What are the trends for the number of cases of various brain cancers over the past 40-50 years?

Vague question: Brain tumors are separated into neural or meningeal in general. Meningiomas have not really increased. There are many different subtypes of brain cancer--and over the past decades the ability to recognize different types has improved. So, a name given to a tumor 40 years ago, now may encompass 6-8 different tumors.

There has been no: Great change in incidence or frequency of any cell type of brain tumor, childhood or adult, in the past 50 years. Thus, the idea that cell phones "cause" cancer, brain tumors in particular, seem fairly far-fetched given this fact. Treatment is a little, not much better. Read "death be not proud" by john gunhter's son, written about 1950.