Do you realize how delusional that is?
Somatic mutations are a fact - even if you think God would not allow it - it is obvious God does in fact allow somatic mutations. Grey hair in old people is physical evidence that the genes that would produce and place melanin inside the hair have been mutated in those cells producing gray hair.
That somatic mutations of those genes that regulate cell division can (and do) cause cancer is also a fact - irrespective of what you think God would allow or not allow.
Good and God fearing people without any deficit in spirituality can and do get and die of cancer.
Way to blame the victim. I guess they only died of cancer because they lacked sufficient faith in God and the supposedly ironclad knowledge of the mind of God that you possess.