Parotid Gland Dose in Intensity-Modulated Radiotherapy for Head and Neck Cancer: Is What You Plan What You Get?

Journal Article · Thu Nov 15 04:00:00 EST 2007 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2007.07.2345· OSTI ID:21039647

O'Daniel, Jennifer C ^[1]; Garden, Adam S; Schwartz, David L ^[2]; He, Wang ^[1]; Ang, Kian K; Ahamad, Anesa; Rosenthal, David I; Morrison, William H; Asper, Joshua A ^[2]; Lifei, Zhang; Shihming, Tung; Mohan, Radhe ^[1]

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1. Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)
2. Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)

Purpose: To quantify the differences between planned and delivered parotid gland and target doses, and to assess the benefits of daily bone alignment for head and neck cancer patients treated with intensity-modulated radiotherapy (IMRT). Methods and Materials: Eleven head and neck cancer patients received two CT scans per week with an in-room CT scanner over the course of their radiotherapy. The clinical IMRT plans, designed with 3-mm to 4-mm planning margins, were recalculated on the repeat CT images. The plans were aligned using the actual treatment isocenter marked with radiopaque markers (BB) and bone alignment to the cervical vertebrae to simulate image-guided setup. In-house deformable image registration software was used to map daily dose distributions to the original treatment plan and to calculate a cumulative delivered dose distribution for each patient. Results: Using conventional BB alignment led to increases in the parotid gland mean dose above the planned dose by 5 to 7 Gy in 45% of the patients (median, 3.0 Gy ipsilateral, p = 0.026; median, 1.0 Gy contralateral, p = 0.016). Use of bone alignment led to reductions relative to BB alignment in 91% of patients (median, 2 Gy; range, 0.3-8.3 Gy; 15 of 22 parotids improved). However, the parotid dose from bone alignment was still greater than planned (median, 1.0 Gy, p = 0.007). Neither approach affected tumor dose coverage. Conclusions: With conventional BB alignment, the parotid gland mean dose was significantly increased above the planned mean dose. Using daily bone alignment reduced the parotid dose compared with BB alignment in almost all patients. A 3- to 4-mm planning margin was adequate for tumor dose coverage.

• OSTI ID: 21039647
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 4 Vol. 69; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ALIGNMENT
COMPUTERIZED TOMOGRAPHY
GLANDS
HEAD
IMAGE PROCESSING
IMAGES
NECK
NEOPLASMS
PATIENTS
PLANNING
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOTHERAPY
VERTEBRAE