ESTRO 2020 Abstract book

S163 ESTRO 2020

human studies was applied. Articles were excluded when the relationship between hyperthermia dose and outcome in patients with breast cancer was not analyzed, less than 10 patients or lesions were reported, concurrent chemotherapy or drugs were given or when articles were updated in a later publication by the same author(s). Results A total of 1249 articles were identified through the search and were screened. Twenty-two articles were included in the systematic review, reporting on 2330 patients with breast cancer treated with re-RT+HT. In total, thirty-two different HT dose parameters were tested for a correlation with tumor response and thermal toxicity. Thermal dose showed a significant correlation with clinical complete response in 10/15 studies, in 10/13 studies for duration of local control, in 2/2 studies for overall survival and in 7/11 studies for thermal toxicity. Patients who received a high thermal dose, had on average 34% (range 27-53%) more complete responses than patients who received a low thermal dose. Low dose hyperthermia combined with RT is comparable to RT alone (Figure 1). The incidence of thermal toxicity increased with higher maximum skin temperature. Patients who achieved higher HT dose had increased odds/ probability on improved clinical outcome and on thermal toxicity.

supraclavicular (SC) nodes with IMRT-VMAT-SIB modalities 50 Gy/2Gy/fr and 48 Gy/1.92 Gy/fr and baseline normal thyroid function tests (TFTs), were retrospectively analyzed. Patients assuming antipsychotic were excluded. The thyroid gland had been already contoured for each pts at the planning time giving a constraint of V30 <50%. Each patient's dose volume histogram (DVH), whole thyroid volume (TYV) , the SC PTV volume, the volume percentages of the thyroid receiving 30 Gy (V30), the D mean (average dose in whole volume of gland) and the ratio between the whole thyroid volume and the SC -PTV (thyroid irradiated ratio or TYR) were then estimated. Free triiodothyronine (FT3), free thyroxin (FT4), and thyrotropin (TSH) , TG (thyroglobulin), and thyroid antibodies (anti-TG, antimicrosomal, and antiperoxidase) were monitored before and performed every six months after RT completion. The risk of HT according to dosimetry and other clinic factors were also performed. Univariate with χ 2 , t-test and Pearson covariance for multivariate analyses adjusted per age were used for statistical analysis to exclude the bias of advanced age . A p <0.05 was considered statistically significant. Results The median follow-up was 36 (6 -72) months. The median age was 54 years (32-80). Of 50 patients, 16 pts (32%) were diagnosed with HT. The median time to the onset of HT was 18 months (4-30). The mean SC PTV value was 108 cc ( 41-145cc) , the mean thyroid volume of was 15.6 cc (11.5- 38 cc) and D mean of thyroid gland was 22.5 Gy (18-35 Gy). The mean V30 Gy was 38 % ( 28- 45 %). In univariate analysis age > 70 yrs , D mean > 20 Gy , the TYV < 18 cc , the SC-PTV > 85 cc, the V30 Gy > 40 % and the TYR > 0.2 were significant associated prognosticators for HTy The D mean > 20 Gy (p < 0.001, odds ratio (OR) 20 [95%CI 18-30]) and the TIR > 0.2, (p < 0.001, OR15 [95%CI 10-25]) , age > 70 yrs (p < 0.005, OR 6.07 [CI 2.36–15.59]) were significant prognosticators of HT in multivariate analysis. No statistical correlation was found for chemotherapy (p = 0.35, OR 0.61 [95%CI 0.2-30.8]), TYV (p = 0.15, OR 0.53 [95%CI 0.2-1.2]), SC PTV (p = 0.18, OR 0.54 [95%CI 0.7- 1.8]), and V30 Gy > 40 % (p = 0.11 , OR 0.52 [95%CI 0.23- 1.19]). Conclusion With the limits of a retrospective analysis, despite the gland V30 < 50%, the risk of hypothyroidism in BC pts after SC-IMRT -VMAT seems t depend on several factors as the D mean > 20 Gy and a TYR > 0.2. Dosimetric efforts should be done to minimized the risk of HTy mainly in younger patients. PD-0295 FAST approach in early breast cancer irradiation: toxicity and outcome in a 3DCRT vs IMRT comparison M.A. Zerella 1,2 , S. Arculeo 1,2 , S. Dicuonzo 1 , V. Dell'Acqua 1 , M.A. Gerardi 1 , A. Morra 1 , L. Bergamaschi 1,2 , S. Frassoni 3 , V. Bagnardi 3 , C. Fodor 1 , F. Cattani 4 , V. Galimberti 5 , P. Veronesi 5 , R. Orecchia 6 , M.C. Leonardi 1 , B.A. Jereczek- Fossa 1,2 1 IEO European Institute of Oncology- IRCCS, Division of Radiation Oncology, Milan, Italy ; 2 University of Milan, Department of Oncology and Hemato-oncology, Milan, Italy ; 3 University of Milan-Bicocca, Department of Statistics and Quantitative Methods, Milan, Italy ; 4 IEO European Institute of Oncology- IRCCS, Unit of Medical Physics, Milan, Italy ; 5 IEO European Institute of Oncology- IRCCS, Division of Breast Surgery, Milan, Italy ; 6 IEO European Institute of Oncology- IRCCS, Scientific Direction, Milan, Italy

Figure 1. The beneficial effect of hyperthermia therapy (HT) when added to radiotherapy (RT) may require a high HT dose in patients with locoregional recurrent breast cancer. Data from Datta et al. (2016) are compared to the results of this review. Conclusion Higher thermal dose during HT improved complete response, duration of local control and overall survival of patients with recurrent breast cancer treated with re- RT+HT. Higher maximum skin temperature increased incidence of thermal toxicity. PD-0294 Hypothyroidism in IMRT-VMAT breast cancer supraclavicular radiotherapy : a retrospective study G. Lazzari 1 , A. Terlizzi 2 , M.G. Leo 2 , G. Silvano 1 1 Azienda Ospedaliera SS. Annunziata Presidio Osped, Radiology, Taranto, Italy ; 2 Azienda Ospedaliera SS. Annunziata Presidio Osped, Department of Fisica Sanitaria, Taranto, Italy Purpose or Objective to estimate the incidence of hypothyroidism (HTy) and to evaluate the predictors affecting its development after IMRT-VMAT among breast cancer (BC) patients (pts) receiving supraclavicular (SC) radiation therapy (RT). Material and Methods Between May 2013 to May 2019, consecutive 50 BC pts undergoing adjuvant RT on breast/chest wall and

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