Life insurance does not cover suicide in the first two years you are insured, one year in some states like Colorado.
However, if you die from cancer within 2 years of becoming insured for life insurance, the insurance company has the option of contesting the payout and reviewing your health records to find out if you had any form of cancer prior to becoming insured.
If you lied on your application for life insurance coverage, or made any material misrepresentation, the insurer may be able to decline the claim on your life insurance.
But, if cancer stars after getting insured for life insurance, and is not the result of any undisclosed health issue, the claim on a life insurance policy should be paid out if death of the insured person results from cancer.
If you have had cancer in the past and it is in remission, you may still be able to qualify for life insurance coverage. Learn more about life insurance for cancer survivors.