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Conformal orbit sparing radiation therapy: a treatment option for advanced skin cancer of the parotid and ear region

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: New surgical methods have enabled resection of previously in‐operable tumours in the region of the parotid gland and ear. This has translated to deeper target volumes being treated with adjuvant radiotherapy. Due to the limitations of existing conformal techniques, alternative planning approaches are required to cover the target volume with appropriate sparing of adjacent critical structures. Although intensity modulated radiation therapy (IMRT) may be able to achieve these goals compared with the existing conformal method, a new orbital sparing radiation therapy (OSRaT) technique was evaluated as an alternative conformal planning process. The study objective was to evaluate the dosimetry of three planning methods: pre‐existing conformal, IMRT and OSRaT techniques.

Methods: Ten patients were planned retrospectively using the existing three‐dimensional conformal radiotherapy (3DCRT), IMRT and OSRaT techniques. Dosimetry was analysed using the homogeneity index (HI), conformity index (CI), the volume of planning target volumes (PTV) under and over treated by the 95% isodose and dose to critical structures.

Results: OSRaT achieved superior 95% coverage of the high‐dose PTV while delivering HI similar to IMRT for intermediate and high‐dose PTVs. The CI for the high‐dose PTV was comparable between the three techniques, however IMRT was statistically better for the low‐ and intermediate dose PTVs. All three techniques showed adequate orbital sparing, however OSRaT and IMRT achieved this with less under dosing of the PTVs.

Conclusion: For the treatment of patients with advanced skin cancer of the parotid and ear, both IMRT and the OSRaT techniques are viable options.

No MeSH data available.


Box and whisker plots depicting dosimetric indices of reported organs at risk doses for each technique. 3DCRT, three‐dimensional conformal radiation therapy; IMRT, intensity modulated radiation therapy; OSRaT, orbital sparing radiation therapy.
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jmrs161-fig-0005: Box and whisker plots depicting dosimetric indices of reported organs at risk doses for each technique. 3DCRT, three‐dimensional conformal radiation therapy; IMRT, intensity modulated radiation therapy; OSRaT, orbital sparing radiation therapy.

Mentions: All three techniques provided clinically adequate optical sparing, however differences were seen between the brain doses between the three techniques as displayed in Figure 5.


Conformal orbit sparing radiation therapy: a treatment option for advanced skin cancer of the parotid and ear region
Box and whisker plots depicting dosimetric indices of reported organs at risk doses for each technique. 3DCRT, three‐dimensional conformal radiation therapy; IMRT, intensity modulated radiation therapy; OSRaT, orbital sparing radiation therapy.
© Copyright Policy - creativeCommonsBy-nc-nd
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016620&req=5

jmrs161-fig-0005: Box and whisker plots depicting dosimetric indices of reported organs at risk doses for each technique. 3DCRT, three‐dimensional conformal radiation therapy; IMRT, intensity modulated radiation therapy; OSRaT, orbital sparing radiation therapy.
Mentions: All three techniques provided clinically adequate optical sparing, however differences were seen between the brain doses between the three techniques as displayed in Figure 5.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: New surgical methods have enabled resection of previously in‐operable tumours in the region of the parotid gland and ear. This has translated to deeper target volumes being treated with adjuvant radiotherapy. Due to the limitations of existing conformal techniques, alternative planning approaches are required to cover the target volume with appropriate sparing of adjacent critical structures. Although intensity modulated radiation therapy (IMRT) may be able to achieve these goals compared with the existing conformal method, a new orbital sparing radiation therapy (OSRaT) technique was evaluated as an alternative conformal planning process. The study objective was to evaluate the dosimetry of three planning methods: pre‐existing conformal, IMRT and OSRaT techniques.

Methods: Ten patients were planned retrospectively using the existing three‐dimensional conformal radiotherapy (3DCRT), IMRT and OSRaT techniques. Dosimetry was analysed using the homogeneity index (HI), conformity index (CI), the volume of planning target volumes (PTV) under and over treated by the 95% isodose and dose to critical structures.

Results: OSRaT achieved superior 95% coverage of the high‐dose PTV while delivering HI similar to IMRT for intermediate and high‐dose PTVs. The CI for the high‐dose PTV was comparable between the three techniques, however IMRT was statistically better for the low‐ and intermediate dose PTVs. All three techniques showed adequate orbital sparing, however OSRaT and IMRT achieved this with less under dosing of the PTVs.

Conclusion: For the treatment of patients with advanced skin cancer of the parotid and ear, both IMRT and the OSRaT techniques are viable options.

No MeSH data available.