And the tissues surrounding the organ inevitably receive a large dose of radiation.

BBC: Surgery

Most prominently, teenager Jesse Gelsinger died from multiple organ failure a few days after receiving a massive dose of virus-based gene therapy in a trial at the University of Pennsylvania.

FORBES: Glaxo Brings Gene Therapy Back From The Dead

But to ensure that all cancerous cells are destroyed, an even dose of neutrons has to be given to the entire organ.

BBC: Surgery