BNCT in Japan: Approved Indications, Evaluation Records and Decision Process

Short answer

Japan was among the first countries to use boron neutron capture therapy (BNCT) in routine care. In 2020 a boron-10 drug (borofalan, brand name Steboronine) and an accelerator-based neutron irradiation system were approved separately for unresectable locally advanced or locally recurrent head and neck cancer. This does not mean that every head and neck cancer, or other cancers, can be treated with BNCT. Suitability depends on pathology, extent of recurrence, tumour depth, prior radiotherapy dose and general condition, and must be judged by specialists using complete records.

1. How BNCT differs from conventional radiotherapy

BNCT works in two steps. A boron-10 drug is infused so that it accumulates in tumour cells as much as possible; the lesion is then irradiated with neutrons. When boron-10 captures a neutron, a nuclear reaction releases energy over a very short distance, so the effect is, in principle, concentrated near cells that took up the drug.

Effectiveness and safety therefore depend on two conditions: whether the tumour takes up enough boron drug, and whether the lesion lies within the depth that neutrons can effectively reach. This is why tumour location and previous imaging are examined closely during evaluation.

2. What is formally approved in Japan

• Boron drug: borofalan (Steboronine), approved in 2020 for unresectable locally advanced or locally recurrent head and neck cancer.
• Treatment system: an accelerator-based BNCT system and dose-calculation program, approved separately in the same year for the same head and neck cancer indication.
• Recurrent meningioma: in October 2026 the device and dose-calculation program received an additional intended use for recurrent meningioma. The matching drug indication had not completed formal approval as of the date this page was checked (14 November 2026). Device approval and drug approval are separate steps and should not be read together.
• Other cancers: glioma, malignant melanoma and others remain in clinical research or earlier stages, not routine approved use.

The approved scope is the starting point for evaluation. Approval does not mean every patient is suitable, nor that a hospital will accept a given patient.

3. Who may be worth evaluating

Situations where specialist review of records is often worthwhile:

• locally recurrent head and neck cancer where further surgery is considered difficult;
• previous full-course radiotherapy, leaving limited room for re-irradiation;
• relatively localised disease without widespread distant metastasis, or with distant disease under control;
• general condition that allows intravenous infusion and holding a fixed position for some time.

Situations that need particular caution and often require prior management or re-assessment:

• tumour in contact with or surrounding the carotid artery, or signs of bleeding;
• tumour extending deeper than neutrons can effectively reach;
• severe local infection, fistula or non-healing wounds;
• clearly impaired kidney function (the boron drug is mainly excreted by the kidneys);
• rapid weight loss or repeated aspiration.

4. Records needed for an evaluation

1. Pathology: initial and recurrence pathology reports; slides or blocks may be requested to confirm the tumour type.
2. Original imaging: recent (generally within about one month) contrast MRI or CT as original DICOM files, preferably with earlier scans for comparison; PET-CT if available.
3. Previous radiotherapy: treatment plan, field, total dose and fractionation, and end date. These determine the safety margin for further treatment.
4. Treatment timeline: dates and responses for surgery, chemotherapy, targeted therapy and immunotherapy.
5. Current status: blood tests (including kidney function), performance status, swallowing and airway status, current medications.

The more complete the records, the more reliable the judgement. Missing original images or radiotherapy dose data often prevent any conclusion.

5. How the decision process works

1. Check your records: confirm what you have and what is missing.
2. Written specialist opinion: BNCT screening is strict. We suggest that a relevant Japanese specialist first reviews the complete records and gives a written opinion on whether a formal evaluation request is worthwhile; the written opinion is decision support, not a commitment by any hospital to accept the patient.
3. Formal evaluation by the treating facility: if criteria appear to be met, the facility reviews the records under its own procedure and may require an in-person examination.
4. Treatment and follow-up: regular imaging follows treatment; early imaging changes do not necessarily mean progression and must be interpreted clinically.

6. Risks and limitations to understand in advance

• BNCT is not a universal "last option" for recurrence; after evaluation, re-surgery, re-irradiation, drug therapy or a clinical trial may be more appropriate.
• Common side effects include mucositis, dry mouth, hair loss and skin reactions; bleeding risk needs special assessment when the tumour is near major vessels.
• Outcomes vary by person; published study data cannot predict an individual result.
• Overseas patients must separately confirm whether a facility accepts international patients and how costs are calculated; news reports are not a reliable basis.

7. Related reading

This English page summarises the Chinese-language guide. Our detailed articles, the BNCT 100-question set and the record checklist are in Chinese.

This page is medical information for education. It does not replace diagnosis, prescription or treatment decisions by your doctors. If symptoms are urgent or worsening quickly, seek local care first.