About 20-68% of patients who have undergone surgery for breast cancer experience chronic postoperative breast pain, commonly known as post-mastectomy pain syndrome. Usually neuropathic in origin, this pain can begin in the immediate postoperative period but may be delayed for 6 or more months after surgery and characteristically persists beyond the normal healing period. The exact mechanism is unknown, but damage to the intercostobrachial nerve has been a proposed source. We alternatively hypothesize that as the T4 and T5 sensory cutaneous branches come off the chest wall accompanied by a blood vessel to enter the breast, they are cut and cauterized during the mastectomy procedure, which can damage the nerve and lead to neuroma formation and postoperative neuropathic pain along the distribution of these specific dermatomes.
Neuropathic pain involves both inflammatory and immune mechanisms, which sensitize nociceptors. Perineural infiltration of dexamethasone and local anesthetic has been found to be effective in alleviating neuropathic pain. We use the same principle to treat neuropathic pain for post-mastectomy patients, targeting injections at areas of point tenderness where the T4 and T5 nerves likely egress from the chest wall.
Beginning in January 2011, we treated and prospectively tracked patients who presented with postmastectomy burning or shooting pain and point tenderness located at either the inframammary fold directly inferior to the nipple or laterally along the midaxillary line. The point of maximal pain was identified and injected at the level of the chest wall under sterile conditions followed by 1-2 minutes of massage. Each injection consisted of 2mL of an equal ratio of 0.5% bupivacaine and 4mg/mL dexamethasone.
Over the past 18 months, we treated 19 patients who underwent partial mastectomy (3), partial mastectomy with breast reduction (3), or total mastectomy with immediate reconstruction (12), all with chronic breast pain. One patient had neuropathic pain after a lateral core biopsy. Among the 19 patients, there were a total of 29 sites injected at points of tenderness. All patients achieved relief of their pain within minutes of the injection. Point pain decreased from 8-9 to 0-1 on a 0-10 pain scale after the injection. 18 injections (62%) in 11 patients resulted in long term relief after 1 injection. 9 injections (31%) had to be repeated in 8 patients, one of which was subsequently repeated a third time, with long term relief. 1 patient who experienced neuropathic pain after stereotactic biopsy did not get relief, likely because the site of nerve injury was not properly targeted.
Perineural infiltration with a combination of bupivacaine and dexamethasone is a simple and effective potential treatment option for chronic neuropathic pain after mastectomy. Surgeons and nurses should routinely check for postoperative neuropathic pain as there is a simple and safe intervention that has a dramatic impact on alleviating this pain. This study also emphasizes the need for careful dissection of the T4 and T5 sensory nerves during surgery to avoid postoperative neuroma formation, which may play a larger role in post-mastectomy pain than the intercostobrachial nerve.
Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-10-03.