Disability claim for cancer patient

[Snoop7]

I am the primary caregiver for my father. He is a Vietnam Vet, recently diagnosed with a presumptive disease, multiple myeloma. I went through a VSO to file a disability claim on his behalf. She listed his myeloma, along with other health conditions on his application.  We faxed all requested health records and needed information. He has now been told he needs to go to two different C & P exams. My father is unable to complete these exams due to his physical condition and extremely compromised immune system. He is in the middle of an intense chemo cycle. It is extremely difficult to get him to his chemo appointment once a week in a cancer center. We can not risk him getting an illness from visiting one of these appointed sites. I believe these C & P exams are likely for the conditions listed by the VSO other than his cancer.  Can his claim possibly be approved , considering he has a presumptive disease, if we cancel these appointments? 

[Snoop7]

Just a quick update. After reading all your responses and getting advice from our VSO and doctors, we decided to make sure dad got to both C & P exams. Even the one that was an hour away. We figured it was better to not leave anything to chance, but do everything we possibly could. Hoping he receives 100% if not for his cancer diagnosis than maybe with all of his issues combined. If it gets denied at least we know we did all that we were asked to do. Thank you to all who answered my question.