Abstract PD10-05: Do the Results of Metastatic Breast Tumour Biopsies Affect Patient Survival Outcomes? Results from a Large Prospective Trial

Background: Differences in receptor status between primary and metastatic breast cancer are well recognized. We have previous demonstrated substantial receptor discordance rates resulting in a change in management in 14% of patients. However, while retrospective studies suggest that discordance can be associated with a worse patient prognosis, there are currently no prospective data assessing the impact of such discordance on survival outcomes. Methods: A single-center prospective biopsy study was performed. Patients with either recurrent or progressive disease underwent biopsy of their metastases. Subsequent treatment choices were modified according to the results and patients were followed up for progression or death. To account for the differing times at which patients entered the study, progression-free survival (PFS) was calculated as the duration between biopsy and either progression or death. Overall survival (OS) was defined as the duration from diagnosis of metastatic disease to death. A Cox propotional hazards model accounting for duration of metastatic disease and visceral versus non-visceral metastatic disease was utilized. Results: 121 biopsies were completed and 38% of cases showed discordance between the primary and the recurrence. Survival data were available from 96 patients. After a median follow-up of 11 months, 76 patients (79%) had progressed and 38 (40%) had died. There was no difference in median PFS between concordant and discordance cases (5.9 vs. 6.5 months, HR 0.89, p=0.61). There was a non-significant trend towards worse OS in discordant cases (50.6 vs. 57.8 months, HR 0.77, p=0.47). When compared with the primary tumour a gain of HER2 was associated with a poor survival, while loss of HER2 was associated with improved outcome. Metastatic biopsies showed a trend towards better prediction of response to endocrine therapy with tumors losing progesterone receptor expression between primary and metastatic disease having worse DFS on endocrine therapy. Conclusion: We have previously shown that performing metastatic biopsies is associated with a substantial rate of receptor discordance between primary and metastatic disease. The current analysis demonstrates that this discordance is associated with a trend towards worse OS, but not PFS. Knowledge of the receptor status of metastatic disease allows better prognostication between HER2-postive and HER2-negative disease and also allows for improved prediction of response to endocrine therapy. Metastatic biopsies should therefore be considered in patients with recurrent breast cancer. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD10-05.