ESTRO 2023 - Abstract Book

S761

Monday 15 May 2023

ESTRO 2023

Conclusion Thoracic reRT is applied in patients with locally recurrent and metastatic cancer to achieve different treatment goals, mostly using modern, conformal techniques or SBRT. Clinical practice diverges regarding patient selection, the minimum interval after primary RT, and acceptable OAR dose constraints. Thus, prospective investigation to guide harmonization of decision making and treatment management would be desirable. OC-0916 2nd conservative treatment for 2nd breast tumor event: a GEC-ESTRO prognostic factor analysis J. Hannoun-Levi 1 , J. Gal 2 , C. Polgar 3 , V. Strnad 4 , K. Loessl 5 , B. Polat 6 , D. Kauer-Domer 7 , R. Schiappa 2 , C. Gutierrez 8 1 Antoine Lacassagne cancer center, Radiation Oncology, Nice, France; 2 Antoine Lacassagne Cancer Center, Epidemiology and Biostatistics, Nice, France; 3 National Institute of Oncology, Radiation Oncology, Budapest, Hungary; 4 Erlangen University Hospital, Radiation Oncology, Erlangen, Germany; 5 Inselspital, Bern University Hospital, Radiation Oncology, Bern, Switzerland; 6 Wurzburg University, Radiation Oncology, Wurzburg , Germany; 7 Medical University of Vienna, Radiation Oncology, Vienna, Austria; 8 Catalan Institute of Oncology, Radiation Oncology, Barcelona, Spain Purpose or Objective In case of ipsilateral 2nd breast tumor event (2ndBTE), mastectomy or 2nd conservative treatment (2ndCT) combining lumpectomy plus accelerated partial breast re-irradiation (APBrI) represent the two salvage therapeutic options. We aimed to address the lack of evidence regarding 2ndCT prognostic factors in case of 2ndBTE. Materials and Methods The GEC-ESTRO prospective database was updated (7 hospitals/cancer centres from 6 European countries). In this study, patients (pts) with 2ndIBTE underwent 2ndCT with APBrI (multicatheter interstitial brachytherapy MIB). Pts were categorized using APBI and molecular classifications. Scoring systems were generated by combining APBI + Molecular classifications ([APBI/Mol] class.) and APBI + Molecular + Time interval between 1st/2nd lumpectomy ([APBI/Mol/TIS1S2] class.) (Fig. 1). Oncological outcome focused on 3rdIBTE (3rdIBTE-FS), regional relapse- (RRFS) and metastatic disease- (MD-FS) free survivals as well as disease-free (DFS), specific (SS) and overall (OS) survival. Prognostic factors for oncological outcome were explored by uni- and multivariate analysis. Late toxicity and cosmetic results were reported. Figure 1:

Results etween 07/1994 and 01/2022, 508 pts experiencing a 2ndIBTE underwent a 2ndCT. Median age at the time of 2ndIBTE was 66 years [31–90], the median TIS1S2 was 152 months [12–437]. 2ndBTE occurred at distance from the primary tumor bed in 30%. Median tumor was 10 mm [7-15] while invasive ductal carcinoma was the most frequent histology (70%). Low risk (APBI class.) and HR+/Her2- (molecular class.) pts were 313 (62%) and 346 (68%) respectively, while TIS1S2 was >60 months for 438 pts (86%). High-dose rate brachytherapy was used for 390 pts (77%). Endocrine therapy, chemotherapy