Purpose/Objective(s):To evaluate volumetric changes and positional changes of parotid and submandibular glands in patients treated for head and neck cancers with IMRT within our institution (n=16).Materials/Methods: We carried out a retrospective review of patients treated for squamous cell carcinoma of the head and neck from January 2008 until August 2012. All patients must have been treated utilizing IMRT with KV IGRT (n=16). KV CT scans from daily IGRT were retrieved on all patients for fractions 1, 11, 21, and 31 (with minor deviations of fraction number used in a few patients). The parotid glands and submandibular glands were contoured by a single physician. In order to decrease intra-observer variations, contours were compared slice by slice on each gland to ensure that arterial structures within the gland were contoured in or out of the gland in a similar fashion. Volumetric changes were measured and center of mass (COM) of each gland was obtained. The positional changes of the glands were measured by inter-parotid and inter-submandibular gland distances. Gland contours were also done on CT component of follow up PET/CT scans done on 11 of the 16 patients 3 months after radiation completion to determine if the glands' volume change persisted.Results: A total of 16 head and neck cancer patients were used for this analysis. Primary sites included oropharynx (n=10), hypopharynx (n=1), and larynx (n=5). 14 of 16 patients received concurrent chemotherapy (carboplatin/paclitaxel = 3, cisplatin = 9, cetuximab = 2). The median percent change of gland volume from fraction 1 to fraction 31 was 27.9 % for the right parotid, 27.8 % for the left parotid, 23.4 % for the right submandibular, and 24.1 % for the left submandibular gland. All of the mentioned changes represent a decrease in gland volume. COM changes reveal a decrease in inter-parotid distance of 5.5 mm ± 2.3 mm and a decrease in inter-submandibular distance of 3.6 mm ± 2.0 mm. Preliminary calculations show an even greater change in distance from the glandular COM to each plan’s Isocenter. Gland volumes from the CT component of follow up PET/CT did not show large changes when compared to the gland volumes from fraction 31. A median change of 0.9%, 3.3% , -9.1%, and -4.9% for the right parotid, left parotid, right submandibular and left submandibular gland were observed, respectively. Negative percentages denote an increase in gland volume. Conclusions: Both parotid and submandibular glands decrease significantly in volume during the course of radiation therapy. Our results are consistent with previously published studies. This is likely due to migration of these glands into higher dosage regions during shrinkage of adjacent normal tissue and of gross tumor volume.
Botros, M,
Positional and Volumetric Changes of Salivary Glands in Head and Neck Cancer Patients Treated with IMRT Utilizing Daily KV IGRT. Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL.
http://archive.rsna.org/2014/14044069.html
