Can Silicone Sheeting Be Used on Old Keloid Scars?

I developed a keloid scar on my stomach after undergoing surgery three years ago and I developed another keloid scar after undergoing a partial mastectomy three months ago. My dermatologists/surgeons at the time told me that there was nothing I could do to minimize the appearance of the scars, so I accepted it and did not try to find a remedy. Recently, however, I learned that silicone sheeting effectively reduces keloid size. Are my keloids too "old" for me to attempt to use the sheets? Is there another option for me?