Produção Nacional
Revisado por pares
Dosimetric distribution to the teeth of patients with head and neck cancer who underwent radiotherapy
2015; Elsevier BV; Volume: 120; Issue: 3 Linguagem: Inglês
10.1016/j.oooo.2015.05.009
ISSN2212-4411
AutoresKarina Morais-Faria, Gisela Menegussi, Gustavo Nader Marta, Patrícia Maria Fernandes, Reinaldo Brito e Dias, Ana Carolina Prado Ribeiro, Márcio Ajudarte Lopes, Claudio Roberto Cernea, Thaís Bianca Brandão, Alan Roger Santos‐Silva,
Tópico(s)Advanced Radiotherapy Techniques
ResumoThe present study determined the mean dosages delivered to the incisors, premolars, and molars of a series of patients with head and neck cancer (HNC) treated with tridimensional conformal radiotherapy, aiming to contribute to the development of a radiotherapy planning protocol for reduced teeth radiation. Fifty HNC patients who had received radiotherapy were enrolled in a retrospective study approved by the local Institutional Ethics Committee (protocol 171.972). Patients' medical records were evaluated with regard to epidemiologic and clinicopathologic information, such as age, gender, tumor location, and clinical stage of the malignant disease. Patients were further divided into five groups according to the primary tumor location (oral cavity, lateral border of tongue, oropharynx, nasopharynx, and larynx). All selected patients underwent tridimensional conformal radiotherapy in 6-mV linear accelerators on Synergy Platform (Elekta AB, Stockholm, Sweden) with radiation doses ranging between 50 and 70 Gy. Dosimetric analyses were performed for all patients by retrieving treatment planning and using calculation algorithms that incorporate tridimensional beam modeling on CMS XiO (Elekta CMS Software, St. Louis, MO) version 4.60. A dental oncologist, assisted by a medical physicist, reviewed each patient's computerized treatment plans based on axial slices of computed tomography scans to calculate the cumulative dose for the crowns of each group of radiated teeth. The teeth of patients were divided into three groups: incisors, premolars, and molars. The groups were further classified into right and left sides for the maxilla and the mandible. The teeth were evaluated on both the ipsilateral and contralateral sides of the primary tumor location. After selecting different groups of teeth, the mean dose delivered to each group of teeth was determined by individually contouring tooth crowns on the treatment planning systems and cumulative dose–volume histograms were produced for each group of teeth in each patient; the mean and maximum point doses for each defined group were calculated. A descriptive analysis was performed for the clinicopathologic and dosimetric results, which were analyzed by using descriptive statistics by the means of absolute values and percentages. The clinicopathologic profile of the patients is presented in Table I. All patients were affected by squamous cell carcinoma of the head and neck. The percentages of the maximum doses in relation to the total dose delivered to tumors were estimated for groups of teeth; the results are presented in Table II.Table IPatient's clinicopathologic featuresPatientsNumber of patientsMale6Female44Age (years)Mean55.7Range25-77Location of primary tumor Oral cavity∗Corresponds to tumors of the buccal mucosa (1); hard palate (5); floor of the mouth (3), and gingiva (1).10 Tongue10 Larynx10 Oropharynx10 Nasopharynx10T stage T12 T26 T315 T427N stage N010 N112 N222 N36M stage Mx16 M027 M17∗ Corresponds to tumors of the buccal mucosa (1); hard palate (5); floor of the mouth (3), and gingiva (1). Open table in a new tab Table IIEstimated percentages of maximum radiation doses delivered to groups of teeth in relation to the total dose delivered to tumorsTumor siteMaxillaMandibleIi (%Gy)Pmi (%Gy)Mi (%Gy)Ic (%Gy)PMc (%Gy)Mc (%Gy)Ii (%Gy)Pmi (%Gy)Mi (%Gy)Ic (%Gy)PMc (%Gy)Mc (%Gy)Oral cavity∗Corresponds to tumors of the buccal mucosa (1); hard palate (5); floor of the mouth (3), and gingiva (1).59.9874.4590.6348.7059.4883.1363.8773.2570.1049.4756.1894.24Tongue52.0849,4666.7319.8325.8957.4884.7899.0496.9091.3886.9777.54Larynx4.705.338.093.742.297.243.514.996.883.474.0410.38Oropharynx55.4174.0289.4354.9564.8575.8755.6768.9471.2349.0068.5682.84Nasopharynx47.4062.3491.1942.4054.5582.2054.4168.3295.6346.9159.8791.66Ii, Ipsilateral incisor; PMi, ipsilateral premolar; Mi, ipsilateral molar; Ic, contralateral incisor; PMc, contralateral premolar; Mc, contralateral molar.