Approved treatment — approved in Japan in 2020; covered by public insurance since June 2020 (unresectable locally advanced or locally recurrent head and neck cancer) Other cancers are being studied in clinical trials at several Japanese centers
BNCT (boron neutron capture therapy) first gives a boron drug by infusion that collects in cancer cells, then irradiates the area with neutrons so that strong radiation is released only inside the cells holding boron. Japan approved the boron drug and the accelerator system together in 2020, and patients with unresectable locally advanced or locally recurrent head and neck cancer are treated under public insurance. Treatment is, in principle, a single irradiation session, and in nationwide post-marketing surveillance of 162 patients the response rate for squamous cell carcinoma was 72.3%.
What is BNCT? How boron neutron capture therapy works
BNCT needs two things to work: a drug carrying boron-10 (¹⁰B) and low-energy neutrons (epithermal neutrons). The drug used in Japan, borofalan (brand name Steboronine), resembles an amino acid, so cancer cells that take up many amino acids absorb more of it than normal cells.
When neutrons reach boron that has gathered in cancer cells, boron-10 captures a neutron and splits, releasing an alpha particle and a lithium nucleus. Both travel only about the width of one cell (within roughly 10 µm), so the energy stays inside the cell holding the boron. That is why BNCT is sometimes called "cell-selective radiation therapy." Because neutrons weaken as they go deeper, BNCT is best suited to tumors relatively close to the body surface.
How BNCT differs from X-ray and proton therapy
| Item | BNCT | Proton therapy | Standard X-ray radiation |
|---|---|---|---|
| How the target is chosen | Cells where the boron drug collects | Controlling the depth where the beam stops | Shaping beams from several directions |
| Number of sessions | In principle, one | Usually many (5 days a week) | Usually many (5 days a week) |
| Japan insurance (head and neck) | Unresectable locally advanced or recurrent head and neck cancer | Some head and neck tumors | Most head and neck cancers |
| Best-suited location | Tumors fairly close to the surface | Wide range, including deep sites | Wide range |
Sources: Okayama University BNCT overview, Stella Pharma approval announcement; for proton therapy coverage in Japan see our proton therapy articles. Individual suitability is decided by the treating doctor.
BNCT draws particular attention for head and neck cancer that has returned after earlier radiation. Even when the same area cannot safely receive another large X-ray dose, BNCT concentrates energy where boron has gathered in cancer cells, offering a new option. You can compare it with the daily schedule of proton therapy in Proton therapy process and duration.
BNCT insurance coverage in Japan: who can receive it
On March 25, 2020, Japan's Ministry of Health, Labour and Welfare approved the boron drug Steboronine together with the NeuCure BNCT System accelerator. The indication is locally recurrent head and neck cancer that cannot be removed surgically, or unresectable locally advanced head and neck cancer. The drug was listed on the national drug price list on May 20, 2020, and insured treatment began in June 2020.
Head and neck cancer includes cancers of the mouth, tongue, pharynx, larynx, salivary glands, nasal cavity and sinuses. The trial included not only squamous cell carcinoma but also non-squamous cancers such as salivary gland tumors. Another option available in Japan for recurrent head and neck cancer is photoimmunotherapy; see Head and neck cancer photoimmunotherapy results.
The BNCT treatment process: one day, in principle one session
- Consultation and eligibility — doctors check tumor location and depth using imaging, pathology and records of earlier radiation (site and dose).
- Treatment planning — the treatment position is set and a CT scan is used to design the neutron direction and dose. In the phase II trial, a cap on mucosal dose protected normal tissue.
- Treatment day — the boron drug (borofalan) is infused over about two hours, then a single neutron irradiation is delivered from the accelerator. In post-marketing surveillance, 96.9% of patients completed the planned irradiation.
- Follow-up — mouth inflammation, salivary gland swelling and similar effects are managed over the following weeks, and the response is assessed by imaging at about three months (90 days).
Unlike standard radiation, which needs weeks of daily visits, irradiation is completed in a single day, which eases scheduling for patients traveling from far away. Hospital stay and pre-treatment tests vary by center, so confirm them at consultation.
BNCT results: phase II and real-world outcomes
The Japanese phase II trial JHN002, which supported approval, enrolled 21 patients with recurrent or locally advanced head and neck cancer between 2016 and 2019. The overall response rate 90 days after irradiation was 71.4%, with no deaths or discontinuations during the primary evaluation period. After approval, nationwide post-marketing surveillance collected real-world results for 162 patients.
| Study | Patients | Response rate | Complete response |
|---|---|---|---|
| JHN002 phase II (all) | 21 | 71.4% | — |
| JHN002 recurrent squamous cell | 8 | 75% | 50% |
| JHN002 non-squamous | 13 | 70% | 8% |
| Post-marketing, squamous cell | 144 | 72.3% | 46.0% |
| Post-marketing, non-squamous | 17 | 64.7% | — |
Sources: Stella Pharma approval announcement (2020); Hirose et al., J Radiat Res 2022 (citing JHN002 complete and partial response rates); Sato et al., Cancers 2024. Response rate = share of patients whose tumors shrank by at least 30% (complete plus partial response). JHN002 subgroup rates are complete plus partial response.
