|Year : 2017 | Volume
| Issue : 4 | Page : 652-657
Molecular subtypes as a predictor of response to neoadjuvant chemotherapy in breast cancer patients
Shanmugam Subbiah, Govindasamy Gopu, P Senthilkumar, P Muniasamy
Department of Surgical Oncology, Government Royapettah Hospital, Chennai, Tamil Nadu, India
|Date of Web Publication||30-Jul-2018|
Department of Surgical Oncology, Government Royapettah Hospital, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
PURPOSE: The objective of this study was to assess response to neoadjuvant chemotherapy in molecular subtypes of breast cancer. METHODS: This study included 60 patients with locally advanced and metastatic breast cancer. The authors excluded patients who already underwent mastectomy or were given any chemotherapy/radiotherapy. They analyzed the clinical and immunohistochemical characteristics using core biopsy specimens to determine their correlations with response to chemotherapy. RESULTS: A clinical complete response was observed in 19 patients (31.7%), a clinical partial response in 30 patients (50%), clinical stable disease in 8 patients (13.3%), and progressive disease in 3 patients (5%). A pathologic complete response (pCR) was observed in 7 (21.87%) of 32 patients who underwent surgery. High Ki-67 was associated with human epidermal growth factor receptor 2 (HER2)-positive status (P = 0.027) and triple-negative breast cancer (TNBC) (P = 0.006). Multiple logistic regression analysis showed that pCR was correlated with HER2 status (odds ratio 26.589, confidence interval [CI] =1.606–44.190), P = 0.022. Of the seven patients found to have pCR, six patients (85.7%) were treated with taxol-containing regimen. The other parameters that were correlated with pCR are TNBC and estrogen receptor/progesterone receptor status. Tumor size, Ki-67 value, and grade of the tumor were not correlated with clinical response. CONCLUSION: Molecular subtype in breast cancer is an effective factor for predicting response to neoadjuvant chemotherapy. HER2-positive status was associated with high Ki-67 and high clinical and pathological response rate. Taxol needs to be added in neoadjuvant chemotherapy to improve pCR. Luminal subtypes respond poorly to chemotherapy.
Keywords: Carcinoma breast, Ki-67 antigen, molecular subtypes, neoadjuvant chemotherapy, response assessment
|How to cite this article:|
Subbiah S, Gopu G, Senthilkumar P, Muniasamy P. Molecular subtypes as a predictor of response to neoadjuvant chemotherapy in breast cancer patients. Indian J Cancer 2017;54:652-7
|How to cite this URL:|
Subbiah S, Gopu G, Senthilkumar P, Muniasamy P. Molecular subtypes as a predictor of response to neoadjuvant chemotherapy in breast cancer patients. Indian J Cancer [serial online] 2017 [cited 2020 Jan 28];54:652-7. Available from: http://www.indianjcancer.com/text.asp?2017/54/4/652/237888
| » Introduction|| |
Breast cancer is a heterogeneous disease, and different biological subtypes have different prognostic impacts. Pathologic complete response (pCR) is defined as the absence of residual invasive cancer in the breast and axilla following preoperative therapy. Increasing the rate of pCR became the endpoint of neoadjuvant trials with the expectation of translation into improved survival.
Prospective, randomized trials of patients with operable breast cancer have demonstrated that clinical response rates to neoadjuvant chemotherapy are high, ranging from 50% to 85% in many studies. pCRs in the breast range from 15% to 45%. In patients who overexpress human epidermal growth factor receptor 2 (HER2), the preoperative administration of anti-HER2 therapy in combination with chemotherapy has been associated with high rates of pCR. Clinical trials have confirmed that adding trastuzumab to chemotherapy improves the pCR rate among women with HER2-positive breast cancer receiving neoadjuvant therapy and improves long-term survival,, consistent with the survival benefit observed for trastuzumab when given with chemotherapy in adjuvant setting.
A meta-analysis of nine randomized trials of preoperative chemotherapy revealed no increase, or decrease, in survival with preoperative compared with postoperative treatment.
