Onabotulinum toxin injections for shoulder and chest wall muscle pain in breast cancer survivors: retrospective study - preliminary report

Objectives: The primary objective of this retrospective review is to describe patient-reported improvement in muscular pain after initial treatment with onabotulinum toxin. A secondary objective was to determine other physiatry (physical medicine & rehabilitation (PM&R)) interventions ordered. Methods: Preliminary retrospective review of physiatry interventions for 47 patients referred by breast radiation oncology to PM&R at a tertiary referral-based academic cancer centre clinic from 1 January 2018 to 31 December 2021 for muscular shoulder/chest wall pain. Results: Patients were most commonly diagnosed with muscle spasm 27/47 (58%), lymphedema 21/47 (45%), myalgia/myofascial pain 16/47 (34%), radiation fibrosis 14/47 (30%), fatigue/deconditioning 13/47 (28%), neurological impairment 11/47 (23%) and joint pathology 3/47 (6%). The top three physiatric interventions were home exercise programme education (17/47, 36%), botulinum toxin injection (17/47, 36%) and physical or occupational therapy referral (15/47, 32%). Patients who had muscle spasms documented were more likely to have botulinum toxin recommended by physiatry (24/24) compared with those with questionable spasms (4/7) and those without spasms(0/16) (p=0.0005). 17/28 (60.7%) received botulinum toxin injection, and a total of 35 injections were performed during the study period. 94% (16/17) of patients who received botulinum toxin injection voiced improvement in pain after injection. Conclusion: Botulinum toxin injections may play a role in the treatment of muscle spasm-related pain in breast cancer survivors. Additional blinded controlled research on the effectiveness of botulinum toxin injection after breast cancer treatment with spastic muscular shoulder/chest wall pain is needed.