We used the following inclusion criteria: histology confirmed by pathology, reirradiation as radiotherapy performed after previous radiotherapy of 30 Gy/10 fractions (equivalent 2-Gy fractions = EQD2 ≥36 Gy, using α/β = 10 Gy) or more, pathological or radiological diagnoses obtained for patients presenting for salvage therapy after curative treatment including radiotherapy (definitive or postoperative), no distant metastasis, an Eastern Cooperative Oncology Group performance status of 0-2, and recurrence after curative treatment including surgery or chemotherapy with radiotherapy. Patients with histologically confirmed recurrent and very rare diseases after the previous radiotherapy with significant overlap were included. We defined “rare disease” incidence < 0.06% = 600/1000000 as according to Rare Diseases Act of 2002 . Patients with a recurrent very rare head or neck tumor treated at five Japanese institutes between 20 were recruited.

The purpose of the present study was to analyze the efficacy and toxicity of reirradiation for very rare tumors in the head and neck. Therefore, we examined the outcome of reirradiation for rare tumors, including of the eye, ear, and salivary glands, based on multi-institutional data accumulation . As many heterogeneous malignancies arise from many locations with various histological species, there are few reports of reirradiation for rare tumors, except for the oral and laryngopharyngeal areas. Reirradiation is a challenging field for anticipating severe toxicities, including those that are lethal . Thus, reirradiation could be an option for unresectable head and neck cancer to alleviate symptom palliation and improve oncologic outcomes . For those patients, surgery is a curative salvage treatment to prolong survival however, it is difficult in almost all cases and the majority received palliative chemotherapy with limited efficacy . Recent advancements in multidisciplinary approaches, both in radiotherapy and systemic therapy, have improved outcomes however, locoregional recurrence is a predominant pattern of failure, which has been reported in up to 50% of cases . Radiotherapy with or without systemic therapy is a standard treatment approach for locally advanced laryngeal and pharyngeal squamous cell carcinoma (SCC).

Auditory organ