Undo Sun Damage with a New "Burn"

I have spent the last 2 month being treated with Levulan.  I read about it and its efficacy rate was quite high, so I decided to proceed.  I have had one basal cell and one squamous cell skin cancer on my calves.  They were removed and the nurse practitioner told me I still had many more actinic keratoses that could lead to future skin cancers.  I have been treated 3 times on the calves and my back.  I have had little to no response.  I have waited 2 hours for the Levulan to soak in at each treatment.  Then I sat under the U Blue light for 8, 10 & 12 minutes.  No response.  After talking with the Dr. who help create the drug, I found I should have waited no less than 5 hours after the Levulan soaked in and I should have stayed under the light no less than 16 minutes 40 seconds.  He also said sometimes the area is wrapped in Saran wrap while the drug soaks in.  There is no standard of treatment for using Levulan on areas other than face/scalp.  However, the protococl for the most delicate of skin, would lead one to believe that at least a 5 hour soak and 16 min. 40 seconds light treatment would be necessary.  Ask questions of your Dr. before agreeing to this very expensive treatment.  Make sure it is done according to Dusa Pharmaceutical standards.