Approved treatment — Japan has widened public insurance coverage step by step since 2016 (early lung cancer added in 2024) Durations and session counts follow hospital guidance — they vary by condition and center
The proton therapy process usually runs in five steps: ① consultation and eligibility review → ② making immobilization devices and a planning CT → ③ about one to two weeks of planning and verification → ④ daily treatment five days a week → ⑤ regular follow-up after treatment. Each day, lining you up takes longer than the beam itself, so a visit lasts roughly 30 minutes to 1.5 hours. The total proton therapy duration ranges from one week (5 sessions) to nine weeks (40+ sessions) depending on the condition, and in prostate cancer a 5-session course has achieved results on par with a 9-week course.
Proton therapy process at a glance: 5 steps
Proton therapy is radiation treatment that accelerates the nuclei of hydrogen atoms (protons) and aims them at a tumor. Protons release most of their energy at a set depth and then stop, so the plan can spare normal tissue behind the tumor. Making the most of this requires matching the exact same position every time, which is why there are several steps between the first consultation and the first beam. The times below are examples that hospitals in the U.S., U.K. and Japan give to patients.
| Step | What happens | Typical time (hospital guidance) |
|---|---|---|
| ① Consultation | Review of imaging and pathology, eligibility, number of sessions and dose, consent | One or more visits |
| ② Immobilization & planning CT | Mask, cushion or other devices made; CT in treatment position (MRI/PET if needed) | The scan itself is brief |
| ③ Planning & verification | Beam design, plan measured on dedicated equipment, dry run | About 10 days to 2 weeks |
| ④ Daily treatment | Position imaging, then irradiation; weekly review | 15–90 min per session, 5 days a week |
| ⑤ Follow-up | Checking response and side effects | Regularly from about 1 month to 6 weeks after |
Sources: National Cancer Center Hospital East, Japan (about 2 weeks from planning CT to start, about 15 min per session); Johns Hopkins (start within 10 days of consultation, about 30 min per session); The Christie, U.K. (20–90 min per session); Penn Medicine (review about 1 month after treatment). Details vary by center and site.
Step 1, consultation: records to prepare for proton therapy
At the first consultation, a radiation oncologist reviews your CT, MRI or PET images and biopsy (pathology) results to decide whether proton therapy suits you. If it does, the team sets the treatment area, total dose and number of sessions, explains short- and long-term side effects, and asks for your consent. Johns Hopkins notes that if you do not sign on the day, you will need another visit before simulation.
When asking a hospital abroad for a consultation, preparing these records speeds up the review:
- Recent original images (standard medical imaging format, e.g. on CD) and radiology reports
- Biopsy reports and records of surgery, chemotherapy and any previous radiation (including site and dose)
- A list of current medications and any implanted devices such as a pacemaker
For interpreting and document preparation, see preparing for an interpreter before visiting a Japanese hospital.
Steps 2–3, immobilization and treatment planning: about 2 weeks
The planning CT is taken in exactly the same position as treatment. For the head and neck, a plastic mask molded to the face and a custom cushion are used; for the chest and abdomen, supports that hold the arms raised, among others. For organs that move with breathing, that motion is measured as well. Alignment marks are placed on the mask or the skin. Johns Hopkins says the planning CT scan itself takes less than 30 seconds.
Medical physicists and dosimetrists then design the direction and number of beams under the doctor's guidance. National Cancer Center Hospital East checks each finished plan by actual measurement on dedicated equipment before treatment and says it takes about 2 weeks from planning CT to the first session. Some centers, such as Penn Medicine, run a dry run in the treatment room to confirm position and dose. Because the plan is based on your current body shape, The Christie advises against deliberately gaining or losing a lot of weight during treatment.
Step 4, daily treatment: how many sessions and how long?
Treatment is usually given once a day, five weekdays a week. On the table, the immobilization devices are put back on and X-ray images confirm your position; the beam starts once any difference from the plan is very small. National Cancer Center Hospital East states that it treats after matching the planned position to within 1 mm. You feel no pain or heat during irradiation, though you may hear the machine. Staff watch you on cameras throughout and can stop at once if needed.
Session length is given as about 15 minutes at National Cancer Center Hospital East, about 30 minutes at Johns Hopkins (up to 1.5 hours in the department) and 20–90 minutes at The Christie, mostly for position checks. Many patients return to work or daily life the same day. During the course you see your doctor and nurse once a week, and a repeat CT may be taken to adjust the plan as the tumor changes. The total number of sessions is decided at consultation according to the condition and goal.
Shorter proton therapy courses: phase III results with 5 sessions
Clinical trials are also confirming ways to finish treatment in fewer sessions. The randomized phase III trial PCG GU002, led by Mayo Clinic in the U.S., compared the conventional schedule (44 sessions over 9 weeks) with stereotactic proton therapy (5 sessions over 1 week) in 133 patients with low-risk early prostate cancer.
| Measure | 5 sessions (1 week) | 44 sessions (9 weeks) |
|---|---|---|
| Patients | 88 | 45 |
| 5-year freedom from failure | 100% | 97.4% |
| 5-year overall survival | 95.5% | 97.1% |
| 5-year cumulative grade 3 side effects | 5.7% | 0% |
Source: ASTRO 2023 final analysis (Toesca et al., reported by JNCCN 360); median follow-up 5 years. Differences in survival and side effects were not statistically significant.
