Carbon ion therapy at Kanagawa i-ROCK is carbon ion cancer treatment delivered at the Ion-beam Radiation Oncology Center in Kanagawa (i-ROCK), part of Kanagawa Cancer Center in Yokohama, Japan. The center treated its first patient on 15 December 2015, and 2,842 patients had been treated by the end of March 2023. Patients from abroad without Japanese public health insurance apply only through one of three medical coordinators certified for the center, and the Advanced Medical Care technical fee for insured patients in Japan is JPY 3.5 million (Kanagawa Prefecture notice, posted 23 April 2026). This article covers the application route, documents to send, treated sites and number of sessions, cost structure, and the center's published 5-year prostate cancer results. To find out whether your records qualify for i-ROCK, please contact us for an eligibility and cost consultation.
What kind of carbon ion cancer center is i-ROCK?
i-ROCK was the fifth carbon ion center in Japan and the eleventh in the world. Because it sits within Kanagawa Cancer Center, a specialist cancer hospital, treatment plans can be made together with surgeons, oncologists and imaging specialists. It is located in Asahi Ward, Yokohama; the center's English guide says it is about 45 minutes from Haneda Airport and about 120 minutes from Narita Airport.
Its key feature is high-speed three-dimensional pencil-beam scanning, which "paints" the tumor point by point with a narrow beam, making it easier to cover irregularly shaped tumors evenly. There are four treatment rooms: two with horizontal beams only and two with both horizontal and vertical beams. Each room has a robotic couch and in-room CT to check the patient's position before every session. The synchrotron accelerates carbon ions to 70% of the speed of light, up to 430 MeV/n. Learn how the beam works in What Is Carbon Ion Therapy? and see all Japanese centers in Japanese Institutions.
How do patients from abroad apply?
i-ROCK asks patients who are not covered by Japanese public health insurance not to contact the center directly, but to go through an AMTAC-certified medical coordinator. The coordinator forwards records, arranges the schedule and provides a medical interpreter during treatment; the patient pays the coordination fee. The center's English page lists three companies:
| Coordinator | Languages listed | Contact |
|---|---|---|
| Emergency Assistance Japan | English, Russian, Korean, Japanese; separate Chinese lines | Phone, email |
| JTB Japan Medical & Health Tourism Center | Japanese, English, Chinese, Korean | Phone, email |
| Aisel Networks | English, Chinese, Korean, Japanese | Website form |
Coordinators are not physicians, so incomplete records slow the center's preliminary review. i-ROCK does not publish a step-by-step procedure, but international intake at Japanese carbon ion centers usually follows this order: send records, preliminary medical review, visit and examination in Japan, treatment decision, irradiation, and follow-up after returning home. Compare other centers in 7 Carbon Ion Therapy Hospitals in Japan.
If you need help deciding which coordinator to contact and what to send, contact us or call +82-2-517-5117. We review your records first and explain the preparation steps.
Which documents should you prepare?
i-ROCK's English page does not list required documents, so it helps to follow the published criteria of another Japanese center. Based on the FAQ of Osaka Heavy Ion Therapy Center:
- A referral letter from your current doctor: diagnosis, stage and treatment so far
- Imaging on CD: original CT, MRI and PET files (DICOM) with radiology reports, ideally taken within 3 months
- Recent blood test results
- Pathology report from biopsy or surgery
- Lung function test results for lung cancer
- If you had radiotherapy before, the treated area and dose records
Documents in other languages are usually sent with English or Japanese translations, and images must be original files so physicians can measure the tumor and its distance from nearby organs. See the full checklist in Carbon Ion Therapy Documents.
Which cancers are treated, and in how many sessions?
The i-ROCK brochure states that it treats localized solid tumors with curative intent. Cancers with widespread metastases, leukemia and malignant lymphoma are not treated. The sites listed by the center in 2023:
| Site | Condition in center materials | Related article |
|---|---|---|
| Prostate cancer | 12 sessions over 3 weeks (conventional radiotherapy: 7–8 weeks) | Prostate cancer |
| Pancreatic cancer | Unresectable cases | Pancreatic cancer |
| Hepatocellular carcinoma | Under 4 cm, or 4 cm or larger when surgery is not suitable | Liver cancer |
| Head and neck tumors | Including skull base tumors; excluding oral squamous cell carcinoma | Head and neck cancer |
| Bone and soft tissue tumors | Unresectable cases | Sarcoma |
| Lung, esophageal, kidney cancer | Decided by stage and location | Stage I lung cancer |
| Uterine cancer, pelvic recurrence of colorectal cancer, intrahepatic bile duct cancer, oligometastases | Recurrence and metastases judged by number and location | Metastatic cancer |
Treatment takes 4 to 16 sessions depending on the disease. Sessions are usually given once a day on weekdays, so irradiation alone takes from 1 to 4 weeks. The first consultation, immobilization device and planning CT require extra preparation time, so the actual stay is longer. See schedule examples in Carbon Ion Therapy Duration.
