I am 39 yrs old, female with hyperpigmentation on my upper back, arms and chest area. Looking for an effective treatment?

I have have been having this hyperpigmentation since past 20 years on upper back. However, in the last 7-8 years the hyperpigmentation has progressed to upper arms and upper chest area as well. I consulted dermatologist and was diagnosed as having Macular Lichen Amyloidosis. He prescribed me Dermovate cream which i applied for 3 weeks with no positive effects observed. Can you please advise on an effective treatment for this condition? Thank you!