Abstract CT109: Radiomic features in tumor assessment, preliminary results from a phase 2 study of intratumoral administration of BO-112 with pembrolizumab in patients with anti PD1 refractory melanoma

Abstract Background: There is a lack of predictive biomarkers for immunotherapy in melanoma. Immunohistochemistry and gene sequencing are frequently assessed as part of clinical research. Radiomic signatures may also add valuable information, based on parameters which can be related to immune infiltration, therefore defining an imaging biomarkers panel for this clinical scenario. BO-112 is a double stranded synthetic RNA formulated with polyethyleneimine (PEI) that, by mimicking the effect of a viral infection, mobilizes the immune system. The role of imaging biomarkers is being explored in the present phase II clinical trial. Study design: Single arm study with BO-112 plus pembrolizumab (NCT04570332) in patients with advanced melanoma in progression to anti-PD1 therapy. As part of exploratory objectives, a radiomics analysis was performed to detect changes in lesion texture features. Quantitative features were obtained by using Quibim Precision 2.9 platform (Quibim, Valencia, Spain) after the manual delineation of lesions on the CT study of each subject at each timepoint to obtain information about injected/non-injected lesions. Images were normalized by taking into account Hounsfield Units (HU) bias across scanners in a cross-calibration phantom and the Z-score. The difference (Delta) in the features between baseline and week 8 was calculated. Results: Studies were assessed based on event (progression) and based on whether lesions had been injected. Patients with only cutaneous disease were not included in this analysis. Out of 23 patients who had at least two imaging assessments, 6 developed progressive disease by week 8, and 17 subjects had no event by that time. Due to the small sample size, the radiomic analysis was based on hypothesis testing. With regards to volume, 50% of the non-progressing lesions reduced their value from that of the baseline. Regarding injected versus non-injected changes, up to 50% of injected lesions decreased their volume after 8 weeks of injected treatment whereas in non-injected lesions volume decreased in less than 25% of lesions. From the independent sample t-test of delta radiomics features against the injected/non-injected lesions variable, there were 4 features with a statistically significant difference between groups; all of them related to the Low Grey-Level Zone Emphasis. Specifically, Delta original GLRLM Low Grey-Level Run Emphasis showed the highest significant difference between injected and non-injected lesions (p=0.004), with higher and positive delta values in the injected group (75% injected lesions were above 0). Conclusions: Imaging biomarkers provide a large number of quantitative image features with a wide span of information, from size to heterogeneity of the tissue which may be indicator of tumor progression and immune infiltrate. In the analysis of radiomics features, delta GLRLM low grey-level zone emphasis was sensitive to the tumoral changes happening in injected lesions at week 8. This might add insights into the imaging-based evaluation of immune infiltration in intratumoral immunotherapy and the creation of associated imaging biomarkers panels. Citation Format: Paula Moreno, Philippe Saiag, Luis de la Cruz Merino, Caroline Dutriaux, Eduardo Castanon Álvarez, Caroline Robert, Juan F. Rodríguez-Moreno, Pablo Cerezuela-Fuentes, Ana M. Arance, Henry Montaudié, Miguel F. Sanmamed, María González Cao, María Pilar López Criado, Julie Charles, Alfonso Berrocal, Enrique de Miguel, Elisa Funk-Brentano, Pablo Sau Llanas, Sorilla Prey, Eva Muñoz-Couselo, Delvys Rodríguez Abreu, Juan Martin-Liberal, Ángel Alberich-Bayarri, Javier Sánchez López, Sonia Macia, Marisol Quintero, Marya F. Chaney, Stéphane Dalle, Iván Márquez-Rodas. Radiomic features in tumor assessment, preliminary results from a phase 2 study of intratumoral administration of BO-112 with pembrolizumab in patients with anti PD1 refractory melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT109.