Importance of Physical Medicine and Rehabilitation in a Patient With Bilateral Lumbosacral Plexopathy Following the Course of Ladiratuzumab Vedotin for Breast Cancer: A Case Report

A 74-year-old female with metastatic triple-negative breast cancer was admitted to the acute care hospital after several ground-level falls and a two-week history of bilateral lower extremity weakness with foot drop, numbness, and tingling. She was on ladiratuzumab vedotin (SGN-LIV1A) and pembrolizumab for four months prior to cancer treatment. Lumbar and sacral imaging studies did not identify neoplastic invasion into the bone or lumbosacral plexus. Electrodiagnostic findings suggested bilateral lumbosacral plexopathy (L3-S1). In the setting of rapid functional decline, medications were reviewed, and SGN-LIV1A was held. On initial evaluation, she required significant assistance with ambulation, transfers, and activities of daily living (ADLs). She remained off SGN-LIV1A and was discharged to acute inpatient rehabilitation. One month following discharge from acute inpatient rehabilitation, she exhibited improvements in right lower extremity strength and foot drop and progressed to modified-independent with ADLs, ambulating with a walker. In a discussion between cancer rehabilitation and oncology with consideration of the timing of presentation, distribution of symptoms, nerve conduction study and electromyography (NCS/EMG) findings, and improvement after SGN-LIV1A discontinuation, the patient was diagnosed with lumbosacral plexopathy from SGN-LIV1A administration. This is the only reported case of lumbosacral plexopathy secondary to SGN-LIV1A and addresses the importance of early consultation with cancer rehabilitation to address sequelae stemming from cancer therapy.