Welcome to NeuroTalk...

People who have had cancer treatments, may have damage to the mitochondria of the cells. Did you have chemo too?

Swelling like you describe can come from some uncommon drug reactions. Do you take an ACE inhibitor for blood pressure?
These can cause tissue swelling, with burning pain...it is called angioedema. Angioedema also accompanies some cancer, mostly leukemia or lymphoma types. There are special tests for immune markers for this....

This link explains the testing for the various types of angioedema....
http://www.haea.org/professionals/angioedema/

Some are acquired (cancers, drugs) and some are hereditary.
This is difficult to diagnose, but the blood tests are explained in the link.

Certain activities cause it to flare. Repetitive motion is one trigger. So is stress, trauma or pressure on a body part.

So I think the answers for you are going to difficult to get.

All people with PN symptoms should be screened first for low B12 and low Vit D. If your B12 is low (below 400pg/ml US units), then you can supplement to bring it up.

Some people with a cancer history may find acetyl carnitine helpful, 2 grams a day in divided doses. It can be used with chemo to protect the mitochondria of the cells so damage would be less for them.