The block (ESP or PVB) will be performed preoperatively in the recovery room under standard monitoring. After setting a peripheral venous access, patient will be installed on lateral decubitus position on the opposite side of the block.

The block will be performed with IV Remifentanil sedation Target-Controlled Infusion mode at 2ng/ml and oxygen therapy.

For the erector spinae plane block:

The puncture will be performed with ultrasound guidance. The ultrasound probe will be placed parallel to the spine parasagittally at the T3 transverse process level. The needle will be introduced and visualized to the plane of the ultrasound image ("in plane").

The desired injection site is between the fascia of the erector muscle of the spine and the transverse process at the T3 level. The operator ensures the correct localization of the needle with saline solution. Then 0.50% Ropivacaine hydrochloride will be injected at a dose of 0.6 ml/kg of actual weight, without exceeding 30 ml.

For paravertebral block:

The T2 intervertebral space will be located by identifying compared to C7, a prominent cervical vertebra, or by ultrasound by counting the thoracic vertebrae from the first rib. The paravertebral space will be identified by placing the ultrasound probe in a parasagittal or transverse position. The needle will go through the paravertebral muscles and the costo-transverse ligament or by a latero-medial approach using ultrasound. The block will be performed using a 22-gauge 8cm long needle. When the paravertebral space has been reach, an aspiration test will be performed and then 0.6 ml/kg of solution (Ropivacaine hydrochloride solution at 5 mg/ml up to 30 ml) will be injected.

Inclusion Criteria:

1. Woman with breast adenocarcinoma without metastasis or breast in situ adenocarcinoma (with or without breast reconstruction by prosthesis) to by treated:

   • either by breast-conserving surgery with axillary dissection,
   • either by modified radical mastectomy with axillary dissection
   • either by modified radical mastectomy with lymph node dissection
   • either by modified radical mastectomy without axillary

2. Patients aged between 18 and 85 years old.

3. ASA class 1, 2 or 3 (Physical Status Classification System of American Society of Anesthesiologists (ASA)).

4. Signed informed consent form.

5. Patient able to answer self-assessment questionnaires (sufficient understanding of evaluations and in French).

6. Patient affiliated to the health care insurance.

Exclusion Criteria:

1. Preoperative consumption of opioid in the patient's current medications within three months before inclusion.
2. Ipsilateral breast surgery during 3 months prior to the inclusion.
3. Allergy to local anaesthetics and morphine and NSAID.
4. Local skin inflammation at the puncture area.
5. Bilateral breast surgery planned at inclusion.
6. Major immediate ipsilateral breast reconstruction by using tissue flap procedure (example: latissimus dorsi flap, Deep Inferior Epigastric Perforator (DIEP), Transverse Rectus Abdominis Musculocutaneous (TRAM)…).
7. Any contra-indication or patient's refusal for regional anesthesia.
8. Male subjects.
9. Pregnant woman or breastfeeding.
10. B blocker medication.
11. Patient already participating in an analgesia protocol that may interfere with the pain assessment criteria.
12. Patient under legal protection.
13. Inability to undergo medical monitoring of the trial for geographical, social or psychological reasons.

Sponsor will share de-identified data sets. Documents generated under the project will be disseminated in accordance with Institut Curie policies.

Data requests can be submitted starting 9 months after last article publication and will be made accessible for up to 12 months.

Access to trial individual participant data can be requested by qualified researchers engaging in independent scientific research, and will be provided following review and approval of a research proposal and Statistical Analysis Plan (SAP) and execution of a data sharing agreement (DSA).