Women diagnosed with early-stage breast cancer who have lumpectomy usually have radiation therapy after surgery. Radiation therapy after lumpectomy lowers the risk of the breast cancer coming back (recurrence) and makes lumpectomy as effective as mastectomy. Radiation can be delivered to the entire breast (called whole-breast irradiation) or to just the area of the breast where the cancer was (called partial-breast irradiation).
The study reviewed here compared partial-breast irradiation to whole-breast irradiation and found no differences in survival or the risk of the cancer spreading to other parts of the body (metastatic recurrence). Still, there was a difference in the risk of the cancer coming back in the same breast or the lymph nodes near the same breast (locoregional recurrence). The results were presented at the 2009 American Society of Clinical Oncology (ASCO) Annual Meeting.
The researchers analyzed the results from three earlier studies. All of the 1,140 women in the studies had been diagnosed with early-stage breast cancer and had had lumpectomy followed by radiation therapy. Some of the women got whole-breast irradiation and some received partial-breast irradiation. The women who got partial-breast irradiation:
compared to women who had whole-breast irradiation.
The researchers explained that the higher risk of the cancer coming back in the same breast or lymph nodes near the same breast could have been because the original studies had a flaw in their design. More research is needed to see if this higher risk of locoregional recurrence continues to happen with partial-breast irradiation.
Whole-breast irradiation is the most common type of radiation therapy used to treat breast cancer. Whole-breast irradiation is delivered by an external bream of radiation. A large machine, called a linear accelerator, aims a beam of high-energy radiation at the breast area affected by the cancer. Whole-breast irradiation usually is given 5 days a week for 5 to 7 weeks as an outpatient procedure.
External partial-breast irradiation is a less common type of radiation therapy that focuses only on the area where the cancer was, meaning the rest of the breast area receives little or no radiation. Studies are comparing the benefits of external partial-breast irradiation to whole-breast irradiation.
Most partial-breast irradiation is delivered internally, rather than externally. Internal partial-breast irradiation, also called brachytherapy, uses small pieces of radioactive material ("seeds") that are placed in small tubes or catheters around the area where the cancer was. The area that's near the site of the original cancer is the area that is at highest risk of recurrence. Brachytherapy usually is given for 5 to 7 days, a much shorter time than external radiation. Brachytherapy systems require a skilled and experienced medical team and available radioactive materials.
Partial-breast irradiation currently is used less frequently than whole-breast irradiation. Still, internal partial-breast irradiation is appealing to many women because the treatment time is shorter (1 week versus 5 to 7 weeks). If radiation therapy is part of your treatment plan, it may seem easier to rearrange your daily routine for 1 week compared to almost 2 months. Internal partial-breast irradiation also can be more convenient for people who live far away from a treatment center. This study gives doctors the confidence that partial-breast irradiation provides benefits that are mostly comparable to whole-breast irradiation.
If surgery and radiation therapy are part of your treatment plan, you and your doctor will talk about which surgery and which radiation therapy method makes the most sense for you. For some women, external whole-breast irradiation is the best approach. For others, internal partial-breast irradiation therapy may be a good option. The Breastcancer.org Radiation Therapy section offers more information, including how radiation works to treat breast cancer and what to expect during and after treatment.
ORLANDO, June 4 (MedPage Today) -- Partial-breast irradiation offers early-stage breast cancer patients equivalent survival and protection against metastasis compared with whole-breast treatment, results of a meta-analysis indicate.
However, an increased likelihood of locoregional recurrence with partial-breast irradiation requires further study to define the risk and potential consequences, Davide Mauri, M.D., said at the American Society of Clinical Oncology meeting.
"Partial-breast irradiation may be safe and feasible for women with early-stage breast cancer because it does not jeopardize patient survival or the risk of metastasis," said Dr. Mauri, of General Hospital of Lamia, Greece.
Partial-breast irradiation involves substantially less time commitment and radiation exposure compared with whole-breast irradiation, which has been the standard for patients with early-stage breast cancer.
The principal benefits of adjuvant whole-breast irradiation pertain to the dose delivered to breast tissue surrounding the tumor bed, said Dr. Mauri.
As a result, targeted-fields partial-breast irradiation might offer an effective alternative to whole-breast irradiation. Whether the partial-breast irradiation involves tradeoffs related to survival and metastasis had not been examined.
To assess the relative risks and benefits of the two treatment modalities, Dr. Mauri and colleagues performed a meta-analysis of three randomized clinical trials comparing whole-breast and partial-breast irradiation. The trials involved a total of 1,140 patients.
The analysis revealed similar survival with the two forms of irradiation, reflected in a hazard ratio of 0.912.
"For each patient who will die with whole-breast radiation treatment, one patient will die with the partial-breast irradiation technique," said Dr. Mauri.
However, the analysis also revealed a significantly increased risk of recurrence in the same breast (OR 2.15, P=0.001) or associated lymph nodes (OR 3.43, P<0.0001) in women treated with partial-breast irradiation.
The risk of distant metastasis or supraclavicular recurrence did not differ between treatment groups.
Dr. Mauri suggested, however, that the increased recurrence risk reflected a fault in the design of two of the three trials analyzed.
Those trials used a standardized radiation treatment field, irrespective of tumor size. As a result, the radiation might have covered an inadequate area and missed areas of residual tumor, predisposing the patients to an increased risk of recurrence.
"This explanation makes the finding of increased local recurrences less concerning," he said.
Although partial-breast irradiation improves adherence to therapy, the increased risk of locoregional recurrence deserves closer examination to determine whether physicians and patients should be considered, Jennifer Obel, M.D., said at a press briefing.
"I think before we say from a meta-analysis that this should be the next standard of care for women with early breast cancer, I would like to tell you that there are many randomized studies, sponsored by major cooperative groups, randomizing women to partial-breast irradiation versus whole breast irradiation," said Dr. Obel, of NorthShore University HealthSystem in Evanston, Ill.
"Those studies will be forthcoming in the next few years," she said. "We probably should await those until we make our decision."
Dr. Mauri and colleagues reported no disclosures.
Dr. Obel disclosed a relationship with Onyx Pharmaceuticals.
Primary source: Journal of Clinical Oncology Source reference: Valachis A, et al "Partial breast irradiation or whole breast radiotherapy for early breast cancer: a meta-analysis of randomized controlled trials" J Clin Oncol 27(15 suppl): Abstract CRA532.
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