Genetic variation in Charcot-Marie-Tooth genes contributes to sensitivity to paclitaxel-induced peripheral neuropathy.

Aim: This study explored whether inherited variants in genes causing the hereditary neuropathy condition Charcot-Marie-Tooth disease are associated with sensitivity to paclitaxel-induced peripheral neuropathy (PN). Patients & methods: Hereditary neuropathy genes previously associated with risk of paclitaxel-induced PN were sequenced in paclitaxel-treated patients. Eight putative genetic predictors in five hereditary neuropathy genes (ARHGEF10, SBF2, FGD4, FZD3 and NXN) were tested for association with PN sensitivity after accounting for systemic exposure and clinical variables. Results:FZD3 rs7833751, a proxy for rs7001034, decreased PN sensitivity (additive model, ß = -0.41; 95% CI: -0.66 to -0.17; p = 0.0011). None of the other genetic predictors were associated with PN sensitivity. Conclusion: Our results support prior evidence that FZD3 rs7001034 is protective of PN and may be useful for individualizing paclitaxel treatment to prevent PN.

Patient factors associated with discrepancies between patient-reported and clinician-documented peripheral neuropathy in women with breast cancer receiving paclitaxel: A pilot study.

PURPOSE: Discrepancies between clinicians' assessment of chemotherapy-induced peripheral neuropathy (CIPN) and patient-reported outcomes (PRO) have been described, though the underlying reasons are unknown. Our objective was to identify potential patient-specific factors associated with under-describing of CIPN to clinicians in women with non-metastatic breast cancer treated with paclitaxel. METHODS: Patients enrolled in an observational study (n = 60) completed weekly CIPN PRO using the EORTC CIPN20. Clinician-documented CIPN using the NCI CTCAE were abstracted from the electronic medical record and paired with CIPN20 data at weeks 7 and 10. Patients were classified as under-describers if their CIPN20 was above the 80th percentile of the CIPN20 distribution for that CTCAE grade from an independent clinical trial (N08CA). Demographics, Assessment of Survivor Concerns (ASC), Trust in Oncologist Scale (TiOS), and health literacy assessment were collected post-treatment via survey. Repeated measures cumulative logistic regression models were used to identify factors associated with under-describing CIPN. RESULTS: Forty-two women completed the survey (response rate 70%). Three and 9 patients were categorized as under-describers at weeks 7 and 10, respectively. Women who were not working (OR = 9.00, 95%CI 1.06-76.15), had lower income (OR = 7.04, 95%CI 1.5-32.99), and displayed higher trust in their oncologist's competence (OR = 1.29, 95%CI 1.03-1.62 for a 0.1-unit increase in score) were more likely to under-describe CIPN symptoms. CONCLUSIONS: This preliminary study identified non-working status, low income and trust in oncologist's competence as potential factors influencing under-description of CIPN to the clinical team. Further work is needed to clarify these relationships and test additional factors.

Vitamin D deficiency increases severity of paclitaxel-induced peripheral neuropathy.

PURPOSE: Approximately 25% of patients receiving weekly paclitaxel for breast cancer require treatment disruptions to avoid severe, irreversible peripheral neuropathy (PN). Vitamin insufficiencies are PN risk factors in many diseases, but their relevance to chemotherapy-induced PN is unknown. METHODS: We investigated whether baseline insufficiency of vitamin D, vitamin B12, folate, or homocysteine increased PN in patients with breast cancer receiving weekly paclitaxel in a retrospective analysis of a prospective observational study. Patient-reported PN was collected at baseline and during treatment on the Quality of Life Questionnaire Chemotherapy-Induced Peripheral Neuropathy (CIPN20). The primary analysis tested associations between vitamin deficiency and the maximum increase from baseline in the CIPN20 sensory subscale (ΔCIPN8). Secondary analyses tested for association with PN-induced treatment disruptions and adjusted associations for treatment and clinical variables. RESULTS: 25-hydroxy-vitamin D was the only nutrient with sufficient deficiency (< 20 ng/mL) for analysis (15/37 = 41%). Vitamin D-deficient patients had a greater mean PN increase than non-deficient patients (ΔCIPN8 ± SD, 36 ± 23 vs. 16 ± 16, p = 0.003) and a non-significant, approximately threefold increase in risk of treatment disruption (OR 2.98, 95% CI [0.72, 12.34], p = 0.16). In multivariable models adjusted for clinical and treatment variables, baseline vitamin D level was inversely associated with PN (ß = - 0.04, p = 0.02). CONCLUSION: Pre-treatment vitamin D deficiency was associated with PN in women receiving weekly paclitaxel for breast cancer. Vitamin D deficiency may be an easily detected PN risk factor that could be resolved prior to treatment to prevent PN, avoid treatment disruptions, and improve treatment outcomes.

