Head and neck cancer and carbon ion therapy
The head and neck brings together functions such as speaking, swallowing, and breathing, so radiotherapy that preserves function plays a large role. Squamous cell carcinoma, about 90% of head and neck cancers, responds relatively well to X-ray therapy and chemotherapy. The remaining 10%, non-squamous cell carcinomas, are often resistant to X-rays and rare, so treatment development has been slow. QST Hospital has focused carbon ion therapy on such X-ray-resistant head and neck cancers.
Insurance coverage in Japan
Currently, all head and neck cancers except squamous cell carcinoma of the oral cavity, pharynx, and larynx are eligible for carbon ion therapy under public health insurance in Japan. Head and neck cancer is treated only under insurance, not Advanced Medical Care, and the brain is not treated.
Target diseases and fractions
All five diseases below receive 16 fractions over 4 weeks; the dose differs by disease. ① Non-squamous cell carcinoma of the head and neck ② mucosal malignant melanoma (with drug therapy if possible) ③ squamous cell carcinoma (excluding oral cavity and pharynx/larynx) ④ bone and soft tissue tumors ⑤ skull base tumors
Disease states eligible for treatment
① Before treatment, confined to the head and neck ② recurrence after treatment, confined to the head and neck ③ residual lesions after surgery ④ cervical lymph node metastases that are difficult to operate on
Cases that are difficult
Distant metastasis or widespread cervical lymph node metastasis is in principle not eligible. However, depending on lesion size or location, a case may be judged difficult even when confined to the head and neck, and conversely may be eligible despite metastasis if long-term survival is expected; the final decision is made by the physicians of the medical institution.
Preparation
If needed, dental treatment comes first (removing metal prostheses in the irradiated area, extracting teeth with poor prognosis, making a mouthpiece for fixation). A dedicated immobilization device is then made, and CT is taken while wearing it to plan the range and directions of irradiation. Because the treatment range is determined from images, MRI, CT, and PET are performed just before treatment.
Side effects
Carbon ion beams make it easy to concentrate the dose on the lesion, but if the tumor invades surrounding organs such as the jawbone, nerves, or brain, those organs cannot be fully avoided. Even with a minimized range, organs within the treatment range may show damage and symptoms over time; the type and frequency of side effects depend on lesion location and treatment range.