Molecular Types and Neoadjuvant Chemotherapy in Patients with Breast Cancer- While Molecular Shifting is More Common in Luminal a Tumors, The Pathologic Complete Response is Most Frequently Observed in Her-2 Like Tumors

Breast cancer is the most common cancer in women in the world. The incidence of BC is increasing in the both western and Asian world of which the incidence rates are below 40 per 100,000 (Ferlay et al., 2010; Keramatinia et al., 2014) Locally advanced breast cancer makes up to 50% of the newly diagnosed breast cancers (Valero et al., 1996). NACT has become commonly used treatment in order to increase the chance of breast-conserving surgery in patients with large operable BC and render inoperable tumors resectable by downstaging of the tumor. Efficacy or unnecessary toxicity of chemotherapy can be evaluated by monitoring the dimensional changes of the tumor allowing the physician to continue the therapy. Also, the use of NACT may succeed in a pathological complete response, which correlates with prolonged periods of remission (Valero et al., 2002). Generally used NACT regimens are antracycline and taxane based therapies.

In present study, we aimed to investigate the relationship between molecular subtypes and NACT in patients with BC.

Materials and Methods
Between 2002 and 2013, 106 BC patients who received NACT for operable BC were retrospectively collected from Akdeniz University database. The patients were divided into four groups; Luminal A (ER+ and/or PR+, HER2-), luminal B (ER+ and/or PR+,HER2+), HER2-like (ER-, PR-, HER2+) and BL/TN (ER-, PR-, HER2-). The age, menopausal status, performance status, histological types, tumor (T) and nodal (N) clinical stage, hormone receptor status, Ki-67 status, grade, lymphatic invasion (LI), vascular invasion (VI), perineural invasion (PNI), NACT agents, trastuzumab as part of NACT (for the patients in whom HER2 positive) and response to NACT were imported into Statistical Package for the Social Sciences version 16.0 (SPSS 16.0). Definition of pCR is the absence of invasive cancer and in-situ cancer in the breast and axillary nodes. Staging was done according to The American Joint Committee on Cancer (AJCC) Staging Manual (7th edition) (Edge et al., 2010). ER and PR status were determined by immunhistochemistry and tumors with >10% positively stained tumor cells were classified as positive for ER and PR. HER2 status was also determined by immunhistochemistry or by fluorescence in situ hybridization (FISH) analysis. HER2-positive tumors were defined as 3+ on immunhistochemistry or as  The histological grade and nuclear grade were identified according to the modified Bloom-Richardson system. LI, VI and PNI were investigated as yes/no form. To determine the features of patients with BC, frequency analysis, two independent samples t test, one way ANOVA and chi-square tests were performed and p<0.05 was considered statistically significant.
Pathological CR in breast after NACT were as follows: 3.8% for luminal A, 35.5% for luminal B, 47.8% for HER2-like type and 61.5% for BL/TN type (p=0.001). pCR rates in axillary after NACT were as follows: 15.8% for luminal A, 38.5% for luminal B, 57.9% for HER2-like type and 693.6% for BL/TN type (p=0.022). pCR in breast and axillary was significantly higher among patients with HER2-like type than the others (p=0.018). pCR rates were shown in Table 3.

Discussion
More than 70% of patients achieve objective response (including pathological complete remission in 10-25% of cases) and many patients experience down-staging via NACT (Ferley et al., 2010).
It had been shown that luminal A group had the best disease free survival (DFS) rate while the worst DFS rate was among the HER2-like group (Najafi, 2013). It had been reported that improved survival outcomes were observed in patients with pCR compared with those with residual tumor. The association between pCR and long-term survival was weakest for luminal groups   and low grade tumors. On the other hand it was shown that association between pCR and long-term outcome was strongest in patients with aggressive breast cancer subtypes. In some studies, it was reported that pCR was not a prognostic factor in luminal A or luminal B and HER2-positive breast cancer (Wolmark et al., 2001;von Minckwitz et al., 2011;von Minckwitz et al., 2012;Cortazar et al., 2014). Some groups have reported that basal-like and HER2like tumors showed the higher pathological complete response rate than luminal groups (Parker et al., 2009;Lv et al., 2011;Khokher et al., 2013). In the present study; relatively higher pCR rates were achieved locally (axillary or breast) among luminal B, HER2-like and TN/ BL subtypes than that in previous studies. But there were relatively lower response rates in luminal A subtype than previous studies. There was no pCR in luminal A subtype for both breast and axillary region.
We found pCR rate was significantly (p=0.018) higher among patients with HER2-like (36.4%) and BL/TN (27.3%) than luminal tumors (0.0% and 21.4% for luminal A and B respectively) in both breast and axillary region. Similarly, it was reported that the pCR to NACT was significantly better among basal-like (27%) and HER2-like tumors versus luminal tumors (7%) (Carey et al., 2007).
In some studies with all stages, high grade was associated with non-luminal subtypes (Kadivar et al., 2012;Engstrøm et al., 2013). This observation is not consistent with present study. In this study luminal B group had the higher grade than the other subtypes. In the other studies the luminal type BC were well differentiated, low TNM profile tumors with a low Ki-67 proliferation index (Irigoyen et al., 2011;Widodo et al., 2014). On the contrary, the basal type and HER2 carcinomas presented higher TNM profile, poorly differentiated tumors with high Ki-67 proliferation indexes (Irigoyen et al., 2011;Chuthapisith et al., 2012). Similarly, in this study earlier stages (stage I-II), lower Ki-67 indexes, lesser axillary nodal involvement associated with luminal A subtype whereas non-luminal subtypes showed more aggressive tumor characteristics especially high grade, Ki-67, LVI, PNI, clinical stage (stage III) tumors.
Breast tumor response to NACT varied among the different molecular subtypes. Ruano, et al reported this response was lowest in luminal A and highest in nonluminal HER2+ group. Also HER2+ and triple-negative were were shown to be the groups with the best axillary histological response (Ruano et al., 2014). Present study was in the same line with literature as follows: primary tumor response rates were 3.8% in luminal A, 47.8% in HER2-like type and 61.5% in BL/TN type. Axillary response rates were 15.8% in luminal A, 57.9% in HER2like, 63.6% in BL/TN type. This study revealed that breast cancer subtypes are in relation with the response to NACT (table 5). In the literature it was reported that after the NACT more than 30% reduction in primary tumor size in 74.2% of patients were observed (Egwuonwu et al., 2013). In present study the most tumoral (T) downstaging was in BL/TN subtype and nodal downstaging was higher in HER2-like and BL/TN subtpypes than luminal subtypes (Figure 1-2).
This study demonstrated that the pCR rate in breast and axillary were the significantly higher in patients with HER2-like type BC. It was known that patients with pCR had excellent prognosis. According to our study results, we speculate that NACT may be offered in early stage HER-2 like especially >2cm tumors as in Techno, NeoALLTo, NeoSphere and GeparQuinto studies Baselga et al., 2012;Gianni et al., 2012;Untch et al., 2012). Molecular shifting after NACT was more frequently observed in Luminal A type tumors. Particularly in this group the treatment schedule should be rewieved again after NACT.