So, I was diagnosed with DSAP (through a biopsy) ~15 years ago. I've found successful treatment with a combo of Tazarotene and Effudex together. I applied Tazarotene 0.1% once daily at bedtime and the Effudex 5% twice daily for 14 days. I did a 'field treatment' instead of 'spot treatment.'
CAUTION: I had an extreme response - very red, scaly, burning and hair falling. I treated my arms from wrist to mid bicep. I do not regret it. My hair grew back and the redness subsided ~1 year post treatment. To be clear: I used Effudex 5% alone, prior to this treatment. It did not work. I had to use the combo.
I had hundreds of spots before treatment and have had very little reoccurrence after 5 years. I would say still 98% clear.
I think some returned because I didn't fully treat the area (i.e. around the edges of the field). Feel free to ask questions.