The correlation between salivary gland uptake in pre- and post-ablative 131I whole body scan and late salivary gland side effect after initial radioactive iodine therapy

Objectives To look for association between salivary gland uptake in pre-ablative and post-ablative 131I whole body scans (WBS) and late salivary gland side effects (SSEs) after initial radioactive iodine ablation therapy (RIAT).

Methods We retrospectively reviewed the WBS of thyroid cancer patients treated with initial RIAT from February 2009 to December 2009. We excluded patients with history of rheumatic disease and sialadenitis. The uptake of WBS was assessed regionally for each of 4 major salivary glands (both parotid and submandibular glands) by visual grading (0, indiscernible; 1, mild; and 2, intense). The SSEs were surveyed by questionnaire for dry mouth, altered taste, salivary gland pain and salivary gland swelling 1 month after RIAT. The uptake degree on WBS, ablation dose and SSEs were compared.

Results Total 65 patients (9 men 56 women; age 49±12 y) were included. The ablation dose was 100 mCi for 32 patients or 150 mCi for 33 patients. There were 80 salivary glands with grade 0 uptake, 75 with grade 1, 91 with grade 2 in the pre-ablative scan, and 123 glands with grade 0 uptake, 57 with grade 1, and 63 with grade 2 in the post-ablative scan. Dry mouth was reported in 31% (20/65), altered taste in 55% (36/65), gland pain in 22% (14/65) and gland swelling in 49% (32/65). Higher degree of each gland uptake on post-ablative scan was significantly associated with development of dry mouth, altered taste, gland pain and gland swelling. And in pre-ablative scan, gland swelling was significantly associated with gland uptake, but other SSEs were not significantly related. On patient based analysis, the sum of grades for all 4 salivary glands on post-ablation WBS did not show significant association with development of symptoms. Patients with higher ablation dose was more likely to develop altered taste, gland pain and gland swelling.

Conclusions The intensity of the salivary gland uptake in post-ablative 131I WBS can help predicting late side effect after initial RAI ablation