Disclosures: James H. Lau, MD: No financial relationships or conflicts of interest

Case Diagnosis: A 74-year-old female with T2N2M1 metastatic to liver and bone triple-negative breast cancer diagnosed with lumbosacral plexopathy secondary to SGN-LIV1A.

Case Description or Program Description: The patient was admitted to acute care after several ground-level falls secondary to a two-week history of bilateral lower extremity weakness with associated right foot drop and bilateral distal upper and lower extremity numbness and tingling. She had been taking SGN-LIV1A and pembrolizumab for 4 months and was initially evaluated by outpatient Cancer Rehabilitation. Nerve conduction studies (NCS) with electromyography (EMG) findings suggested bilateral lumbosacral plexopathy (L3-S1) with concurrent chemotherapy-induced peripheral neuropathy (CIDP) and L4/5 radiculopathy. SGN-LIV1A was held, but she experienced rapid functional decline and was admitted to the hospital. On initial inpatient evaluations, she required stand-by assist and a wheeled walker or gait belt for ambulation, transfers, and activities of daily living. Nuclear medicine (NM) bone scan and MR sacrum did not identify neoplastic invasion into the bone or lumbosacral plexus, respectively. However, she was found to have Baastrup’s disease around the L4/5 region.

Setting: Acute care hospital and tertiary care hospital

Assessment/Results: The patient remained off SGN-LIV1a and was discharged to Acute Rehabilitation. When evaluated by Oncology one month later, she exhibited grade 3 motor neuropathy in bilateral lower extremities with altered gait and significant improvement in right lower extremity strength and foot drop. She remained modified-independent with ADLs, ambulating with a walker.

Discussion (relevance): After a discussion between Cancer Rehabilitation and Oncology with consideration of the timing of presentation, distribution of symptoms, NCS/EMG findings, and improvement after SGN-LIV1a discontinuation, the patient was diagnosed with lumbosacral plexopathy from SGN-LIV1a administration in the setting of L4/5 radiculopathy secondary to Baastrup’s disease and CIDP. This is the only reported case of lumbosacral plexopathy secondary to SGN-LIV1a.

Conclusions: Optimal oncological care requires a multi-disciplinary approach that includes Cancer Rehabilitation experts to address cancer- and therapy-associated sequelae.

Level of Evidence: Level IV

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/bilateral-lumbosacral-plexopathy-secondary-to-a-course-of-ladiratuzumab-vedotin-sgn-liv1a-a-case-report/