Introduction
Paclitaxel is a microtubule-stabilizing agent that has significant therapeutic utility for treating many cancers, including breast cancer. Paclitaxel-induced peripheral neuropathy (PIPN) is a dose-limiting side effect of paclitaxel that could require discontinuation of treatment, and the mechanism has not been fully explained. In clinical practice, PIPN can occur over a period of a few days to several months and mostly causes peripheral sensory neuropathy as well as motor and autonomic neuropathy (1,2). Although the cumulative dose of paclitaxel appears to be the most associated factor with neuropathy, factors such as concomitant medications, comorbidities, older age, and vitamin D levels are also important because PIPN can occur even after the first cycle (3,4).
Many animal studies have shown that the possible neuropathy mechanism induced by paclitaxel includes inflammation, oxidative stress, loss of epidermal nerve fibers, alterations of mitochondrial function, and excitability of neurons, which cause damage to peripheral neurons and the dorsal root ganglion (5-7). Immune upregulation (inducing overexpression of mRNA coding for cytokines such as tumor necrosis factor-alpha, interleukin 1beta (IL-1b), IL-6, CGRP, and substance P) after paclitaxel administration has been shown in previous studies to play an important role in the modulation of cell death (8-10). IL-20 is a proinflammatory and chemoattractant mediator involved in augmenting proinflammatory substances such as IL-6, IL-1, and macrophage inflammatory proteins-1 in astrocytes, monocytes, and epithelial cells (11,12). Previous studies have suggested that IL-20 may function as a proinflammatory mediator in the development of PIPN (13).
In this study, we investigated the relationship between serum IL-20 levels and paclitaxel-related neuropathy.
Methods
Patients
In this prospective observational study, eligible patients were aged >18 years, with histologically proven breast cancer, and planned (adjuvant or neoadjuvant) to receive 4 cycles of epirubicin plus cyclophosphamide and then weekly paclitaxel (80 mg/m2 x12 cycles). Patients with human epidermal growth receptor-2 (HER2) expression received HER2-directed therapy concurrently (trastuzumab, 17 cycles of neoadjuvant and/or adjuvant; if pertuzumab received, only 4 cycles in the NACT period). Patients with a prior history of peripheral neuropathy or diabetes mellitus and those with advanced -stage breast cancer were excluded from the study.
In this study, a total of 115 non-metastatic breast cancer patients receiving adjuvant or neoadjuvant chemotherapy between January 2022 and November 2022 were evaluated. Of the 115 patients, 15 patients with diabetes mellitus or preexisting peripheral neuropathy and 39 patients scheduled to receive docetaxel as a taxane were excluded from the study. Patients who had to discontinue treatment because of neuropathy were also excluded from the study. The study was eventually conducted with 59 eligible patients (Figure 1). The study was approved by the Namık Kemal University Local Ethical Committee under the Helsinki Declaration (approval number: 2021.264.11.08, date: 30.11.2021), and informed consent was obtained from all participants. This study was registered on clinicaltrials.gov under NCT05622617.
Questionnaire
Neuropathy symptoms were evaluated with the patients-reported EORTC chemotherapy-induced peripheral neuropathy questionnaire (QLQ-CIPN20) on the 7th day after the first paclitaxel administration and at the last administration of the treatment (Figure 1). QLQ-CIPN20 contains three types of neuropathy: sensory, motor, and autonomic, and consists of 20 questions scaled each 1 to 4 points (1, not at all; 4, very much). Each question is scored, and the sum of the scores ranges between 20 and 80. Because only female patients were recruited for the study, the question regarding autonomic dysfunction (erectile dysfunction) was omitted. Patients were divided into two groups: if patients rated any question as 2, 3 or 4 points, they were assumed to have neuropathy; if they rated all questions as 1 point, they were assumed to have no neuropathy. The Turkish Validation of QLQ-CIPN20 was used in this study.
Measuring Serum IL-20 Levels
Serum IL-20 levels were measured at three time points. Initial IL-20 measurement was performed before chemotherapy. The second IL-20 measurement time point was on the 7th day after the first paclitaxel treatment, and the third measurement time point was after the last paclitaxel treatment (Figure 1).
Serum IL-20 levels were measured by ELISA analysis method. Bio-Techne (R&D SYSTEM Inc., Bio-Techne Corporation Brands, Minneapolis, USA) commercial ELISA kit (catalog no: DL200) of 96 tests was used for this measurement. Blood samples of the subjects included in the study were collected in a red-capped gel tube. These blood tubes were centrifuged at 4000 rpm (revolutions per minute) for 10 min and, the separated serum samples were divided into microcentrifuge tubes and labeled. Collected samples were stored at -80 °C until the day of analysis.
