Assessment of deep inspiration breath hold (DIBH) amplitude and reduction in cardiac dose in left breast cancer patients

Introduction The primary aim of this study was to examine the impact of deep inspiration breath-hold (DIBH) amplitude on subsequent mean heart dose and V30 during radiotherapy. The secondary aim was to investigate if patient age influenced DIBH amplitude. Method A retrospective study of 30 patients with left-sided breast cancer was completed. Patient were randomly selected from the total number of patients dual scanned in free breathing (FB) and DIBH over a 2-year period. Plans were retrospectively virtually simulated and statistical analysis performed. Results All patients achieved decreased V30 and mean cardiac dose using DIBH. A positive correlation was found between DIBH amplitude and cardiac V30 dose reduction (p=0.007, R=0.48). Ratio of amplitude increase from FB to DIBH and cardiac V30 reduction was positively correlated and statistically significant (p=0.04, R=0.38); Ratio of amplitude increase of at least 15 times FB achieved 100% V30 dose reduction, however this was also achieved with ratio increase as low as 6.25 times FB. A statistically significant positive correlation was identified between DIBH amplitude and mean cardiac dose reduction (p=0.003, R=0.523). No correlation was found between patient age and amplitude ratio increase (p=0.602, R=-0.099) Conclusion A 100% reduction in cardiac V30 can be achieved with a DIBH amplitude increase of 15 times FB. A full reduction can also be achieved at much lower levels (6.25 times FB in current study); however there appears to be no pre-determining patient factors to identify this. DIBH amplitudes of 1cm-4cm reduce cardiac mean dose by at least 50%