ESTRO 2024 - Abstract Book

S1772

Clinical - Lung

ESTRO 2024

We investigated the changes in 18fluoro-misonidazole (18F-MISO) positron emission tomography/computed tomography (PET/CT) parameters of patients with locally advanced non-small cell lung cancer (NSCLC) undergoing carbon-ion radiotherapy (CIRT) and whether the changes predict the outcomes.

Material/Methods:

We retrospectively analysed CIRT-treated patients with stage IIB – IIIC NSCLC who were previously enrolled in a prospective trial comparing photon beam radiotherapy to CIRT. 18F-MISO PET/CT was performed before and after CIRT, and the parameters of lesions ≥3 cm were recorded. Regions of interest (ROIs) were defined as lesions with the highest tumour-to- muscle ratio (TMR); ROIs with TMR ≥1.4 were considered hypoxia -positive.

Results:

Twenty-five eligible patients were included. The median follow-up time was 24.0 months. The median values of the maximum ROI diameter and volume were 6.4 cm and 93.0 cm3, respectively, and the median CIRT dose was 79.2 Gy (RBE weighted dose)/22 fractions. The median maximal standardised update value, TMR, hypoxic volume, and fractional hypoxic volume (FHV) before versus after CIRT were 2.96 versus 1.86, 1.98 versus 1.43, 6.34 versus 0.07 mL, and 5.3% versus 0.08%, respectively (all P<0.05). The 2-year overall survival (OS), progression-free survival (PFS), and local progression-free survival were 72.4%, 48.6%, and 75.5%, respectively. The post-CIRT FHV was independently associated with OS and PFS on multivariate analysis. Six patients who were hypoxia-negative before CIRT (group A) had the best clinical outcomes. The FHV of 7 patients with hypoxia- positive lesions decreased ≥99% after CIRT (group B), while that of 12 did not (group C). The OS and PFS of group A were significantly higher than those of group C; there were no significant differences between groups A and B.

Conclusion:

CIRT significantly reduced tumour hypoxia in patients with locally advanced NSCLC. FHV might be useful for predicting prognosis, and using 18F-MISO PET/CT to guide individualised CIRT dose painting warrants further investigation.

Keywords: 18F-fluoromisonidazole, carbon-ion radiotherapy

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Digital Poster

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Erkuden Burillo 1 , Mikel Rico 1 , Sonia Flamarique 1 , Ignacio Visus 1 , Ujué Ruiz 1 , Libe Amondarain 1 , Darwin Pozo 1 , Sara López 1 , Marisa Fernández 1 , Maribel Martínez 1 , Katty Zavala 1 , Patricia Lorenzana 1 , Paola Jablonska 1 , Irene Martínez 1 , Amaya Sola 1 , Marta Barrado 1 , Ana Manterola 1 , Fernando Mañeru 2 , Santiago Pellejero 2 , Victor De La Llana 2 , Elena Villafranca 1 , Enrique Martínez 1