ESTRO38 Congress Report

Clinical

4. BREAST Antihormones with or without irradiation in breast cancer: 10-year results of the ABCSG 8A trial (E38-1591)

Gerd Fastner MD 1 , Felix Sedlmayer MD 1 , JoachimWidder MD 2 , Martina Metz MD 3 , Hans Geinitz MD 4 , Karin Kapp MD 5 , Lidija Sölkner MSc 6 , Richard Greil MD 7 , Raimund Jakesz MD 6 , Werner Kwasny MD 8 , Dietmar Heck MD 9 , Vesna Bjelic-Radisic MD 10 , Marija Balic MD 11 , Herbert Stöger MD 11 , Ursula Wieder MD 12 , Ronald Zwrtek MD 13 , Dagmar Semmler MD 13 , Wilfried Horvath MD 14 , Elisabeth Melbinger-Zeinitzer MD 15 , Martin Wiesholzer MD 16 , Viktor Wette MD 17 , Michael Gnant MD6, 18 1 Department of Radiotherapy and Radio-Oncology, Paracelsus Medical University, University Hospital Salzburg, Landeskrankenhaus, Salzburg, Austria, 2 Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria, 3 Department of Radiooncology and Radiotherapy, Wiener Neustadt Hospital, Wiener Neustadt, Austria, 4 Department of Radiation Oncology, Ordensklinikum Barmherzige Schwestern Linz, Linz, Austria, 5 Department of Therapeutic Radiology and Oncology, Comprehensive Cancer Center (CCC), Medical University of Graz, Graz, Austria, 6 Austrian Breast and Colorectal Cancer Study Group,Vienna, Austria, 7 Department of Medical Oncology, Paracelsus Medical University, Salzburg, Austria, 8 Department of Surgery, Wiener Neustadt Hospital, Wiener Neustadt, Austria, 9 Department of Surgery, Ordensklinikum Linz Barmherzige Schwestern, Linz, Austria, 10 Department of Gynecology, Medical University of Graz, Graz, Austria, 11 Department of Internal Medicine, Division of Oncology, Medical University of Graz, Graz, Austria, 12 Department of Surgery, Hanusch Spital, Vienna, Austria, 13 Department of Surgery, Mistelbach Hospital, Mistelbach, Austria, 14 Department of Surgery, Guessing Hospital, Guessing, Austria, 15 Department of Surgery, Wolfsberg Hospital, Wolfsberg, Austria, 16 Department of Internal Medicine I, Division of Nephrology and Hematology, University Hospital St. Poelten, Karl Landsteiner University of Health Sciences, St. Pölten, Austria, 17 Department of Surgery, Krankenhaus der Barmherzigen Brüder St Veit an der Glan, St. Veit an der Glan, Austria, 18 Department of Surgery and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria Context of the study

were noted. In our risk analysis the omission of WBI turned out to be the main negative predictor for IBR.Unclassified tumor grading Gx had significant influence, which may be attributable to an unknown portion of a more aggressive undifferentiated grading G3 carcinoma (Figure 3). What impact could your research have? Radiotherapy (RT) still maintains its high potential to significantly improve LC and DFS in combination with AH compared to AH alone also for prognostically favourable breast cancer patients after long term FUP. In the light of current knowledge this does not necessarily address only WBI, since partial breast treatments (PBI) have turned out to be competitive in these low risk settings. PBI are currently carried out either with postoperative hypofractionated external beam radiotherapy (EBRT), intraoperative techniques (electrons (IOERT), 50-kV orthovolt) or interstitial brachytherapy, respectively. Therefore, a carefully performed patient selection on the basis of prognostic risk factors like patients` age, histopathological tumor characteristics as well as modern molecular genetic tests should help to decide about de-escalation of RT in speciic cases. The total omission of RT should only be considered in frail elderly patients who are not resilient for any radio-oncological intervention. Is this research indicative of a bigger trend in oncology? The results of our trial have shown that in postmenopausal “low-risk” breast cancer patients with positive hormonal receptors, RT remains of clinical relevance independently of antihormonal medication. However, our findings corroborate to the necessity of individually tailored and accurate treatment strategies. This includes all involved disciplines from surgery, medical oncology to radio-oncology in order to avoid overtreatment and to minimize treatment related toxicity. Especially in low risk patients, modern RT techniques like hypofractionated WBI or PBI reduce both overall treatment time and irradiated tissue volumes, apparently without compromising oncologic outcome.

It is still amatter of debate weather elderly postmenopausal women with a good prognosis of hormone sensitive breast cancer disease who receive antihormones (AH) profit froman additional course of postoperative whole breast irradiation (WBI) after breast preserving surgery (BPS). Most of the clinical trials, which investigated this issue, published their data after a median observation period of five years. So far, long term experiences are scarce and have been reported only twice by US and UK study groups. Hence, the Austrian Breast cancer and colorectal study group (ABCSG) decided to re-evaluate their data of 2007 (ABCSG 8A trial) after a 10 year follow up (FU), respectively. Overview of abstract The purpose of our research (updated ABCSG 8A trial) was to investigate 10 year long term data of hormonal receptor positive breast cancer patients after BPS (n= 869) who received consecutively AHwith (n= 439, group 1) or without WBI (n=430, group 2). As respective clinical endpoints were defined: local control (LC) in the affected breast, overall survival (OS; i.e. death due to any cause), disease-free survival (DFS; i.e. any clinical event due to breast cancer) and metastases-free survival (MFS; i.e. probability for no distant metastases). Furthermore, we were looking for possible independent risk factors, whichmight be predictive for local breast cancer recurrence. What were the three main findings of your research? After a median FU of 9.89 years, 10 patients developed an in-breast tumor recurrence (IBR) in group 1 (withWBI) and 31 in group 2 (without WBI), which translated into an actuarial 10-year LC of 97.5% and 92.5 %, respectively. As depicted in Figure 1, differences between both groups turned out to be statistical significant (p=0.0004). Moreover, with an 10-year DFS of 94%, breast cancer disease recurred less frequent in group 1 compared to 88.4% in group 2 (p= 0.01) (Figure 2). For all other remaining endpoints no significant differences

Congress report | CLINICAL

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