Our last blog provided a brief overview of accelerated partial breast irradiation (APBI) and brachytherapy, including descriptions of the Mammosite (See photo, top), Contura Multi-Lumen Balloon (See photo, middle) and SAVI Applicator (See photo, bottom) brachytherapy systems.
For women with early-stage breast cancer, brachytherapy may be more convenient than external beam whole breast irradiation, but is it as effective? How does it compare in terms of side effects?
The MD Anderson study
A study presented at the 2011 San Antonio Breast Cancer Symposium in December addressed these questions. The results were covered by The New York Times, Medical News Today, Dr. Susan Love's blog, HealthImaging.com and The NCI Bulletin.
In the study, researchers from MD Anderson reviewed Medicare claims of over 130,000 women over age 66 who were diagnosed with breast cancer between 2000 and 2007. APBI use increased from 1% of patients in 2000 to 13% in 2007.
Four percent of the women treated with brachtherapy eventually had a mastectomy, compared to 2.2 percent of the women who were treated with whole breast irradiation. In addition, the risk of side effects, such as infection, breast pain, fat necrosis and rib fracture was higher in the brachytherapy group.
There are, however, some limitations to the study.
As reported by the NCI Bulletin on January 10, one of the lead researchers noted that the study was observational, had limited follow-up time and did not control for hormone therapy use.
According to HealthImaging.com (Dec. 15), other experts argue that Medicare records are an "inherently inaccurate database" in terms of tumor characteristics and prognostic markers. They note that women receiving APBI may have been "sicker" and therefore not candidates for several weeks of whole breast radiation.
They also question how side effects were measured and defined.
Moreover, they note that APBI delivery methods have improved since 2007.
There's also a question of whether a 4 percent mastectomy rate is clinically significant compared to a 2.2 percent rate. In her blog from the symposium, Dr. Susan Love made the following comment on the study,
"This sounded worrisome, until they said that the risk of needing a subsequent mastectomy was 4% with partial breast radiation and 2% in women with 6-week radiation. We will need to wait for the randomized data to mature to answer this question. At this point I don’t see a significant difference."Additional research is ongoing
A large, randomized, phase III study sponsored by the National Cancer Institute comparing whole breast irradiation to APBI is currently underway. (Link to study protocol.) About half the women in the study will be treated with external whole beam irradiation. The other half will receive accelerated partial breast irradiation, either via one of two brachytherapy methods, or by 3-D conformal radiotherapy, an external form of APBI.
According to Dr. Thomas Julian, associate director of medical affairs for the National Surgical Adjuvant Breast and Bowel Project (NSABP), as quoted in the NCI Cancer Bulletin on January 10,
"We would certainly like to see people waiting for the trial data before broad implementation, but there is more than 10 years of partial-breast irradiation experience that shows that in low-risk women the recurrence outcomes are fairly good, comparable to what happens in low-risk patients who were treated with whole breast radiation. However, for higher-risk women, the data are just not available."Patient selection
How are patients selected for brachytherapy? Part 3 of this blog will highlight a recent study in the Journal of the National Cancer Institute which looked at the use of brachytherapy in different patient populations. Please stay tuned.