Thanks for your question on HCM.
I can understand your father's situation and problem.
Chemotherapy drugs are very toxic to the body.
Along with cancer cells, It also damage and destroy normal body cells.
It also causes
immunosuppression. So patient on chemotherapy is at high risk of infection.
So possibility of
stomach infection causing stomach pain, vomiting and diarrhoea is high.
Better to start
1. Oral rehydration solution (ORS)
2. Start zinc and
multivitamin tablet.
3. Start probiotic and antioxidant drugs.
4. Avoid outside, junk food. Avoid oily and spicy food.
5. Give him only freshly cooked, home made food.
6. He may need short course of antibiotics too.
Do all these for 1 week and if he still have the same complaints, then get done CT scan of abdomen to rule local recurrence of
stomach cancer.