Most of us are familiar with the statistics: One in 35 women die from breast cancer each year. It is the second leading cause of cancer-related death in women. In 2011, 230,480 cases of invasive breast cancer and 57,650 cases of noninvasive breast cancer were diagnosed in women, according to the American Cancer Society.1 In light of these statistics, if you treat women in your practice, some of your patients are likely to have or have survived breast cancer. Advanced practice nurses have a responsibility to not only know how to screen and move patients toward the appropriate specialists—if we are not functioning in the specialist’s role—but to also educate ourselves as well as our patients. Therefore, we must maintain our knowledge of current treatment options and follow-up.
Fairly new to the treatment options for breast cancer is partial breast irradiation (PBI). PBI delivers radiation directly to the tumor via a balloon temporarily implanted in the breast, called an afterloading catheter (ALC). This article provides a brief overview of breast radiation therapy and a more in-depth discussion of PBI using an ALC.
EVOLUTION OF BREAST CANCER RADIATION TREATMENT
Dating back more than 100 years to the mid-19th century, the radical mastectomy, or en bloc removal of the breast as performed by William Halstead, MD, has been the gold standard of care.2 However, the question became, “Does the entire breast need to be removed to effectively treat breast cancer?” In 1971, the National Surgical Adjuvant Breast and Bowel Project (NSABP) asked that question. Trial B-04 found that after 25 years there was no significant difference in survival in patients who underwent mastectomy compared with those who underwent less extensive surgery.3
The NSABP also investigated total mastectomy versus lumpectomy with clear margins versus lumpectomy plus whole breast irradiation (WBI) in trial B-06. While there was no significant difference in overall survival, 20-year follow-up showed a cumulative incidence of ipsilateral recurrence in the lumpectomy plus WBI cohort of 14.3%, whereas ipsilateral recurrence in the lumpectomy alone group was 39.2%.3,4 Therefore, the standard of care became, and still is, lumpectomy followed by WBI for invasive ductal carcinoma.
WBI VS PARTIAL BREAST IRRADIATION
Whole breast irradiation is as it says. External beam radiation is delivered to the entire affected breast, and in certain circumstances, the axillary region is also included. This typically encompasses one treatment a day for 5 consecutive days over 5 to 6 weeks. Hypofractionation, administering a larger dose per day over a shorter period of time, has been investigated and found to be as effective as conventional schedules in diminishing the possibility of recurrence.5,6 One such study from Ontario, Canada, reviewed the 10-year local recurrence and cosmesis in women with invasive breast cancer who underwent breast-conservation surgery in which pathology showed clear margins and axillary lymph nodes were negative.7 After random assignment, the women received either 5 weeks of radiotherapy to a dose of 50 Gray (5,000 cGy) versus 3 weeks of radiotherapy to 42.5 Gray (4,250 cGy). Whelan and colleagues found the 5-week cohort had a 10-year recurrence rate of 6.7% and good cosmesis in 71.3% of patients compared with 10-year recurrence rate of 6.2% and good cosmesis in 69.8% of patients in the 3-week cohort.8
Time has shown that most treatment failures or disease recurrences occur in the vicinity of the original tumor.7,9 In fact, Polgár and colleagues point out that among women with a nonlobular cancer, stage T1N0-N1mi (single micrometastasis), no extensive intraductal component, and negative surgical margins who did not undergo radiation and recurred, 80% of cases were in the original tumor bed area.10 Therefore, a major value to radiating the breast would be to eradicate residual disease in the tumor bed rather than occult disease elsewhere.
Treating only the affected breast tissue was not only an intriguing idea, but a logical hypothesis. Emerging patterns, however, pointed to selection of a specific population for partial breast irradiation. For example, recurrence after 10 years appeared to be related to margin clearance as well as tumor burden in the area of the margin. Reports indicated that local failure was associated with younger age at diagnosis, no tamoxifen use, and negative estrogen receptor status.11
Partial breast irradiation can be accomplished via external beam radiation or brachytherapy, which is the introduction of a radioactive source into a cavity or body area. Brachytherapy is administered via low-dose-rate (LDR) or high-dose-rate (HDR) therapy. Low-dose rate involves implanting a sealed radioactive source in the breast tissue where it remains for the entire treatment period (eg, 4 days). This approach requires hospitalization to maintain radiation precautions and significant skill on the part of the radiation oncologists and physics department, as there are typically multiple catheters placed to house the radiation sources.
High-dose rate therapy involves placing an apparatus, such as an afterloading catheter, that houses the radioactive source; but, the radioactive source is in the catheter for a short period of time (7 to 15 minutes, twice a day for 4 or 5 days). This approach can be managed on an outpatient basis because the source is removed after each treatment, thus radiation precautions are needed only during the time the radioactive source is in the ALC. Several studies found that partial breast radiation HDR brachytherapy had similar outcomes (contralateral failure, excellent cosmesis, ipsilateral failure, relapse-free survival) compared with WBI at 5, 7, and 10 years, in a defined population of women.7,10,12,13