Preoperative Resting-State EEG Features Associated With Chronic Postoperative Pain After Breast Cancer Surgery: A Prospective Cohort Study.

BACKGROUND

Chronic postoperative pain after breast cancer surgery varies substantially among patients and may reflect individual neurophysiological susceptibility. We explored whether preoperative resting-state electroencephalography (EEG) features are associated with clinically significant chronic postoperative pain.

METHODS

In this prospective cohort study, 100 female patients scheduled for mastectomy or breast-conserving surgery were enrolled. After exclusions for incomplete EEG acquisition, protocol changes, loss to follow-up, or poor EEG quality, 84 patients were analyzed. Preoperative variables included age, body mass index, American Society of Anesthesiologists physical status, neoadjuvant chemotherapy, surgical approach, and axillary lymph node dissection (ALND). At 3 months, patients were classified as higher-pain (HP; Numeric Rating Scale [NRS] ≥4) or lower-pain (LP; NRS <4). Exploratory analyses compared clinical characteristics, spectral power, and functional connectivity between groups.

RESULTS

Twenty-seven patients (32.1%) were classified as HP. The median [IQR] 3-month NRS score was 5 [4 to 6] in the HP group and 1 [0 to 2] in the LP group. Mastectomy versus breast-conserving surgery (OR=3.43, 95% CI: 1.31-8.99; P=0.010) and ALND versus no ALND (OR=5.75, 95% CI: 2.12-15.59; P<0.001) were associated with higher pain. Preoperative gamma-band power at F3, Fz, and F4 was higher in HP patients, with no group differences in other bands. Gamma-band connectivity involving frontal, insular, and cingulate regions was also stronger in the HP group.

CONCLUSIONS

Preoperative frontal gamma activity and connectivity may reflect baseline neurophysiological vulnerability to chronic postoperative pain after breast cancer surgery. These exploratory group-level findings warrant validation in larger cohorts.