Endometriosis is caused because of menstrual blood collection in the ovaries, pelvis or in the wall of your uterus. Every period you have will result in more accumulaton of blood and cause symptome like painful periods, low back ache, pain around the rectum and pain during sex . .
The treatment would be to destroy the deposits by cautesising them during surgery or taking medicines to stop the periods so that your deposits dry up
It des not lead to cancer if you stop treatment but symptoms can recur after awhile