Salivary gland function
Scintigraphy in prediction of the salivary gland function after gland-sparing intensity modulated radiation therapy for head and neck cancer

https://doi.org/10.1016/j.radonc.2008.02.017Get rights and content

Abstract

Background and purpose

To evaluate salivary gland scintigraphy in prediction of salivary flow following radiation therapy.

Patients and methods

Twenty patients diagnosed with head and neck cancer were treated with intensity modulated radiation therapy with an intention to spare the salivary gland function. The total quantitative saliva secretion was measured prior to and 6 and 12 months after therapy, and the function of the major salivary glands was monitored using Tc-99m-pertechnetate scintigraphy. Two models were designed for prediction of the post-treatment salivary flow: an average model, based on the average proportions of saliva produced by each of the four major glands in healthy subjects, and an individual model, based on saliva produced by each gland as measured by scintigraphy prior to therapy. These models were compared with volume-based (Lyman) normal tissue complication probability models using two published sets of model parameters.

Results

The D50 for the parotid and the submandibular gland function assessed at 6 and 12 months after radiotherapy was approximately 39 Gy. The scintigraphy-based individual model predicted well the measured post-treatment saliva flow rates. The correlation coefficient between the predicted stimulated and the measured saliva flow rate was 0.77 (p < 0.0001) at 6 months and 0.55 (p = 0.034) at 12 months after completion of radiotherapy. The relative changes in unstimulated and stimulated salivary flow rates showed similar dependency on the cumulative radiation dose.

Conclusions

Salivary gland function assessed by scintigraphy prior to radiotherapy is useful in prediction of the residual salivary flow after radiotherapy.

Section snippets

Patients

The study population consists of 20 subjects diagnosed with head and neck cancer and treated using IMRT with an intention to spare the salivary gland function. Only patients with a good performance status (the World Health Organization, WHO, status 0 or 1) and scheduled to receive bilateral radiotherapy to the neck were entered to the study. The total quantitative saliva secretion was measured prior to initiation of therapy and 6 and 12 months after radiotherapy, and salivary gland scintigraphy

Results

The relative ejection fraction (rEF) as a function of the mean absorbed salivary gland radiation dose was modelled for the parotid and the submandibular glands (Fig. 2). A D50 value of approximately 39 Gy for the gland function was obtained from the fitted dose–response curves for the parotid and the submandibular glands both at 6 and 12 months after completion of radiotherapy. No statistically significant change in the gland function occurred between 6 and 12 months after therapy in the present

Discussion

The aim of the present study was to find a method for prediction of the residual salivary flow following salivary gland-sparing IMRT for head and neck cancer. We first determined the function of the major salivary glands preoperatively using salivary gland scintigraphy and calculated the relative saliva ejection fractions (rEFs, Eq. (1) and Fig. 1). We next fitted decay curves for the salivary gland rEF by longitudinal salivary gland scintigraphy examinations (Fig. 2). This allowed us to

Conclusions

Salivary gland scintigraphy is helpful for prediction of the salivary gland function following radiation therapy administered with a gland-spearing technique for head and neck cancer. We describe two models for estimation of the residual salivary gland function. In the average model, average proportions of saliva produced by each gland are estimated based on prior data obtained from a normal population. In the individual model post-treatment gland function is modelled using data from

Cited by (0)

View full text