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IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients

View Article: PubMed Central - PubMed

ABSTRACT

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).

Material and 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).

Conclusion: 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).

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Related in: MedlinePlus

Mean of the maximum and of the average dental doses delivered by 3DRT and IMRT according to the dental groups investigated. a In the group of patients treated with 3DRT, molars received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, whereas pre-molars received significantly more radiation (maximum and average doses) than anterior teeth. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 31.74 Gy (±23.68 Gy), pre-molars 43.67 Gy (±23.49 Gy) and molars 58.02 Gy (±20.99 Gy). Mean of the average doses: Anteriors 25.20 Gy (±23.03 Gy), pre-molars 36.82 Gy (±23.24 Gy) and molars 50.75 Gy (±21.30 Gy). b In the group of patients treated with IMRT, molars also received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, but there was no significant difference between the last two groups. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 38.19 Gy (±17.30 Gy), pre-molars 39.39 Gy (±17.41 Gy) and molars 49.34 Gy (±16.63 Gy). Mean of the average doses: Anteriors 28.14 Gy (±14.35 Gy), pre-molars 32.43 Gy (±15.18 Gy) and molars 38.74 Gy (±15.36 Gy). c When we compared dental groups according to the technique used, we observed that in patients treated with 3DRT molars received significantly more radiation (maximum and average doses) than those treated with IMRT. Legends: * Statistically significant difference according to t-test
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Fig3: Mean of the maximum and of the average dental doses delivered by 3DRT and IMRT according to the dental groups investigated. a In the group of patients treated with 3DRT, molars received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, whereas pre-molars received significantly more radiation (maximum and average doses) than anterior teeth. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 31.74 Gy (±23.68 Gy), pre-molars 43.67 Gy (±23.49 Gy) and molars 58.02 Gy (±20.99 Gy). Mean of the average doses: Anteriors 25.20 Gy (±23.03 Gy), pre-molars 36.82 Gy (±23.24 Gy) and molars 50.75 Gy (±21.30 Gy). b In the group of patients treated with IMRT, molars also received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, but there was no significant difference between the last two groups. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 38.19 Gy (±17.30 Gy), pre-molars 39.39 Gy (±17.41 Gy) and molars 49.34 Gy (±16.63 Gy). Mean of the average doses: Anteriors 28.14 Gy (±14.35 Gy), pre-molars 32.43 Gy (±15.18 Gy) and molars 38.74 Gy (±15.36 Gy). c When we compared dental groups according to the technique used, we observed that in patients treated with 3DRT molars received significantly more radiation (maximum and average doses) than those treated with IMRT. Legends: * Statistically significant difference according to t-test

Mentions: Radiation doses received by patients treated with 3DRT and IMRT according to dental groups and primary tumors are summarized in Table 2. 3DRT and IMRT both delivered higher radiations doses (maximum and average doses) to molars than to anterior teeth (variance analysis: p < 0.001 for 3DRT and IMRT) (Fig. 3a and b). When both techniques were compared, we found that molars of patients treated with IMRT received significantly less radiation than those of patients treated with 3DRT (p = 0.001 and p < 0.001, for maximum and average doses, respectively), whereas anterior teeth received more radiation with IMRT, but without statistical significance (p = 0.066 and p = 0.363, for maximum and average dose, respectively) (Fig. 3c).Table 2


IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients
Mean of the maximum and of the average dental doses delivered by 3DRT and IMRT according to the dental groups investigated. a In the group of patients treated with 3DRT, molars received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, whereas pre-molars received significantly more radiation (maximum and average doses) than anterior teeth. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 31.74 Gy (±23.68 Gy), pre-molars 43.67 Gy (±23.49 Gy) and molars 58.02 Gy (±20.99 Gy). Mean of the average doses: Anteriors 25.20 Gy (±23.03 Gy), pre-molars 36.82 Gy (±23.24 Gy) and molars 50.75 Gy (±21.30 Gy). b In the group of patients treated with IMRT, molars also received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, but there was no significant difference between the last two groups. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 38.19 Gy (±17.30 Gy), pre-molars 39.39 Gy (±17.41 Gy) and molars 49.34 Gy (±16.63 Gy). Mean of the average doses: Anteriors 28.14 Gy (±14.35 Gy), pre-molars 32.43 Gy (±15.18 Gy) and molars 38.74 Gy (±15.36 Gy). c When we compared dental groups according to the technique used, we observed that in patients treated with 3DRT molars received significantly more radiation (maximum and average doses) than those treated with IMRT. Legends: * Statistically significant difference according to t-test
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Fig3: Mean of the maximum and of the average dental doses delivered by 3DRT and IMRT according to the dental groups investigated. a In the group of patients treated with 3DRT, molars received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, whereas pre-molars received significantly more radiation (maximum and average doses) than anterior teeth. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 31.74 Gy (±23.68 Gy), pre-molars 43.67 Gy (±23.49 Gy) and molars 58.02 Gy (±20.99 Gy). Mean of the average doses: Anteriors 25.20 Gy (±23.03 Gy), pre-molars 36.82 Gy (±23.24 Gy) and molars 50.75 Gy (±21.30 Gy). b In the group of patients treated with IMRT, molars also received significantly higher doses (maximum and average doses) than pre-molar and anterior teeth, but there was no significant difference between the last two groups. Legends: * Statistically significant difference according to One-way ANOVA variance test. Different letters represent statistically different groups according to Tukey’s Post Hoc test. Mean of the maximum doses: Anteriors 38.19 Gy (±17.30 Gy), pre-molars 39.39 Gy (±17.41 Gy) and molars 49.34 Gy (±16.63 Gy). Mean of the average doses: Anteriors 28.14 Gy (±14.35 Gy), pre-molars 32.43 Gy (±15.18 Gy) and molars 38.74 Gy (±15.36 Gy). c When we compared dental groups according to the technique used, we observed that in patients treated with 3DRT molars received significantly more radiation (maximum and average doses) than those treated with IMRT. Legends: * Statistically significant difference according to t-test
Mentions: Radiation doses received by patients treated with 3DRT and IMRT according to dental groups and primary tumors are summarized in Table 2. 3DRT and IMRT both delivered higher radiations doses (maximum and average doses) to molars than to anterior teeth (variance analysis: p < 0.001 for 3DRT and IMRT) (Fig. 3a and b). When both techniques were compared, we found that molars of patients treated with IMRT received significantly less radiation than those of patients treated with 3DRT (p = 0.001 and p < 0.001, for maximum and average doses, respectively), whereas anterior teeth received more radiation with IMRT, but without statistical significance (p = 0.066 and p = 0.363, for maximum and average dose, respectively) (Fig. 3c).Table 2

View Article: PubMed Central - PubMed

ABSTRACT

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&rsquo;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).

Material and 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&rsquo; treatment plans. Clinicopathological data were retrieved from patients&rsquo; medical files.

Results: The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p&thinsp;=&thinsp;0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p&thinsp;=&thinsp;0.012 and p&thinsp;=&thinsp;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&thinsp;&lt;&thinsp;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&thinsp;=&thinsp;0.011 and p&thinsp;=&thinsp;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&thinsp;&lt;&thinsp;0.001).

Conclusion: 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 (&gt;30Gy).

No MeSH data available.


Related in: MedlinePlus