Perioperative oral management has been widely performed to reduce the risk for surgical site infection or postoperative pneumonia in cancer surgery. However, oral management methods have not been standardized. In the study, we discussed appropriate oral management methods for cancer surgery based on our clinical research.
Bacteria in the saliva increase after surgery. Surgical site infection after surgery for head and neck cancer or upper gastrointestinal tract cancer, and postoperative pneumonia may be caused by pathogenic microorganisms in the saliva. In order to reduce the number of bacteria in the saliva, early oral feeding is most important. When oral feeding is impossible, gargling is effective. If patients cannot perform gargling, topical application of antiseptics or antibiotics should be considered. In addition, blood circulation from an oral infection site may cause infection at a distant location, and so it is necessary to treat the source of intraoral infection before surgery.
Our multicenter study showed that perioperative oral management reduces surgical site infection of oral cancer, postoperative pneumonia of esophageal cancer and lung cancer, and surgical site infection of colon cancer. In the future, standardization of oral care methods and verification of their effectiveness will be required.

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A retrospective investigation of oral mucositis and oral candidiasis was conducted in 326 patients with oral or oropharyngeal cancer who underwent radiotherapy. The following results were obtained:
1．Grade 3 oral mucositis occurred in 131 patients （41.7％）.
2．Male, oropharyngeal cancer, concurrent radiotherapy with cisplatin or cetuximab, lower level of leukocytes, lymphocytes, and hemoglobin, and oral feeding were independent risk factors for developing grade 3 oral mucositis.
3．Oral candidiasis occurred in 101 patients （31.0％）.
4．Oropharyngeal cancer, lower level of leukocytes, and oral mucositis of grade 2 or more were independent risk factors for developing oral candidiasis. Topical administration of corticosteroid ointment did not become a risk factor for oral candidiasis.

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Risk factors for development of osteoradionecrosis （ORN） of the jaw in patients with oral or oropharyngeal cancer who underwent radiotherapy between 2008 and 2017 at six hospitals were analyzed by Cox’s proportional hazard model. Periapical lesion, severer periodontal disease, and higher serum creatinine level significantly increased the risk of ORN, whereas IMRT and tooth extraction before RT significantly decreased the risk. Tooth extraction after RT seemed to increase the risk of ORN, though not significantly. It is necessary to establish a method for preventing ORN in future.

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Treatment strategies for cervical lymph nodes in N0 patients with oral cancer include elective neck dissection （END）, and therapeutic neck dissection （TND）. Recently, randomized controlled trials show efficacy of END; however, unnecessary operative treatment is performed in approximately 70％ of patients. In our department, we have adopted a “wait-and-see” policy and do not perform neck dissection in N0 oral cancer patients, except for reconstruction purposes. In the present study, we evaluated the frequency and treatment outcomes of cervical metastasis in cT1-2N0 tongue cancer patients and investigated predictive factors of secondary metastasis.
The study was comprised of 155 patients with primary cT1-2N0 tongue squamous cell carcinoma. Secondary cervical metastasis was observed in 28 patients （18.1％）. TND was performed in 24 of 28 patients （85.7％） with secondary cervical metastasis. The treatment was effective in 21 of the 24 patients （87.5％）. The overall survival rate for all patients was 88.0％. However, the secondary cervical metastasis group had a significantly worse prognosis. Characteristics related to cervical metastasis in most T1-2N0 tongue cancer patients included: pathological depth of invasion （pDOI） ≥ 4.0mm, worst pattern of invasion （WPOI）＝4-5, or tumor budding （TB） ≥ 4.
When excision is performed in cT1-2N0 tongue cancer patients combined with one of the following characteristics, DOI ≥ 4.0mm, WPOI＝4-5, or TB ≥ 4; strict follow-up observations and efforts for early detection should be made. In the future, it will be important to search for factors that are useful for predicting cervical metastasis during preoperative stages.

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The validity of performing elective neck dissection for T1-2N0M0 tongue squamous cell carcinoma was examined. A multicenter retrospective study with decision tree analysis was performed. The results revealed the utility of tumor depth as the criterion for performing elective neck dissection, with a tumor depth of 4-5mm or greater as the criterion. However, it may be necessary also to consider age.

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Despite advances in early detection, diagnosis, and treatment of oral squamous cell carcinoma, the survival rate for patients with early stage has remained at approximately 80％ for the past 30 years. Regional lymph node metastasis is an important prognostic factor. Therefore, early detection of cervical lymph node metastasis is expected to further improve survival. Whether patients with cN0 status should be treated with elective neck dissection or with therapeutic neck dissection after nodal relapse has been a matter of debate. Sentinel node biopsy （SNB） is a widely accepted procedure in various human malignancies. SNB has received considerable attention for its role in deciding whether to perform neck dissection. The main objective in this study is to investigate the topographical distribution of sentinel lymph nodes and occult metastatic lymph nodes to assess the validity of completion neck dissection of level Ⅰ-Ⅲ in early tongue squamous cell carcinoma patients and explain an outline of the current status of SNB in oral cancer.

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This study was carried out to describe the clinicopathologic features of oral squamous cell carcinoma （OSCC） in patients who develop local recurrence. We retrospectively examined 121 patients who underwent surgery for OSCC between 2006 and 2015. Local recurrence was found in 16 of 121 patients （13.2%）. Fourteen patients （87.5%, 14/16） exhibited recurrence within 24 months after their initial treatment. Clinical T stage and perineural invasion were significantly correlated with local recurrence on univariate analysis. Multivariate analysis showed only perineural invasion （odds ratio: 11.2, 95% confidence interval: 2.28-63.4） as independent risk factors for increasing local recurrence. In these 16 patients, salvage treatment was performed in 12 patients （75%）, in whom salvage surgery was performed in 9 patients. The salvage cure rate was 78% （7/9） and median survival time after local recurrence was 40 months （range: 8.5-112 months）. In contrast, the three patients who received radiation and/or chemotherapy as salvage treatment had a poor prognosis: the median survival time after local recurrence was 4.9 months （range: 4.8-11 months）. Clinical T stage, stage of the primary tumor and salvage surgery tended to be poor prognostic factors of salvage treatment. Our results support the recommendation of salvage surgery when patients can tolerate surgery.

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The UICC TNM classification is based on criteria for evaluating the progress of oral cancer. In the 8th edition published in 2016, the depth of invasion （DOI） in T classification and the extra nodal extension （ENE） in N classification were introduced. We evaluated for TNM classification of the cases of tongue squamous cell carcinoma who underwent surgery according to the 7th and 8th editions, and reported the practicality of the matter in the Journal of Japanese Society of Oral Oncology. In addition, UICC published an errata in 2018, and T2, T3 and T4 have been corrected. In this study, 107 cases of tongue squamous cell carcinoma that underwent surgery at our department were evaluated for the corrected TNM classification.
According to the errata, one case was changed from T3 to T2, and three cases were changed from T3 to T4a. Compared with the 7th edition, the rate of cases of cervical lymph node metastasis decreased in T1 and increased in T2, with similar results to the 8th edition. The survival rate decreased as the T stage increased, as in the 8th edition. In addition, since pStage was changed along with the change of pT, the survival rate decreased as the stage increased.
The corrected 8th edition TNM classification faithfully reflects the progress in the cervical lymph node metastasis and survival rate, and it was considered to be practical.

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