Is a woman sinful if she refuses to have her cancerous breast removed, despite doctors' warnings of the disease spreading, and her psychological inability to endure the surgery?

Treatment is permissible or recommended, and it may become obligatory if abandoning it leads to destruction, as Allah Almighty says: "And do not throw yourselves with your own hands into destruction." Treatment becomes obligatory if there is a fear of perishing or if healing is known to be in it. Therefore, accepting to undergo surgical operation is the most religiously cautious course of action for preserving life and striving to prolong it, which is what doctors recommend.