No, it will not be concern on his eligibility.
But, just what I saw. I have close friends in the same situation. The sponsor/she/ have a cancer, but in not good condition and not completed treatment. They included all documents about the treatment in the application. After sponsorship approval she went to her MP. After 1 week her husband was at interview and he is already in Canada- September applicant. I helped them with some documents. I"m August and still waiting. The same VO. Just to mention, she has really difficult time alone with big pain.