Source: jjco.oxfordjournals.org
Authors: Etsushi Tomitaka et al.

Objective:
To evaluate longitudinal changes in parotid volumes and saliva production over 2 years after 30 Gy irradiation.

Methods:
We retrospectively evaluated 15 assessable patients treated for advanced oral cancer. Eligibility criteria were a pathologic diagnosis of squamous cell carcinoma, preoperative radiation therapy with a total dose of 30 Gy delivered in 15 fractions, and the availability of longitudinal data of morphological assessments by computed tomography and functional assessments with the Saxon test spanning 2 years after radiation therapy. In the Saxon test, saliva production was measured by weighing a folded sterile gauze pad before and after chewing; the low-normal value is 2 g/2 min. Repeated-measures analysis of variance with Bonferroni adjustment for multiple comparisons was used to determine the longitudinal changes.

Results:
The normalized ipsilateral parotid volumes 2 weeks and 6-, 12- and 24 months after radiation therapy were found to be 72.5, 63.7, 66.9 and 78.1%, respectively; the normalized contralateral volumes were 69.8, 64.6, 72.2 and 82.0%, respectively. The bilateral parotid volumes were significantly decreased after radiation therapy (P < 0.01). The nadir appeared at 6 months post-radiation therapy and the volumes substantially recuperated 24 months after radiation therapy (P < 0.01). Mean saliva production before radiation therapy was 3.7 g; the longitudinal changes after radiation therapy were 31.3, 38.0, 43.3 and 69.6%, respectively. Substantial recuperation of saliva production was observed 24 months after radiation therapy (P = 0.01). Conclusions: Although parotid volumes and saliva production were decreased after 30 Gy irradiation, we observed the recuperation of morphological and functional changes in the parotid glands 2 years after radiation therapy. Authors: 1. Etsushi Tomitaka1, 2. Ryuji Murakami2,*, 3. Keiko Teshima3, 4. Tomoko Nomura3, 5. Yuji Nakaguchi2, 6. Hideki Nakayama3, 7. Mika Kitajima4, 8. Toshinori Hirai4, 9. Yushi Araki1, 10. Masanori Shinohara3 and 11. Yasuyuki Yamashita4 Authors' affiliations: 1Department of Radiology, National Hospital Organization Kumamoto Medical Center 2Department of Medical Imaging, Faculty of Life Sciences, Kumamoto University 3Department of Oral and Maxillofacial Surgery, Faculty of Life Sciences, Kumamoto University 4Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan