It’s very hard to know how anyone will react to chemo before they start. Some people react badly and almost immediately, others have very limited adverse reactions. Exercise and healthy eating can help. Your immune system may be affected but others find that they are not prone to infections, with not so much as a sniffle. You’ll get a general idea within the first two or three weeks, there may be a pattern of good/bad days between each treatment. Best wishes for an easy run.