Vishal Gupta, Presenter: Nothing to Disclose

Claus Chunli Yang PhD, Abstract Co-Author: Nothing to Disclose

Tianxiao Liu PhD, Abstract Co-Author: Nothing to Disclose

James A. Purdy PhD, Abstract Co-Author: Nothing to Disclose

Allen Chen MD, Abstract Co-Author: Nothing to Disclose

Despite its relative proximity to target volumes among patients treated for head and neck cancer, the pituitary gland (PG) is currently not recognized as an avoidance structure in current Radiation Therapy Oncology Group protocols. The purpose of this study was to analyze the dose to the PG among patients undergoing intensity-modulated radiotherapy (IMRT) for cancers of the nasopharynx (NPX) and paranasal sinuses (PNS).

Five patients with NPX cancer and 5 patients with PNS cancer comprised the study population. Total prescribed dose to the planning target volume (PTV) was 70 Gy delivered in 2 or 2.12 Gy daily fractions using IMRT for all patients. For each patient, the PG was retrospectively contoured on images using non-contrast computed tomography obtained at the time of simulation. Using established anatomical guidelines, the PG was contoured as a circular structure extending from the sella turcica inferiorly to the optic chiasm superiorly. IMRT treatment plans were generated without dose-volume constraints to the PG. Dose volume histograms for each patient’s PG were analyzed to determine a range of dose-volume statistics to the PG.

For all 10 patients, the mean PG volume was 0.40 + 0.03 cm3 (range, 0.33-0.44 cm3). The average maximum dose to the PG was 48.5 + 24.4 Gy (range, 5.3-80.5 Gy) and the average mean dose was 40.5 + 23.4 Gy (range, 4.2-71.5 Gy). The mean volume of the PG receiving at least 20 Gy, 30 Gy and 50 Gy was 75.0 + 40.9% (range, 0-100%), 64.3 + 46.4 % (range, 0-100%), and 33.4 + 47.1% (range, 0-100%), respectively.

Our dosimetric analysis suggests that for patients undergoing IMRT for head and neck cancer, the PG routinely receives significantly high doses. Long-term follow-up with hormonal evaluation is needed to determine if this may be of clinical relevance. Consideration should be given to contouring the PG as a critical structure for patients with head and neck cancer treated with IMRT in the future.

Gupta, V, Yang, C, Liu, T, Purdy, J, Chen, A, Analysis of the Dose Delivered to the Pituitary Gland for Patients Undergoing Intensity Modulated Radiotherapy for Nasopharynx and Paranasal Sinus Cancer.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/7000701.html