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Pooled analysis showed excellent outcomes after surgery, APBI
SAN FRANCISCO — Patients who underwent breast-conserving surgery and accelerated partial-breast irradiation experienced excellent outcomes, according to a large pooled analysis.
Researchers conducted the study to determine whether American Society of Therapeutic Radiation and Oncology (ASTRO) consensus panel recommendations regarding the use of accelerated partial-breast irradiation (APBI) were associated with significantly different outcomes.
In the study, John Ben Wilkinson, MD, of the department of radiation oncology at Oakland University’s William Beaumont School of Medicine in Royal Oak, Mich., and colleagues evaluated 2,127 patients with early-stage breast cancer.
The cohort included 678 patients who were treated at William Beaumont Hospital and 1,449 who were treated as part of the American Society of Breast Surgeons MammoSite registry trial.
Three forms of APBI were used at William Beaumont Hospital: interstitial (n=221), balloon-based (n=255) and 3-D conformal radiation therapy (n=206). All patients in the registry trial underwent balloon-based brachytherapy.
The researchers identified 1,813 patients with complete coding necessary to be stratified in one of three ASTRO consensus panel assignment groups: suitable (n=661, 36.5%), cautionary (n=850, 46.9%) and unsuitable (n=302, 16.7%). Researchers analyzed tumor characteristics and clinical outcomes according to each group.
Median patient age was 65 years, and median tumor size was 10 mm.
After 5 years, the overall rate of ipsilateral breast tumor recurrence was 2.8%, the rate of regional nodal failure was 0.6% and the rate of distant metastasis was 1.6%, according to researchers.
When analyzed by consensus panel group, there was no statistically significant difference in the rate of ipsilateral breast tumor recurrence between patients in the suitable (2.5%), cautionary (3.3%) or unsuitable (4.6%) groups (P=.20).
The higher rates of ipsilateral breast tumor recurrence among patients in the cautionary and unsuitable groups were due to increased elsewhere failures and new primaries (P=.04) rather than true recurrences (1.1%-1.2% for all groups, P=.94), according to researchers.
Rates of distant metastasis were 0.7% among patients in the suitable group, 3.3% for patients in the cautionary group and 3.6% for patients in the unsuitable group (P=.01).
Cause-specific survival was the same for all patient categories (98%-98.6% in all groups, P=.47), study results showed.
Although the analysis showed excellent outcomes after breast-conserving surgery and APBI, the current ASTRO consensus panel guidelines did not adequately differentiate patients who are at increased risk for ipsilateral breast tumor recurrence or tumor bed failure, the researchers said.
“At the present time, it is unclear whether clinical and pathological risk factors listed in the [consensus panel] groups predict for a risk for ipsilateral breast tumor recurrence following APBI alone or if women with particular factors are at risk for locoregional recurrence regardless of the form of adjuvant radiotherapy,” Wilkinson and colleagues wrote.
ASTRO should consider revising its recommendations using recently published data that demonstrate lower rates of ipsilateral breast tumor recurrence for many clinical and pathologic factors currently used to differentiate patients, the researchers said.
For more information:
Wilkinson JB. Abstract #145. Presented at: 2012 Breast Cancer Symposium; Sept. 13-15, 2012; San Francisco.
Disclosure: Wilkinson reports no relevant financial disclosures.
Perspective
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Given that APBI is increasingly offered outside of a clinical trial as an alternative to whole-breast irradiation, it is encouraging to note that excellent outcomes were seen after breast-conserving surgery and APBI in this large pooled analysis of patients treated with APBI. Although the study had some limitations, the current ASTRO consensus panel guidelines did not appear to significantly differentiate which patients were at increased risk of ipsilateral breast tumor recurrence or tumor bed failure. These findings support the use of APBI in select individuals with early-stage breast cancer and may be useful in refining the consensus panel guidelines pending long-term follow-up from phase 3 trials.