Boron Neutron Capture Therapy (BNCT) is an emerging and rapidly developing precision diagnosis and treatment technology in the international field of oncology in recent years. It has been hailed by the Japanese medical community as the "fifth therapy" following surgery, traditional radiation therapy, anti-cancer drugs, and immunotherapy. BNCT has shown outstanding clinical advantages in treating recurrent, invasive, and locally metastatic tumors, and has proven its significant and reliable efficacy in various solid tumors such as recurrent head and neck cancer, malignant brain tumors, melanoma, osteosarcoma, and breast cancer, with over a thousand clinical cases globally.

The principle of BNCT is to first inject a targeted molecular drug carrying 10B (a stable, non-radioactive natural isotope) into the body. Due to the selectivity of the targeted drug, 10B accumulates specifically in tumor tissues. A low-energy, directionally controlled epithermal neutron beam is then used to irradiate the tumor area. Upon irradiation, the 10B in the tumor tissue is activated, triggering a boron-neutron capture reaction that emits two heavy ions: α particles and 7Li particles, each with a range of about 10 microns (roughly the size of a single cancer cell) and high linear energy transfer (LET). These heavy ions break the double-stranded DNA in cancer cells, making the tumor cells irreparably damaged and ultimately leading to their complete destruction, thus achieving the precise elimination of cancer cells at the cellular level without harming normal tissues.

BNCT eliminates the need for the traditional concepts of clinical target volume (CTV) and planning target volume (PTV) in radiation therapy, enabling dual-target precision positioning. Through the use of targeted drugs or molecular probes that carry 10B atoms, the treatment selectively accumulates in tumor cells, locking them in place for a first level of targeting. Then, by selecting the irradiation field of the neutron beam to focus on the tumor area, a second level of precise targeting is achieved.

When epithermal neutrons irradiate the tumor area, they penetrate human tissue and react with the 10B in cancer cells, resulting in the emission of α particles and 7Li heavy ions. These ions, with a range of only 10 microns—the size of a single cancer cell—are extremely lethal, far surpassing traditional photon and proton therapy, earning BNCT the nickname "cell scalpel." The physical nature of BNCT’s damage can effectively avoid the drug resistance concerns associated with chemotherapy and immunotherapy.

The full course of BNCT treatment only requires 1-2 irradiation sessions, far fewer than existing radiation therapies. Compared to other particle radiation therapies, BNCT boasts stronger biological effects, requires less equipment space, can treat a greater number of patients per year, and has higher potential for widespread use and development.

Currently, the most advanced BNCT drug, BPA, can be applied to head and neck cancer, melanoma, osteosarcoma, brain and CNS tumors, and breast cancer. It is particularly suitable for treating cancers that have infiltrated, spread, or metastasized, and cannot be treated by X-rays, protons, heavy ions, or surgery. BNCT therapy is not available in most countries.