Abstract P5-14-03: The impact of adjuvant radiotherapy on survival in primary breast caner: What is the role of guideline adherence in radiotherapy – A retrospective multi-center cohort study of 8935

Abstract

Abstract Introduction: Breast cancer remains the most common malignancy in women in industrialized countries. Over the last decades improved adjuvant therapy strategies were the key for a favorable prognosis in patients. Among these, radiotherapy is one of the important backbones in adjuvant therapy strategies. This study tries to answer the following questions: 1. Does guideline adherent radiotherapy improve survival in primary breast cancer patients? 2. Is breast conserving surgery followed by RT equal to mastectomy in outcome parameters? 3. Is there a difference in survival between patients receiving BCT followed by RT with non guideline conform incomplete tumor resection (R1)? Does adjuvant RT compensate incomplete resection of the tumor? Material and Methods: In this German retrospective multi-center cohort study called BRENDA (breast cancer care under evidence based guidelines) we investigate data of 8.935 primary breast cancer patients recruited from 17 participating breast cancer centers in Germany (all certified breast cancer centers by the German Cancer Society). Guideline adherence is established in all adjuvant treatment modalities based on internationally validated guidelines. Results: Patients who received guideline adherent RT in primary breast cancer were associated with significantly improved survival parameters [RFS: p < 0.001; HR = 0.28 (95% CI: (0.24 – 0.33)] [OAS: p < 0.001; HR = 0.26 (95% CI: 0.19 – 0.36)] compared to patients who did not receive guideline adherent adjuvant RT. Compared to other adjuvant treatment modalities (surgery/chemotherapy/endocrine therapy) guideline violations concerning radiotherapy and chemotherapy have the most important impact on survival parameters. Furthermore, the results of Fisher et al. and Veronesi et al. were confirmed by demonstrating that BCT followed by RT is equal to mastectomy [RFS: p = 0.293; HR = 1.20 (95% CI:0.85-1.70)] [OAS: p = 0.104; HR = 1.31 (95% CI: 0.95-1.81)]. Adjuvant RT could not improve the outcome in patients with non-guideline conform incomplete tumor resection via BCT (R1) showing a significantly impaired RFS [p<0.001; HR = 2.87 (95% CI: 2.00-4.12)] and OAS [p<0.001; HR = 2.06 (95% CI: 1.43-2.98)] compared to guideline conform complete tumor resection via BCT (R0). Additionally, non guideline adherent RT after mastectomy (only T1/T2) (overtherapy) did not influence survival significantly [RFS: p = 0.838; HR = 1.07 (95% CI: 0.57-1.98)] [OAS: p = 0.613; HR = 1.18 (95% CI: 0.63-2.20)]. Discussion: Guideline adherent adjuvant RT is associated with an improvement of survival parameters in primary breast cancer. Patients undergoing guideline conform BCT (R0) followed by RT present an equal outcome as patients undergoing mastectomy. However adjuvant RT can not compensate an inadequate tumor resection via BCT and RT overtherapy after mastectomy does not improve survival parameters. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-14-03.