SAN ANTONIO – Accelerated partial-breast brachytherapy, delivered as part of breast-conserving therapy for early breast cancer, was associated with twice the mastectomy rate when compared with standard whole-breast irradiation in a large study.
Moreover, accelerated partial-breast brachytherapy entailed substantially higher rates of both acute and late complications, Dr. Benjamin D. Smith said in a presentation of the study findings at the San Antonio Breast Cancer Symposium.
Investigators reviewed Medicare claims data for all 130,535 beneficiaries whose early breast cancer was treated with lumpectomy followed by adjuvant radiation during 2000-2007. The use of accelerated partial-breast brachytherapy in this population rose from less than 1% in 2000 to 13% in 2007.
The incidence of mastectomy during 5 years of follow-up was 4% in 7,291 brachytherapy recipients, compared with 2% after whole breast irradiation (P less than .001). Upon adjustment for the brachytherapy recipients’ older average age, more comorbid conditions, and lesser rate of positive axillary lymph nodes, brachytherapy was associated with a 2.2-fold increased risk of losing the treated breast within 5 years, reported Dr. Smith, a radiation oncologist at the University of Texas M.D. Anderson Cancer Center, Houston.
"When we adjusted for various clinical and sociodemographic factors, to our surprise brachytherapy was the variable that had the strongest correlation with the risk of subsequent mastectomy," he noted.
Partial-breast brachytherapy was also associated with significantly higher rates of postoperative wound infection and acute noninfectious complications as well as increased 5-year rates of fat necrosis and breast pain. Fat necrosis is considered a marker of tissue injury caused by surgery and/or radiotherapy.
Within 1 year of breast cancer diagnosis, infectious complications involving breast or surrounding skin or soft tissues occurred in 16% of women treated with brachytherapy vs. 10% of those who received standard whole breast radiation.
Noninfectious complications including surgical wound breakdown, postoperative bleeding, or seroma formation were twice as common with brachytherapy at 16% and 8%, respectively.
Five-year rates of fat necrosis (9% vs. 4%) and breast pain (15% vs. 12%) also were higher with brachytherapy.
Accelerated partial-breast brachytherapy was developed to address the shortcomings of whole-breast irradiation, the historic standard of care, which entails up to 7 weeks of daily Monday-through-Friday treatment. Whole-breast irradiation is inconvenient. Indeed, it’s such a hardship, especially for patients in rural areas distant from a radiotherapy center, that some women opt for mastectomy as a matter of convenience. Moreover, 15%-30% of women who undergo lumpectomy forgo prescribed radiation therapy, placing themselves at increased risk of local recurrence.
Accelerated partial-breast brachytherapy may improve patient compliance with radiotherapy. It shortens the treatment course to 1 week. It entails temporary placement of radioactive beads within the breast via a catheter system. This method delivers radiation only to breast tissue immediately adjacent to the lumpectomy. This technique is but one of several forms of partial breast irradiation, however; the new findings don’t apply to 3-D external beam radiation, for example.
Dr. Benjamin D.Smith
Accelerated partial breast brachytherapy has boomed in popularity in recent years, especially in community practice. But these new data may put the brakes on that trend.
"This study has changed the way that I think about these two different treatment options, and it’s changed the way I practice," Dr. Smith said in an interview.
Dr. Jennifer A. Ligibel, who chaired a press conference where Dr. Smith presented his findings, said the study carries an important message: "Although observational data using a claims database are no substitute for a randomized trial with long-term follow-up, what we see in this study is that this technique was not as effective and it was also associated with a lot more complications. So if your argument in using this is that it’s sparing patients from additional problems, we’re not seeing that in this study.
"I think this study really does give pause to the incorporation of accelerated partial-breast brachytherapy into routine clinical practice. These results should make people wait for the results of the ongoing randomized trials before they offer this as a standard procedure for their patients," added Dr. Ligibel of Dana-Farber Cancer Center, Boston.
The major randomized trial underway is the National Surgical Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 study. The NSABP B-39/RTOG 0413 trial has enrolled 4,000 of a planned 4,500 patients with early breast cancer. The emphasis is on patients under age 50, since they have a higher local recurrence risk than older women. Participants are randomized to whole-breast radiation or various forms of partial breast irradiation after lumpectomy. Mature results aren’t expected until mid-decade.