Plasma MMP‐9 (92 kDa‐MMP) activity is useful in the follow‐up and in the assessment of prognosis in breast cancer patients

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Abstract
Previously we determined that plasma MMP‐9 activity was significantly elevated in breast cancer patients compared to benign mammary pathologies and healthy controls. Now we analyzed its potential usefulness in the follow‐up and in the prognosis of these patients. MMP‐9 activity was measured by gelatin quantitative zymography in the euglobulin plasma fraction of 46 breast cancer patients in a 38‐month follow‐up study. Blood samples were obtained before surgery (S1), 1 month after (S2) and every 3 months. The relapse‐free survival (RFS) and overall survival (OS) analysis was performed along 56 months in 113 patients using the Kaplan‐Meier curves and Cox analysis. In 63% of the S2 analyzed, MMP‐9 decreased after surgery. In 44 patients evaluated during the adjuvant period who developed a complete response, MMP‐9 decreased compared to their S1, whereas 2 patients showed an enhancement in correlation with lack of response. Further analysis indicated that in all patients who never showed evidence of recurrence, plasma MMP‐9 activity remained low, but it increased 1 to 8 months preceding the clinical detection of progression in those patients who relapsed. Kaplan‐Meier curves indicated that high levels of plasma MMP‐9 activity at the moment of breast cancer diagnosis were associated with a worse OS rate. Cox analysis showed it was not associated with tumor stage or patient's age. Our results, which show a good correlation between plasma MMP‐9 activity and the clinical status of each patient, suggest its usefulness as a marker both in the follow‐up and in the prognosis of breast cancer patients.