Background
Neoadjuvant therapy was initially used in patients with inoperable locally advanced tumors. Neoadjuvant and adjuvant administration of chemotherapy are equivalent in terms of overall survival [
1‐
4]. Neoadjuvant chemotherapy used in patients with initially operable tumors is superior for increasing the chance of achieving breast-conserving surgery, evaluating the susceptibility of chemotherapy drugs and assessing the response to chemotherapy. Patients with a pCR after neoadjuvant chemotherapy have better disease-free survival. The FDA recently granted accelerated approval for pertuzumab in combination with trastuzumab and docetaxel as neoadjuvant treatment for patients with Her-2-positive breast cancer as a result of the significant improvement in pCR in patients. pCR has become an important parameter in the approval of a new drug by FDA, so it is important to find a clinical pathological indicator to predict pCR in advance.
Predictive factors of the response to neoadjuvant chemotherapy include tumor size, pathology subtype, and differentiation as well as expression of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and KI67 [
5]. There is increasing evidence that the neutrophil to lymphocyte ratio is associated with long-term outcomes, so this ratio has gained much interest, with several studies over the last 5 years investigating its role in predicting long-term outcomes in various cancer populations, including lung, colorectal, stomach, liver, and pancreatic cancer [
6‐
10]. Based on studies that show the association between high NLR and increased mortality in breast cancer [
11‐
13], we suggest that NLR could be an important predictor of the response to neoadjuvant chemotherapy as an inflammatory indicator. The aim of the present study was to investigate the association of NLR with pCR in patients who received neoadjuvant chemotherapy and the prognostic value of NLR in view of RFS and BCSS.
Discussion
In this study, we examined a cohort of breast cancer patients who received neoadjuvant chemotherapy to provide evidence on the predictive value of pathologic complete response and the prognostic value of NLR. The main finding of our analysis is that high pretreatment NLR was associated with pCR and was a significant independent predictor of RFS and BCSS in breast cancer patients undergoing preoperative chemotherapy.
To date, few studies have examined whether pretreatment NLR is predictive for pCR. Only one study has determined the relationship between pCR and pretreatment peripheral blood NLR in patients who had NAC for locally advanced BC. In that study, Eryilmaz et al. [
22] showed no relationship between pCR and pretreatment NLR value, in contrast to our results. To our knowledge, this is the first time that a strong association between pretreatment NLR and chemotherapy response is described in a breast cancer study. Our results demonstrate that patients with NLR ≥ 2.06 showed poor response to neoadjuvant chemotherapy (Fig.
1). Patients with NLR < 2.06 showed a higher pCR rate than those with NLR ≥ 2.06. The major causes of these contrasting findings may be the insufficient sample size (only 78 patients) and nonstandardized therapies (some patients had anthracycline-taxane based, some had hormonal-based NACs) in the study by Eryilmaz et al. [
22]. For this reason, our results are more reliable. A lower NLR value (<2.06) is more likely to reach pCR, and it is useful in consultation for patients and clinical decision-making.
Patients showing a pCR to neoadjuvant chemotherapy enjoy prolonged disease-free survival [
23], which corroborates our finding that patients with NLR < 2.1 showed a relatively better prognosis. Meanwhile, an elevated pretreatment NLR is associated with worse RFS and BCSS. We found that elevated NLR at initial clinical presentation of breast cancer was an independent factor for poor survival rate in breast cancer patients. This finding is consistent with previous reports in several other cancers as well as breast cancer [
6,
8‐
10,
24,
25]. A higher NLR (NLR > 3.3) has been correlated with an advanced stage of breast cancer [
12]. Additionally, higher-NLR patients (NLR > 2.5), especially with the luminal A subtype, show significantly poorer prognosis than lower-NLR patients [
13]. Previous studies included patients irrespective of whether they received NAC, whereas we only focused on patients who received NAC. Azab et al. [
12] used the 75th NLR percentile as the NLR cutoff, while Noh [
13] used receiver operating characteristic (ROC) curve analysis to determine the NLR cutoff. Our study also used ROC curves to determine the cutoff, and our NLR cutoff was 2.11. Regardless of these differences, the results from our study appear to favor the same conclusion: that patients with an elevated pretreatment NLR show poorer disease-specific survival than patients without elevated NLR.
