The Hokkaido Cancer Center belongs to the national hospital organization and has been designated a state cancer hospital. Many cancer patients from all over Hokkaido visit our hospital for treatment.
To efficiently treat any intraoral adverse events of cancer patients, the department of Dentistry and Oral Surgery was established in 2012, and in 2016 it increased treatment availability from 2 days to 5 days a week.
With the exception of the university hospital, there had been no state cancer hospital with separate oral cancer treatment and oral supportive care departments until the establishment of the Department of Clinical Oral Oncology in our hospital in 2016. Cooperation between other co-medical staff in the hospital is necessary to provide high quality perioperative oral management. In addition to securing continuity of oral management for the cancer patients, cooperation between the general practice dentists is essential.
As dentists working in the department of dentistry and oral surgery in a state cancer hospital, we should recruit cooperative cancer dentists, with assistance from the Hokkaido Dental Association, to treat oral adverse events. In this symposium, we reported on the medical-dentistry cooperation system in our hospital.

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The Japanese Ministry of Health, Labor and Welfare has assigned “prefectural designated cancer hospitals.” In cases where a university hospital is designated, it should also fulfill the role of training human resources responsible for cancer care, which is an important original role of a university.
The Okayama University Hospital established a division of hospital dentistry in 2011, one of its aims being to improve the quality of cancer care via oral supportive care. Oral supportive care is actively performed in several types of cancer therapy, including surgery, radiotherapy, and chemotherapy.
Educational programs were established in this division to educate undergraduate dental students and dental residents regarding oral supportive care. To facilitate gaining exposure beyond their positions and abilities, we allow students in the final year and residents of their respective programs to participate as dental specialists in collaborative groups engaged in various multidisciplinary supportive cancer care efforts in the hospital.
The field of oral supportive care in cancer must continue to be developed as an indispensable area in cancer care. Further development in dentistry requires more general medical knowledge, psychological ability to support patients with cancer, and ability to build good relationships with other occupations; furthermore, a philosophical understanding, such as thanatology, is also required.
These observations apply not only to cancer care but also to dental practitioners contributing to a healthy society with longevity in Japan. Such efforts are necessary to produce young dentists with erudition.

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Perioperative oral function management was introduced in 2012 and has been taken up throughout Japan. However, except for some dental clinics, most are limited to dental hospitals, which cannot be said as enough.
In order to widely apply this in the regions, it is important to establish a collaborative system between cancer hospitals and dental clinics. In addition, it is important to continue the oral function management after the patient’s discharge. Especially, the collaboration between dental hygienists is also important in order to perform a high-quality oral function management.
Looking forward, we need to think about future measures to make greater contributions to the health and welfare of not only the cancer patients but of all local residents.

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Carbon ion radiotherapy （C-ion RT） is a high linear energy transfer radiation, and is associated with higher probability of tumor control compared with photon RT.
Additionally, the physical characteristics of C-ions offer the theoretical benefit of a more localized delivery of the radiation dose than that of photons.
Here, we report the safety and efficacy of C-ion RT for oral malignancies in the single-institutional study and multicenter study.
A single-institutional study was conducted on 77 patients of oral malignancies treated with C-ion RT at the National Institute of Radiological Science between April 1997 and March 2016. Forty-three patients had salivary gland carcinomas, 29 patients had mucosal melanoma, and 5 patients had other carcinomas. The median follow-up was 48 months. The 5-year local control, progression free survival, and overall survival rates of all patients were 79.4％, 34.6％, and 57.4％, respectively. Although 11 patients developed grade 3 osteoradionecrosis after the C-ion RT, all patients maintained their mastication and deglutition functions after sequestrectomy and prosthesis.
A multicenter study was conducted on 83 patients of oral malignancies treated with C-ion RT at the 4 institutions in Japan between November 2003 and December 2014.
Forty-six patients had salivary gland carcinoma; 27 had mucosal malignant melanoma, and 10 had other carcinomas. Median follow-up was 30 months. The 3-year local control, progression free survival, and overall survival were 81.0％, 59.8％ and 73.3％, respectively. Grade 3 or higher late morbidities were observed in 18.
It appears that C-ion RT provides therapeutic effectiveness with acceptable toxicities for oral malignancies, which were mainly salivary gland carcinoma and mucosal melanoma.

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Interstitial brachytherapy （ISBT） for oral cancer patients, especially for tongue cancer patients, is one of the radical treatments because of high local control rate and preservation of oral function. Low-dose-rate （LDR） ISBT was the main treatment modality in ISBT for oral cancer patients. However LDR ISBT has the problems of irradiation for medical staff and radioactive source supply, and so on. High-dose-rate （HDR） ISBT can resolve these problems of LDR ISBT. This review was conducted to report the advantage of HDR ISBT for oral cancer patients, the treatment method of HDR ISBT for tongue cancer patients, the treatment results of HDR ISBT for tongue cancer patients, and the modular resin spacer with lead for HDR ISBT correspondent to CT based image guided brachytherapy.

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Radiotherapy is classified into external beam radiotherapy and brachytherapy. Recently, advancement of precision radiotherapy including stereotactic radiotherapy and intensity-modulated radiotherapy （IMRT） has brought remarkable clinical outcomes and high treatment quality. Indeed, chemoradiotherapy for pharyngeal cancer is now considered as definitive treatment by overcoming the parotid gland damage using IMRT. On the other hand, most of oral cancer patients are still treated by surgery. Two main reasons could be the anatomical position of oral cancer surrounded by maxilla and mandible, and cellular radioresistance of oral cancer cells compared to pharyngeal cancer cells. In this situation, only brachytherapy, giving radiation from inside of tumor tissues by implanting sealed radioisotopes, has been applied as definitive radiotherapy for early stage oral cancer with good clinical results. Two types of brachytherapy exist in terms of dose rate, high and low. In this review, the status quo and biological superiority of low-dose rate brachytherapy will be described.

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