Rotational arc treatments with static ports and dynamic collimation reduces cardiopulmonary dose for esophageal cancer patients and diminishes model-based predicted benefit of proton therapy

Background and purpose

Reducing dose to the lungs and heart is essential to minimize toxicity in esophageal cancer patients undergoing trimodality therapy. This study compared a new technique combining rotational arcs, static beam angles and dynamic collimation (RAD) against standard intensity-modulated radiotherapy (IMRT) and proton therapy (PT).

Materials and methods

RAD-plans were created for ten patients from the PROTECT trial who had high mean lung doses in their clinical IMRT-plan. For all techniques, optimization prioritized lung sparing. Predicted pulmonary complication risks were estimated using a validated NTCP-model. Comparisons were made between IMRT, RAD, and PT, and the impact on model-based PT-referral (ΔNTCP > 10 %) was assessed.

Results

RAD lowered mean lung dose compared with IMRT (median 10.2 Gy [range 8.3–12.5 Gy] versus 12.0 Gy [10.2–16.3 Gy], p < 0.01) and also incidentally reduced mean heart dose (median 24.1 Gy [20.9–25.0 Gy] versus 25.7 Gy [21.9–26.1 Gy], p < 0.01). PT achieved the greatest sparing, with mean lung dose reduced to 5.1 Gy [2.8–7.1 Gy] and mean heart dose to 9.8 Gy [6.4–13.6 Gy] (both p < 0.01 compared to RAD). RAD reduced the predicted pulmonary complication risk versus IMRT on average 7 % (p < 0.01), with individual patient ΔNTCPs ranging from 2 % to 19 %. PT offered further benefit, with an additional average ΔNTCP reduction of 11 % compared to RAD (p < 0.01). Model-based PT-referral was indicated for nine IMRT-plans versus only five RAD-plans.

Conclusion

RAD reduced lung and heart dose compared to IMRT in esophageal cancer patients undergoing trimodality treatment, lowering predicted risk for pulmonary complications, which influenced PT-referral decisions.