Some treatments can affect your dog’s sense of smell and taste. These treatments may also cause nausea making them less inclined to eat.
You could try hand feeding your dog. Some dogs who are not feeling well respond to this. If that works, more smaller meals may be preferred by your dog. Your veterinarian can also prescribe an appetite stimulant or nausea medication which are helpful for some dogs. Canine Biologics also sells ultra-high-quality CBD oil which may help. The WebMD website says, “the benefits (of CBD) include reduction of pain and increase in appetite.” Many dog parents report success using CBD oil for dogs with cancer.