A New Method for Identifying Sensory Changes in Painful Chemotherapy-induced Peripheral Neuropathy (CIPN)

Painful chemotherapy‐induced peripheral neuropathy (CIPN) is a common side effect of chemotherapy, occurring in more than 60% of patients at some point during the course of cancer treatment with commonly used drugs such as taxanes and platinum compounds. It potentially may result in severely diminished quality of life and dose reduction or/and treatment delay, which may ultimately impact survival. The mechanisms by which chemotherapy‐induced nerve damage ultimately leads to pain are poorly understood, because virtually no structural or functional differences in nerve fibers between painless and painful peripheral neuropathy have been identified. As a result, there is no reliable way to predict which patients will develop persistent painful chemotherapy‐induced peripheral neuropathy. The ultimate goal of this study is to develop a non‐invasive, bedside quantitative test that is specific for painful CIPN. If our initial hypothesis is confirmed, the next step would be to design a prospective longitudinal study and assess changes in DLss early after initiation of chemotherapy, to determine whether this approach can help identify early predictive parameters of painful CIPN. In this other interventional study, we will test the utility of the Diode Laser fiber type Selective Stimulator (DLss) to identify sensory changes that are unique to patients with painful chemotherapy induced peripheral neuropathy (CIPN) vs. controls. Painful symptoms of CIPN develop in patients with differential nerve damage to Aδ vs C‐type peripheral nerve fibers. We hypothesize that Aδ:C fiber threshold ratio, as measured by the DLss, will be different between patients with painful CIPN compared to control patients who received a similar regimen of chemotherapy, but did not develop painful CIPN. The confirmation of hypothesis may lead to a novel approach for early detection of CIPN. Subjects: 20 evaluable patients with painful CIPN following treatment with oxaliplatin, cisplatin, paclitaxel, docetaxel (or any combination of above) will be included in painful CIPN group, and 20 controls matched by the type of chemotherapy received, who did not develop painful CIPN. The study procedure will include a one‐time visit for sensory assessments including: 1. Spontaneous pain at baseline on 0‐10 Numerical Rating Scale (NRS); 2. Assessment of pain symptoms on Neuropathic pain Symptom Inventory (NPSI) and Brief Pain Inventory (BPI). 3. Assessment of mood on hospital anxiety and depression scale (HADS) 4. Quantitative sensory testing (QST): thermal detection and pain thresholds, mechanical detection threshold, temporal summation (TS), and conditioned pain modulation (CPM). The primary outcome is the comparison of Aδ:C fiber threshold ratio between patients who have developed painful CIPN, and the control subjects. In secondary analyses, we will generate Spearman correlation coefficient between the "Aδ:C fiber threshold ratio" and the severity of painful CIPN on NPSI scale.