278 - Low Radiation Doses to Peripheral Tumor Tissue in Metabolism Guided Lattice Irradiation Based on LATTICE-01 Study: A Search for Dose Constraints to Determine a "Spatial Analysis of Peripherical Tissue Effects in the Clinic (SpatialP-TEC)"
Presenter(s)
G. Ferrantelli1, S. Parisi2, A. Brogna3, G. Iati'2,4, V. Venuti5, F. Chillari5, P. Lanza1, I. Finocchiaro1, C. Siracusa6, A. Pontoriero2, S. Leotta7, A. Santacaterina7, and S. Pergolizzi2; 1University of Messina, BIOMORF Department, Messina, Italy, 2Radiation Oncology Unit - Department of Biomedical, Dental Sciences and Morphological and Functional Images, University of Messina, Messina, Italy, 3Medical Physics Unit - Department of Biomedical, Dental Sciences and Morphological and Functional Images, University of Messina, Messina, Italy, 4University of Messina, Radiation Oncology Unit, Messina, Italy, 5Radiation Oncology Unit, Villa S. Teresa-Bagheria, Bagheria, Italy, 6University hospital "G. Martino", Messina, Messina, Italy, 7Radiation oncology Unit, AO Papardo, Messina, Messina, Italy
Purpose/Objective(s): To evaluate clinical outcomes in stage IV patients treated with metabolism guided-LATTICE radiotherapy (LRT) techniques related to the dose delivered in the peritumoral area. The hypothesis is that low doses delivered to the periturmoral tissue (PTT) can modulate PTT immune microenvironment, affecting survival status and guaranteeing impressive results in some studies. The aim is to determine a constraints of dose that can enhance/maximize the immunogenic effect on the PTT to design a Spatial analysis of Peripherical Tissue Effects in the Clinic (SpatialP-TEC).
Materials/Methods: From December 2021 to January 2025, we retrospectively analyzed clinical metastatic patients with bulky lesions treated with spatially fractionated-metabolism guided-LATTICE radiotherapy (SFRT-LATTICE) according to LATTICE-01 multicentric study. It is a special kind of dose delivering where high spherical conformed doses are delivered within the GTV and placed at the edges of tumour areas with different metabolism on 18-FDG-PET/CT according to a non-geometric arrangement. On day 1, high radiation dose was delivered to the spheres. Within 7 days, a homogeneous Gross Tumor Volume (GTV) irradiation started. Here we present the analysis of sphere(s) dose distribution only on PTT. We collected and analyzed the average, minimum and maximum doses at GTV and the V0.5, V1, V2, V3 (expressed in % value) distributed on PTT [(GTV+ 0.5 mm) – GTV)]. We searched, as well, the possible correlation to clinical outcomes by uni and multivariate backward stepwise logistic regression.
Results: 64 treatment plans have been revised. The histological types were heterogeneous. All treated lesions exhibited an inhomogeneous tissue appearance, likely due to the alternating presence of hypoxic and normoxic areas within them. The median GTV volumes were 224.41 cc (range = 6.84-1707.01 cc). A median of 2 spheres were allocated within the GTVs (range 1-9) and were planned to receive a median of 12Gy/1fraction (range 10-15 Gy). V0.5, V1, V2 and V3 PTT values were: Median V3 percentage was 21.01% (range 0%-71.14%), median V2 percentage was 40.05% (range 0.2%-90.15%), median V1 percentage was 62.04% (range 9.8%-97.86%) and median V0.5 percentage was 74.99% (range 15.98%- 99.69). Median Dmax to PTT was 9.97 Gy (range 2.46-16.29 Gy); Median Dmin to PTT was 3.3 Gy (range 0-31.6). Median FU time 20 months (range 2-46 months). At the time of study analysis (Jan 2025) we observed local control in 42/63 patients with 37/63 death. Analysing the dose interval within PTT we found that there is a significant correlation between V2/OS status (p=0.021, Odd Ratio 1.079) and V3/OS status (p=0.038, Odd Ratio 0.921).
Conclusion: Despite the low number of cases in our analysis, it seems that V2 and V3 on PTT could be related to Overall Survival and that we have to deliver a high percentage of V3 in PTT. It is possible to suppose that dose constraints in PTT is a value comprised between 2 and 3 Gy. Further studies are needed in this range of dose a to determine a SpatialP-TEC.