Statistical Analysis
Data were analyzed using SPSS version 26. Descriptive statistics and frequency distributions were calculated for the clinicopathological characteristics of patients. Differences between neuropathy and laboratory, clinical, and pathologic characteristics of patients were evaluated using Independent sample t-tests, chi-square analyses, or Mann-Whitney U tests. Receiver operating characteristic analysis was used to calculate the ideal cut-off value for predicting neuropathy. Logistic regression models, including univariate and multivariate analyses, were established to identify predictors of PIPN. A P-value of ≤0.05 was considered statistically significant.
Results
Fifty-nine female patients with a median age of 52.9 (33-78) years were included in this study. During the study, 47 patients (79.6%) reported any degree of neuropathy, whereas 12 patients (20.4%) had no neuropathy. On the 7th day after the first administration of paclitaxel, a rating score of 2, 3, or 4, which indicates the development of neuropathy, by patients for any of the questions in the QLQ-CIPN20 questionnaire was seen in 38.9% (n=23) patients (Table 1).
In the analysis of factors associated with neuropathy, serum IL-20 levels measured on day 7 (p=0.022), and last cycle serum IL-20 level (p=0.010) were statistically significant regarding the development of neuropathy. The serum IL-20 levels measured on day 7 and on the last cycle day were significantly higher in patients who developed neuropathy on day 7. There were no relationships between neuropathy and, chemotherapy type, estrogen receptor (ER) status, progesterone receptor (PR) status (p=0.670), HER2 expression, tumor size, first IL-20 level, and last serum IL-20 level (Table 1).
In the analysis of the relationship between the 7th-day serum IL-20 level and clinicopathological factors, a significant relationship was observed with the type of chemotherapy. The 7th-day serum IL-20 level was significantly higher in patients receiving adjuvant chemotherapy than in those receiving neoadjuvant settings (p=0.032). No significant difference was observed between the second serum IL-20 level and the following: age, body mass index (BMI), ER status, PR status, HER2 expression, Ki-67 level, and tumor size (Table 2).
Univariate and Multivariate Analyses
Univariate analysis to predict neuropathy measured on day 7 after first paclitaxel administration demonstrated that age [odds ratio (OR): 4.58, confidence interval (CI): 95%, 1.38-15.20, p=0.013], BMI (OR: 3.21, CI: 95%, 1.03-9.98, p=0.034), Lymphocyte count (OR: 8.33, CI: 95%, 1.43-48.54, p=0.018), 7th-day serum IL-20 level (OR: 10.42, CI: 95%, 1.17-93.20, p=0.036), and last cycle serum IL-20 level (OR: 4.58, CI: 95%, 1.38-15.20, p=0.013) were predictive for PIPN. In the multivariate regression model including predictive markers, age (OR: 3.45, CI: 95%, 0.93-12.80, p=0.064), lymphocyte count (OR: 4.16, CI: 95%, 1.10-15.74, p=0.036), and last cycle serum IL-20 level (OR: 4.79, CI: 95%, 1.24-18.46, p=0.023) were found to be independent predictors for PIPN (Table 3).
Discussion
In this study, we addressed PIPN, a dose-limiting side effect of paclitaxel chemotherapy that is a substantial component of breast cancer treatment management, which can jeopardize breast cancer treatment and quality of life of breast cancer patients. Univariate regression analysis revealed that PIPN detected on day 7 after the first paclitaxel cycle was associated with increased day 7 serum IL-20 levels and last cycle serum IL-20 levels as well as age, lymphocyte count, and BMI. A multivariate regression model investigating PIPN detected on day 7 showed age, lymphocyte count, and last cycle serum IL-20 levels as independent predictors of neuropathy.
The 2012 Early Breast Cancer Trialists’ Collaborative Group meta-analysis showed that anthracycline plus taxane chemotherapy resulted in better progression-free survival and overall survival than CMF, which was the standard treatment at that time (14). Since then, taxanes have been an integral component of the management of early or locally advanced breast cancer. However, despite its strong survival effect, taxane-induced neuropathy is an important limiting factor. This may cause patients to discontinue chemotherapy, affect their quality of life, and lead to chronic neuropathic diseases. In our study, 47 patients (79.6%) reported any degree of neuropathy, and two patients who were receiving chemotherapy in neoadjuvant settings discontinued treatment because of peripheral neuropathy and were referred for surgery.
