We retrospectively analyzed the treatment results in 543 oral cancer patients who were admitted to our department between September 1999 and March 2023. The tongue was the most common primary subsite, followed by the gingiva and oral floor. Among the total of 543 cases of oral cancer, there were 132 clinical node-positive cases (24%). The overall 5-year disease-specific survival (DSS) rate was 71.8%, and the 5-year DSS rates in the stage I, II, III, and IV oral cancer cases were 91.5%, 81.2%, 62.1%, and 48.5% respectively. The 5-year DSS rates in the stage I, II, III, and IV tongue cancer cases were 91.4%, 80.6%, 59.5%, and 44.9%, respectively. The new N classification was more reliably associated with the survival as compared with previous N classifications in the tongue carcinoma cases. Among the 184 cases with T2 oral cancer, 77 (42%) were node-positive. An advanced T stage and a positive neck nodal status were significantly associated with poorer 5-year DSS rates.

We retrospectively analyzed the treatment results in 57 patients with nasopharyngeal cancer who were admitted to our department between September 1999 and March 2023. The laterally extending type of carcinoma was the most common subsite, followed by the posterosuperiorly extending type. We administered induction chemotherapy followed by (chemo)radiotherapy for stage II, III, and IV patients. The overall 5-year disease-specific survival (DSS) rate was 61.2%. The 5-year DSS rates in the stage I, II, III, and IV cases were 100%, 60.1%, 71.4%, and 40.9%, respectively. The 5-year DSS rates in the T3, T4, and N3 cases were all under 50%. In regard to the therapeutic efficacy of induction chemotherapy, cases that were rated as showing complete or partial response showed significantly better prognoses than those that were rated as showing stable or progressive disease in response to the treatment.

We retrospectively analyzed the treatment results in 199 patients with mesopharyngeal cancer who were admitted to our department between September 1999 and March 2023.

The lateral wall was the most common subsite, followed by the anterior wall. The numbers of p16-positive and p16-negative cases were almost equal. While (chemo)radiotherapy was administered to both p16-positive cases with early T stage and advanced T stage disease, radical surgery was selected for p16-negative cases with advanced T stage/node-positive. Moreover, the overall 5-year disease-specific survival (DSS) rates were 66.3% and 61.8% in the p16-positive and p16-negative cases, respectively, the difference not being statistically significant. Among the p16-positive cases, the 5-year DSS rate in the stage III cases was significantly worse than the rates in the stage I and II cases. The 5-year DSS rate in the stage I, II, III, and IV cases were 100%, 82.2%, 63.1%, and 38.2%, respectively, in the p16-negative group. Although the N classification differs according to the p16 expression status, N2 cases had a poor prognosis in both the p16-positive and p16-negative groups.

We evaluated the management and outcomes of hypopharyngeal cancer treated at our department between September 1999 and March 2023. Data of a total of 315 patients were analyzed. We performed total pharyngolaryngectomy and total neck dissection for the patients with advanced T stage disease, and transoral resection for early T-stage and node-negative patients. Postoperative radiotherapy was instituted for advanced T-stage and/or node-positive cases. The overall 5-year disease-specific survival (DSS) rate was 46.2%. The 5-year DSS rates in the stage I, II, III, and IV were 67.8%, 66.2%, 50.6%, and 33.6%, respectively. Classification of the outcomes according to the T and N stages revealed that the 5-year DSS rates in the T3, T4, and N-positive were all under 50%. Prophylactic neck dissection for clinically node-negative (cN0) cases of pyriform sinus cancer is still controversial. Since the rate of pathologically node-positive cases (pN+) in cN0 pyriform sinus carcinoma cases was over 50%, prophylactic neck dissection on the affected side should be performed. On the other hand, in the case of ipsilateral cN+ pyriform sinus carcinoma cases, neck dissection of the opposite side could be omitted because of the low incidence of pN+.

We retrospectively analyzed the treatment results in 512 patients with laryngeal cancer who were admitted to our department between September 1999 and March 2023. The cancer was located in the glottis in 315 patients and in the supraglottis in 197 patients. The node-positive differed significantly according to the tumor location; 4.8% in patients with cancer of the glottis and 54.3% in patients with cancer of the supraglottis. (Chemo)radiotherapy was selected for cases with early T-stage disease (T1-, T2-, T3-stage cancer of the glottis and T1-, T2-stage cancer of the supraglottis), while total laryngectomy was performed for advanced T-stage cancer cases of both the glottis and supraglottis. The 5-year disease-specific survival (DSS) rate was 91.5% in the patient group with glottic cancer, and 67.5% in the patient group with supraglottic cancer. The 5-year DSS rates in stage I, II, III, and IV glottic cancer cases were 98.2%, 94.5%, 75.7%, and 58.6%, respectively, and those in stage I, II, III, and IV supraglottic cancer cases were 100%, 90.5%, 74.8%, and 51.7%, respectively. Regarding the N status, the 5-year DSS rate in N2 cases, both in the glottic and supraglottic cancer groups, was much poorer. Following total laryngectomy, serious pharyngo-cutaneous fistula formation after radiotherapy occurred in 21% of cases, especially in cases who received radiotherapy over a wide radiation field.

