Incidence and implications of oligometastatic breast cancer.

Abstract

e11512 Background: There is increasing evidence that prolonged disease control is possible in patients with a limited number of metastatic sites compared to those with more diffuse disease, especially when aggressive local therapy (surgery and/or stereotactic radiation) is administered. The objective of this study is to describe the frequency of oligometastatic breast cancer in patients who develop distant disease and to characterize their disease course. Methods: A retrospective review was performed of a tri-institutional database of Stage I-III breast cancer patients treated from 1978 to 2005. Patients were categorized as "oligometastatic" (OM) if ≤ 5 sites of disease were identified at time of first failure or “polymetastatic” (PM) if failure occurred at > 5 sites. Patients were followed for ≥ 3 y after first metastasis, until death, or until development of > 5 sites of metastatic disease. T and N stage, hormone receptor status, presenting symptoms of metastasis, number and site of metastases, actuarial overall survival (OS), and overall survival after first failure (OSAF) were examined. Kaplan-Meier, chi-square, and log-rank tests were used for statistical analysis. Results: Of 2,249 patients reviewed, 114 (5.1%) failed at distant sites and met inclusion criteria. The OM phenotype was observed in 21.9% (25/114). Of patients presenting with symptoms of metastasis, 18.3% were OM, whereas patients with metastases identified incidentally or by screening were OM in 42.1% of cases (p = 0.02). Median OSAF was significantly longer in OM patients (44.7 mos) than PM patients (18.1 mos) with 5 y OS of 48.5% and 10.7% respectively (p < 0.001). Outcome of OM patients compared favorably to that of patients with bone-only metastases in whom the median OSAF was 25 mos and 5 y OS was 12.5%. Baseline features of OM and PM patients did not differ according to initial tumor size (p = 0.94), nodal stage (p = 0.5), or ER+ (p = 0.28). Conclusions: A significant proportion of early stage breast cancer patients with distant failure will have OM disease, and this subset is expected to have prolonged overall survival. The relatively favorable prognosis of patients with OM disease warrants consideration of aggressive local therapy and may have implications in the design of future clinical trials.