For recurrent squamous cell carcinoma, median locoregional progression-free survival (time without regrowth at the treated site) was reported as 11.5 months. Real-world response rates closely matched the phase II results, showing that the benefit carries over to patients treated outside trials. The response rate was 75.8% in patients without lymph node involvement and 65.2% in those with it, so results tended to be better when disease was more localized.
BNCT side effects and recovery time
In the JHN002 side-effect analysis, most events were grade 1–2; grade 3 oral mucositis and dermatitis each occurred in 5%. Common symptoms were nausea, loss of appetite, parotid swelling and vomiting. A rise in blood amylase appeared temporarily in nearly all patients and returned to normal without treatment. Median recovery time was 23 days for oral mucositis, 40 days for dermatitis, 58 days for taste changes and 156 days for hair loss.
In the 162-patient post-marketing surveillance, salivary gland inflammation (50.0%), hair loss (49.4%) and stomatitis (grade 1–2 40.7%, grade 3 10.5%) were most common. Among late effects, difficulty swallowing was the most frequent but occurred in only a few percent. Telling the care team about symptoms early, together with mouth care and fluid and nutrition support, helps recovery.
Where BNCT is offered and how to check costs
Insured treatment is provided at the Southern Tohoku BNCT Research Center in Koriyama, Fukushima, and at the Kansai BNCT Medical Center of Osaka Medical and Pharmaceutical University. Research to widen the indications continues at the National Cancer Center Hospital (skin cancer trial), Edogawa Hospital (breast cancer recurring after radiation), Osaka Medical and Pharmaceutical University (recurrent malignant glioma) and the University of Tsukuba, among others. Abroad, clinical trials are under way in Taiwan and China, and facilities such as Helsinki University Hospital in Finland are being commissioned.
Steboronine is listed in Japan at JPY 444,215 per 300 mL bag. Total cost depends on the drug amount (based on body weight) and on hospital stay and tests; residents of other countries who are not enrolled in Japan's public insurance may be billed differently, so ask the center directly for an estimate. More on head and neck cancer care in Japan is in Head and neck cancer information.
What to check and questions for your doctor
- Are the location and depth of my tumor suitable for BNCT?
- Given my earlier radiation records (site and dose), can I receive BNCT?
- How many days must I stay in Japan from pre-treatment tests to discharge?
- How will side effects such as mouth inflammation and salivary gland swelling be managed?
- When and where will the imaging to assess the response be done?
Frequently asked questions
How many BNCT sessions are needed?
In Japanese insured care and in the phase II trial, a single neutron irradiation is given after the boron drug infusion. Irradiation is completed in one day, and the response is assessed by imaging about three months later.
Which cancers does insurance cover for BNCT?
In Japan, unresectable locally advanced or locally recurrent head and neck cancer has been covered by public insurance since June 2020. Skin cancer, breast cancer, brain tumors and others are being studied in clinical trials to expand the indications.
How effective is BNCT?
The response rate was 71.4% in the 21-patient phase II trial and 72.3% (complete response 46.0%) in 144 squamous cell carcinoma patients in nationwide post-marketing surveillance. Individual results depend on the tumor.
How is BNCT different from proton therapy?
Proton therapy aims at the tumor by controlling the depth where the beam stops and is given over many sessions. In BNCT, boron that has gathered in cancer cells reacts with neutrons and releases energy inside the cells, usually in a single session.
Related: Proton therapy process and duration · Head and neck cancer photoimmunotherapy results · All proton therapy articles
Sources
- Stella Pharma — Steboronine® approval for head and neck cancer (2020-03-25)
stella-pharma.co.jp
Checked: 2026-10-21 - Stella Pharma — Steboronine® NHI price listing and launch (2020-05)
stella-pharma.co.jp
Checked: 2026-10-21 - Hirose K, et al. Profile analysis of adverse events after BNCT for head and neck cancer: a sub-analysis of the JHN002 study. J Radiat Res 2022;63(3):393–401
doi.org/10.1093/jrr/rrac012
Checked: 2026-10-21 - Sato M, et al. Safety of BNCT with borofalan(10B) and its efficacy on recurrent head and neck cancer: real-world outcomes from nationwide post-marketing surveillance. Cancers 2024;16(5):869
doi.org/10.3390/cancers16050869
Checked: 2026-10-21 - Okayama University — BNCT research and clinical status in Japan
okayama-u.ac.jp
Checked: 2026-10-21 - Tanaka H. Accelerator-based BNCT facilities (BIPM webinar, 2025-01-23)
bipm.org
Checked: 2026-10-21
Written by the FTH editorial team. Sources checked 2026-10-21 · Medical review: not applicable
This article is general information based on public sources and does not replace diagnosis or treatment. Please discuss treatment decisions with your medical team.