Data of a total 254 patients with parotid cancer were analyzed. Mucoepidermoid carcinoma (MEC) was the most common histologic type, followed by carcinoma ex pleomorphic adenoma (CEPA). High-grade malignancy accounted for 110 cases, and low-/intermediate-grade malignancy in 144. The 5-year disease-specific survival and disease-free survival rates in the stage IV cases were 56.2% and 30.8%, respectively. The prognosis was much worse in the T4 and N+ cases than in the early-T stage and N0 cases. The grade of malignancy was identified as an independent prognostic factor; the 5-year disease-free survival rates in the patient groups with high-grade and low-/intermediate-grade malignancy were 34.4% and 91.5%, respectively. High-grade parotid carcinoma comprises 4 major histological types, including salivary duct carcinoma, MEC, CEPA, and adenoid cystic carcinoma; the 10-year disease-free survival rates in patients with the aforementioned types of cancer were 16.4%, 34.9%, 46.1%, and 47.4%, respectively; thus, all of these types carry a poor prognosis. Each histological type was found to have its own characteristic pathological and clinical features, so that the diagnosis, treatment, and follow-up methods also vary accordingly.

We evaluated the management and outcomes of patients with submandibular gland cancer treated at our department between September 1999 and March 2023. Data of a total of 34 patients were analyzed. Adenoid cystic carcinoma and salivary duct carcinoma were the most common histologic types, followed by mucoepidermoid carcinoma and carcinoma ex pleomorphic adenoma. High-grade tumors accounted for 19 patients, and low-/intermediate-grade for 15 patients. The overall 5-year disease-specific survival (DSS) rate estimated by the Kaplan-Meier method was 59.5%, and the rates in the stage I, II, III, and IV cases were 100%, 68.6%,100%, and 25.0%, respectively. The 5-year DSS rates in the patient groups with high-grade and low-/intermediate-grade tumors were 43.8% and 83.3%, respectively. When classified according to the T stage, the 5-year DSS rates in the T1, T2, T3, and T4 were 100%, 65.3%, 33.3%, and 25.0%, respectively. Node-positive cases had a much worse prognosis than the N0 cases. Advanced-stage disease, node-positive status, and advanced age were identified as significant predictors of disease recurrence. The patient group with submandibular gland cancer had a much poorer prognosis than the patient group with parotid gland cancer, because the frequency of low-/intermediate-grade carcinomas, such as basal cell carcinoma, secretory carcinoma, and epithelial-myoepithelial carcinoma, is much lower among patients with submandibular gland cancer whereas these are the major types of cancer encountered in the patient group with parotid gland carcinoma.

We evaluated the management and outcomes of patients with thyroid cancer treated at our department between September 1999 and March 2023. Data of a total of 586 patients were analyzed. When classified according to the histopathology, papillary thyroid carcinoma and poorly differentiated carcinoma accounted for 380 and 143 cases, respectively. We performed total thyroidectomy in the high-risk group, and hemi-thyroidectomy in the low-/intermediate-risk group. Central neck dissection was performed in all cases; ipsilateral dissection with hemithyroidectomy, and bilateral dissection with total thyroidectomy. Selective neck dissection (level II to V) was the standard treatment for patients with lateral node positivity. The 5-year disease-specific survival (DSS) rate was 98.5% in the group with papillary thyroid carcinoma, and 90.6% in the group with poorly differentiated carcinoma. In the patient group with papillary thyroid carcinoma, the 5-year DSS was almost 100%, irrespective of the T and N stages. In the patient group with poorly differentiated carcinoma, the 5-year DSS rate was especially poor in the patients with advanced-stage disease who were over 55 years old. One of the most controversial issues in the treatment of thyroid cancer is the management of the central neck nodes in patients who are clinically node-negative. We concluded that prophylactic central neck dissection should be performed in all cases, because of the high pathological node-positive rate in the level VI lymph nodes.

We performed a retrospective analysis of the data of patients who underwent the initial operation for a benign parotid tumor in our department between September 1999 and March 2023. Data of a total of 1228 patients were analyzed. The most commonly diagnosed tumor was pleomorphic adenoma (764 patients), followed by Warthin tumor (257 patients). In regard to the tumor localization, superficial lobe tumors accounted for 56.7% of all tumors, deep lobe tumors for 19.6% of all tumors, and lower pole tumors for 23.7% of all tumors. Fine-needle aspiration cytology and frozen-section histopathological examination were used to identify the tumor histopathology. The overall rate of postoperative facial nerve palsy was 19%. A multivariate analysis was performed, which identified large-diameter tumors and deep-lobe tumors as the most important predictors of facial palsy. The postoperative facial palsy improved within 12 months of surgery in all cases, and there were no cases of permanent facial palsy. It is important to explain the risks of the postoperative complications to the patients so as to obtain appropriate informed consent from them for surgery.

Boron neutron capture therapy (BNCT) is a new cancer treatment modality that is based on a nuclear reaction occurring between boron atoms concentrates within a tumor and a neutron beam. Since the alpha particles and Li (lithium) nuclei generated by the reaction of ¹⁰B (n, α) ⁷Li, have a short range (less than the diameter of a cell), BNCT can selectively destroy tumor cells in which this reaction occurs without serious damage to the surrounding normal cells. BNCT for unresectable locally advanced and/or recurrent head and neck cancers using an accelerator-based BNCT system was approved by the Japanese government for coverage by the national health insurance program in June 2020. Entire tumors could be expected to be irradiated with at least 20 Gy-Eq. (D80 >20 Gy-Eq, calculated based on a tumor/blood boron concentration ratio of 2.5). This treatment is contraindicated in patients with a high risk of carotid artery rupture and infectious meningitis. We have treated 150 unresectable head and neck cancer cases who met the entry criteria between June 2020 and March 2023. We propose to investigate the short- and long-term outcomes of BNCT and establish appropriate indications for this treatment in patients with recurrent/unresectable head and neck cancer.