The association between an elevated NLR and poor prognosis is complex. Increasing evidence suggests that cancer progression is influenced by the systemic inflammatory response [
26]. Components of this inflammatory response are associated with patients’ prognostic outcomes. An elevated NLR is due to a relative neutrophilia and lymphocytopenia that occurs as part of the systemic inflammatory response triggered by cancer [
27‐
30]. First, neutrophils may inhibit immune system function. Neutrophils promote remodeling the extracellular matrix, which promotes tumor growth and metastasis via its enzymatic actions, including the release of reactive oxygen species (ROS), nitric oxide (NO), and anginas [
31‐
33]. In addition, relative neutrophilia enhances tumor growth and progression by activating inflammatory markers that include pro-angiogenic factors (VEGF), growth factors (CXCL8), proteases and anti-apoptotic markers (NF-kB) [
9,
12,
34,
35]. In breast cancer, neutrophil-derived oncostatin M signals human breast cancer cells to secrete VEGF and increases breast cancer cells’ detachment and invasiveness [
36]. On the other hand, lymphocytic response is the main component of controlling cancer progression. Increased lymphocyte infiltration has been correlated with higher pCR rate and a better prognosis in breast cancer patients who received neoadjuvant chemotherapy [
37‐
39]. Lymphocytes (especially T4 helper and T8 suppressor lymphocytes) decline markedly in the cell-mediated immune system [
29]. Moreover, immune modulators, including TGF β, IL10 and CRP, released by tumor cells impair lymphocyte action in systemic inflammation [
40]. Tumor-infiltrating lymphocytes such as natural killer and T helper type 1 are effective components against cancer growth and/or metastasis in several cancers via their production of interferon gamma [
41]. Chemotherapy might be an effective immunotherapy against such tumor types, and the combined effect of chemotherapeutic destruction of tumor cells and increased immune response may result in a pCR [
39,
42]. Thus, a low lymphocytic infiltration at tumor margins corresponds with a poorer prognosis [
27,
43,
44].
In this study, patients in the higher pretreatment NLR group tended to have higher staging. This corroborates previous reports that these preoperative characteristics are associated with vascular invasion and a more aggressive phenotype [
44‐
46]. Stage is directly representative of tumor progression and is subsequently reflective of the immune response (neutrophilia and lymphocytopenia), and it is not surprising that higher stages correspond to higher NLR and therefore worse survival [
43].
There was a significant discordance of NLR cutoffs used in previous studies [
47]. Most of the studies have used an NLR of 5 as the cutoff based purely on previous work. Only four studies used ROC sensitivity and specificity analyses to determine an NLR cutoff. Azab et al. [
12] used 75th NLR percentile as the NLR cutoff. Although most studies used NLR > 5 as the cutoff, this does not imply that patients with an NLR < 5 were not at an increased risk. In fact, several other studies demonstrated NLR ranges of 4 and below (even as low as 1.9) as having prognostic significance in overall survival [
47]. We used ROC curve analysis to determine the NLR cutoff. ROC curve analysis suggested that the optimum NLR cut-off point was 2.11 (AUC: 0.589, 95 % CI: 0.511- 0.686,
p < 0.05) with a sensitivity of 66.7 % and specificity of 55.7 %. Pichler et al. [
48] mentioned that the ideal cutoff value for a continuous NLR was calculated by testing all possible cutoffs that would discriminate between survival and cancer-related death by Cox proportional analysis. We tested all possible cutoffs in this way from 2.0 to 2.9, and the ideal cutoff value was 2.1 for survival as well as 2.06 for pCR
+ and pCR
− patients. Most studies focus on different tumors, which tend to have different inflammatory status. Even in breast cancer patients, different age, stage and phenotype correspond with different immune response and therefore different NLR.
Additionally, we are interested in the relationship between the change in NLR (ΔNLR) and its relationship with pCR or relapse-free survival. We found no significance in the relationship between ΔNLR and pCR or RFS (data not shown). Different chemotherapy regimens may lead to different degrees of neutropenia, as anthracycline and taxane-based regimens can cause severe neutropenia. Patients with neutropenia after NAC were suggested to take granulocyte colony-stimulating factors (G-CSF) to stimulate the release of leucocytes, which may also have affected neutrophil and lymphocyte counts. That would result in different baseline NLR after NAC. So we believe that the pretreatment NLR is likely to be the most robust NLR value to use.
The major limitation of our study is the retrospective nature. Many patients whose records lacked information or who were lost to follow-up were not enrolled in the study, and that may have led to selection bias. Second, it was beyond the scope of this study to make clear whether patients with Her-2 positive tumors had taken Herceptin as adjuvant treatment because not all the patients could afford the high price before 2010 in China. This might have had some statistical influence on survival because Herceptin has made such an enormous impact, particularly on disease-free survival. Third, patients with different ages, stages and phenotypes corresponded to different immune responses, and we were not able to conduct a stratified analysis on such small subgroups of patients. Moreover, our study lacked any evaluation of tumor-associated neutrophils and lymphocytes. Furthermore, analysis about local recurrence-free survival and metastasis-free survival relating to long-term outcome were limited by the patients’ records. Besides, further study into the relationship between tumor-infiltrating lymphocytes and NLR is needed to validate our results. The aforementioned limitations taken together with the relatively small sample size suggest that our results need to be validated in additional independent cohorts of breast cancer patients, ideally through large-scale prospective clinical studies.
Pretreatment NLR represents a simpler, more robust and more convenient parameter compared with other pathological indicators, such as KI67. The use of pretreatment NLR may facilitate the administration of NAC therapy in patients with lower NLR to reach a better pCR rate and to enhance long-term outcomes.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
YC carried out the conception and design and drafted the manuscript. KC participated in the design of the study and performed statistical analysis. XX coordinated and helped to draft the manuscript. YN carried out the collection and assembly of data. SQ participated in the design of the study. CG performed statistical analysis. FS conceived of the study and participated in its design. ES coordinated and approved the final manuscript. All authors read and approved the final manuscript.