The story reveals the new heroine to be Dr. Jane Foster, a former girlfriend of the hero who has been battling breast cancer.It seems that her cancer doesn't affect her when she is transformed into Thor, but it comes back stronger than ever when she transforms back into Jane.
“Jane Foster has been part of the Thor comics and the Thor mythology from almost the very beginning,” Mr. Aaron said. “The very act of picking up this hammer, of becoming Thor, is killing her. Where we go from here is the real story.”
But it appears that she is willing to make that sacrifice for the greater good.