NAC is able to convert cN + BC patients into cN0 in about 70% of the cases for specific BC subtypes7,8. For this reason, axillary involvement is usually considered an indication to NAC in most T1-T2 operable BC presenting nodal involvement at diagnosis. Unfortunately, when cN + does not convert to cN0 after NAC, ALND is recommended14. Therefore, the identification of pre-NAC markers that are predictive of axillary response might be useful in selecting those patients who may benefit from chemotherapy in terms of lymph node downstaging.
In the present large multicenter study, two biological markers of systemic immune-inflammation (NLR and PIV) were evaluated as potential predictors of nodal response in a multivariable model, together with some relevant clinical-pathological variables.
NLR is the most extensively studied among inflammatory biomarkers. In primary operable BC, a recent meta-analysis on 42 studies demonstrated that higher NLR was associated with worse overall survival (OS) (HR 1.75, 95% CI 1.52 to 2.00; P < 0.001), disease-free survival (DFS) (HR 1.67, 95% CI 1.50 to 1.87; P < 0.001), and BC-specific survival (BCSS) (HR 1.89, 95% CI 1.35 to 2.63; P < 0.001)27. In particular, the prognostic role of this systemic inflammatory marker was investigated in some specific subsets where risk stratification is more challenging, like HER2 positive and triple negative BC. A recent meta-analysis on triple negative BC, suggested that higher NLR is an indicator of poorer prognosis28. These data conferred a great interest in this biological marker for timely and non-invasive evaluation of the oncologic outcome.
In the NAC setting, a meta-analysis on 8 relevant studies demonstrated that a lower NLR was associated with a greater rate of pCR (OR 1.83, 95% CI 1.15–2.91, p = 0.0003)29. Another subsequent meta-analysis on 19 studies, confirmed this result (OR 1.6, 95% CI, 1.2–2.1, I2 66%, p > 0.001)30. When specific subsets of BC were explored, NLR provided additional information regarding the likelihood of obtaining a pCR to NAC in postmenopausal Luminal B/HER2 positive31 and in triple negative BC32.
Studies on other blood cell ratios as platelet to lymphocyte ratio (PLR) and monocyte to lymphocyte ratio (MLR) showed conflicting results about their value as a predictive and/or prognostic factors and there are conflicting reports about which index provides the best prediction for the efficacy of NAC in BC33. However, it has been hypothesized that the combination of multiple biomarkers could better define the patients’ inflammatory status34.
PIV is a blood-based biomarker integrating different peripheral blood immune cell subpopulations as neutrophils, platelets, monocytes, and lymphocytes. Due to its potential to represent comprehensively patient’s immunity and systemic inflammation, PIV was proposed as a stronger predictor of outcomes in advanced cancer patients receiving systemic therapies21.
Two studies focused on PIV analysis reported that this index has a significant predictive value and outperforms other inflammatory biomarkers in predicting overall survival in HER2 positive advanced BC (HR 7.96; 95% CI: 2.18–29.09 p < 0.0001)22 and in predicting pCR to NAC (OR, 3.32; 95% CI, 1.53–7.21, p = 0.002)35.
In the present study, we selectively investigated the role of both NLR and PIV in predicting the axillary response in node positive BC patients undergoing NAC.
Baseline NLR and PIV were calculated in 1274 cN + BC patients and their cutoff values were identified based on the analysis of the ROC curves for the prediction of axillary pCR. Classical BC poor prognostic factors, including ki67 over 14%, HER2 positivity, pre-treatment advanced T stage, were all associated with axillary clearance in our series. Additionally, low NLR and low PIV independently predicted axillary pCR (OR = 0.71; 95% CI, 0.51–0.98; p-value = 0.04 for NLR; OR = 0.63; 95% CI, 0.44–0.90; p-value = 0.01 for PIV). PIV was also an independent predictor of axillary pCR in ER-/HER2+ (OR = 0.31; 95% CI, 0.12–0.83; p-value = 0.02) and ER-/HER2- subtypes (OR = 0.41; 95% CI, 0.17–0.97; p-value = 0.04).
It is interesting to note that when a sub-analysis was performed on cN1 patients, NLR and PIV were confirmed to be independent predictors of axillary pCR, with low levels of the biomarkers being significantly associated with axillary pCR to NAC (NLR: OR = 0.62; 95% CI, 0.43–0.90; p-value = 0.01; PIV: OR = 0.62; 95% CI, 0.42–0.93; p-value = 0.02).
Considering that a pCR in axillary lymph nodes after NAC can be considered an early surrogate marker of the long-term outcome3, the identification of pre-NAC predictors of axillary response may provide timely additional information on the oncological outcome. In other words, as future perspective, a patient’s inflammatory phenotype could discriminate a population of newly diagnosed BC patients with poor prognosis. This potential role would be particularly relevant in cN1 BC patients.
Furthermore, in literature it was clearly demonstrated that the presence of tumor-infiltrating lymphocytes (TILs) in BC, as expression of intra-tumor immunity, correlates with better response to systemic treatment, a lower recurrence rate, and a better overall survival, regardless of BC subtype36–40. However, whether the TILs reflect the antitumor immunity status of the patients is still to clarify. A correlation between peripheral indicators of immunity, such as NLR and PIV, and TILs in the microenvironment might be the next step to better define an immune signature of cN + BC patients who will benefit the most from NAC.
Ideally, if these data are confirmed, a novel axillary immune-oncology algorithm might be designed for cN + operable BC undergoing NAC to achieve a more precise definition of axillary surgery.
Limits of the study mainly consist into its retrospective nature. Another limitation is that different cutoffs for blood cell ratios are applied in different studies and different patient’s cohorts. Further prospective studies, as well as the definition of reliable and shared cutoff values are needed to validate the role of inflammatory biomarkers in selecting those patients with high probability of achieving N0 through NAC.
The strength of this study lies in its multicentric nature (11 major certified Breast Units) and the large sample size (1274 cN + BC patients). Moreover, there are only few studies reporting the role of inflammatory biomarkers in predicting axillary pCR, and the majority of literature reports consider a single biomarker and analyzes small populations. This is the first study, so far, where two biomarkers were simultaneously evaluated for the prediction of axillary pCR, thus providing a more comprehensive overview of the role of systemic immune inflammation in nodal response to NAC.
In conclusion, our results document that low NLR and low PIV predict axillary pCR in cN + BC patients undergoing NAC, and results were confirmed also in the sub-analysis on cN1 BC patients. Further prospective trials will be needed to validate the use of these systemic inflammatory markers as clinical indicators of axillary response in nodal positive BC patients undergoing NAC, for a better refinement of axillary surgery.