KEY TAKEAWAYS
- The study aimed to assess the efficacy of PBS PT in DIBH for mediastinal lymphoma.
- The results demonstrated that PBS PT in DIBH is a reliable method for treating mediastinal lymphomas, emphasizing reproducibility monitoring needs.
Filip Hörberger and the team aimed to assess the effectiveness of pencil beam scanning (PBS) proton therapy (PT) in deep inspiration breath-hold (DIBH) for patients with mediastinal lymphoma. This was done by retrospectively evaluating the robustness of treatment plans to the clinical target volume (CTV) and organs at risk (OARs) using repeated CT images acquired during treatment.
About 16 patients diagnosed with mediastinal lymphoma treated with PBS-PT in DIBH were enrolled. Treatment plans (TPs) were robustly optimized for the CTV using a margin of 7 mm and a dose variation of 4.5%.
Throughout the treatment course, repeated verification CTs (vCTs) were obtained, totaling 52 images for the entire patient cohort. Employing deformable image registration, the CTV and OARs were transferred from the planning CT to the vCTs. Subsequently, the TPs were recalculated based on the vCTs. Target coverage and OAR doses at the vCTs were compared to those of the nominal plan. Additionally, the deviation in lung volume was computed.
The results demonstrated that the TPs maintained consistently high target coverage throughout the treatment course, with a D98% of the clinical target volume (CTV) within a 2% deviation for 14 patients. Moreover, target coverage exceeded 95% in 49 of 52 verification CTs (vCTs), meeting the desired criteria.
However, in 2 patients, robust dose delivery to the CTV was not achieved due to inadequate reproducibility of DIBH, resulting in D98% of the CTV at 78% and 93%, respectively. Replanning was necessary for one patient. Adequate sparing of OARs was attained in all cases. Lung volume variation remained below 10% in 39 out of 52 vCTs.
The study concluded that PBS PT in DIBH represents a robust approach for treating mediastinal lymphomas. Nonetheless, vigilant monitoring of DIBH reproducibility during treatment is crucial to prevent potential underdosing of the CTV and to ensure adequate sparing of OARs. No funding information was available.
Source: https://pubmed.ncbi.nlm.nih.gov/38415848/
Hörberger, F., Andersson, K. M., Enmark, M., et al. (2024). “Pencil beam scanning proton therapy for mediastinal lymphomas in deep inspiration breath-hold: a retrospective assessment of plan robustness.” Acta Oncologica, 63(1), 62–69. https://doi.org/10.2340/1651-226X.2024.23964