Neoadjuvant chemotherapy reduces tumor size, which enables patients who were initially inoperable to undergo mastectomy, and makes breast-conserving surgery possible in patients who otherwise would have required mastectomy. The outcome of neoadjuvant chemotherapy can be determined in a relatively short time, which makes this approach useful for deciding which drugs or regimens are effective for specific pathologic conditions. Moreover, this is a useful modality for investigating the efficacy of specific biologic markers as predictive and prognostic factors. Neoadjuvant chemotherapy does not provide a survival advantage compared with postoperative adjuvant therapy. However, patients who achieve a pCR have significantly improved disease-free survival and overall survival (OS) compared with those with residual cancer.
Ki-67 is a nuclear antigen that is expressed in the growth and synthesis phases of the cell cycle. Ki-67 protein is associated with cell proliferation; therefore, increased Ki-67 levels in cancer tissue have been considered a poor prognostic factor, while also being a positive predictive factor for response to chemotherapy.,
However, the clinical role of Ki-67 has not been established; therefore, the routine use of Ki-67 as a predictor of prognosis and treatment response in patients with breast cancer is not recommended. Data that support the routine use of Ki-67 are currently insufficient, and the cutoff values to define high versus low Ki-67 expression are vague and inaccurate. In this study, greater than 25 was considered as high Ki-67.
The objective of this study was to assess response to neoadjuvant chemotherapy in molecular subtypes of patients with breast cancer. The authors also correlated Ki-67 expression with different clinical characteristics.
| » Methods|| |
This prospective study included patients with locally advanced and metastatic breast cancer between August 2015 and December 2016. Of the 66 patients, 60 patients were taken for analysis (3: defaulted, 2: intolerance to chemotherapy, 1: death). All patients were diagnosed with invasive breast cancer via core needle biopsy. At diagnosis, 34 patients had clinical Stage III and 26 patients had Stage IV tumors by staging workup which included chest and abdominal computed tomography and bone scintigraphy. The clinical and pathologic characteristics of all patients were obtained. The characteristics of patients included were age, menopausal status, clinical stage, histological grade, hormone receptor status, HER2 status, Ki-67 expression level, molecular subtypes, systemic chemotherapy regimen, clinical response, and pathologic stage. The Institutional Review Board of Kilpauk Medical College Hospital approved this study.
All patients enrolled in this study received anthracycline-based chemotherapy. In this hospital, the common chemotherapy regimens were three cycles of AT (50 mg/m2 doxorubicin and 150 mg/m2 paclitaxel every 3 weeks) and four cycles of AC (600 mg/m2 cyclophosphamide, 60 mg/m2 doxorubicin). Modified radical mastectomy was performed 3 weeks after the final dose of neoadjuvant chemotherapy in locally advanced breast cancer and selected cases of metastatic breast cancer.
Pathologic specimens of the tumors of all patients were analyzed from the samples obtained through core needle biopsy before initiating chemotherapy and the samples obtained through surgical resection. Histological type, histological grade, estrogen receptor (ER) status, progesterone receptor (PR) status, HER2 status, cytokeratins 5 and 6, Ki-67 expression level, and pathological response of the specimens obtained through surgery were evaluated. We used pathologic and immunohistochemical (IHC) findings of core needle biopsy specimens to analyze the predictive factors associated with a response to neoadjuvant chemotherapy. Patients were grouped into molecular subtypes based on IHC reports [Table 1].
|Table 1: Molecular subtypes of breast cancer according to immunohistochemistry|
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ER and PR statuses were determined using Allred scoring system, and a positive result was defined as a total score of ≥3. The HER2 status was determined using HercepTest (Dako), and 3+ reactions were considered to be positive results, whereas 1+ reaction was considered negative. If 2+ results were obtained using the HercepTest scoring system, fluorescence in situ hybridization was performed to determine HER2 status. The Ki-67 expression levels were expressed as the percentage of cells with positive nuclear staining among the total number of tumor cells (at least 1000 were counted).
Evaluation of response to chemotherapy
Before the start of chemotherapy, the size of the breast tumor and axillary lymph node status of all patients were measured. After chemotherapy, the authors measured tumor size and axillary lymph node status again to evaluate clinical response to chemotherapy.
