institute’s Radiation Oncology Branch. The patients in this trial were highly selected for low risk disease, “If people see this data and start extrapolating it to less-selected patients, then that’s a problem.”
Comments
For women with early stage, low-risk breast cancer, “[The shorter course of radiation therapy] was associated with excellent long-term local control and limited late morbidity, similar to that seen with conventional fractionation for whole breast irradiation. Given the benefits of convenience and cost, such an approach should be considered for women with early breast cancer,” conclude the authors.
Follow-up data from an additional five years or more (for a total of at least 15 years of follow-up) would be valuable, concludes Camphausen, because low-risk early stage breast cancer may take longer to recur.
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