Recent Breast Cancer Studies

Posted on: March 4, 2016

Dr. Tiffany Svahn is a breast cancer specialist in the San Francisco Bay Area

Written by Dr. Tiffany Svahn, Breast Cancer Specialist

At the San Antonio Breast Cancer Symposium held in December 2015, there were some important data presented that directly affect our treatment of patients in the clinic.  In the realm of local therapy, there were two breast cancer studies out of the Netherlands that have important implications.  Both studies were large registry studies rather than randomized trials, so all results must be interpreted with caution, but they both had very interesting findings.

The first Danish study looked at outcomes in women treated with breast conservation (BC) versus mastectomy for early stage breast cancer (stages I-III).

The data of 37,207 women were analyzed.  Interestingly, the 10-year overall survival was higher for women who had BC (76.8%) versus women who were treated with mastectomy (59.7%).  Similarly, the 10-year disease-free survival was higher for BC versus mastectomy (83.6% vs 81.5%).  In addition, rates both distant metastatic disease and regional recurrence were higher in mastectomy patients, but there was no difference in local recurrence.  All differences were statistically significant.  Some experts postulate that perhaps it was the addition of radiation therapy in breast conservation that accounts for the improved outcomes with breast conservation over mastectomy.  There has been a recent rise in increased bilateral mastectomies in women with early stage breast cancer who would have likely done just as well with breast conservation.  Many women choose to have bilateral mastectomies because they incorrectly believe that it will improve their outcomes.  It is important for clinicians to educate patients that choosing bilateral mastectomies does not change the risk of distant metastatic disease and thus overall survival, and this study indicates that perhaps mastectomy may even lead to worse outcomes. The second Danish study looked at margin width and re-excision at the time of lumpectomy.  Data from 11,900 women were analyzed, with a median follow-up of 4.9 years.  Not surprisingly, women who had a final positive margin had an increased risk of ipsilateral breast tumor recurrence (IBTR) by 2.5-fold.  However, there was no difference in IBTR if margins were 0-1 mm vs 2-4 mm vs > 5 mm, supporting the concept of “no tumor on ink” is a negative margin.  11% of the women had re-excision, and of those women, 20% had residual disease at the time of re-excision.  Residual disease at the time of re-excision led to a 3-fold higher risk of IBTR even if final margins were negative.  No difference was seen in overall survival.

There were two important breast cancer studies presented that pertain to systemic treatment of early stage breast cancer.

IBIS-II is a randomized trial looking at outcomes of 2980 postmenopausal women with estrogen receptor-positive ductal carcinoma in situ (DCIS) who were randomized to receive 5 years of either tamoxifen (the current standard-of-care) or anastrozole (an aromatase inhibitor (AI), widely used for the treatment of invasive breast cancer).  Earlier in 2015, the results of NSABP-B35 showed better outcomes for aromatase inhibitors over tamoxifen for DCIS, specifically in women less than 60 years of age.  In this IBIS-II trial, with a median follow-up of 7.2 years, there was a trend toward lower invasive recurrence with AI vs tamoxifen (6.6% vs 7.4%).  There was no difference in overall survival, and there was a decrease in both endometrial and ovarian cancers seen with the use of AI.  Tamoxifen is known to increase the risk of endometrial cancer, and appears that AIs may be protective against ovarian cancer. The Create-X trial addressed an important issue in the use of adjuvant capecitabine (Xeloda) chemotherapy in women who had been treated with neoadjuvant chemotherapy and did not achieve a complete pathologic response.  This was a phase III randomized trial looking at 910 women with HER2-negative breast cancer, with a median follow-up of two years.  All tumors were either node-positive or greater than 5 cm.  The use of 8 cycles of adjuvant capecitabine chemotherapy led to a 31% decreased risk of recurrence.  The disease-free survival was 87.3% vs 80.5%, and the overall survival was 96.2% vs 93.9% (not statistically significant).  The study was discontinued early because it met its primary endpoint of disease-free survival.  This is the first data we have that supports the use adjuvant chemotherapy in patients who received neoadjuvant chemotherapy and did not achieve a complete pathologic response.  This is particularly important for women with triple-negative breast cancer, as they do not have the option of receiving targeted treatment (anti-estrogen therapy for ER+ disease, and trastuzumab for HER2+ disease) that will benefit them in the adjuvant setting. As illustrated in the breast cancer studies discussed above, the outcomes for women with early stage breast cancer are excellent, and continue to improve.   Tags: