We evaluated, for the first time to our knowledge, the association between elevated NLR values and the development of cardiotoxicity among patients with breast cancer. We found that NLR values ≥ 2.58, following ANT exposure (T2), were associated with a 4-fold increased risk for developing significant LV GLS deterioration, with incremental increases of 1-point NLR adding an additional 15% risk.
The use of NLR measurements as a surrogate marker of poor outcomes is gaining popularity, both in the field of cancer and cardiovascular disease (CVD). Past studies have shown that high baseline NLR values are associated with poor overall survival in different types of cancer, including breast cancer[13, 14]. This may be explained[14, 22, 23] by the fact that neutrophils have been shown to promote cancer development while lymphocytes play a key role in the immune reaction against neoplasm development and proliferation. Furthermore, when associating NLR with CVD, higher NLR values have also been associated with worsening CV outcomes and mortality among patients with ST-elevation myocardial infarction (STEMI) and heart failure (HF)[18, 24]. Arbal et al.[18] have similarly shown an association between high NLR values and reduced LVEF. Relative neutrophilia reflects a systemic inflammatory physiologic state and promotes the creation of oxygen-free radicals, thus perpetuating further myocardial tissue damage. Furthermore, associated lymphopenia, promoted by elevated cortisol levels during a physiologically stressed state, has been shown to promote apoptosis[18]. While the role of high NLR as an independent predictor for poorer outcomes in both cancer and CVD patient populations has been well studied, its role in predicting cardiotoxicity development in cancer patients is yet unknown. Our study showed NLR at T2 was significantly associated with LV GLS deterioration while baseline NLR (T1) was not, which is likely explained by the significant NLR increase from T1 to T2 (Fig. 2) following ANT exposure. Of note, patients were also treated with Granulocytes-Colony Stimulating Factor (GCSF) during ANT therapy which may have caused an increase in NLR. However, we saw that the change in NLR in our study was mainly a result of a reduction in the absolute lymphocytes count rather than an elevated absolute neutrophil count that is seen with GCSF exposure. Furthermore, based on the timing of NLR increase, it is suggested that it was more likely a result of ANT exposure rather than a baseline inflammatory state from cancer. Importantly, there were no differences in baseline clinical characteristics or blood tests between the groups that may confound or falsely elevate the measured NLR or act as a risk predictor of LV GLS deterioration.
Our findings are consistent with recent papers, showing a statistically significant increase in NLR values over time in patients who developed Immune Checkpoint Inhibitors (ICI)-associated myocarditis[25], as well as an [25] association with MACE development.
In our study, the optimal NLR predictive cut-off value for LV dysfunction was found to be ≥ 2.58, in concordance with past studies of breast cancer patients that have used a NLR cut-off value of 3 as predictive for overall survival[13].
With a growing need for improved risk stratification of patients at risk for the development of cardiotoxicity, the search for an early, easily accessible marker is necessary. Surveillance with serial LVEF measurements is advised for patients treated with ANT, however, the current guidelines[26] regarding the timing of follow-up lack uniformity. Furthermore, LVEF reduction is usually evident only after significant, oftentimes irreversible, myocardial damage has occurred[27]. NLR is an inexpensive, readily available marker that is performed routinely in simple blood test, and is thus has great potential utility as an early detection tool for cardiotoxicity.
Our study has several limitations. First, it is a single-center study, however, its strength is the prospective nature that enrolls a homogenous population and contains uniformity of all echocardiography exams performed by the same vendor, technician, and interpreting physician. Second, we acknowledge that the relatively small number of patients reduces the statistical power of our results and larger trials are needed. Third, the relatively short period of follow-up did not allow us to evaluate the association or predictability between high NLR values and the development of LVEF reduction, cardiac morbidity, and all-cause mortality.
In summary, our study provides novel data that high NLR, following ANT exposure, have an independent association with the development of LV GLS deterioration, a parameter of LV dysfunction. Routine surveillance of NLR values may be an effective and rapid means of risk-stratifying and predicting early systolic dysfunction among patients with breast cancer following ANT therapy.