Need help regarding an IV use to treat cancer.

One of my extremely close has been affected by breast cancer. In addition to the current chemotherapy, there is one more injection called PEMBROLIZUMAB required. It's mostly available in Tata Memorial, Mumbai. If someone has any idea or have used it in the past, kindly let me know. I have been told that it is costly. Mostly below are the information I need. 1. How can I procure the above injection? I have prescriptions. 2. How much would it cost me? 3. Can this be ordered/delivered to other parts of the country? Any info is extremely appreciated. Thanks.