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. 2010 Jul 1;77(3):950-8.
doi: 10.1016/j.ijrobp.2009.09.062. Epub 2010 Apr 6.

Emphasizing conformal avoidance versus target definition for IMRT planning in head-and-neck cancer

Paul M Harari  1 , Shiyu Song, Wolfgang A Tomé
Affiliations

Emphasizing conformal avoidance versus target definition for IMRT planning in head-and-neck cancer

Paul M Harari et al. Int J Radiat Oncol Biol Phys. .

Abstract

Purpose: To describe a method for streamlining the process of elective nodal volume definition for head-and-neck (H&N) intensity-modulated radiotherapy (IMRT) planning.

Methods and materials: A total of 20 patients who had undergone curative-intent RT for H&N cancer underwent comprehensive treatment planning using three distinct, plan design techniques: conventional three-field design, target-defined IMRT (TD-IMRT), and conformal avoidance IMRT (CA-IMRT). For each patient, the conventional three-field design was created first, thereby providing the "outermost boundaries" for subsequent IMRT design. In brief, TD-IMRT involved physician contouring of the gross tumor volume, high- and low-risk clinical target volume, and normal tissue avoidance structures on consecutive 1.25-mm computed tomography images. CA-IMRT involved physician contouring of the gross tumor volume and normal tissue avoidance structures only. The overall physician time for each approach was monitored, and the resultant plans were rigorously compared.

Results: The average physician working time for the design of the respective H&N treatment contours was 0.3 hour for the conventional three-field design plan, 2.7 hours for TD-IMRT, and 0.9 hour for CA-IMRT. Dosimetric analysis confirmed that the largest volume of tissue treated to an intermediate (50 Gy) and high (70 Gy) dose occurred with the conventional three-field design followed by CA-IMRT and then TD-IMRT. However, for the two IMRT approaches, comparable results were found in terms of salivary gland and spinal cord protection.

Conclusion: CA-IMRT for H&N treatment offers an alternative to TD-IMRT. The overall time for physician contouring was substantially reduced (approximately threefold), yielding a more standardized elective nodal volume. Because of the complexity of H&N IMRT target design, CA-IMRT might ultimately prove a safer and more reliable method to export to general radiation oncology practitioners, particularly those with limited H&N caseload experience.

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Figures

Figure 1
Figure 1
Conventional field design for a patient with T2N2b squamous cell carcinoma of the left tonsil.
Figure 2
Figure 2
Contouring of the GTV and the conformal avoidance structures for a patient with squamous cell carcinoma of the left tonsil. OAR shown are the parotid glands (P), mandible, and spinal column.
Figure 3
Figure 3
The contouring of the elective nodal volume as indicated by 85% isodose volume is shown.
Figure 4
Figure 4
Definition of total CTV.
Figure 5
Figure 5
Additional examples of clinical target volumes contoured using the CAD methods on patients with tumor arising from supraglottic larynx (A), nasopharynx (B).
Figure 6
Figure 6
Comparison of clinical target volumes that have been drawn using the TD-IMRT and CAD-IMRT method.
Figure 7
Figure 7
Comparison of dose distributions of the conventional field arrangement (CFA) (A), target defined IMRT (TD-IMRT) (B) conformal avoidance defined IMRT (CAD-IMRT) (C).
Figure 8
Figure 8
DVH comparisons for TD-IMRT, CAD-IMRT), and the corresponding CFA.
Figure 8
Figure 8
DVH comparisons for TD-IMRT, CAD-IMRT), and the corresponding CFA.
See this image and copyright information in PMC

References

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