Assessment of chemotherapy-induced peripheral neuropathy using the LDI(FLARE) technique: a novel technique to detect neural small fiber dysfunction

INTRODUCTION: The diagnosis and quantification of chemotherapy-induced peripheral neuropathy (CIPN) remains a challenge. Conventional methods including quantitative sensory testing (QST), nerve conduction tests, and biopsy are unable to detect subclinical changes, and do not consistently correlate with severity of patients' symptoms and functional impairment. This study aims to determine the utility of the LDI (laser Doppler imager) (FLARE) technique in the diagnosis of CIPN and whether it correlates with symptom severity. MATERIALS AND METHODS: We assessed 24 patients with established CIPN [12 due to platinum analogs (P(A)) and 12 to Taxanes (T(X))] and 24 matched healthy controls (H(C)). All underwent neurophysiological examination including vibration perception threshold (VPT), sural nerve amplitude (SNAP) and conduction velocity (SNCV), LDI(FLARE), and fasting biochemistry. The QLQ-CIPN20 questionnaire was used to assess symptom severity. RESULTS: H(C), combined chemotherapy (C(G)), P(A)(,) and T(X) groups were matched for age, sex, BMI, and blood pressure. The LDI(FLARE) was significantly reduced in C(G) compared to H(C) (P =< 0.0001), whereas SNAP (P = 0.058) and SNCV (P = 0.054) were not. The LDI(FLARE) correlated with the QLQ-CIPN20 symptom scores in all three categories namely, C(G) (P =< 0.0001), P(A) (P = 0.001) and T(X) (P = 0.027) whilst, VPT, SNAP, and SNCV did not. CONCLUSION: Our findings suggest that the LDI(FLARE) technique is more helpful in confirming the diagnosis of CIPN in patients with distal sensory symptoms than current commonly used methods. Moreover, this novel test fulfils the unmet need for a diagnostic test that relates to the severity of symptoms. This may be useful in quantifying early changes in small fibre function indicating early CIPN.