I am not sure what medication the last post referred to. If it is decadron, it is very commonly used here in the U.S. to treat swelling in the brain after surgery or swelling from cancer growth.
The side effects from decadron can be horrible. It breaks down bone tissue as well as the connective tissues and muscles. My husband has been on a very high dose for almost a year, and he has horrible stretchmarks as well. We have not found a good solution to the stretchmark issue.
Although decadron helps keep brain swelling down, it truly is very wasting on the body. Thankfully, we have been able to reduce my husband's dose down to 3 mg but it still has not eliminated all the side effects yet. One thing the doctor suggested is going on a medication to increase calcium absorption to counteract the decadron's effects. A very common result from longterm use is spinal fractures. Would drugs like fosamax, actonel, or boniva be available to you? Also, has your son had a bone density test to see if that is the cause of his back pain? Is your son able to get the necessary chemo to treat his cancer?
I don't feel like my answer is very helpful. I wish I could tell you more.
Jackiekay