Hello
First of all clear one thing from your brain that this itching is due to cancer , no way , not at all.
Reasons of this itching which is spreading may be , these includes.
1
Eczema , as this is a chronic skin disease , so
consult a dermatologist and get his opinion as physical examination is important in this case.
2 Dermatitis , again this type of itching may be due to
contact dermatitis , so due to clothes or unhygienic care , be careful about that.
3 As you mentioned that this itching is spreading so may be
scabies .
In my opinion consult a dermatologist and get his opinion as swab from this area will find out the disease.
Hope this information will,be helpful for you.