ESTRO 2024 - Abstract Book

S4022

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

Figure 2: Histogram of fraction number where D98%,CTV < 95% for the 5mm (blue) and 2mm (orange) plans separately.

Conclusion:

The results reveal that 2mm plans present challenges in daily CTV coverage, requiring adaptation at least once for about half the patients. However, the accumulated dose analysis suggests that both the 5mm and the 2mm plans are robust with respect to CTV coverage against anatomical changes. The results in Figure 2 show that the frequency of adaptation is not needed at one or two fixed time during the treatment. For a 2 mm margin, adaptation is essential to account for more random changes, suggesting the need for an online ART approach. Importantly, 2mm plans offer significant reductions in mean OAR doses. Any potential clinical gain of online ART in H&N cancer may require a synchronous PTV margin reduction.

Keywords: Adaptive, HNSCC, dose-tracking

1271

Digital Poster

Improving breast cancer radiotherapy: determine need for plan adaptation based on corrected CBCTs

Hanna R. van de Glind, Vincent C. Hamming, Nick Fuhler, Johannes A. Langendijk, Nanna M. Sijtsema, Stefan Both

University Medical Center Groningen (UMCG), Radiotherapy, Groningen, Netherlands

Purpose/Objective:

Currently, repeatCT (rCT) is acquired for breast cancer patients when significant (≥ 7 mm) anatomical deformations are visible on the CBCT. Only 46.2% of these rCTs need plan adaptation based on dosimetrical evaluation, resulting