Pancreatic cancer essentially forms a barrier around the cancer that prevents drugs from reaching the tumors as I understood layman's descriptions of the diseas

Pancreatic cancer essentially forms a barrier around the cancer that prevents drugs from reaching the tumors as I understood layman's descriptions of the disease when one of my friends died of it. I think there was some initial success in attaching vitamin d to some drugs to bypass the "firewall", but it was still hard.