Hello my brother suffering from brain tumor which is 5mm in size. Is it easily curable from medicine?

Need to know more. About the tumor. Some tumors can be watched, if believed to be benign. Others cannot be definitely diagnosed by imaging and may need to be biopsied or removed. Then decisions about additional treatment can be made. Please make sure the patient's doctor is involved. A neurologist and neurosurgeon may also need to be involved.
Brain Tumor. I am sorry to hear this and send our condolences to you and your family. This question is nearly impossible to answer given we do not know what type of tumor he has, where it is, what his other health history is and such. I wish you well, but your doctors there hopefully with all of the facts can answer that question for your family.