Reporting of paclitaxel-induced peripheral neuropathy symptoms to clinicians among women with breast cancer: a qualitative study.

PURPOSE: Cases of chemotherapy-induced peripheral neuropathy (CIPN) under-reporting have been sporadically described in the literature, but no studies have focused on actively examining this behavior. Our primary aim was to identify women who purposefully under-reported CIPN, along with reasons for doing so. A secondary aim was to explore factors enabling or hindering communication of CIPN to clinicians. METHODS: Semi-structured interviews were conducted with women with breast cancer who had received paclitaxel in a prospective observational study. The interview guide was developed based on factors hypothesized to influence side effect disclosure to clinicians. Interviews were recorded, transcribed verbatim, and thematically content analyzed. RESULTS: Thirty-four women were interviewed. Three main themes emerged from the analysis: (1) enablers of CIPN reporting (e.g., positive relationship with the oncology team, sufficient appointment time, existence of alternative communication channels to office visits, expectation of CIPN as a side effect); (2) deterrents to CIPN reporting (e.g., perception of need to complete the full course of therapy, fear of treatment discontinuation, lack of knowledge of long-term consequences of CIPN); and (3) balancing survival versus functional impairment due to CIPN. Women prioritized efficacy over CIPN until physical functioning was meaningfully affected. No patients reported purposeful CIPN under-reporting, but three women admitted having considered doing so. CONCLUSIONS: Despite the lack of evidence of CIPN withholding, women considered both the effectiveness and the toxicity of paclitaxel treatment, as well as beliefs about treatment and long-term consequences of CIPN and relationship with the oncology team, when deciding whether to report CIPN symptoms.

Genetic variation in EPHA contributes to sensitivity to paclitaxel-induced peripheral neuropathy.

AIMS: Chemotherapy-induced peripheral neuropathy (PN) is a treatment limiting toxicity of paclitaxel. We evaluated if EPHA genetic variation (EPHA4, EPHA5, EPHA6, and EPHA8) is associated with PN sensitivity by accounting for variability in systemic paclitaxel exposure (time above threshold). METHODS: Germline DNA from 60 patients with breast cancer was sequenced. PN was measured using the 8-item sensory subscale (CIPN8) of the patient-reported CIPN20. Associations for 3 genetic models were tested by incorporating genetics into previously published PN prediction models integrating measured paclitaxel exposure and cumulative treatment. Significant associations were then tested for association with PN-related treatment disruption. RESULTS: EPHA5 rs7349683 (minor allele frequency = 0.32) was associated with increased PN sensitivity (ß-coefficient = 0.39, 95% confidence interval 0.11-0.67, p = 0.007). Setting a maximum tolerable threshold of CIPN8 = 30, optimal paclitaxel exposure target is shorter for rs7349683 homozygous (11.6 h) than heterozygous (12.6 h) or wild-type (13.6 h) patients. Total number of missense variants (median = 0, range 0-2) was associated with decreased PN sensitivity (ß-coefficient: -0.42, 95% confidence interval -0.72 to -0.12, P = .006). No association with treatment disruption was detected for the total number of missense variants or rs7349683. CONCLUSION: Isolating toxicity sensitivity by accounting for exposure is a novel approach, and rs7349683 represents a promising marker for PN sensitivity that may be used to individualize paclitaxel treatment.

Patients carrying CYP2C8*3 have shorter systemic paclitaxel exposure.

AIM: First, evaluate if patients carrying putatively diminished activity CYP2C8 genotype have longer paclitaxel exposure (e.g., time above threshold concentration of 0.05 µM [Tc >0.05]). Second, screen additional pharmacogenes for associations with Tc >0.05. Methods: Pharmacogene panel genotypes were translated into genetic phenotypes for associations with Tc >0.05 (n = 58). RESULTS: Patients with predicted low-activity CYP2C8 had shorter Tc >0.05 after adjustment for age, body surface area and race (9.65 vs 11.03 hrs, ß = 5.47, p = 0.02). This association was attributed to CYP2C8*3 (p = 0.006), not CYP2C8*4 (p = 0.58). Patients with predicted low-activity SLCO1B1 had longer Tc >0.05 (12.12 vs 10.15 hrs, ß = 0.85, p = 0.012). CONCLUSION: Contrary to previous publications, CYP2C8*3 may confer increased paclitaxel metabolic activity. SLCO1B1 and CYP2C8 genotype may explain some paclitaxel pharmacokinetic variability.