How is the cost of carbon ion therapy at i-ROCK structured?
Cost depends on Japanese public insurance status and the disease. Published amounts and dates:
| Category | Carbon ion technical fee | Other costs | Source |
|---|---|---|---|
| Insured in Japan, Advanced Medical Care diseases (esophageal, kidney cancer, etc.) | JPY 3.5 million, fully self-paid | Consultation, tests and drugs at insurance co-pay | Kanagawa Prefecture, 2026-04-23 |
| Insured in Japan, insurance-covered diseases (prostate, pancreatic cancer, etc.) | Disease-specific amount; high-cost medical expense system applies | Co-pay rate depends on age and income | Kanagawa Prefecture, 2026-04-23 |
| Patients from abroad (no Japanese insurance) | No published amount; ask the coordinator for a quote | Coordinator and interpreter, flights, lodging | i-ROCK English page |
Because the international fee is not published, ask the coordinator for a quote that separates the technical fee from consultation and test costs. For reference, other centers publish international technical fees of JPY 5.786 million including tax (QST Hospital) and JPY 4.8 million plus consumption tax (Osaka Heavy Ion Therapy Center). Kanagawa's treatment subsidy (up to JPY 350,000) and interest support are only for people registered as Kanagawa residents for at least one year. Compare hospitals in Carbon Ion Therapy Cost.
What were the 5-year prostate cancer results?
In 2024 i-ROCK physicians published 5-year outcomes of scanning carbon ion therapy for prostate cancer in PLoS One. All 253 consecutive patients treated from December 2015 to December 2017 were analyzed; each received 51.6 Gy (RBE) in 12 sessions over 3 weeks. Median follow-up was 61.1 months.
| Measure | 5-year result |
|---|---|
| Free of PSA relapse (all patients) | 93.3% |
| Intermediate risk / high risk | 93.7% / 93.4% |
| 5-year overall survival | 97.5% |
| Late urinary side effects, grade 2 or higher | 7.4% |
| Late bowel side effects, grade 2 or higher | 1.2% |
High-risk patients stayed free of PSA relapse at a rate similar to intermediate-risk patients. Bowel side effects affected about 1 in 100 patients, and urinary symptoms are managed with medication and follow-up. The authors concluded that scanning carbon ion therapy is effective with low toxicity for prostate cancer, and longer follow-up is continuing. Side-effect care is covered in Carbon Ion Therapy Side Effects.
Frequently asked questions
Can patients from abroad receive carbon ion therapy at Kanagawa i-ROCK?
Yes. Patients without Japanese insurance apply through one of three coordinators certified for the center, all of which list Korean, English and Chinese support. Eligibility is decided by the center's physicians after reviewing records.
How much does carbon ion therapy at i-ROCK cost?
The Advanced Medical Care technical fee for insured patients in Japan is JPY 3.5 million (Kanagawa Prefecture, posted 23 April 2026). The fee for patients from abroad is not published, so a quote is requested through the coordinator. Interpreter, lodging and flights are extra.
How long do I need to stay in Yokohama?
Irradiation takes 4 to 16 sessions, or 1 to 4 weeks. Consultation and preparation add time, so confirm the exact stay with the coordinator after the preliminary review.
Why choose i-ROCK among Japan's carbon ion centers?
It is a relatively new center with pencil-beam scanning and four treatment rooms, close to Haneda Airport. The best center depends on the cancer type, schedule and cost together.
Related articles
Wondering if carbon ion therapy is possible for you, and what it costs?
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Free consultationCall +82-2-517-5117Sources
- Kanagawa Cancer Center i-ROCK: Information on accepting international patients
- i-ROCK English brochure (2017)
- i-ROCK insurance coverage and treated sites (Japanese, 2023)
- Kanagawa Prefecture: Carbon ion therapy at Kanagawa Cancer Center (Japanese, posted 2026-04-23)
- Five-year clinical outcomes of scanning carbon-ion radiotherapy for prostate cancer (PLoS One, 2024)
- Osaka Heavy Ion Therapy Center FAQ (Japanese)
- Osaka Heavy Ion Therapy Center treatment fees (Japanese)
General information based on public sources; not a substitute for diagnosis or treatment. Eligibility is decided by the treating physicians. Written by the FTH editorial team.