The goal of this clinical trial is to learn if the AMADeuS care pathway is as safe as usual hospital care and works as well for pain control in women having mastectomy with immediate prepectoral breast reconstruction. The study will also look at quality of life, satisfaction with care, hospital resource use, and environmental impact.

The main questions it aims to answer are:

1. Does the AMADeuS pathway control pain during the first 48 hours after surgery as well as usual hospital care?
2. Is the AMADeuS pathway as safe as usual hospital care during the first 30 days after surgery?
3. Can the AMADeuS pathway improve recovery, reduce hospital stay and hospital visits, and lower the environmental impact of care?

Researchers will compare the AMADeuS pathway with usual hospital care. In the AMADeuS pathway, participants will have awake surgery with monitored anesthesia care, same-day discharge when safe, and follow-up that includes telemedicine. In the usual care group, participants will receive the hospital's standard perioperative care, which usually includes admission to the ward and follow-up visits at the hospital.

Participants may be women 18 to 75 years old who need nipple-sparing or skin-sparing mastectomy with immediate prepectoral reconstruction for early breast cancer or to lower future breast cancer risk. Participants must be suitable for day surgery and telemedicine follow-up. This includes having home support during the first 24 hours after surgery and living close enough to the hospital for safe discharge.

Participants will:

• be assigned by chance to the AMADeuS pathway or to usual hospital care have mastectomy with immediate prepectoral reconstruction report their pain during the first 48 hours after surgery
• be checked for medical problems during the first 30 days after surgery complete questionnaires about quality of life, symptoms, and satisfaction with care during follow-up
• have follow-up visits either through telemedicine and planned local care support or through standard hospital follow-up, depending on the group they are assigned to

Breast cancer remains one of the most common indications for mastectomy, despite the increasing use of breast-conserving approaches in selected patients. In current practice, nipple-sparing mastectomy and skin-sparing mastectomy followed by immediate implant-based reconstruction aim to maintain oncologic safety while improving aesthetic, functional, and psychosocial outcomes. Within implant-based reconstruction, the prepectoral approach avoids elevation of the pectoralis major muscle and may reduce muscle-related morbidity, postoperative pain, and animation deformity in appropriately selected participants.

Perioperative breast surgery pathways are also evolving toward higher-value care models based on enhanced recovery after surgery, opioid-sparing anesthesia, day surgery, and structured remote follow-up. Existing evidence supporting same-day discharge after mastectomy with immediate reconstruction suggests that this approach can be feasible and safe in selected patients when perioperative criteria and post-discharge support are standardized. In parallel, healthcare systems are increasingly required to consider resource use and environmental impact in addition to conventional clinical outcomes.

The AMADeuS protocol (Awake MAstectomy in Day surgery with immediate prepectoral implant reconstruction and muscle Sparing) was developed to integrate these elements into a single perioperative pathway for patients undergoing nipple-sparing or skin-sparing mastectomy with immediate prepectoral prosthetic reconstruction. The study is a prospective randomized single-center trial comparing the AMADeuS pathway with the institution's standard perioperative management. Its overall aim is to determine whether this integrated pathway can maintain clinical safety and adequate postoperative pain control while improving recovery, reducing hospital resource use, and lowering the environmental burden of care.

In the experimental arm, the AMADeuS pathway combines outpatient-oriented pre-admission planning, enhanced recovery principles, awake monitored anesthesia care with local anesthesia and interfascial locoregional blocks when appropriate, multimodal opioid-sparing analgesia, same-day discharge when discharge criteria are met, and structured telemedicine-supported follow-up. Preoperative management includes reduced fasting, carbohydrate loading, and risk-adapted thromboprophylaxis. Intraoperative management includes systematic antiemetic prophylaxis, targeted oxygen delivery, and minimization of unnecessary drug and material use according to a "do not open unless needed" approach. The operating room workflow is also organized to reduce waste through modular instrument sets opened only if required, reduced use of disposable devices, monitoring of personnel present in the room, and segregation of waste into predefined categories for environmental assessment. Postoperatively, the pathway promotes early oral intake, early mobilization, short ambulatory observation, same-day discharge when clinically appropriate, telemedicine review at 7 days, and suture removal either in clinic or through local primary care support.

