If you are diagnosed with a type of cancer that is not on the compassionate allowance list, it doesn't mean that you are ineligible for Social Security disability benefits. (Some medical conditions are so serious that the Social Security Administration (SSA) has determined that a simple diagnosis of the illness or disease automatically means the person has met the standard for disability, and the application will be processed quickly. These are called "compassionate allowance conditions.")
But it is true that if your cancer is not on the compassionate allowance list (CAL), your application will not be expedited through the compassionate allowance program. This means it will take longer for the SSA to come to a decision on whether you are disabled, compared to people who have a compassionate allowance condition. But it does not necessarily mean that you are less likely to get disability benefits.
The SSA has official impairment listings for 26 different kinds of cancer. If your condition matches the requirements of the impairment listing for your particular cancer, you will automatically be eligible for disability benefits (provided you have met the other, non-medical eligibility requirements for SSI or SSDI). You can read more about getting disability benefits for cancer here.)
It is true that the requirements of many of the cancer listings are very similar to the requirements of getting benefits for that cancer through the compassionate allowance listing, but the listings don't match the CAL requirements exactly. For example, lung cancer qualifies for the compassionate allowances program if it is small cell cancer or is metatastic, inoperable, unresectable, or recurrent. Lung cancer will be approved under the lung cancer listing under these same conditions, plus one or two more. This means that more types of lung cancer are eligible for benefits under the cancer listing than under the compassionate allowance list.
Plus, if your condition does not meet the cancer listing's requirements, you still may be eligible for disability benefits, under what is called a “medical-vocational allowance.” Under this analysis, if the SSA determines that your impairments and the symptoms associated with your impairments are so limiting that there is no job you can perform, you will be awarded benefits under a medical-vocational allowance.