∗ Corresponds to tumors of the buccal mucosa (1); hard palate (5); floor of the mouth (3), and gingiva (1). Open table in a new tab Ii, Ipsilateral incisor; PMi, ipsilateral premolar; Mi, ipsilateral molar; Ic, contralateral incisor; PMc, contralateral premolar; Mc, contralateral molar. The average mean doses for the incisors, premolars, and molars from the right and left sides (ipsilateral and contralateral sides of the primary tumor location) for both the maxilla and the mandible are presented in Fig. 1, Fig. 2.Fig. 2Mean radiation doses (Gy) for groups of mandibular teeth.View Large Image Figure ViewerDownload (PPT) A total of 1,100 teeth from 50 patients were evaluated, with an average of 22 teeth per patient. In general, tumor location drove the levels of radiation doses received by each group of teeth, and ipsilateral teeth received higher dosages than their contralateral counterparts in both the maxilla and the mandible. Posterior teeth, including molars, followed by premolars were exposed to higher dosages of radiation compared with anterior teeth (incisors), regardless of tumor location. All tumor sites led to higher radiation doses to the mandibular teeth if compared with maxillary teeth. Tumors of the oral cavity and of the oropharynx, followed by those of the nasopharynx and tongue, were associated with higher dosages of radiation to mandibular and maxillary teeth, whereas reduced cumulative doses were observed in all maxillary and mandibular teeth in tumors of the larynx. Because of the anatomic complexity of the head and neck region, both primary tumor volume and normal structures of the maxillofacial region are included in the main fields of radiation during medical planning of head and neck radiation (HNR).1Hansen H.J. Maritim B. Bohle 3rd, G.C. et al.Dosimetric distribution to the tooth-bearing regions of the mandible following intensity-modulated radiation therapy for base of tongue cancer.Oral Surg Oral Med Oral Pathol Oral Radiol. 2012; 114: 50-54Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Thus, major salivary glands and teeth often receive high doses of radiation and collectively cause postradiation damage to the dentition mediated by hyposalivation and a possible direct radiogenic enamel and dentin destruction, with an apparent additive impact as total doses to teeth increase.2Walker M.P. Wichman B. Cheng A.L. et al.Impact of radiotherapy dose on dentition breakdown in head and neck cancer patients.Pract Radiat Oncol. 2011; 1: 142-148Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar The present study confirmed recent evidence2Walker M.P. Wichman B. Cheng A.L. et al.Impact of radiotherapy dose on dentition breakdown in head and neck cancer patients.Pract Radiat Oncol. 2011; 1: 142-148Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar that teeth are often exposed to cumulative radiation doses that can be as high as the final radiation dose delivered to the gross tumor volumes during HNR. One of possible limitations of this study is that patients were treated with tridimensional conformal technique only. Intensity-modulated radiation therapy (IMRT) is a sophisticated system of tridimensional conformal radiotherapy that uses nonuniform beams to raise the delivery of radiation to the target volume and also allows protection of normal tissue. Although there are clear benefits with the use of IMRT in the management of HNC patients in terms of less treatment toxicities, many centers in the world still routinely use tridimensional conformal radiotherapy.3Marta G.N. Silva V. de Andrade Carvalho H. et al.Intensity-modulated radiation therapy for head and neck cancer: systematic review and meta-analysis.Radiother Oncol. 2014; 110: 9-15Abstract Full Text Full Text PDF PubMed Scopus (191) Google Scholar This is because of IMRT unavailability and the fact that IMRT requires extra work from clinicians to delimit all the volumes of interest; supplementary physicists' time is also needed to execute more complicated quality assurance, resulting in a cost increase.4Miles E.A. Clark C.H. Guerrero Urbano M.T. et al.The impact of introducing intensity modulated radiotherapy into routine clinical practice.Radiother Oncol. 2005; 77: 241-246Abstract Full Text Full Text PDF PubMed Scopus (95) Google Scholar, 5Van de Werf E. Lievens Y. Verstraete J. et al.Time and motion study of radiotherapy delivery: economic burden of increased quality assurance and IMRT.Radiother Oncol. 2009; 93: 137-140Abstract Full Text Full Text PDF PubMed Scopus (51) Google Scholar Furthermore, it is important to highlight that the use of the tridimensional conformal technique is still widely accepted, because no overall survival benefits have been observed compared with the IMRT technique in patients with HNC.3Marta G.N. Silva V. de Andrade Carvalho H. et al.Intensity-modulated radiation therapy for head and neck cancer: systematic review and meta-analysis.Radiother Oncol. 2014; 110: 9-15Abstract Full Text Full Text PDF PubMed Scopus (191) Google Scholar The results from the present study may guide future experimental designs for in vitro and in situ irradiation protocols used for analysis of the direct effects of radiation to enamel, dentin, the dentin–enamel junction, and the dental pulp from different anatomic groups. Moreover, this seems to be the first study to present in detail the mean doses delivered to each group of teeth according to different tumor locations. Hence, the dosimetric distribution to the teeth of patients with HNC who have undergone radiotherapy provided by the present study may be taken into consideration by radiation oncologists during the planning processes for tridimensional conformal HNR, as it may contribute to the development of a planning protocol to reduce radiation to teeth.
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