ESTRO 2023 - Abstract Book

S1069

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ESTRO 2023

Conclusion IBH did not improve relevant NTCPs for both proton and photon plans for lung cancer patients, even though for a specific subset of patients, the decrease in grade 2 radiation pneumonitis NTCP could be clinically relevant. This is in contrast with in-house results for mediastinal lymphoma patients. Further margin reduction, as well as patient or plan specific parameters that predict if a patient would benefit overall from IBH, require further investigation. [1] Bosmans G et al., Radiother Oncol. 2006;81(1):73-80 [2] Appelt et al., Acta Oncol 2014;53(5):605-612

[3] Darby et al., NEJM 2013;368:987-998 [4] Wijsman et al., R&O 2015;117(1):49-54

PO-1335 Second SABR course in local pulmonary relapses: cumulative doses in OARs

D. caivano 1 , V. Puccini 2 , I. Angelicone 3 , R.C. Sigillo 3 , M. Rotondi 4 , A. Fontana 5 , M.F. Osti 3

1 Ospedale Santa Maria Goretti , Radioterapia, Latina, Italy; 2 Azienda Ospedaliera Universitaria Sant'Andrea, UOC Radioterapia, Roma, Italy; 3 Azienda Ospedaliera Universitaria Sant'Andrea, UOC Radioterapia, Roma, Italy; 4 Azienda Ospedaliera Universitaria Sant'Andrea, UOC Radioterapia, Italy, Italy; 5 Ospedale Santa Maria Goretti, Radioterapia, Latina, Italy Purpose or Objective Stereotactic ABlative Radiotherapy (SABR) is a technique able to give high dose of radiation on the target sparing organs at risk (OARs). SABR can be used in the treatment of primary lung tumors or secondary lung lesions, in inoperable patients or patients who refuse surgery, with a curative intent. In a percentage of case, depending on the histology, localization and dose/regimen used, patients can have a local recurrence. Aim of this study is to evaluate the safety and clinical outcomes of a second in field SABR course. Materials and Methods From 2011 to 2021 we have re-treated by a second course of SABR 16 in field recurrent lung lesions. The median age was 76 years (range: 68– 87years). The ECOG Performance status was ≤ 2. Five lesions were form Colon Rectal Cancer (CRC); 1 lesion was from Gynecological primary, 9 form lung tumor and for one lesion we did not have an histology. The medium EQD2(10) of first treatment was 94,5 Gy (range: 63,25-126 Gy) and the medium BED (10) of first treatment was 113,46 Gy (range: 75,9-151,2 Gy). The medium EQD2(10) of second treatment was 76,9 Gy (range: 40-126 Gy) and the medium BED (10) of second treatment was 92,25 Gy (range: 48-151,2 Gy). The medium time between two treatments was 19 months (range: 6 – 47 months). The medium PTV was 31,08 cc (range: 8,90- 94,6cc). Two lesions were re-treated with a single fraction, 14 lesions were re-treated with multiple fractions. Results The Local Control was 46,67 % with rates at 1 year of 62% and at 3 years of 33%. At univariate analysis we had a statistically correlation of LC and time between two treatments, we recorded worse results in patients re-treated in a time ≤ 19 months (P = 0,0435). The rates of Progression Free Survival at 1 year and 3 years were 68% and 23% respectively. The rates of Disease Specific Survival (DSS) at 1 years and 3 years were 87% and 45% respectively. The rates of Overall Survival at 1 years and 3 years were 81% and 41 % respectively. At univariate analysis we had a statistically correlation of OS and number of comorbidity (P = 0,0077). The best response was achieved in a 7-month time average (range 1-33 months) in terms of complete response (7%),