ESTRO 2023 - Abstract Book

S102

Saturday 13 May

ESTRO 2023

161 patients were recruited between 2016 and 2020. Demographic characteristics of the two groups of patients were well balanced. 83.1% of patients were treated according to study protocol. RTOG ≥ 1 score was 90.7% vs 94.9% and RTOG ≥ 2 was 9.3% vs 13.9% (in Mepitel arm vs ST respectively). RTOG toxicity ≥ 1 was observed after median 26 days in Mepitel arm vs 21 days in ST arm (p=0.0052), with a reduction in median recovery times (19 vs 32 days) (p=0.0068). Multivariate analysis, controlled for age, diabetes, BMI and smoking exposure, showed a 41% reduction in the risk of RTOG ≥ 1 (HR=0.59 95% CI (0.42-0.84), p=0.0036. In the Mepitel arm, the median time to evidence of RTOG ≥ 2 was 51 days vs 57 (p=0.0569) and multivariate analysis showed a reduction in the risk of RTOG ≥ 2 of 71% (HR=0.29 95% CI (0.09-0.92), p=0.0357. Conclusion The study showed overall improved toxicity control for the experimental arm, a reduction in the risk of toxicity and a reduction in recovery times. The device was well tolerated by patients, as reported by questionnaires. MO-0140 Predictive role of microvascular health status for RT acute toxicities in breast cancer patients. E. La Rocca 1 , F. Pisani 2 , F. Badenchini 2 , L. Possenti 2 , A. Cicchetti 2 , E. Gioscio 2 , C. Giandini 3,4 , R.R. Colciago 3,5 , M.C. De Santis 3 , R. Valdagni 3,2,4 , T. Rancati 2 1 Fondazione IRCCS Istituto Nazionale Tumori di Milano , Department of Radiation Oncology, Milano, Italy; 2 Fondazione IRCCS Istituto Nazionale Tumori di Milano, Prostate Cancer Program, Milano, Italy; 3 Fondazione IRCCS Istituto Nazionale Tumori di Milano, Department of Radiation Oncology, Milano, Italy; 4 University Of Milan, Department of Oncology and Hemato-Oncology, Milano, Italy; 5 University of Milan Bicocca, School of Medicine and Surgery, Milano, Italy Purpose or Objective To study the role of healthy/unhealthy microcirculation in predicting acute toxicity after adjuvant RT for breast cancer (BC). Materials and Methods We enrolled BC patients (pts) treated with hypofractionated RT after conservative surgery. The total dose delivered was 42.4 Gy plus 10 Gy for the boost on the tumour bed. We assessed each patient's baseline sublingual microvasculature (MV) health status on the first day of RT. A sidestream dark field camera coupled to the GlycoCheck™ software (Microvascular Health Solutions Inc, USA) was placed under the tongue by the pt herself. The system records videos showing the live movement of red blood cells (RBCs) in the microvessels and automatically computes functional parameters. Specifically, the following parameters were calculated (figure 1): -Perfused boundary region (PBR, in µ m), an estimate of the dynamic lateral movement of RBCs into the permeable part of the endothelial glycocalyx layer. Higher PBR values result from damaged glycocalyx (i.e. indicate an impaired microcirculation) -Total density of capillaries -Blood Flow in the analysed area (103 µ m3/s/mm2) -MV Health Score (MVHS™), higher values indicate healthier MV. MVHS is computed by weighting the information from the capillary density, the PBR, the blood flow and the recruitment capacity. Calculating MVHS requires at least 8 videos (i.e. needs more pts compliance), while the 3 functional parameters can be evaluated even with a single video. One radiation oncologist scored the toxicities before and at the end of RT, according to CTCAE v.4.0. We used univariate and multivariate logistic regression to assess the association between MV functional parameters and toxicity.

Results We evaluated 63 pts. The median age at RT start was 55 yrs (range 40-75 yrs); 45 (71%) had an evaluation of the MVHS. After RT, 13 pts experienced G1+ oedema (20.6%) and 23 G2+ erythema (36.5%). The MVHS was associated with erythema, a healthy MV protects from this toxicity (OR=0.49, p=0.007, AUC=0.81). A multivariate model including the separated functional parameters was also associated with erythema (figure 2, AUC=0.72): higher PBR is a risk (p=0.025, OR=1.04), higher capillary density protects (p=0.05, OR=0.99), while a higher blood flow is a risk (p=0.04, OR=1.006). Oedema associated with flow (risk factor, p=0.06, OR=1.0023) and PBR (risk factor, p=0.06, OR=1.03), AUC=0.74.