It can be. But if your age is below 40 than chance is also very low. You can not tell without confirmation and some investigation. From Your history it seems like you have spotting due to your fibroid. You didn t mentioned size of the fibroid and number and expected positions of fibroid in your uterus as per sonography. Due to fibroid uterus can not able to contract completely and you can bleed more than regular. It is expected. As you are not one progesterone, some more bleeding can be there, so don t worry. But if you have increased bleeding than past than repeat sonography to see the size of fibroid whether increasing or not. do one haemogram to see your hemoglobin level. This is to know that whether bleeding affecting your health or not. In other term we can continue with medications if all symptoms are routine and your health is not being compromised by fibroid. Otherwise we have to remove it surgically according to your past pregnancy status. If you are near menopause than we can continue with medication if fibroid is less symptomatic because once the menopause sets, fibroid will decrease in size automatically. Because it depends on hormones (Chemicals) produced by your body during normal cycle. Once it stops size and symptoms automatically stops. For uterine cancer it is less likely in your case. but to confirm that whether it is there or not, final confirmation can only done after removing uterus and send it for Laboratory (HPE) examination. before that as a screening we can do diagnostic dilatation and curattage (Cleaning ) of uterus and send the material for laboratory examination to find out chances of uterine cancer. Some other blood test like CA125, Sonography, CT Abdo Pelvis, and clincal Examinations are combine can dianose high risk patient.