MMP9 and breast cancer: At the clinical level, Susskind et al. measured plasma levels of MMP-9 and TIMP-1 in lung and breast cancer patients and observed very high levels before initiation of fractionated radiotherapy (66 Gy, 2.0 Gy/fx), a sharp decline in MMP-9 levels within 10 days of completion of RT, but no change in TIMP-1 levels (64).