Analysis of mandibular dose distribution in radiotherapy for oropharyngeal cancer: dosimetric and clinical results in 18 patients

• Published in: Radiotherapy and oncology 2003-01, Vol.66 (1), p.49-56
• Main Authors: Jereczek-Fossa, Barbara A, Garibaldi, Cristina, Catalano, Gianpiero, d'Onofrio, Alberto, De Pas, Tommaso, Bocci, Chiara, Ciocca, Mario, DePaoli, Fiora, Orecchia, Roberto
• Format: Article
• Language: English
• Subjects: Adult; Aged; Cohort Studies; Dose Fractionation, Radiation; Dose-Response Relationship, Radiation; Female; Follow-Up Studies; Humans; Male; Mandible - radiation effects; Maximum Tolerated Dose; Middle Aged; Neoplasm Staging; Oropharyngeal Neoplasms - mortality; Oropharyngeal Neoplasms - pathology; Oropharyngeal Neoplasms - radiotherapy; Osteoradionecrosis - prevention & control; Prospective Studies; Radiation Dosage; Radiotherapy, Conformal - adverse effects; Radiotherapy, Conformal - methods; Risk Assessment; Survival Analysis; Treatment Outcome
• ISSN: 0167-8140
• DOI: 10.1016/S0167-8140(02)00191-3

The relationship between the radiation dose and the risk of the osteoradionecrosis is well known. However, the dose to the mandible is not routinely assessed in the radiotherapy for head and neck cancer. The aim of our study was to analyze the mandibular dose distribution in the patients administered curative radiotherapy for squamous cell carcinoma of the oropharynx. Moreover, the clinical results have been analyzed. We examined the clinical records and treatment plans in 18 patients treated with bifractionated radiotherapy for stage II-IV oropharyngeal cancer. In 17 patients, the total radiotherapy dose prescribed in the International Committee of Radiation Units and Measurements (ICRU) reference point was 74.4 Gy administered in 62 fractions (1.2 Gy twice daily with 6h interfraction interval) and one patient received a dose of 75.6 Gy. The whole dose to the mandibular-orophryngeal region was delivered with 6 MV photons. The mandible was contoured manually on computed tomographic scans and the point doses at the both mandibular condyles, ascending ramus, mental symphysis, molar and retromolar regions were assessed. Moreover, the cumulative dose-volume histograms (DHVs) were evaluated. The median follow-up period for alive patients is 30 months (range, 21-44+ months). Tumor remission was observed in 17 patients: in 11 cases, complete remission was achieved and in six cases, only partial remission was possible. One patient was lost to follow-up before the first response evaluation. The median survival for all patients is 22 months (range, 3-44+ months). Ten patients are alive and seven died. In six cases, the cause of death was head and neck tumor and in one died due to pancreatic cancer (second primary). No late bone post-radiation complication was seen. The highest radiotherapy doses were observed in the retromolar regions. The mean percentage doses at the right and left retromolar regions were 101.3+/-3.8% (range, 90.2-109.1%) and 101.7+/-2.5% (range, 95.2-105.8%), respectively. Lower doses were seen in ascending ramus (the mean percentage doses at right and left ascending ramus were 97.3+/-8.5% and 97.8+/-7.6%, respectively), the molar regions (the mean percentage doses at right and left molar regions were 86.0+/-13.5% and 88.1+/-12.9%, respectively), and at the mandibular condyles (the mean percentage doses at the right and left mandibular condyles were 72.6+/-18% and 77.0+/-16.5%, respectively). The volume of the mandible ranged from 60.1 to 110.1cm(