Clinical response to chemotherapy was determined by comparing baseline tumor size to tumor size after chemotherapy using clinical and radiological imaging. For quantitative analysis of clinical response to chemotherapy, the authors used Response Evaluation Criteria in Solid Tumors (RECIST) guidelines version 1.1 as follows: clinical complete response (cCR) is the disappearance of all lesions; clinical partial response (cPR) is a decrease of at least 30% in the diameters of lesions; clinical overall response is the sum of complete response and partial response; clinical progressive disease (cPD) is an increase of at least 20% in the diameter of the breast lesions; and clinical stable disease (cSD) is the presence of lesions with neither sufficient shrinkage to qualify as cPR nor sufficient increase to qualify as cPD.
Pathologic response to chemotherapy was determined by analyzing surgical tumor specimens. Residual tumor size and lymph node status were evaluated to assess pathologic response to neoadjuvant chemotherapy. pCR was defined as no pathologic evidence of a residual invasive carcinoma in the breast or axillary lymph nodes. Residual ductal carcinoma in situ was included under pCR.
To determine the predictive factors for a clinical response after chemotherapy, the baseline characteristics of patients with overall response and no response were compared. Pearson's Chi-square test was used to compare categorical characteristics. To identify predictive factors for overall response, the baseline characteristics of patients with overall response and those of patients without response were compared. Student's t-test was used to compare quantitative characteristics, and Pearson's Chi-square test was used to compare categorical characteristics. Receiver operating characteristic (ROC) curve analysis was performed to assess sensitivity and specificity. To identify the predictive factors associated with overall response after chemotherapy, multiple logistic regression analysis was performed. Statistical significance was calculated at 95% confidence interval (CI) (P < 0.05) and all analyses were performed using SPSS version 22.
| » Results|| |
Out of 60 patients (mean age 49 ± 9.44 years and mean body surface area 1.92±0.16 m2), 34 (56.7%) were clinical Stage III and 26 (43.3%) were Stage IV patients. Sixteen patients (26.7%) were Luminal A, 11 (18.3%) patients were Luminal B, 21 patients were HER2-enriched, and 12 patients were triple-negative; of them, 9 were basal-like molecular subtypes. All patients received anthracycline-based chemotherapy (AC regimen: 22 patients, AT: 30 patients, TAC: 8 patients).
In all, 48 patients (80%) were in the age group of more than 40 years; of them, 27 (56%) patients had low Ki-67 values. Low grade was noted in 38 (63.3%) patients. Premenopausal women were 23 (38.3%). A total of 27 patients were ER/PR-positive (45%); 28 (46.7%) patients were HER2-positive. TNBC was noted in 12 patients (20%).
After chemotherapy, 19 patients (31.7%) showed a cCR, 30 patients (50%) showed a cPR, 8 patients (13.3%) showed cSD, and 3 patients (5%) had progressive disease, based on RECIST criteria. After neoadjuvant chemotherapy, seven patients (21.9%) showed a pCR based on the analysis of surgical specimens.
Clinical characteristics were grouped according to Ki-67 values [Table 2]. On analysis, high Ki-67 was associated with HER2 status (P = 0.027) and TNBC (P = 0.006).
49 (81.6%) patients responded to chemotherapy; out of them, 39 (79.6%) patients were in the age group of more than 40 years; 33 of 38 low-grade tumor and 31 of 37 postmenopausal women responded to chemotherapy.
27 of 33 were ER/PR-negative patients, 90% (25 of 28) were HER2 patients, 45 of 53 patients (85%) had a size of 10 cm or less, and 75% of TNBC responded to chemotherapy. 33 of 38 patients (86.8%) who had been treated with adriamycin and paclitaxel combination chemotherapy showed response. 28 of 33 nonluminal subtype patients responded to chemotherapy. Clinical response according to molecular subtypes is grouped in [Table 3].
|Table 3: Grouping of patients according to response in various molecular subtypes|
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Nonresponded patients include static disease and progressive disease. Of the 11 nonresponded patients, 8 had static disease and 3 had progressive disease. Nine patients were more than 40 years of age. Six patients had low-grade tumors and were postmenopausal women. Eight of 11 patients who showed no response were HER2-negative. Clinical [Table 4] and pathological [Table 5] responses to chemotherapy according to patients' characteristics were analyzed.
