2860 - Long-Term Outcomes of Risk-Adapted Targeted Intraoperative Radiotherapy vs. External Beam Radiotherapy in Early Breast Cancer: Post-Hoc As-Treated Analysis of the German Cohort of the TARGIT-A Trial
Presenter(s)
G. R. Sarria1, S. Pigorsch2, M. Pazos3, C. Roedel4, J. Fleckenstein5, T. W. park-Simon6, R. Voelker7, M. K. Bulsara8, J. S. Vaidya9, F. Wenz10, and E. Sperk11; 1Instituto Nacional De Enfermedades Neoplasicas, Lima, Peru, 2Technical University Munich, Munich, Germany, 3Ludwig Maximilian University Munich, Munich, Germany, 4Goethe-University Frankfurt am Main, Department of Radiotherapy and Oncology, Frankfurt, Germany, 5Department of Radiation Oncology, Homburg/Saar, Germany, 6Medizinische Hochschule Hannover, Hannover, Germany, 7Sankt Gertrauden-Krankenhaus, Berlin, Germany, 8University of Notre Dame, Fremantle, Perth, Australia, 9University College London, London, United Kingdom, 10University Medical Center Freiburg, Freiburg University, Freiburg, Germany, 11Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
Purpose/Objective(s):
Targeted intraoperative radiotherapy (TARGIT) delivered during lumpectomy is an alternative to whole-breast external beam radiotherapy (EBRT) for selected patients with early breast cancer. We report a post-hoc as-treated analysis of the German cohort of the randomized TARGIT-A trial, evaluating long-term outcomes according to radiotherapy actually delivered.Materials/Methods:
Between 2000 and 2012, 725 patients were randomized to TARGIT (n=362) or EBRT (n=363). In this post-hoc analysis, patients were reclassified according to radiotherapy received. The risk-adapted TARGIT group included patients treated with intraoperative radiotherapy (IORT) alone or IORT followed by EBRT; the comparator group consisted of patients who received EBRT. Patients undergoing mastectomy or no radiotherapy were excluded (n=39), yielding 686 evaluable patients (EBRT n=360; risk-adapted TARGIT n=326, including IORT-only n=214 and IORT+EBRT n=112). Endpoints included early local recurrence, local recurrence-free survival, invasive local recurrence-free survival, distant disease-free survival (DDFS), metastasis-free survival (MFS), overall survival (OS), and cause-specific mortality. Time-to-event outcomes were analyzed using Kaplan–Meier estimates and Cox proportional hazards models. As a post-hoc as-treated analysis, results are exploratory and not protected by randomization.Results:
After a median follow-up of 9 years (range, 0–17 years), early local recurrence occurred in 6 of 326 patients (1.84%) in the risk-adapted TARGIT group and in 2 of 360 patients (0.56%) in the EBRT group. All early events in the TARGIT arm occurred among patients receiving exclusive IORT (6/214; 2.8%), whereas no early recurrences were observed among patients treated with IORT followed by EBRT. Long-term survival outcomes did not differ significantly between groups. The hazard ratio for overall survival was 0.79 (95% CI, 0.47–1.33; p=0.37), with estimated 10-year OS rates of 91.5% for risk-adapted TARGIT and 88.6% for EBRT. Corresponding hazard ratios were 0.92 (95% CI, 0.58–1.46; p=0.73) for DDFS and 0.99 (95% CI, 0.61–1.62; p=0.97) for MFS. Local recurrence-free survival and invasive local recurrence-free survival were likewise not significantly different, with hazard ratios of 1.26 (95% CI, 0.81–1.96; p=0.30) and 1.17 (95% CI, 0.74–1.83; p=0.51), respectively. Breast cancer–specific and non–breast cancer mortality did not differ significantly.Conclusion:
In this post-hoc as-treated analysis of the German TARGIT-A cohort, risk-adapted TARGIT was associated with long-term survival outcomes comparable to EBRT. The modest increase in early local recurrence was confined to patients receiving exclusive IORT and was not associated with inferior overall survival. This approach provides clinically relevant insight into outcomes according to radiotherapy actually delivered and supports the continued evaluation of risk-adapted TARGIT in appropriately selected patients.