Assessment of salivary gland function after head and neck radiotherapy using 3DCRT and VMAT: a comparative clinical study

Salivary gland hypofunction is a common consequence of radiotherapy in patients with head and neck malignancies. Reduced salivary secretion may result in hyposalivation and may contribute to oral dryness and other oral complications. This study compared objective measures of salivary gland function and oral mucosal moisture in patients treated with three-dimensional conformal radiotherapy (3DCRT) and volumetric modulated arc therapy (VMAT) three months after completion of radiotherapy.

This comparative cross-sectional study included 60 patients with confirmed oropharyngeal malignancies evaluated three months after completion of radiotherapy. Thirty patients had been treated with three-dimensional conformal radiotherapy (3DCRT), while 30 patients with oropharyngeal malignancies had been treated with volumetric modulated arc therapy (VMAT) combined with concurrent weekly cisplatin. Unstimulated whole saliva was collected using the spitting method into SimplOFy collection tubes. Oral mucosal moisture was assessed using a modified Schirmer test. Following a 30-minute interval, stimulated whole saliva was collected using SimplOFy tubes after electrical stimulation with a SaliPen device. Stimulated parotid salivary flow was subsequently assessed using modified Lashley cups with gustatory stimulation.

All four evaluated parameters showed statistically significant differences between the treatment groups. Median unstimulated salivary flow was 0.07 (IQR 0.05-0.08) mL/min in the 3DCRT group and 0.14 (IQR 0.10-0.20) mL/min in the VMAT group (p < 0.001). Median stimulated whole-saliva flow was 0.25 (IQR 0.20-0.30) mL/min and 0.50 (IQR 0.40-0.60) mL/min, respectively (p < 0.001). Median stimulated parotid salivary flow was 0.10 (IQR 0.09-0.12) mL/min in the 3DCRT group compared with 0.24 (IQR 0.20-0.29) mL/min in the VMAT group (p < 0.001). Median oral mucosal moisture was 7 (IQR 5-8) mm in the 3DCRT group and 13 (IQR 11-18) mm in the VMAT group (p < 0.001).

Three months after radiotherapy, patients treated with VMAT demonstrated significantly higher unstimulated and stimulated salivary flow rates, stimulated parotid salivary flow, and oral mucosal moisture than patients treated with 3DCRT. These findings suggest better objective salivary function in the VMAT cohort; however, the cross-sectional post-treatment design and potential differences in clinical and treatment-related characteristics between the groups preclude conclusions regarding causality or definitive preservation of salivary gland function.