Depends. For most people boost shakes provide enough protein and other nutrients. However, for diabetics there are lower sugar options. For an expensive way to make a shake similar to boost - add carnation instant breakfast to whole milk.
CanOrWise? Big Issue. Since may chemo Tx's interfere with cell reproduction, intestinal lining cells typically replace every 3 days, GI problems very common. A high quality shake you make yourself from quality ingredients might assist digestion/nutrition & side effects. Most commercial shakes are ↑↑carb, not ↑↑protein/fat (more likely helpful). Why? Carbs ↓$, ? ↑taste appeal & easier to mix in water than protein & fat.
Yes. During chemotherapy you need to maintain a good level of nutrition intake however you can get it. Protein shakes are a very good choice, Good luck to you!