The goal of this prospective clinical trial is to improve patient compliance and performance of deep inspiration breath hold (DIBH) to further reduce the cardiac dose from left breast radiation, and to improve cooperation and patient satisfaction through an active and formal pre-treatment respiratory training program combined with relaxation training (R&R) in breast cancer patients undergoing adjuvant radiotherapy for left sided breast cancer.

The main questions the study aims to answer are:

• Does the use of communication training and the use of relaxation techniques (R&R) reduce the Maximum dose to the heart (Dmax) and improve further heart dose parameters in deep inspiration during adjuvant radiotherapy for breast cancer?
• Does R&R improve longitudinal anxiety and quality of life under patients undergoing DIBH adjuvant radiotherapy for left sided breast cancer?

Participants will be randomly assigned to either an experimental arm, which will receive the R&R, versus a standard arm that will not receive the R&R.

• training program in the experimental arm includes breath hold training, music, and nature sounds that patients can listen to on an MP3 player
• both groups complete standardized questionnaires about their well-being and satisfaction at prospective time points before, during the radiation treatment course, as well as at 6 weeks follow-up

Researchers will compare the R&R group (interventional arm) to current conventional DIBH instruction (standard group) to see if Dmax to the heart decreases and compliance and satisfaction under patients rises.

Postoperative radiotherapy is widely practiced and highly effective in enabling breast conserving therapy in early stage tumors, and decreasing recurrence while improving survival in patients with advanced-stage breast cancer, the most common cancer in women. However, these benefits of radiotherapy are associated with a long-term risk of cardiac morbidity and mortality in breast cancer survivors. The unintended cardiac radiation exposure due to the heart's proximity to the treatment target has been well recognized, particularly in left-sided breast cancer. Because there is no lowest "safe" threshold radiation dose level for radiation-induced cardiac complications, the dose to the heart must be kept as low as possible to reduce the complications risk.

Recent advances in high-precision 3D conformal and intensity-modulated radiotherapy techniques have enabled better protection of the heart. Treatment in deep inspiration breath hold (DIBH) is indispensable to realize these technological capabilities by taking advantage of the greater distance created between the radiotherapy target and the contralaterally and inferiorly displaced heart during deep inspiration. While many studies have demonstrated reduction of the heart dose with DIBH, challenges in decreasing heart dose to a minimum remain.

Radiotherapy in DIBH requires active and complex cooperation from the patient, and its success critically depends on how well patients are capable to perform the prolonged extended deep breathing maneuver on a repetitive basis every day during their weeks-long treatment course. Both the physical demands and profound anxiety and stress, which are highly prevalent in breast cancer patients, additionally interfere with patients' DIBH performance. Anxiety is well known to directly adversely affect breathing patterns, thereby challenging patients' ability to perform DIBH optimally.

Preliminary research explored the role of physical training and showed that targeted DIBH training improves patients' cooperation and the ease of the DIBH procedure, and reduces the radiation dose to the heart. However, while DIBH training regimens may improve patients' physical respiratory skill levels, they do not address their mental stress and anxiety. Relaxation techniques to alleviate anxiety and stress have been rarely used in complex radiotherapy procedures, particularly not in DIBH. Preliminary studies in diagnostic radiology procedures suggest that advanced communication and relaxation techniques, targeted to relieve anxiety and stress, improve patients' procedural performance, anxiety and comfort. The investigators hypothesize that implementing both, DIBH Respiratory Training and advanced communication and Relaxation Training (R&R), improve patients' DIBH performance skills and further reduce heart dose, while alleviating anxiety and stress and improving quality of life during and after radiation therapy.

The investigators propose to test this hypothesis in a clinical trial randomizing R&R vs. standard-of-care management in patients with radiotherapy in DIBH for left breast cancer. The investigators primary endpoint will assess heart dose (Dmax), and secondary endpoints include longitudinal anxiety and quality of life assessment and clinic workflow efficiency. The ultimate goal of this proposal is to develop a validated patient-centered training and integrative health regimen to further improve the success of advanced-technology-based cardiac dose reduction, and improve cardiac health in breast cancer survivors.

Inclusion Criteria:

• Female breast cancer patients
• Left sided breast cancer
• Treated with surgery prior to radiotherapy
• Age >18 years at time of inclusion
• WHO performance status 0-1
• Planned for radiotherapy alone to the breast, the chest wall and/or the lymph node areas
• Radiotherapy based on planning-CT scan using either 3D-CRT, IMRT, or VMAT/RapidArc
• Written Informed consent

Exclusion Criteria:

• Age <18 years
• Pregnancy, Breastfeeding
• Previous thoracic or mediastinal radiation
• Bilateral breast cancer
• Partial breast irradiation
• M1 disease (metastatic breast cancer)
• Severe lung disease