Effects of pectoralis nerve block on quality of recovery after breast surgery has been debated. We hypothesized there might exist relevant psychosocial factor or variable of pain sensitivity which would influence on the benefit of nerve block.

This study aims to assess effect of pectoralis nerve block on QoR-15 score in subgroups stratified by such factors.

Study population All of patients will undergo partial mastectomy. 140 patients will be enrolled.

Intervention Pectoralis nerve block will be performed in the Block group.

Psychosocial factor screening Pain-detect, HADS, EQ-5D, PHQ-15 (somatic symptom), PCS (pain catastrophizing), BFI (big five inventory), HAM-A&D, Pressure algometry (Pain sensitivity), Quantitative sensory test (pinprick)

Study endpoints Quality of recovery (QoR)-15 Pain visual analogue scale Opioid consumption Breast Cancer Pain Questionnaire (BCPQ)

Inclusion Criteria:

• Patients aged 20 to 80 years who underwent partial mastectomy for breast cancer.

Exclusion Criteria:

• Patients with a history of previous breast surgery
• Patients with a history of adverse reactions to local anesthetics
• Patients with a history of drug addiction
• Patients with cancer other than breast
• Patients with chronic pain who require analgesics
• History of hospitalization for psychiatric disorders
• Preoperative pulse oximetry (SpO2) < 95 %
• Left ventricular ejection fraction < 40%
• Moderate or severe hepatic impairment
• Body mass index over 35 kg/m2
• Blood clotting disorders
• Pregnant/lactating women
• Inability to understand consent forms and answer research questionnaires due to cognitive impairment
• Unable to read consent form (eg illiterate, foreigner, etc.)
• do not perform axillary lymph node dissection

All researchers other than the anesthesiologist who manage the randomization table and the medical staff in charge of the patient must keep the group assignment blinded until the end of the study.