What are chancs that adenosene stress test is false positive?

I had an adenosine nuclear stress test  this week that showed a reduced blood flow on images in the LAD.  I had a cath done Oct 2005 that was clear.  Can a blockage form in 3 1/2 yrs?  I am 62 yr old female.  Have pulmonary hypertension, diastolic dysfunction, left ventricular hypertrophy with heart failure symptoms.  Had more chest pain than usual climbing stairs recently.  Have excisional breast biopsy scheduled for next week.  Cardiologist wanted to follow up on chest pain before signing off on surgery.  Now he wants me to have another cath and may need a stent if there is truly a blockage.  If I do need a stent, would be on blood thinner for a year.  So need the biopsy now before the cath.  I am concerned if I need more extensive surgery if biopsy shows cancer.  How long can I wait for this cath?  What are the chances that the stress test was false positive?