A new meta-analysis of previously published studies has reported that circulating tumor cells in the blood is associated with poor prognosis in breast cancer patients. The prognostic significance of circulating tumor cells in breast cancer patients is controversial. To conduct the study, the authors searched the Medline, Science Citation Index, and Embase databases, as well as reference lists of relevant articles (including review articles) for studies that evaluated the prognostic relevance of tumor cells in the peripheral blood. The final analysis included 24 eligible studies with 4,013 breast cancer cases and 1,333 cancer-free controls.

Breast cancer patients with circulating tumor cells were found to have approximately three times the risk of breast cancer recurrence and death from all causes than similar breast cancer patients without circulating tumor cells. Breast cancer characteristics of women with circulating tumor cells included a significant tendency toward high tumor grade, tumor size greater than 2 cm, and one or more positive lymph nodes. However, the presence of circulating tumor cells was not found to be associated with negative estrogen receptor status (ER-), negative progesterone receptor status (PR-), or human epidermal growth factor receptor type 2 overexpression (HER2+). The authors comment that larger studies are required to further evaluate the role of circulating tumor cells in clinical practice.