|Table 4: Patients' characteristics according to clinical response to neoadjuvant chemotherapy|
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|Table 5: Characteristics of the patients according to pathologic response to neoadjuvant chemotherapy|
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ROC curve analysis was used to calculate sensitivity and specificity of predicting factors that are responsible for pathological complete response to neoadjuvant chemotherapy. The area under the ROC curve (AUC) for HER2 status expression was 0.749 (P = 0.047, CI = 0.553–0.944), indicating that HER2 status is a very sensitive marker for pCR to neoadjuvant chemotherapy [Figure 1]. The AUC for ER status was 0.383 (P = 0.350), the AUC for Ki-67 status was 0.531 (P = 0.802), and the AUC for tumor size was 0.246 (P = 0.043) [Figure 1]. It was also observed that other variables had a relatively lower significance as predictors of response to neoadjuvant chemotherapy.
|Figure 1: Receiver operating characteristic curve analysis to calculate sensitivity and specificity of predicting factors|
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Multiple logistic regression analysis [Table 6] also showed that pCR was correlated with HER2 status (odds ratio 26.589, CI = 1.606–44.190), P = 0.022. The other parameters that are very well-correlated with pCR are TNBC, ER/PR status, taxol-containing chemotherapy regimen, and age 40 years or less. Tumor size, Ki-67 value, and grade of the tumor were not well-correlated with pCR.
|Table 6: Multiple logistic regression analysis of predictive factors for pathologic complete response to neoadjuvant chemotherapy|
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| » Discussion|| |
The purpose of neoadjuvant therapy is to improve survival, render locally advanced cancer amenable to surgery, or to aid in breast conservation. In that setting, the absence of cancer cells in resected breast tissue has been used to define a pCR. The rate of pCR has been proposed as a surrogate endpoint for event-free survival (EFS) or OS to support approval of new agents or combinations of agents tested in clinical trials. In a pooled analysis of 11,955 patients enrolled on 12 neoadjuvant trials, individual patients with pCR had improved EFS and OS. However, at trial level, pCR rates did not correlate with EFS or OS, a problem likely because of heterogeneity of breast cancer subtypes among the trials.
A number of clinical trials have been undertaken to determine the predictive factors for clinical and pathologic responses to neoadjuvant chemotherapy. Because most chemotherapy drugs are associated with severe adverse effects, it is important to avoid unnecessary systemic chemotherapy that delays the administration of other treatments.
In a study by Schott et al., 4 of 41 patients had a pCR to chemotherapy (9.8%) as against 7 (21.9%) of 32 patients in our study.
In Zambetti et al., overall response rates (ORRs) ranged from 88% to 97%. In our study, ORR is 81.9%.
Many clinicians have examined the relationship between molecular subtypes and chemotherapy response in patients with breast cancer. Rouzier et al. showed that HER2 neu subgroup was associated with highest rates of pCR [45% (95% CI = 23–68)], whereas luminal tumors had a pCR rate of 6% (95% CI = 1–21). No pathologic CR was observed among normal-like cancers (95% CI = 0–31).
In this study, HER2-positive subgroup was associated with 40% pCR (odds ratio 26.589, 95% CI = 1.606–44.190; P = 0.022), whereas luminal tumors were associated with 13.3% pCR only and Luminal A subtypes are associated with 12.5% pCR only. No pCR was observed in TNBC (odds ratio 21.159, 95% CI = 1.466–30.334; P = 0.025).
HER2-enriched and TNBC subtypes are hormone receptor (ER/PR) negative and hence can be called as nonluminal subtypes.
Taxol-containing regimen had 33.3% pCR as against 7% pCR for nontaxol-containing regimen. To improve pCR, taxol must be included in neoaduvant chemotherapy regimen.
Limitation of this study
Only a small number of patients (60) were analyzed; of them, only 32 patients underwent surgery. Hence, pathological response was analyzed in this group of patients. Patients with breast cancer responded clinically to chemotherapy, and pathological response could not be assessed except in selected cases of metastasis to bone and lymph nodes. Even though all patients received adriamycin-based chemotherapy, bias in selection of regimen (AC, AT) might be present. A wide variation in 95% CI even with a high relative risk in logistic regression analysis reduces the impact of each factor influencing the outcome.
| » Conclusion|| |
Molecular subtype in breast cancer is an effective factor for predicting response to neoadjuvant chemotherapy. HER2-positive status was associated with high Ki-67 and high clinical and pathological response rate. Taxol needs to be added in neoadjuvant chemotherapy to improve pCR. Luminal subtypes poorly respond to chemotherapy.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]