In the control arm, participants undergo the same underlying surgical indication and reconstructive strategy within the hospital's usual care pathway. Standard care includes inpatient admission, perioperative management according to routine anesthetic and surgical practice, postoperative ward stay, and in-person postoperative follow-up. In this arm, anesthesia technique, airway management, instrument preparation, and operating room waste handling are left to standard institutional practice and clinician preference rather than protocolized sustainability measures.

The study is centered on early postoperative pain control as the primary efficacy objective and 30-day postoperative safety as a key safety objective. In addition, the protocol prospectively evaluates postoperative recovery, patient-reported outcomes, healthcare use, and environment-related outcome measures. Patient-reported assessments include global and breast-specific quality of life, reconstruction-related satisfaction and well-being, general health status, satisfaction with care, telemedicine satisfaction, and chronic postsurgical pain over follow-up. Environment-related measures quantify the carbon footprint of the care pathway through transport-related burden, operating room waste and resource use, and hospitalization-related impact.

The statistical framework includes randomized group comparison with intention-to-treat as the primary analytic approach, supported by per-protocol and safety analyses. The trial is powered on a non-inferiority hypothesis for early postoperative pain control. Based on the protocol assumptions, the planned enrollment is 100 participants overall, with 50 participants per group. Because uncommon postoperative adverse events would require a much larger sample size for a formal non-inferiority demonstration, the 30-day safety endpoint will be interpreted primarily through effect estimates and confidence intervals, with an additional supportive non-inferiority analysis specified in the protocol.

Overall, AMADeuS is intended to test a structured model of breast surgery that combines oncologically standard mastectomy and immediate prepectoral reconstruction with awake perioperative management, day-surgery organization, telemedicine-enabled follow-up, and sustainability-oriented operating room practices. The study is designed to evaluate whether this pathway can support a broader transition toward more efficient, patient-centered, and environmentally responsible surgical care without compromising early clinical outcomes.

**Inclusion Criteria:**

• Biologically female participants aged 18 to 75 years
• Oncologic or prophylactic indication for nipple-sparing mastectomy or skin-sparing mastectomy with immediate prepectoral reconstruction using a definitive implant or tissue expander, including early breast cancer or a high-risk genetic condition such as BRCA
• Eligible for prepectoral reconstruction based on clinico-anatomic criteria, including adequate skin flap thickness, no relevant vascular compromise, body mass index less than 35, and no severe prior chest radiotherapy
• American Society of Anesthesiologists (ASA) class I to III
• Eligible for day surgery, defined by home autonomy, caregiver availability during the first 24 hours after surgery, and distance from the hospital compatible with home management
• Able and willing to complete telemedicine follow-up, including completion of protocol-required patient-reported outcome measures
• Written informed consent provided

**Exclusion Criteria:**

• Chronic opioid use or treatment for pre-existing chronic pain that could interfere with assessment of the primary postoperative pain endpoint
• Contraindications to locoregional anesthesia techniques or to the awake/monitored anesthesia care protocol, including allergy to local anesthetics, coagulation disorders, or inability to cooperate during surgery
• Body mass index 35 or greater, or anatomic conditions contraindicating prepectoral reconstruction
• Previous high-dose chest radiotherapy with significant tissue compromise
• Pregnancy or breastfeeding
• Inability to guarantee planned follow-up or lack of adequate home support
• Psychiatric or cognitive conditions preventing correct completion of patient-reported outcome measures

De-identified individual participant data underlying the results reported in publications may be shared with qualified researchers on reasonable request after publication of the primary results. Data sharing will be subject to institutional approval, compliance with applicable privacy and data protection regulations, and execution of an appropriate data sharing agreement.

This is an open-label trial for participants and treating clinicians because the study compares 2 different perioperative care pathways. An independent blinded outcome assessor will review prespecified postoperative clinical outcomes, including 30-day complications, whenever feasible.