(Kiosk 1) Pembrolizumab-induced Peripheral Neuropathy: A Case Report of an Uncommon Adverse Effect

Case Diagnosis: Chemotherapy-Induced Peripheral Neuropathy (CIPN) secondary to Pembrolizumab

Case Description or Program Description: 92-year-old female with history of bladder cancer presented with 10th rib fracture and rhabdomyolysis after an unwitnessed fall. Patient was diagnosed with bladder cancer in 2018 and was treated only with pembrolizumab. She subsequently developed hypothyroidism and paresthesias. Since her chemotherapy, she had multiple falls due to imbalance and loss of sensation in her feet. On presentation, she endorsed bilateral, burning foot pain of moderate intensity. Of note, the patient is a social alcohol drinker, has a 60 pack-year smoking history, and previously lived in pre-war buildings. Patient was managed on the surgical service, and when medically stable was admitted for acute rehabilitation.

Setting: Inpatient rehabilitation facility

Assessment/Results: On examination, she had 4/5 strength throughout upper and lower extremities, dispersed purpura, hyperesthesia on light palpation of shins and feet, and severely decreased sensation to vibration bilaterally in a stocking glove distribution. Her pain was controlled with acetaminophen and gabapentin. She participated well in a therapy-program and showing promising improvement in functional gains.

Discussion (relevance): CIPN affects millions of patients yearly with reduced quality of life and increased healthcare costs. It presents with sensory and sometimes motor symptoms including numbness, tingling, impaired vibratory sense, paresthesias, and gait disturbances. Severity is dose-dependent, and may be worse with older age and increased comorbidities. CIPN is commonly associated with platinum-based antineoplastics, vinca alkaloids, and taxanes. Immune-checkpoint inhibitor (ICI) monoclonal antibody drugs, like pembrolizumab, are part of a new class of chemotherapy. Long term side-effects have not been well studied. Some research studies are showing that the adverse effect of ICI-induced peripheral neuropathy may have an incidence rate of up to 7%.

Conclusions: CIPN is an uncommon side effect of ICI medications. Early recognition of symptoms is vital so early treatment can be tailored to minimize severity and impairment.