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Intensity-modulated radiotherapy of nasopharyngeal carcinoma: a comparative treatment planning study of photons and protons.

Taheri-Kadkhoda Z, Björk-Eriksson T, Nill S, Wilkens JJ, Oelfke U, Johansson KA, Huber PE, Münter MW - Radiat Oncol (2008)

Bottom Line: Both treatment techniques were equal in terms of averaged mean dose to target volumes.IMPT plans significantly improved the tumor coverage and conformation (P < 0.05) and they reduced the averaged mean dose to several organs at risk (OARs) by a factor of 2-3.The practicality of IMPT in NPC deserves further exploration when this technique becomes available on wider clinical scale.

View Article: PubMed Central - HTML - PubMed

Affiliation: Göteborg University and Department of Oncology, Sahlgrenska University Hospital, Göteborg, Sweden. zahra.taheri-kadkhoda@vgregion.se

ABSTRACT

Background: The aim of this treatment planning study was to investigate the potential advantages of intensity-modulated (IM) proton therapy (IMPT) compared with IM photon therapy (IMRT) in nasopharyngeal carcinoma (NPC).

Methods: Eight NPC patients were chosen. The dose prescriptions in cobalt Gray equivalent (GyE) for gross tumor volumes of the primary tumor (GTV-T), planning target volumes of GTV-T and metastatic (PTV-TN) and elective (PTV-N) lymph node stations were 72.6 GyE, 66 GyE, and 52.8 GyE, respectively. For each patient, nine coplanar fields IMRT with step-and-shoot technique and 3D spot-scanned three coplanar fields IMPT plans were prepared. Both modalities were planned in 33 fractions to be delivered with a simultaneous integrated boost technique. All plans were prepared and optimized by using the research version of the inverse treatment planning system KonRad (DKFZ, Heidelberg).

Results: Both treatment techniques were equal in terms of averaged mean dose to target volumes. IMPT plans significantly improved the tumor coverage and conformation (P < 0.05) and they reduced the averaged mean dose to several organs at risk (OARs) by a factor of 2-3. The low-to-medium dose volumes (0.33-13.2 GyE) were more than doubled by IMRT plans.

Conclusion: In radiotherapy of NPC patients, three-field IMPT has greater potential than nine-field IMRT with respect to tumor coverage and reduction of the integral dose to OARs and non-specific normal tissues. The practicality of IMPT in NPC deserves further exploration when this technique becomes available on wider clinical scale.

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Comparison of dose distributions between IMPT (right) and IMRT (left) plans in T2N3M0 NPC in axial (above) and coronal (below) views. Dotted lines denote 95% of the prescribed dose to PTV-TN.
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Figure 3: Comparison of dose distributions between IMPT (right) and IMRT (left) plans in T2N3M0 NPC in axial (above) and coronal (below) views. Dotted lines denote 95% of the prescribed dose to PTV-TN.

Mentions: The individual and mean values for CI were always better in the IMPT plans for all targets except in one case (T3N2M0) for PTV-TN, where they were almost equal for both plans (1.07). In both techniques, the best CI values were obtained for PTV-TN volumes (average value,1.02 vs. 1.12). The corresponding values were much higher for GTV-T (average value; 2.36 vs. 4.68) reflecting the difficulty both treatment techniques had in avoiding small islands of 95% isodose in the rest of the treatment/target volumes. The evaluation of dose inhomogeneity measured by IC showed significant superiority of IMPT for GTV-T (mean value: 0.11 vs. 0.17). There was no significant difference between the two techniques for other target volumes. However, the latter result could be misleading since inclusive volumes of PTV-TN and PTV-N were used for DVH calculations. Figure 2 and 3. present the dose distribution in different planes for two NPC cases.


Intensity-modulated radiotherapy of nasopharyngeal carcinoma: a comparative treatment planning study of photons and protons.

Taheri-Kadkhoda Z, Björk-Eriksson T, Nill S, Wilkens JJ, Oelfke U, Johansson KA, Huber PE, Münter MW - Radiat Oncol (2008)

Comparison of dose distributions between IMPT (right) and IMRT (left) plans in T2N3M0 NPC in axial (above) and coronal (below) views. Dotted lines denote 95% of the prescribed dose to PTV-TN.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2265732&req=5

Figure 3: Comparison of dose distributions between IMPT (right) and IMRT (left) plans in T2N3M0 NPC in axial (above) and coronal (below) views. Dotted lines denote 95% of the prescribed dose to PTV-TN.
Mentions: The individual and mean values for CI were always better in the IMPT plans for all targets except in one case (T3N2M0) for PTV-TN, where they were almost equal for both plans (1.07). In both techniques, the best CI values were obtained for PTV-TN volumes (average value,1.02 vs. 1.12). The corresponding values were much higher for GTV-T (average value; 2.36 vs. 4.68) reflecting the difficulty both treatment techniques had in avoiding small islands of 95% isodose in the rest of the treatment/target volumes. The evaluation of dose inhomogeneity measured by IC showed significant superiority of IMPT for GTV-T (mean value: 0.11 vs. 0.17). There was no significant difference between the two techniques for other target volumes. However, the latter result could be misleading since inclusive volumes of PTV-TN and PTV-N were used for DVH calculations. Figure 2 and 3. present the dose distribution in different planes for two NPC cases.

Bottom Line: Both treatment techniques were equal in terms of averaged mean dose to target volumes.IMPT plans significantly improved the tumor coverage and conformation (P < 0.05) and they reduced the averaged mean dose to several organs at risk (OARs) by a factor of 2-3.The practicality of IMPT in NPC deserves further exploration when this technique becomes available on wider clinical scale.

View Article: PubMed Central - HTML - PubMed

Affiliation: Göteborg University and Department of Oncology, Sahlgrenska University Hospital, Göteborg, Sweden. zahra.taheri-kadkhoda@vgregion.se

ABSTRACT

Background: The aim of this treatment planning study was to investigate the potential advantages of intensity-modulated (IM) proton therapy (IMPT) compared with IM photon therapy (IMRT) in nasopharyngeal carcinoma (NPC).

Methods: Eight NPC patients were chosen. The dose prescriptions in cobalt Gray equivalent (GyE) for gross tumor volumes of the primary tumor (GTV-T), planning target volumes of GTV-T and metastatic (PTV-TN) and elective (PTV-N) lymph node stations were 72.6 GyE, 66 GyE, and 52.8 GyE, respectively. For each patient, nine coplanar fields IMRT with step-and-shoot technique and 3D spot-scanned three coplanar fields IMPT plans were prepared. Both modalities were planned in 33 fractions to be delivered with a simultaneous integrated boost technique. All plans were prepared and optimized by using the research version of the inverse treatment planning system KonRad (DKFZ, Heidelberg).

Results: Both treatment techniques were equal in terms of averaged mean dose to target volumes. IMPT plans significantly improved the tumor coverage and conformation (P < 0.05) and they reduced the averaged mean dose to several organs at risk (OARs) by a factor of 2-3. The low-to-medium dose volumes (0.33-13.2 GyE) were more than doubled by IMRT plans.

Conclusion: In radiotherapy of NPC patients, three-field IMPT has greater potential than nine-field IMRT with respect to tumor coverage and reduction of the integral dose to OARs and non-specific normal tissues. The practicality of IMPT in NPC deserves further exploration when this technique becomes available on wider clinical scale.

Show MeSH
Related in: MedlinePlus