IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients.
BACKGROUND
Radiotherapy (RT) is frequently used in the treatment of head and neck cancer, but different side-effects are frequently reported, including a higher frequency of radiation-related caries, what may be consequence of direct radiation to dental tissue. The intensity-modulated radiotherapy (IMRT) was developed to improve tumor control and decrease patient's morbidity by delivering radiation beams only to tumor shapes and sparing normal tissue. However, teeth are usually not included in IMRT plannings and the real efficacy of IMRT in the dental context has not been addressed. Therefore, the aim of this study is to assess whether IMRT delivers lower radiation doses to dental structures than conformal 3D radiotherapy (3DRT).


METHODS
Radiation dose delivery to dental structures of 80 patients treated for head and neck cancers (oral cavity, tongue, nasopharynx and oropharynx) with IMRT (40 patients) and 3DRT (40 patients) were assessed by individually contouring tooth crowns on patients' treatment plans. Clinicopathological data were retrieved from patients' medical files.


RESULTS
The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p = 0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p = 0.012 and p = 0.011, respectively). Molars received more radiation with both 3DRT and IMRT, but the latter delivered significantly lower radiation in this group of teeth (p < 0.001), whereas no significant difference was found for the other dental groups. Maxillary teeth received lower doses than mandibular teeth, but only IMRT delivered significantly lower doses (p = 0.011 and p = 0.003). Ipsilateral teeth received higher doses than contralateral teeth with both techniques and IMRT delivered significantly lower radiation than 3DRT for contralateral dental structures (p < 0.001).


CONCLUSIONS
IMRT delivered lower radiation doses to teeth than 3DRT, but only for some groups of patients and teeth, suggesting that this decrease was more likely due to the protection of other high risk organs, and was not enough to remove teeth from the zone of high risk for radiogenic disturbance (>30Gy).
Departments of Radiation Oncology and Oral Medicine, Sírio-Libanês Hospital, São Paulo, Brazil.
Eduardo Rodrigues
ER
Fregnani
Departments of Radiation Oncology and Oral Medicine, Sírio-Libanês Hospital, São Paulo, Brazil.
Cláudia Joffily
CJ
Parahyba
Department of Oral Diagnosis (Pathology and Semiology), Piracicaba Dental School, University of Campinas, Av. Limeira, 901 CEP 13414-903, Piracicaba, São Paulo, Brazil.
Karina
K
Morais-Faria
Department of Oral Diagnosis (Pathology and Semiology), Piracicaba Dental School, University of Campinas, Av. Limeira, 901 CEP 13414-903, Piracicaba, São Paulo, Brazil.
Felipe Paiva
FP
Fonseca
Departments of Radiation Oncology and Oral Medicine, Sírio-Libanês Hospital, São Paulo, Brazil.
Pedro Augusto Mendes
PA
Ramos
Departments of Radiation Oncology and Oral Medicine, Sírio-Libanês Hospital, São Paulo, Brazil.|Radiation Medicine Program, Princess Margaret Hospital, University of Toronto, Toronto, ON, Canada.
Fábio Yone
FY
de Moraes
Dental Oncology Service, Instituto do Câncer do Estado de São Paulo (ICESP), Faculdade de Medicinada Universidade de São Paulo, São Paulo, Brazil.
Karina Gondim Moutinho
KG
da Conceição Vasconcelos
Dental Oncology Service, Instituto do Câncer do Estado de São Paulo (ICESP), Faculdade de Medicinada Universidade de São Paulo, São Paulo, Brazil.
Gisela
G
Menegussi
Department of Oral Diagnosis (Pathology and Semiology), Piracicaba Dental School, University of Campinas, Av. Limeira, 901 CEP 13414-903, Piracicaba, São Paulo, Brazil. alanroger@fop.unicamp.br.
Alan Roger
AR
Santos-Silva
Dental Oncology Service, Instituto do Câncer do Estado de São Paulo (ICESP), Faculdade de Medicinada Universidade de São Paulo, São Paulo, Brazil.
Thais B
TB
Brandão
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006258:Head and Neck Neoplasms / Q000150:complications / Q000532:radiotherapy*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008875:Middle Aged; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D014070:Tooth / Q000528:radiation effects*; D055815:Young Adult
3D radiotherapy; Dental structures; Head and neck cancer; Intensity-modulated radiotherapy; Teeth