My Wife Had Lumpectomy In 2011 And Subsequent She Underwent

My wife had lumpectomy in 2011 and subsequent she underwent 6 cycles chemotherapy and radiotherapy and she was on daily dose of tamoxifen.In 2014 there was metastasis in the body of sternum and every three months she was having zobone injection with daily dose of anastrazole.In 2016 the cancer has spread to the liver extensively and she had 12 weekly cycles of paclitaxel.After one month PET CT was done and the response found is partial.She has been advised to take Exmestane 25 mg daily and a ultrasound after 3 months.She is suffering from gastritis and unable to eat anything.What should I do to reduce this gastritis.