Triple negative breast cancer is the most aggressive subtype of breast cancer, characterized by a lack of targeted therapy. Neoadjuvant chemotherapy is used to understand disease biology; patients who attain a complete pathologic response have improved outcomes compared to those who have residual disease. Locoregional treatment options remain similar to other types of breast cancer. Further research to identify druggable targets is ongoing and new agents appear to be on the horizon.
Triple negative, radiation therapy, neoadjuvant chemotherapy
Tara Sanft and Meena S Moran have nothing to disclose in relation to this article. No funding was received in the publication of this article. This article is a short opinion piece and has not been submitted to external peer reviewers.
This article is published under the Creative Commons Attribution Noncommercial License, which permits any non-commercial use, distribution, adaptation and reproduction provided the original author(s) and source are given appropriate credit.
April 04, 2016 Accepted
April 26, 2016
Meena S Moran, Therapeutic Radiology, Yale School of Medicine, P.O. Box 208040, New Haven CT 06520-8040, US. E: firstname.lastname@example.org
Triple negative breast cancer (TNBC) is a subtype of breast cancer that comprises 15–20% of all breast cancer cases and is characterized by aggressive clinical features.1 Compared to estrogen receptor (ER)-positive cancers, it carries an increased risk for relapse within five years of diagnosis, increased propensity for spread to viscera like lungs and brain, and a lower incidence for bony metastases. TNBC is more common in younger women (<50 years old), African Americans, and those with BRCA1 germline mutations. Although only 10–20% of all TNBCs harbor BRCA1 mutations, TNBC is the subtype seen in 75% of BRCA1 carriers who develop cancer. Because TNBC is the dominant subtype in BRCA1 carriers, genetic testing is recommended for all cases of TNBC in women younger than 60 years. The results, if positive, have implications in choices of local treatment, including a propensity to select ipsilateral and prophylactic contralateral mastectomies over a breast conserving treatment approach.
By definition, treatment options for these tumors do not include endocrine or human epidermal growth factor receptor 2 (HER2)- directed therapies, thus existing combinations of cytotoxic agents are the backbone of systemic treatment for TNBC. Delivering therapy in the neoadjuvant setting provides the added benefit of obtaining prognostic information, since patients without pathologic complete response (pCR) fare significantly worse than those with pCR. For example, TNBC with pCR is reported to achieve three-year overall survival (OS) of 94%, similar to survival outcomes of non-TNBC (p=0.24), compared to three-year overall survival (OS) of 68% for patients with residual disease, which is significantly worse than non-TNBC subtypes (p<0.0001).1 Identifying those who benefit from neoadjuvant therapy is important not only for optimization of regimens that result in a pCR, but to further identify or elucidate common characteristics of subgroups who do not respond and develop novel approaches to this subgroup.
The recent reports at the 2015 San Antonio Breast Cancer Symposium (SABCS) lend some insight into translating pCR into survival outcomes. The German GeoparSixto study reported improved disease free survival (DFS) in TNBC patients receiving neoadjuvant platinum-based chemotherapy compared to standard chemotherapy alone.2Of TNBC patients treated with carboplatin, 35-month DFS was 85.8% compared to 76.1% in the control arm (hazard ratio [HR] 0.56 p=0.035). Though results came from a subset analysis of the TNBC subtype population, the findings are concordant with initial findings of improved pCR rates with platinum-based chemotherapy. The authors concluded the results support the use of platinum agents in neoadjuvant regimens for TNBC. Though additional subset analysis of TNBC patients with and without BRCA germline mutations suggested that DFS benefit was higher in those with wild-type BRCA status, these data should be considered hypothesis generating as the number of women with BRCA mutations was small (n=50) and this finding conflicts with previous studies that found platinum compounds were not active in BRCA wild-type patients.
Similarly, the CALGB 40603 study reported statistically significant higher rates of pCR in TNBC who received neoadjuvant platinum-based chemotherapy.3 In contrast, however, the secondary endpoints of event-free survival (EFS) and OS presented at SABCS 2015 showed that the presence of pCR predicted improved EFS and OS, regardless of chemotherapy arm.4 The authors acknowledged the study was underpowered to detect a significant advantage when comparing carboplatin or bevacizumab with standard neoadjuvant chemotherapy. Additional data are necessary beforeneoadjuvant platinum-based therapy can be considered standard treatment for TNBC. Current investigations of the homologous recombination deficiency (HRD) assay, a marker of genomic instability, may allow for further prediction of patients who respond to platinum-based chemotherapy.5
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Triple negative, radiation therapy, neoadjuvant chemotherapy