DEAR DR. ROACH: I am an 81-year-old female who has been on Xarelto for years due to deep vein thrombosis (DVT). I also have an inferior vena cava (IVC) filter. I read that lowdose aspirin (325 mg) is just as effective in preventing clots in the legs as Xarelto, which is very expensive. My doctor advises against changing to aspirin, but won’t give me an explanation as to why....