BACKGROUND
To decrease the severity and frequency of radiation sialoadenitis, postponement of the use of sialagogues has been proposed for the first 24 hours after (131)I treatment for well-differentiated thyroid cancer. One proposed mechanism is that sialagogues increased salivation and salivary blood flow resulting in greater radioiodine uptake in the salivary glands-a rebound effect. This case study demonstrates no rebound effect.
METHODS
A 33-year-old woman with well-differentiated thyroid cancer desired to know whether she would have a rebound effect if she used sialagogues during the 24-hour period after her (131)I treatment. Salivary images of the parotid glands were initiated 2 hours after the administration of (131)I for her whole body scan. Lemon juice was administered. Background corrected time-activity curves were obtained for both parotid glands. The potential reduction in radiation absorbed dose to the parotid glands secondary to the administration of lemon juice was calculated.
RESULTS
The time-activity curves demonstrated that the (131)I in the right and left parotid glands decreased rapidly after lemon juice by 87% and 83%, respectively, with return to pre-lemon juice levels by 30 and 13 minutes in the right and left parotid glands, respectively. However, at no time during the 1 hour of imaging did the uptake in either parotid gland significantly exceed the pre-lemon juice levels of activity. The potential reduction of radiation absorbed dose to the parotid glands secondary to the use of lemon juice ranged from as much as 30% to 67%.
CONCLUSION
This case study demonstrates 1) an approach to assess whether an individual patient will have increased or decreased radioiodine uptake in the salivary glands after administration of sialagogues without the administration of any additional radioiodine, 2) a decrease of radioiodine uptake in the salivary glands after lemon juice without a rebound effect, and 3) a potential reduction of radiation absorbed dose with administration of sialagogues.