Pharmacometabolomics reveals a role for histidine, phenylalanine, and threonine in the development of paclitaxel-induced peripheral neuropathy.

PURPOSE: Approximately 25% of breast cancer patients experience treatment delays or discontinuation due to paclitaxel-induced peripheral neuropathy (PN). Currently, there are no predictive biomarkers of PN. Pharmacometabolomics is an informative tool for biomarker discovery of drug toxicity. We conducted a secondary whole blood pharmacometabolomics analysis to assess the association between pretreatment metabolome, early treatment-induced metabolic changes, and the development of PN. METHODS: Whole blood samples were collected pre-treatment (BL), just before the end of the first paclitaxel infusion (EOI), and 24 h after the first infusion (24H) from sixty patients with breast cancer receiving (80 mg/m2) weekly treatment. Neuropathy was assessed at BL and prior to each infusion using the sensory subscale (CIPN8) of the EORTC CIPN20 questionnaire. Blood metabolites were quantified from 1-D-1H-nuclear magnetic resonance spectra using Chenomx® software. Metabolite concentrations were normalized in preparation for Pearson correlation and one-way repeated measures ANOVA with multiple comparisons corrected by false discovery rate (FDR). RESULTS: Pretreatment histidine, phenylalanine, and threonine concentrations were inversely associated with maximum change in CIPN8 (ΔCIPN8) (p < 0.02; FDR ≤ 25%). Paclitaxel caused a significant change in concentrations of 2-hydroxybutyrate, 3-hydroxybutyrate, pyruvate, o-acetylcarnitine, and several amino acids from BL to EOI and/or 24H (p < 0.05; FDR ≤ 25%), although these changes were not associated with ΔCIPN8. CONCLUSIONS: Whole blood metabolomics is a feasible approach to identify potential biomarker candidates of paclitaxel-induced PN. The findings suggest that pretreatment concentrations of histidine, phenylalanine, and threonine may be predictive of the severity of future PN and paclitaxel-induced metabolic changes may be related to disruption of energy homeostasis.

Paclitaxel Plasma Concentration after the First Infusion Predicts Treatment-Limiting Peripheral Neuropathy.

Purpose: Paclitaxel exposure, specifically the maximum concentration (Cmax) and amount of time the concentration remains above 0.05 µmol/L (Tc>0.05), has been associated with the occurrence of paclitaxel-induced peripheral neuropathy. The objective of this study was to validate the relationship between paclitaxel exposure and peripheral neuropathy.Experimental Design: Patients with breast cancer receiving paclitaxel 80 mg/m2 × 12 weekly doses were enrolled in an observational clinical study (NCT02338115). Paclitaxel plasma concentration was measured at the end of and 16-26 hours after the first infusion to estimate Cmax and Tc>0.05 Patient-reported peripheral neuropathy was collected via CIPN20 at each dose, and an 8-item sensory subscale (CIPN8) was used in the primary analysis to test for an association with Tc>0.05 Secondary analyses were conducted using Cmax as an alternative exposure parameter and testing each parameter with a secondary endpoint of the occurrence of peripheral neuropathy-induced treatment disruption.Results: In 60 subjects included in the analysis, the increase in CIPN8 during treatment was associated with baseline CIPN8, cumulative dose, and relative dose intensity (P < 0.05), but neither Tc>0.05 (P = 0.27) nor Cmax (P = 0.99). In analyses of the secondary endpoint, cumulative dose (OR = 1.46; 95% confidence interval (CI), 1.18-1.80; P = 0.0008) and Tc>0.05 (OR = 1.79; 95% CI, 1.06-3.01; P = 0.029) or Cmax (OR = 2.74; 95% CI, 1.45-5.20; P = 0.002) were associated with peripheral neuropathy-induced treatment disruption.Conclusions: Paclitaxel exposure is predictive of the occurrence of treatment-limiting peripheral neuropathy in patients receiving weekly paclitaxel for breast cancer. Studies are warranted to determine whether exposure-guided dosing enhances treatment effectiveness and/or prevents peripheral neuropathy in these patients. Clin Cancer Res; 24(15); 3602-10. ©2018 AACR.