The 5-session course proved as effective as the 9-week course (non-inferior), and urinary, bowel and sexual quality-of-life scores at 2 years were similar in both groups. Mayo Clinic announced that this cut treatment time from more than two months to under two weeks, greatly easing the burden on patients. Short courses are not suitable for every cancer and stage, so discuss with your doctor whether one applies to you.
Step 5, side effect care and follow-up
Side effects depend on the treated area. Common ones are fatigue, sunburn-like skin redness, dryness or itching, and temporary hair loss at the treatment site. According to The Christie, most appear in the second half of the course, may continue for a while after it ends, and gradually settle over 4–6 weeks; most can be managed with medication. The best care is to tell your team about any symptom right away rather than putting up with it.
When treatment ends, keep a treatment summary (site, dose, side effects). The Christie schedules follow-up at 6 weeks, at 6 months and then yearly for 5 years, and Penn Medicine arranges the first review about 1 month after treatment. If you were treated abroad, agree in advance how follow-up will be shared with your hospital at home.
Proton therapy in Japan: wider insurance coverage
In Japan, proton therapy has been moving step by step from Advanced Medical Care to public insurance. Coverage began with pediatric cancer in 2016, extended in 2018 to bone and soft tissue tumors, some head and neck cancers and prostate cancer, and in 2022 to liver cancer, pancreatic cancer and recurrent colorectal cancer (Sakurai et al., 2023); in June 2024 early lung cancer (stage I–IIA) where surgery is difficult was added. The Japanese Society for Radiation Oncology (JASTRO) has registered every patient treated under Advanced Medical Care since 2016 to collect outcomes.
Conditions outside insurance are treated under Advanced Medical Care or self-pay care; at the Fukui Prefectural Proton Therapy Center, the Advanced Medical Care fee is listed at about 2.4–2.6 million yen depending on the number of sessions. Residents abroad who are not enrolled in Japanese public insurance may be billed differently, so check with the institution directly. For the difference between the systems, see proton therapy in Japan: insurance, Advanced Medical Care and self-pay; for institution information, see proton therapy medical information.
What to check and questions for your doctor
- For my cancer and stage, what are the advantages of proton therapy over standard X-ray radiation?
- How many sessions and weeks will treatment take? Am I a candidate for a shorter course?
- How long from the planning CT to the first session? Do I need to stay nearby in the meantime?
- What side effects are common for my treatment area, and how are they managed?
- Where and when will follow-up take place? Can I receive a treatment summary?
Frequently asked questions
How long does proton therapy usually take?
It depends on the condition and goal. Once a day, five days a week is typical, and the full course ranges from one week (5 sessions) to nine weeks (40+ sessions). One to two weeks of planning come before that.
Does proton therapy hurt?
There is no pain or heat during irradiation. Wearing the immobilization device and keeping still is the main thing to get used to, and many patients return to daily life the same day.
When do proton therapy side effects appear and when do they improve?
It varies by area, but fatigue and skin changes usually appear in the second half of the course and gradually improve over 4–6 weeks after it ends. Most are managed with medication.
What happens if I miss a day of treatment?
Days lost to maintenance or breakdowns are usually made up by adding sessions at the end or by giving two sessions in one day with enough of a gap. The Christie explains these catch-up options to patients in advance.
Related: Phase III results of proton therapy for liver cancer · Proton therapy information in Japan · All proton therapy articles
Sources
- National Cancer Center Hospital East, Japan — Proton beam therapy treatment flow (Japanese-language source)
ncc.go.jp
Checked: 2026-10-19 - Johns Hopkins Medicine — Proton Therapy at Johns Hopkins: What to Expect
hopkinsmedicine.org
Checked: 2026-10-19 - Penn Medicine — What to expect from your proton therapy
pennmedicine.org
Checked: 2026-10-19 - The Christie NHS Foundation Trust — Proton beam therapy – adult/young adult (TYA): a guide for patients and their carers
christie.nhs.uk
Checked: 2026-10-19 - Sakurai H, et al. Current status and future prospects of particle therapy (proton beam and heavy ion therapy) in Japan. J Radiat Res 2023;64(Suppl 1):i1
doi.org/10.1093/jrr/rrad034
Checked: 2026-10-19 - Fukui Prefectural Proton Therapy Center — Insurance coverage expansion under the 2024 fee revision (Japanese-language source)
pref.fukui.lg.jp
Checked: 2026-10-19 - JNCCN 360 — Conventional versus stereotactic proton therapy for early-stage prostate cancer (PCG GU002, ASTRO 2023)
jnccn360.org
Checked: 2026-10-19 - Mayo Clinic — Shorter proton therapy regimen eases patient burden while maintaining efficacy (2025-10-21)
mayoclinic.org
Checked: 2026-10-19
Written by the FTH editorial team. Sources checked 2026-10-19 · 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.
