LBA10 - Insights into the natural history of subclinical breast cancer: a biological fall out from the TARGIT-A trial

Date 30 September 2012
Event ESMO Congress 2012
Session Breast cancer, early stage
Topics Breast Cancer, Early Stage
Surgery and/or Radiotherapy of Cancer
Presenter Michael Baum
Authors M. Baum1, J.S. Vaidya1, M.K. Bulsara2, F. Wenz3, J.S. Tobias4, W. Eiermann5, D. Joseph6
  • 1Clinical Trials Group, University College London, N195LW - London/UK
  • 2Biostatistics, Institute of Health and Rehabilitation Research, University of Notre Dame, 6959 - Fremantle/AU
  • 3Department Of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, D-68167 - Mannheim/DE
  • 4Department Of Oncology, University College London NHS Foundation Trust, NW1 2PG - London/UK
  • 5Medical, Interdisciplinary Oncology Center, Munich/DE
  • 6Surgery, The University of Western Australia, 6009 - Crawley/AU

Abstract


Insights into the natural history of subclinical breast cancer: a biological fall out from the TARGIT-A trial. Michael Baum, Jayant S Vaidya, Max Bulsara, Frederik Wenz, Jeffrey S Tobias, Wolfgang Eiermann, David Joseph on behalf of the TARGIT trialists group.

Introduction We recently presented an updated analysis of the TARGIT-A trial (n=2232) in which we found that the risk adjusted approach using targeted intra-operative radiotherapy (TARGIT) achieves local control that is non-inferior to conventional whole breast radiotherapy (EBRT), and is associated with a lower overall mortality. [1]

Method Patients could be randomised and receive TARGIT either at the time of the lumpectomy (prepathology stratum), or afterwards as a second procedure (postpathology stratum). In the prepathology stratum, if protocol-defined adverse pathological features were found post operatively, the whole breast was irradiated (avoiding boost) in addition to intra-operative radiotherapy. This analysis looks at deaths and the pattern of local recurrence (LR) in the prepathology stratum (n=716), 64% of whom were screen detected.

Results In this group there were 28 deaths in the TARGIT group and 42 in the EBRT group (p=0.019). The 5-year KM estimate of local recurrence outside the index quadrants was similar in the two randomised groups (TARGIT: 0.8% vs. EBRT 0.4%, p=0.709). Subsequently we were able to derive a group of 498 patients who received no treatment to the ipsilateral breast beyond the index quadrant, only 2 of whom experienced a LR that was outside the index quadrant following1923 woman-years exposure to risk. If we assume that approximately 60% of these patients had occult disease outside the index quadrant [2], then we have 296 women with locally untreated occult foci of breast cancer that failed to progress with a median of 3.9 years follow up.

Conclusion These data illustrate the danger of over-diagnosis and overtreatment of subclinical breast cancer and together add further fuel to the debate on the harms versus benefits of mammographic screening.

References 1. Vaidya JS on behalf of the TARGIT collaborative group, ASCO Breast, San Francisco September 2012 2. Vaidya JS, Vyas JJ, Chinoy RF, Merchant N, Sharma OP, Mittra I. Multicentricity of breast cancer: whole-organ analysis and clinical implications. Br J Cancer 1996;74(5):820-4.