J Korean Med Sci.  2009 Apr;24(2):248-255. 10.3346/jkms.2009.24.2.248.

Multi-institutional Comparison of Intensity Modulated Radiation Therapy (IMRT) Planning Strategies and Planning Results for Nasopharyngeal Cancer

• Park SH
• Park HC
• Park SW
• Oh DH
• Choi Y
• Kim JK
• Ahn YC
• Park W
• Suh HS
• Lee R
• Bae H

• KMID: 1779126
• DOI: http://doi.org/10.3346/jkms.2009.24.2.248

Abstract

The intensity-modulated radiation therapy (IMRT) planning strategies for nasopharyngeal cancer among Korean radiation oncology facilities were investigated. Five institutions with IMRT planning capacity using the same planning system were invited to participate in this study. The institutions were requested to produce the best plan possible for 2 cases that would deliver 70 Gy to the planning target volume of gross tumor (PTV1), 59.4 Gy to the PTV2, and 51.5 Gy to the PTV3 in which elective irradiation was required. The advised fractionation number was 33. The planning parameters, resultant dose distributions, and biological indices were compared. We found 2-3-fold variations in the volume of treatment targets. Similar degree of variation was found in the delineation of normal tissue. The physician-related factors in IMRT planning had more influence on the plan quality. The inhomogeneity index of PTV dose ranged from 4 to 49% in Case 1, and from 5 to 46% in Case 2. Variation in tumor control probabilities for the primary lesion and involved LNs was less marked. Normal tissue complication probabilities for parotid glands and skin showed marked variation. Results from this study suggest that greater efforts in providing training and continuing education in terms of IMRT planning parameters usually set by physician are necessary for the successful implementation of IMRT.

Keyword

Radiotherapy; Intensity-Modulated; Radiotherapy Planning Computer-Assisted; Quality Assurance; Nasopharyngeal Neoplasms

MeSH Terms

Female
Humans
Male
Middle Aged
Nasopharyngeal Neoplasms/*radiotherapy
Parotid Gland/radiation effects
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted/*methods
Radiotherapy, Intensity-Modulated/*methods
Relative Biological Effectiveness
Skin/radiation effects
Tumor Burden
Young Adult

Figure

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  Fig. 1 Variation in the delineation of GTV (A), PTV1 (B), PTV2 (C) among institutions. Color key: red, institution 1; green, institution 2; blue, institution 3; yellow, institution 4; magenta, institution 5. GTV, gross tumor volume; PTV, planning target volume.

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  Fig. 2 Variation in the parotid gland delineation among institutions. Color key: red, institution 1; green, institution 2; blue, institution 3; yellow, institution 4; magenta, institution 5.

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  Fig. 3 Types of delineated pseudo-targets.

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  Fig. 4 Variation of isodose distribution among participating institutions (Case 2).

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  Fig. 5 Variation of the dose volume histogram for planning target volumes among participating institutions (Case 2). Color key: red, institution 1; green, institution 2; blue, institution 3; yellow, institution 4; magenta, institution 5.

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