ESTRO 37 Abstract book

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ESTRO 37

Conclusion With the proposed fully automated re-optimization technique, the percentage of daily plans with adequate target coverage increased from 1.1% to 97.7%, and all plans showed decreased OAR doses. With an average re- optimization time of 3 minutes, this method is an important step towards real-time adaptive proton therapy.

Conclusion High pre-treatment CAC based on planning CT scans is associated with ACE in BC patients treated with postoperative RT, even after correction for confounding factors such as MHD. radiodermatitis: final results of a RCT in bre ast cancer patients J. Robijns 1 , S. Censabella 2 , S. Claes 3 , L. Pannekoeke 3 , L. Bussé 1 , I. Kaminksi 1 , D. Colson 1 , A. Maes 3 , P. Bulens 3 , L. Noé 3 , M. Brosens 3 , A. Timmermans 4 , I. Lambrichts 5 , V. Somers 1 , J. Mebis 1,2,3 1 Hasselt University - Faculty of Medicine and Life Sciences, Immunology-biochemistry, Hasselt, Belgium 2 Jessa hospital, Medical Oncology, Hasselt, Belgium 3 Jessa hospital, Limburg Oncology Center, Hasselt, Belgium 4 Jessa hospital, Dermatology, Hasselt, Belgium 5 Hasselt University - Faculty of Medicine and Life Sciences, Morphology, Hasselt, Belgium Purpose or Objective Acute radiodermatitis (RD) occurs in about 95% of the patients undergoing radiotherapy (RT) as part of their cancer treatment. We studied the benefit of photobiomodulation therapy (PBMT) in the prevention of acute RD in breast cancer patients undergoing RT. Material and Methods Between April 2015 and June 2017, 120 breast cancer patients undergoing an identical RT regime post- lumpectomy were enrolled in this study. Patients were randomly assigned to the control group (n=60), receiving a placebo treatment (i.e. inactive laser diode) or the laser group (n=60), receiving PBMT. Placebo or PBMT was applied twice a week after the RT session from the first until the last day of RT. All patients were blindfolded during the sessions. PBMT was delivered using a class IV MLS® M6 laser that combines two synchronized laser diodes in the infrared range (808-905 nm) with a fixed energy density (4 J/cm 2 ). A blinded RT nurse evaluated the patients’ skin reactions based on the criteria of the Radiation Therapy Oncology Group (RTOG) at the first day, at fraction 20, and at the end of RT. Results In both groups, most patients presented RTOG grade 1 at fraction 20 of RT, with no significant difference in RTOG grades (p= .562) between the groups. In contrast, at the end of RT, the severity of the skin reactions was significantly lower in the laser than in the control group (p= .004). A larger percentage of patients demonstrated RD grade 2 or higher in the control than in the laser group (30% vs. 6.7%, for the control and laser group, resp.). As such, the skin reactions worsened in the control group (p= .008), while in the laser group they stabilized (p= .204) towards the end of RT. OC-0092 Photobiomodulation prevents acute

Proffered Papers: RTT 1: Innovative strategies for improving patient care

OC-0091 Prognostic value of calcium score in breast cancer patients treated with radiotherapy C. Roos 1 , V. Van den Bogaard 1 , M. Greuter 2 , R. Vliegenthart 2 , E. Schuit 3 , J. Langendijk 1 , A. Van der Schaaf 1 , A. Crijns 1 , J. Maduro 1 1 University of Groningen- University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands 2 University of Groningen- University Medical Center Groningen, Center for Medical Imaging, Groningen, The Netherlands 3 University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht, The Netherlands Purpose or Objective Recent studies on dose-effect relationships showed that acute coronary events (ACE) already occur in breast cancer (BC) patients within the first 9 years after RT and that the absolute excess risk depends on pre-existent cardiovascular risk factors and age. Therefore, it becomes increasingly important for radiation oncologists to identify which baseline factors are important for BC patients. The coronary artery calcium (CAC) score is a well-established and reliable early predictor of ACE in the general population. The CAC score is normally measured using diagnostic electrocardiogram (ECG) triggered Computed Tomography (CT) scans. In this study we tested whether pre-treatment CAC based on non-triggered planning CT scans was associated with the cumulative incidence of ACE among BC patients treated with postoperative RT. Material and Methods The study population consisted of 939 consecutive female BC patients treated with RT. The CAC score was established on non-triggered pre-treatment RT planning CT scans. The CAC score was classified into widely used clinical CAC score categories: CAC zero (0), low CAC (>0 - <100), intermediate CAC (100 – 400) and high CAC (≥400). Due to limited number of events in the high CAC score category the high CAC score category was combined with intermediate category to maintain sufficient statistical power. The association between CAC and ACE was tested using Cox-proportional hazard models. Known cardiovascular risk factors for ACE and the individual mean heart dose (MHD), collected from the three- dimensional CT planning scans, were tested for confounding of the association between CAC and ACE. Results CAC scores varied from 0 to 2,859 (median 0). The 9-year cumulative incidence of ACE was 3.2% and was significantly associated with the pre-treatment CAC score (low CAC p=0.043, Intermediate + high CAC p=<0.001). After correction for confounders, age, history of ischemic heart disease, diabetes, Body Mass Index ≥30, MHD, hypercholesterolemia and hypertension, the hazard ratio for ACE for the low and the combined intermediate and high CAC score category were 1.42 (95% CI: 0.49-4.17; p=0.519) and 4.95 (95%CI:1.69-14.53; p=0.004) respectively, compared to the CAC zero category.

Severity of radiodermatitis expressed in RTOG grades for the control and laser group at fraction 20 and at the end of RT. *Significant difference within the control group between the two time points and between the two groups at the end of RT (p<0.05; χ² or Fisher’s exact tests, two-tailed). RTOG Radiation Therapy Oncology Group; LT: laser therapy