This study compares two nerve block techniques-Rhomboid Intercostal with Sub-Serratus Plane Block versus Erector Spinae Plane Block-for pain relief after breast cancer surgery. It aims to determine which method provides better postoperative pain control, reduces opioid use, and improves recovery in patients undergoing modified radical mastectomy at the National Cancer Institute, Cairo University.

This randomized controlled trial aims to evaluate the analgesic efficacy of two ultrasound-guided regional anesthesia techniques-Rhomboid Intercostal Block with Sub-Serratus Plane Block (RIB + SSP) and Erector Spinae Plane Block (ESB)-in patients undergoing Modified Radical Mastectomy (MRM) for breast cancer. Eighty female patients aged 18-65 years with ASA physical status II or III will be enrolled and randomly assigned to receive either RIB + SSP or ESB prior to surgery. Both blocks will be performed under ultrasound guidance 30-45 minutes before induction of general anesthesia.

The primary outcomes are postoperative pain scores measured using the Visual Analog Scale (VAS) and total opioid consumption in the first 24 hours after surgery. Secondary outcomes include intraoperative and postoperative hemodynamic parameters, time to first analgesic request, total intraoperative opioid use, recovery time, patient satisfaction, and incidence of adverse effects such as nausea and vomiting.

The study will be conducted at the National Cancer Institute - Cairo University from June 2025 to June 2026. Ethical approval will be obtained, and written informed consent will be collected. This study aims to identify the more effective and safer regional technique to improve postoperative recovery and reduce opioid dependence in breast cancer patients.

Inclusion Criteria:

• Female breast cancer patients undergoing Modified Radical Mastectomy (MRM)

ASA physical status II or III

Age between 18 and 65 years

Body Mass Index (BMI) > 20 kg/m² and < 35 kg/m²

Exclusion Criteria:

• Patient refusal

ASA physical status IV

Age <18 years or >65 years

BMI < 20 kg/m² or > 35 kg/m²

Known allergy or contraindication to local anesthetics or opioids

History of psychological disorders or chronic pain

Contraindications to regional anesthesia (e.g., coagulopathy, local infection, peripheral neuropathy)

Severe respiratory, cardiac, hepatic, or renal disease

Individual Participant Data (IPD) will not be shared due to institutional policies regarding data confidentiality and privacy. Additionally, there is no established infrastructure for secure data sharing or monitoring of secondary data use at this time.

Double-blind design: Participants, anesthesia providers, investigators, and outcome assessors will be blinded to group allocation. Group assignments will be concealed using opaque sealed envelopes, and blocks will be performed by anesthesiologists not involved in intraoperative care or postoperative evaluation.