Hi there, Welcome to Justanswer! I am Dr. Hoellering and pleased to help you. If your son in law didn't have radiation, I don't thing that this lung fibrosis is related to the chemotherapy. I's necessary to check out viral, bacterial or fungal infections. A good reason to develop a fibrosis would be the exogen allergic alveolitis, an issue you get from contact with birds, but from frequent air conditioning as well. You can stop the fibrosis from getting worse by medication (anti inflammation, anti bronchial constriction), but you unluckily cannot reverse it. I wish your son in law the very best!