In a study that included female patients receiving paclitaxel as adjuvant therapy, neuropathy started within the first week of paclitaxel treatment, whereas PIPN according to CTCAE v3.0 was observed in 97% of patients during 57 months of long follow-up (15). In another prospective study evaluating patients receiving paclitaxel with QLQ-CIPN-20, neuropathy was observed in 76 of 85 patients (16). In our study, 79.6% of patients developed paclitaxel-associated neuropathy during follow-up, as measured by QLQ-CIPN20. In Chen et al. (13) study, serum IL-20 samples obtained in the first week serially from patients receiving paclitaxel for gynecological cancers showed a positive correlation with patients who developed neuropathy as assessed by QLQ-CIPN-20. They also reported that they regressed paclitaxel-associated neuropathy with IL-20-targeting antibodies in a mouse model (13). Another study in the literature investigating paclitaxel neuropathy using the QLQ-CIPN-20 questionnaire showed that the highest neuropathy score was observed in the first 7 days after the first cycle of paclitaxel. Higher pain scores in the first chemotherapy cycle did not predict higher neuropathy scores in subsequent cycles (17). In accordance with the hypothesis of our study, IL-20 increases with paclitaxel administration and may contribute to the development of neuropathy by probably regulating chemoattractants. The fact that serum IL-20 measured before paclitaxel treatment was not associated with neuropathy and that IL-20 measured on day 7 after treatment and the last cycle of paclitaxel treatment was associated with neuropathy suggests that IL-20 may be one of the mediators contributing to the development of PIPN.
The association of PIPN with older age, lymphocyte count, and BMI in our study is consistent with the studies investigating PIPN in the literature. Ghoreishi et al. (18) showed that age, BMI, and PR positivity were predictive of PIPN in their study investigating PIPN in 56 breast cancer patients receiving paclitaxel. In another study exploring chemotherapy-associated neuropathy in patients who had received cisplatin or paclitaxel, older age was found to be predictive for chemotherapy-associated neuropathy (19). Mizrahi et al. (20) demonstrated that patients receiving paclitaxel or oxaliplatin, low hemoglobin before treatment, high body mass index, advanced age, and female gender were more likely to develop paclitaxel- or oxaliplatin-induced CIPN after treatment. It is very valuable for clinicians to identify markers that predict PIPN. In this study, we identified predictive markers in a well-selected (excluding diseases that may cause neuropathy) patient population with early-stage breast cancer. However, nevertheless, the key significance of this study is the insight into the relationship between IL-20 and PIPN, which can be an important marker in the future for the prevention or treatment of neuropathy.
Although the exact mechanism of paclitaxel-induced neuropathy is not clearly understood, treatments for possible causes have been investigated. Several studies have reported that approved therapies such as duloxetine, melatonin, minoxidil, N-acetylcysteine, or statins may diminish PIPN because of their anti-inflammatory, anti-oxidative, or neuroprotective effects (21-23). However, these studies appear to be experimental and mostly empirically applied treatments, and these treatments do not provide a standard treatment approach to prevent or treat PIPN. Moreover, studies with other and/or the same medications with similar mechanisms have shown that these agents do not prevent or reduce PIPN (24-26). These findings suggest that a lack of a clear understanding of the pathophysiology of paclitaxel-associated neuropathy makes an effective prevention or treatment option impossible. The association between neuropathy and IL-20 obtained from our study can be interpreted as the detection of an amplifier signal that triggers multiple mechanisms in the pathogenesis of the disease and may be the target of future therapies.
Study Limitations
This study is not without limitations. First, although the QLQ-CIPN-20 is a questionnaire with high sensitivity and specificity for neuropathy, it includes subjective assessment because it is self-administered. Second, the fact that IL-20 level measurement and neuropathy questionnaire could not be performed in every paclitaxel cycle is an important limitation. In addition, the lack of long-term follow-up neuropathy results on the patients is another limitation. The lack of long-term follow-up neuropathy results in the patients and small population are other limitations. The strength of our study is its prospective design and the exclusion of patients with neuropathy and those with diseases that may affect neuropathy, such as diabetes.
Conclusion
In conclusion, with this study, we showed that age, BMI, and lymphocyte count may be predictors for the development of PIPN in patients receiving paclitaxel with curative intent for treating breast cancer. We also demonstrated the relationship between IL-20 and the pathophysiology of paclitaxel-associated neuropathy for treating breast cancer. Future studies targeting the significance of IL-20 in the development of neuropathy are needed to prevent and treat neuropathy in larger patient populations.
Ethics Committee Approval: The study was approved by the Namık Kemal University Local Ethical Committee under the Helsinki Declaration (approval number: 2021.264.11.08, date: 30.11.2021).
Informed Consent: Informed consent was obtained from all participants.
Peer-review: Externally peer-reviewed.
Authorship Contributions: Concept - K.K., E.Ç., O.A.; Design - Y.İ., A.Y., A.Ç.; Data Collection or Processing - K.K., E.Ç.; Analysis or Interpretation - E.Ç., O.A.; Literature Search - E.Ç., O.A.; Writing - K.K., E.S.S.
Conflict of Interest: No conflict of interest was declared by the authors.
Financial Disclosure: The authors declared that this study received no financial support.