P5-14-22: Prospective Observational Study To Describe the Clinicopathological and Biological Characteristics and the Management of Metastatic Breast Cancer Patients Who Experienced Complete or Partial Remission or Disease Stabilization during at Least 3 Years.

Background Trastuzumab has shown an improvement in survival outcomes among patients with HER2+ metastatic breast cancer (MBC). Identification of pathological, clinical factors and tumor genetic profile that may predict long-term remission has become a key-issue. We aimed to describe the clinicopathological and biological characteristics of MBC patients who experienced complete response (CR), partial response (PR), or stable disease (SD) during at least 3 years and their management in routine clinical practice. Methods : Multicenter, observational, cross-sectional study. Data were collected from women with HER2+ MBC treated with a trastuzumab-based regimen who maintained a partial or complete remission or disease stabilization beyond 3 years. The interim results from the first 65 patients evaluated are presented. Results : Median age: 59 (52-70) years. Metastatic disease was diagnosed after a median of 23.5 (1.6−48.8) months since primary tumor diagnosis. The predominant tumor type was ductal carcinoma (89.2%) and 47% showed histological grade III. Mean tumor size: 3.6±2.2cm (anatomical pathology), 5.1±2.8cm (imaging studies). Hormonal status: Progesterone receptor positive 46% and estrogen receptor positive 43%. Most common metastatic sites: lung (23%), liver (17%) and bone (14%). Overexpression of HER2 was assessed by IHC in 97% of patients, of whom 94% were HER2+ (3+) and 17% had FISH+ HER2 status. Tumor was positive for p53 and Ki67 in 23% and 41.5%, respectively. Surgery was performed on 83% of patients, of which 73% underwent radical mastectomy; 96% had their axillary nodes removed. Surgery of metastases was performed on 7.8%. First line chemotherapy was received by 91% with the most frequent schemes being paclitaxel (24%), vinorelbine (15%) and paclitaxel/carboplatine (14%). First line hormonal therapy and radiotherapy was used in 45% and 12%, respectively. All patients received first line trastuzumab, administered on a weekly schedule in 51%. Trastuzumab was used in combination in most of patients (89.2%) with a median number of cycles of 18 (7.0−41.5) and during a median of 53.3±25 months. 66% of patients achieved a CR, 21% PR and 13% had SD. Median time since trastuzumab was initiated to CR, PR or SD was 5 (4-7) months. Median duration of CR, PR or SD was 56 (44.5−78.0) months. Trastuzumab was maintained beyond CR, PR or SD in 99% during a median of 46.5 (35-67) months. 75% of patients continue on treatment with trastuzumab. Only 2 patients discontinued trastuzumab due to toxicity. At the time of the analysis, 19% had progressed, 57% were alive and free of disease and among patients on treatment (93%), 54% were on trastuzumab. Cardiac toxicity was the most common toxicity (36%) among those suffering at least one (22%). Conclusions : The preliminary findings support that trastuzumab provides a substantial long-term survival benefit with a manageable safety profile in HER2+ MBC patients. This study adds to the evidence that there may be benefit in continuing trastuzumab after achieving remission or disease stabilization. Final results will be presented in the forthcoming congress. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-14-22.