Abstract BL2: Changing paradigms in the local therapy of breast cancer: Making less more

Abstract

Abstract The ability of surgery to cure breast cancer has not changed over time. What has changed is that the cancers seen in the screening era are smaller and have fewer nodal metastases, making them more amenable to surgical cure. Only 25% of patients enrolled in the landmark NSABP B-06 trial had cT1N0 disease compared to 80% of those enrolled in NSABP B32, which began 15 years later. At the same time, improved systemic therapy options and a better understanding of tumor biology have led to greater success in treating micrometastatic disease. Systemic therapy is now widespread for early-stage breast cancers and often for longer durations with anti-HER2 therapy given for 12 months and endocrine therapy for 5-10 years. The progressive addition of therapies has increased the burden of treatment for patients at the same time it has improved outcomes. The beneficial effect of systemic therapy on local control and the lower disease burden seen today offer the opportunity to decrease the morbidity of surgery without compromising outcomes. The ACOSOG Z011 trial, now with follow-up of 10 years, demonstrated no difference in locoregional recurrence or survival among patients with metastases in 1–2 sentinel nodes after sentinel node biopsy alone or axillary dissection (ALND) when treated with breast-conserving surgery (BCS) and whole breast irradiation (RT). In 9/2010 we began prospectively utilizing Z11 eligibility criteria in patients with cT1-2 N0 cancers undergoing breast conservation with ALND reserved for those with >2 nodal metastases or gross extracapsular extension. Of the initial 723 consecutive, unselected patients, ALND was avoided in 84%. At a mean follow-up of 33 months (12–68), there were no isolated axillary recurrences. The 5-year Kaplan Meier rate of any nodal recurrence was 98% (95% CI 96–99). In the 251 patients considered “high risk” based on triple negative, HER2+, or age <50 years or a combination of these factors, ALND was required in 15.5% vs 15.9% of postmenopausal, ER+ patients (p=.89). The same principles led us to address the issue of what constitutes an optimal negative margin in women with invasive breast cancer undergoing BCS and RT. After a metaanalysis and review of other relevant literature, an SSO-ASTRO sponsored consensus committee concluded that evidence did not support routinely obtaining margins more widely clear than no ink on tumor, and that adherence to this recommendation, disseminated in late 2013 and published 2/14, had the potential to significantly reduce the use of re-excision. Since that time, the proportion of surgeons in a population-based sample endorsing no ink on tumor as an adequate margin rose to over 60%, compared to 11% in a similar survey conducted in 2006–7. This change in attitude has translated into a reduction in the use of additional surgery, both re-excision and mastectomy after initial lumpectomy. In a SEER sample from 2013–15, this resulted in a 9% absolute increase in the use of BCS during the study period. The use of neoadjuvant therapy offers further opportunities to decrease the morbidity of surgery and individualize local therapy in the future. Citation Format: Morrow M. Changing paradigms in the local therapy of breast cancer: Making less more [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr BL2.