To review our institutional clinical experience of applying the AlignRT system to monitor patient setup and reproducibility when using ABC and DIBH techniques in the treatment of left-sided breast cancer patients.

To review our institutional clinical experience of applying the AlignRT system to monitor patient setup and reproducibility when using ABC and DIBH techniques in the treatment of left-sided breast cancer patients.

To review our institutional clinical experience of applying the AlignRT system to monitor patient setup and reproducibility when using ABC and DIBH techniques in the treatment of left-sided breast cancer patients.

Reproducibility of set-up will be evaluated by determining discrepancies in patient's surface between treatment and CT simulation which will be acquired with the Align RT system using multiple measures along with daily portal images during treatment and weekly CBCTs.

Estimate the change in mean heart dose for each breath-hold/heart sparing strategy by:

i. Converting differences in heart position on 2D portal images acquired during treatment to 3D volumes on Pinnacle plans.

ii. Using the CBCT images (acquired weekly), to recalculate dose to heart based on the patient's position and anatomy that day.

QoL will be assessed using the EORTC core QoL questionnaire (QLQ-C30) which is a well-validated and widely used QoL questionnaire available in multiple languages (12,13). QLQ-C30 is composed of 30 questions that represent 5 functional scales (physical, role, cognitive, emotional and social), 3 symptom scales (fatigue, nausea and vomiting, and pain), and a global health / QoL scale. The questionnaire will be completed by patients at time of radiation simulation as baseline, at completion of RT (during routine review) and at the 6-8 week follow-up.