ESTRO 2024 - Abstract Book

S2215

Clinical - Upper GI

ESTRO 2024

The curative treatment of esophageal cancer (EC) is challenging and the prognosis of these patients remains poor. Although the mortality of EC is mostly tumor-related, patients face considerable risk of death from cardiopulmonary diseases, partly due to radiation-induced toxicities. Furthermore, to overcome inter-fractional esophageal motion during radiotherapy, large clinical target volumes (CTVs) are needed. With the possibility of daily re-planning, online adaptive radiotherapy (oART) has the potential to improve target coverage and spare OARs. In this study, we report our first clinical experiences and dosimetric investigations of CBCT-based oART in EC performed on the Ethos machine (Varian, Palo Alto, CA).

Material/Methods:

Treatment fractions of the first ten patients with EC receiving CBCT-based oART at our institution in 2022 were retrospectively analyzed. Prescription dose was 50.4 Gy in 28 fractions. The same CTV and PTV margins as in the non-adaptive situation were used. For all 280 fractions, the timestamp of each oART workflow step and target volume doses, mean heart dose and lung V20Gy of both the scheduled and the adapted treatment plan were analyzed.

Results:

After automatic propagation of target volumes from planning-CT to the daily CBCT, CTVs was adapted by the physician in 164 (59%) fractions. The adapted treatment plan was selected in 276 (99%) fractions. The median time needed for the oART process was 28 minutes (range, 14.8 - 43.3). In all 10 patients, an improved minimal (= D99%) and coverage (= D95%) PTV dose and lower lung V20Gy was observed with the adapted plan, while a reduced mean heart dose was achieved in 8 patients. Comparing the adapted with the scheduled treatment plans in all 280 fractions, the D99%PTV and D99%CTV dose could be increased from 79.7% to 94.1% and 93.4% to 98.2%, respectively. Similarly, with the adaptive plan a gain from 92.4% to 97.3% and 97.8% to 98.9% of the D95%PTV and D95%CTV dose was observed, respectively. Concurrently, a reduction of the mean heart dose from 18.5 to 16.8 Gy and the V20Gy of the lung from 15.9% to 13.6% was observed with the adapted plan.

Conclusion:

Although being resource-intensive, oART for EC is feasible and can be performed in a reasonable timeframe. To our knowledge, we show here for the first time, that oART for EC results in improved coverage of target volumes and sparing OAR at the same time, even without reduction of contouring margins. A prospective trial to analyze whether these dosimetric benefits translate into a meaningful clinical benefit is planned.

Keywords: Esophageal Cancer, Online Adaptive Radiotherapy

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Poster Discussion

Cardiac complications after esophageal cancer trimodality therapy are related to left ventricle dose