VMAT plans were more robust on average than conventional 3DCRT plans for DIBH when localization errors were taken into consideration. The combination of robust VMAT planning and DIBH generally improves the homogeneity and target doses.

In radical RT for prostate cancer, daily CBCT IGRT with reduced PTV margins demonstrated no advantage with respect to patient reported side effects at end of RT as compared to weekly orthogonal offline portal imaging with standard PTV margins.

This study shows that there is a substantial baseline drift in free breathing BCRT patients. No clear baseline drift was observed during the first treatment session; however, baseline drift was markedly present at the rest of the sessions. Intrafraction motion due to baseline drift should be accounted for in margin calculations.

Deep inspiration breath hold (DIBH) in left‐sided breast cancer radiotherapy is a technique to reduce cardiac and pulmonary doses while maintaining target coverage. This study aims at evaluating an in‐house developed DIBH system. Free‐breathing (FB) and DIBH plans were generated for 22 left‐sided localized breast cancer patients who had radiation therapy (RT) after breast‐conserving surgery. All patients were treated utilizing an in‐house laser distance measuring system. 50 Gy was prescribed, and parameters of interest were target coverage, left anterior descending coronary artery, (LAD) and heart doses. Portal images were acquired and the reproducibility and stability of DIBH treatment were compared to FB. The comparing result shows there is a significant reduction in all LAD and heart dose statistics for DIBH compared to FB plans without compromising the target coverage. The maximum LAD dose was reduced from 43.7 Gy to 29.0 Gy and the volume of the heart receiving >25 Gy was reduced from 3.3% to 1.0% using the in‐house system, both statistically significant. The in‐house system gave a reproducible and stable DIBH treatment where the systematic error ∑, and random error σ, were less than 2.2 mm in all directions, but were not significantly better than at FB. The system was well tolerated and all patients completed their treatment sessions with DIBH.

Highlights Modern IGRT has given new insight regarding organ motion in radiotherapy. Rectal volume variation may increase the risk of biochemical and local failure. Rectal volume decreased significantly during eight weeks of radiotherapy. The percentage of irradiated rectal volume did not change statistically significant. Our study shows that IGRT ensures a close to stable dose to the rectum.