Question: "What does the Bible say about cancer?"
Answer: The Bible does not say anything specifically about the disease of cancer. However, that does not mean that it does not address the issue of diseases. King Hezekiah was sick of a "boil", which could have in reality been cancer under a different name. So, although the word "cancer" is not in Scripture there are incidences where the circumstance could very well have been cancer. When Jesus was on earth He healed all the diseases that were brought (obviously that could include cancer) to Him as a sign to the Jews that He was their Messiah. However, cancer - like all disease is a result of the curse of sin upon the world. In Genesis 3:17 we read, "cursed is the ground for thy sake". The word is better translated "earth". The earth has been cursed because of sin and all men die - we all return to dust and the method of death may be from disease that is a natural outcome of the curse upon the earth. Diseases are not "punishment" - they are a result of living in a fallen world and upon a cursed earth and believer and unbeliever alike develop cancer or other diseases that lead to death. We need to remember that in the life of the believer, God "works all things together for good" (Romans 8:28) and that includes cancer.
The wonderful thing is that even though in this life here on the cursed earth we are subject to diseases like cancer we have "hope". I especially am thankful for the Psalms. One in particular, Psalm 103 has a wonderful passage that gives me a confident assurance that there will be an end to the ills of this world. Psalm 103:1-4 (KJV) " Bless the LORD, O my soul: and all that is within me, bless his holy name. Bless the LORD, O my soul, and forget not all his benefits: Who forgiveth all thine iniquities; who healeth all thy diseases; Who redeemeth thy life from destruction; who crowneth thee with loving-kindness and tender mercies."
Does this passage mean that we are guaranteed that God will heal us of cancer or other diseases in this life? I don't think that is the meaning of this passage. Rather, the same God who forgives us our sin will one day bring us to "a place He has prepared for us". His redemption preserves us from destruction and then there will be no more curse and no more disease and no more death and we will be forever crowned with His goodness and grace. The final victory over the curse of sin is already ours IN Christ.