SAN ANTONIO – Perineural injection of bupivacaine and dexamethasone was a simple and effective treatment for chronic neuropathic pain following mastectomy, based on results of a pilot study.
The effectiveness of this novel therapy strongly suggests the source of this common pain syndrome is damage to the T4 and T5 sensory nerves during surgery, rather than damage to the intercostobrachial nerve, as traditionally thought, according to Dr. Cathy J. Tang of the University of California, San Francisco.
The T4 and T5 sensory nerves come off the chest wall and enter the breast accompanied by a blood vessel. When these nerves are cut and cauterized during mastectomy, the resultant nerve damage can manifest as neuroma formation and neuropathic pain along the two dermatomes, she said at the San Antonio Breast Cancer Symposium.
Chronic postmastectomy breast pain is commonly referred to as postmastectomy pain syndrome. Published estimates of its incidence after mastectomy range from 20% to 68%. The pain can start in the immediate postoperative period, or onset can be delayed up to 6 months or more post mastectomy. The pain is typically experienced as a shooting or burning pain, with point tenderness. It persists well after the expected healing period.
The intervention involves identifying a patient’s points of maximum pain or tenderness, usually located laterally along the midaxillary line or at the inframammary fold directly below the nipple. These points are injected at the level of the chest wall. Each injection consists of 2 mL of an equal ratio of 0.5% bupivacaine plus 4 mg/mL of dexamethasone followed by a minute or two of massage to enhance infiltration of the area.
Dr. Tang reported on 19 patients who developed postmastectomy pain syndrome after either partial mastectomy, total mastectomy with immediate reconstruction, or lateral core biopsy in one case. A total of 29 points of maximum tenderness were identified and treated. All patients had pain relief within minutes, with point pain scores on a 0-10 scale falling from 8-9 to 0-1. Long-term pain relief was experienced after 17 of the 29 initial injections (59%) in 11 patients. Pain was resolved at another nine sites after a second injection. A third injection at one recalcitrant site led to long-term pain relief. Thus, perineural injections alleviated pain at 27 of 29 treated sites, or 93%, at a mean of 10.7 months of follow-up.
In light of how simple and safe this treatment is, Dr. Tang urged routine inquiry about postmastectomy neuropathic pain. Patients with postmastectomy pain often report an inability to lie on the affected side or to wear a bra.
The study also indicates the importance of careful dissection of the T4 and T5 sensory nerves during mastectomy in order to minimize the risk of postoperative neuroma formation.
Dr. Tang reported having no financial conflicts regarding this unfunded study.