Abstract| Volume 14, ISSUE 4, SUPPLEMENT , S28, April 2013

Variations in potassium channel genes are associated with persistent severe arm pain after breast cancer surgery

      Pain at the site of injury is a common symptom in women who undergo breast cancer surgery. Pain occurs in the axilla and arm ipsilateral to the affected breast. Recently, we used growth mixture modeling to identify latent classes (i.e., subgroups) of patients with distinct trajectories of worst arm pain scores using a 0-10 numeric rating scale (NRS), reported monthly for 6 months after surgery. Using GMM, patients were classified into “No” (41.6%), “Mild” (23.6%), and “Severe” (34.8%) pain groups. Given their role in nociceptive transmission and our previous finding of an association with breast pain, we hypothesized that variations in potassium (K+) channel genes would be associated with persistent arm pain after breast cancer surgery. Therefore, the purpose of this study was to test for associations between single nucleotide polymorphisms (SNPs) among 10 K+ channel genes and persistent breast pain after surgery. Differences in a number of demographic (i.e., age, ethnicity, income), clinical (i.e., body mass index, functional status, number of comorbidities), preoperative (i.e., number of breast biopsies, neoadjuvant chemotherapy, stage of disease, breast pain), intraoperative (i.e., number of lymph nodes removed, number of drains placed, type of surgery, axillary lymph node dissection, intercostobrachial nerve sacrificed), and postoperative (number of postoperative complications, severity of average and worst postoperative pain, placement of a surgical drain, received biological therapy or physical therapy during the 6 months) characteristics among the pain classes (all p<.05). Significant associations were found between variations in 5 genes [KCND2 (n=6, p<.05), KCNJ3 (n=6, all p<.05), KCNJ6 (n=4, all p<.05), KCNJ9 (n=1, p=.005) and KCNK5 (n=9, both p<.05)] and pain group membership. K+ channel gene variations and distinct demographic and clinical characteristics are associated with a novel phenotypic characterization of severe persistent arm pain after breast cancer surgery.