ESTRO 2024 - Abstract Book

S647

Clinical - Breast

ESTRO 2024

1 Fondazione I.R.C.C.S Istituto Nazionale Tumori di Milano, Radiation Oncology, Milan, Italy. 2 Fondazione I.R.C.C.S Istituto Nazionale Tumori di Milano, Data Science Unit, Milan, Italy. 3 Aazienda Ospedaliero Universitaria Integrata, Radiation Oncology, Verona, Italy. 4 Fondazione I.R.C.C.S Istituto Nazionale Tumori di Milano, Medical Oncology 1, Milan, Italy

Purpose/Objective:

The increase in the conformal accuracy for dose delivery and and the enhanced routine use of image guidance have highly lowered the doses to the Organs at Risk and the uncertainties in dose distributions. Both processes have contributed to reducing the dose importance to predict the development of the historically called radiation-induced side effects. Radiogenomics studies on the influence of genetic variation on the specific patient response to radiation are widespread and involve multicenter involvement and data collection, dealing with the idea of identifying genetic signatures describing a limited percentage of patients at high risk of toxicity. The microvascular health of each patient highly modulates the inflammatory response caused by radiotherapy. Studies in the literature report cardiovascular diseases, hypertension and diabetes as risk factors for acute and late toxicity in a partially quantitative way. This confirms that the systemic condition impacts the local outcome even if radiotherapy is locally delivered. This study presents a predictive model for acute skin erythema in breast cancer (BCa) patients based on a combined quantitative score describing the patient's microvascular status at systemic and local levels as determined using two non-invasive tools.

Material/Methods:

We enrolled 88 BCa patients treated at 40 Gy in 15 fractions to the whole breast; 54 had a sequential dose boost.

We evaluated all patients before radiotherapy and derived the following objective measures of their microvascular status :

• Microvascular health score (MVHS, systemic score, range 1-10 with higher values describing a better condition). We used sublingual videomicroscopy to compute MVHS. The system analyzes videos of red blood cells circulating into arterioles, venules and capillaries, computes specific morphological/functional parameters and proposes MVHS as a global index. • The concentration of hemoglobin in skin capillaries (local score). We used a spectrophotometer to acquire and analyze reflectance spectra from the breast skin. The spectrophotometer works as the green light for smartwatches and measures the dermis reflectance spectra. A mathematical deconvolution of such spectra determines the hemoglobin concentration for a single patient. The concentration of hemoglobin is associated with the circulating oxygen within the skin capillary network. Higher values represent more irrorated tissues.

We used logistic regression to analyze the association between grade≥2 acute erythema and a score combining MVHS (systemic descriptor) and hemoglobin concentration (local descriptor).

Results: