Individualized Neoadjuvant Chemotherapy Based On Molecular Subtype Classification For Breast Cancer And Multiple Gene Expression Detection In Efficacy Prediction

Breast cancer is the most common malignant disease worldwide. In China, the incidence of breast cancer is the highest in all cancers for females in big cities with an tendency of inclination. For a long time, the mature treatment model for breast cancer either domestic or abroad is multiple disciplinary standardized comprehensive treatment. However, for the highly heterogeneous characteristic for malignant disease, there are obvious individual differences between breast cancer patients. Even patients with the same histologic type, TNM staging or even the same hormonal receptor status undergoing the same standard treatment recommended by clinical guidance display quite different treatment efficacies and final outcomes. Thus individualized treatment for breast cancer is of great importance. Nonetheless, traditional clinicopathologic staging is limited in effectively stratifying breast cancers with various biological behaviors drawing back individualizing treatments.With the development and application of molecular biology in breast cancer, this disease can be classified in the level of malignant biological behavior via multiple gene expression detection into molecular subtypes. The novel treatment model that making treatment decisions based on various biological behavior of different breast cancer with traditional clinopathologic staging translated into individualized treatment is now challenging the conventional standardized treatment model based on clinical trials.Meanwhile, neoadjuvant chemotherapy itself is the best in vivo drug sensitive experiment. According to response to chemotherapy help deciding effective treatment regimens later on. Therefore, it is an important pathway towards individualized treatment for operable breast cancer. On the other hand, conventional clinopathologic staging is not effective in the prediction for the efficacies of various treatments in breast cancer. In recent years, with the development of multiple gene expression detection, several gene set that can effectively predict how much benefit breast cancer patients can get from chemotherapy have been developed and become important aiding tools for specialists in the making of individualized treatment strategies.Therefore, establishing individualized neoadjuvant chemotherapy system based on molecular subtype classification in Chinese breast cancer patients and using multiple gene expression detection for efficacy prediction to further improve individualized treatment is of importance in clinical practice.In the first part of this study, we carried out a single center open-labeled stageⅡclinical trial. By performing molecular subtype classification for Chinese breast cancer patient before neoadjuvant chemotherapy and provide best regimen based on updated evidences, we established a treatment model of individualized treatment.In this part of the study, we designated molecular subtypes according to the receptor status of tumor cells. Luminal A, luminal B, HER2 positive and triple negative subtypes were established and individualized neoadjuvant chemotherapy regimens were used. For luminal A subtype, capecitabine combined with docetaxel were used. For the luminal B and HER2 positive subtypes that overexpressing HER2, trastuzumab combined with paclitaxel was used. For triple negative breast cancer, weekly paclitaxel combined with cisplatinum was used. Breast conserving surgery or mastectomy with complete axillary lymph node dissection were performed after 4 cycles of therapy. Pathologic complete remission rate and overall response rate were calculated accordingly.Our results showed that, in the 102 patients included, individualized neoadjuvant chemotherapy obtained pCR rate as high as 36.3%(37/102), suggesting this novel treatment model can at least gain a 10% increase in patients that have improved DFS and OS. Statistical analyzes showed that, stage I patients were more likely to achieve pCR. Compared to Luminal A subtype, other subtypes were more like to achieve pCR, odds ratio were 6.4(95%CI 1.66—24.8, P=0.007),11.8(95%CI 3.05—46.0,P<0.001) and 3.88 (95%CI 0.874—17.2,P=0.075), respectively.Compared to standardized neoadjuvant chemotherapy based on clinopathologic staging, the novel treatment model established in this study further improved the efficacy of neoadjuvant chemotherapy. Long term survival benefit is waiting for future follow-up data for validation. XT, TH and PT neoadjuvant regimens have good efficacy and well tolerability in Chinese breast cancer patients. More aggressive subtypes other than luminal A and early stage patients with less tumor burden are more likely to benefit from individualized neoadjuvant chemotherapy. Further study using multiple gene expression detection to stratifying the two subtypes that account for 66.7% of all breast cancer and sensitive to hormonal treatment is important for making more delicate indivicualized treatment strategies.The distinct difference between luminal type breast cancers is hormonal receptor positive and sensitive to hormonal therapy. Luminal A and B subtypes accounts for the majority of breast cancer in this study while their pCR rate is lower than HER2 positive subtype and triple negative breast cancer. Thus to further stratify patients of luminal types who benefit little from therapy and treating with single hormonal therapy for luminal A patients or combined with HER2 targeted therapy will greatly improved the individualized treatment system established in the previous part of this study.21 gene recurrence score RS has been demonstrated to be powerful in the prediction of benefit from adjuvant chemotherapy or hormonal therapy or local recurrence, distant metastasis or death risk in hormonal receptor positive breast cancer. However, only few small scaled report using this RS score in the prediction for neoadjuvant chemotherapy benefit without and data based on Chinese patients.Therefore, in the second part of this study, we performed 21-gene expression detection for hormonal receptor positive patients included in the first part of this study to obtain data based on Chinese breast cancer patients using RNA originated form fresh frozen tissues. We tried to further validate whether RS can be used to predict benefit from neoadjuvant chemotherapy in Chinese HR positive breast cancer patients.Currently, the 21-gene OncotypeDX kit has been widely used for the detection of 21 gene expression using RNA generated from paraffin-embedded tissues. By strict quality control, we established a multiple gene expression system using RNA generated from fresh frozen tissues with satisfactory and reliable results.21-gene expression detection was performed in 65 HR positive Chinese patients using fresh frozen tumor tissues. RS was calculated according to methods reported in other studies. The mean RS in our study was 46.3±2.26, ranging from 11.3 to 100, with the median RS 45. Only 9 patients had a RS lower than 31. Statistic analyzes showed that RS can independently predict pCR after neoadjuvant chemotherapy with significance level better than staging and HER2 status. Compared to the median RS 31 in most other studies using 21-gene OncotypeDX, RS in our study was obviously higher. Possible reasons were:different detection system, small case number with non-randomization of our study and different races. On the other hand, the cutoff point for RS in our study was different from other studies. Obvious, the distribution of RS in our cohort is different that most patients had a RS greater than 31. After performing ROC figure, we found that if the RS cutoff point is set at 44, the sensitivity and specificity would be both acceptable. If patients were divided into high RS group with RS>44 and low RS group with RS≤44, patients in the high RS group were more like to achieve pCR (odds ratio 6.19, 95%CI 1.58-24.28,χ2=7.869, P=0.005). This result was similar to the 5.0 odds ratio reported by other studies, suggesting that cutoff point set at 44 can effectively decide benefit from neoadjuvant chemotherapy.Originally, pCR is still a clinopathologic parameter while RS is a biological marker based on multiple gene expression. It is interesting that which one of RS and pCR is more powerful in the prediction for long term survival benefit patients obtained from neoadjuvant chemotherapy in HR positive patients. To answer this question, we need long term follow-up data in the future.The second part of this study demonstrated that 21-gene expression detection using RNA generated from fresh frozen tissues is reliable and RS calculated based on data obtained from this detection system can predict benefit from neoadjuvant in Chinese HR positive patients. For non high RS score patients, little benefit will be obtained from chemotherapy. Whether neoadjuvant single hormonal therapy or combined with targeted therapy can still benefit these patients deserves further study.