Optimal administration time of vitamin C after 131I therapy in differentiated thyroid cancer based on propensity score matching

Abstract

Objectives: This study aimed to investigate the protection of the salivary glands by vitamin C administration at 2 and 24 h after an initial treatment using iodine-131 (¹³¹I) in patients with differentiated thyroid cancer (DTC) and examined the optimal administration time of vitamin C to protect the salivary glands from radiation injury.

Method: The clinical data of patients with differentiated thyroid carcinoma who had been treated with ¹³¹I in the Department of Nuclear Medicine in Shanxi Bethune Hospital from January 2014 to December 2020 were retrospectively analyzed. The propensity score matching method was adopted to match patients who received the administration of vitamin C at 2 h with those receiving administration at 24 h. A total of 230 pairs/460 patients were enrolled in the study. The chi-squared (χ ²) or Fisher's exact test was used to compare the indicators representing the incidence of salivary gland injury between the two groups.

Results: The incidence of salivary gland injury (17.39%) with acidic substances at 2 h was lower compared with administration at 24 h (26.96%). The incidence of acute salivary gland injury (15.22%) and chronic salivary gland injury (26.09%) in the 24-h group were higher than those in the 2-h group (4.78% and 18.26%, respectively). The differences in the left submandibular gland concentrate index and right submandibular gland concentrate index were statistically significant before and after treatment in both the 2 and the 24-h groups; these functions had been impaired after treatment.

Conclusions: Following treatment with ¹³¹I, the protective effect of acidic substances administered at 2 and 24 h on the salivary glands were different. The incidence of salivary gland injury in the 2 h acid stimulation group was lower than in the 24 h acid stimulation group. The present study revealed that ¹³¹I treatment did cause some injury to the salivary glands and that the protective effect of administering vitamin C at 2 and 24 h may be limited. Accordingly, protection against salivary gland injury should be conducted using comprehensive measures.

Keywords: radioiodine therapy; salivary glands; sialadenitis; thyroid cancer; vitamin c.

Figure 1

Dynamic salivary gland scintigraphy. (A) is the frame with the highest radioactive count uptake by the salivary glands, and (B) is the frame with the lowest radioactive counts after the salivary gland secretion. In (A), a is the right parotid gland, b is the left parotid gland, c is the right submandibular gland, d is the left submandibular gland, and e is the background, draw the ROI to obtain the radioactivity count, which is (B) in the formula. The red arrow is the saliva secreted by the salivary glands. In (A), the red circle outlines the right parotid gland, and the ROI is drawn to obtain the radioactive count, which is the highest count concentrated by the right parotid gland, which is the C_max in the formula. In (B), the green circle outlines the right parotid gland, and the ROI is drawn to obtain the radioactive count, which is the lowest count after the secretion by right parotid gland, that is C_min in the formula. Draw b, c, d in turn, and calculate the concentrate index and secretion index of each gland according to the following formulas. Concentrate index (CI) = (C_max–B)/ B secretion index (SI) = (C_max–C_min)/C_max × 100%. C_max = gland highest radioactive count; C_min = the lowest gland radioactivity count after vitamin C stimulation; B = background radioactivity count.

Figure 2

Comparison of concentrate index and secretion index in the parotid and in the parotid and submandibular glands between 2-h group and 24-h group. There was no significant difference in the concentrate and secretion functions in the parotid and submandibular glands after treatment with ¹³¹I between the 2 and the 24-h group.

Figure 3

Comparison of concentrate index and secretion index in the parotid and in the parotid and submandibular glands before and after ¹³¹I treatment in 2-h group. The left submandibular gland concentration index and right submandibular gland concentration index after ¹³¹I treatment in the 2 h group (2.843 ± 0.916, 2.929 ± 0.898)were lower than those before ¹³¹I treatment (3.234 ± 1.093, 3.233 ± 1.129), and the changes before and after treatment were statistically different (P = 0.001, P = 0.002). There was no significant difference in concentration index of the left parotid gland before and after treatment (2.670 ± 1.048, 2.605 ± 1.028, P = 0.505), no significant difference in secretion index of the left parotid gland before and after treatment (0.451 ± 0.132, 0.454 ± 0.127, P = 0.772), no significant difference in concentration index of the right parotid gland before and after treatment (2.789 ± 1.107, 2.639 ± 0.965, P = 0.122), no significant difference in secretion index of the right parotid gland before and after treatment (0.437 ± 0.118, 0.450 ± 0.115, P = 0.236), no significant difference in secretion index of the left submandibular gland before and after treatment (0.327 ± 0.111, 0.310 ± 0.095, P = 0.080), no significant difference in secretion index of the right submandibular gland before and after treatment (0.311 ± 0.100, 0.309 ± 0.092, P = 0.867).

Figure 4

Comparison of concentrate index and secretion index in the parotid and in the parotid and submandibular glands before and after ¹³¹I treatment in 24-h group. The concentration index of the left submandibular gland and the concentration index of the right submandibular gland in the 24 h group after ¹³¹I treatment (3.000 ± 1.075, 3.082 ± 1.097) were lower than those before ¹³¹I treatment (3.205 ± 1.142, 3.318 ± 1.229), and the changes before and after treatment were statistically different (P = 0.048, P = 0.030). There was no significant difference in concentration index of the left parotid gland before and after treatment (2.552 ± 1.011, 2.493 ± 0.979, P = 0.526), no significant difference in secretion index of the left parotid gland before and after treatment (0.444 ± 0.123, 0.426 ± 0.250, P = 0.324), no significant difference in concentration index of the right parotid gland before and after treatment (2.613 ± 1.004, 2.586 ± 0.982, P = 0.087), no significant difference in secretion index of the right parotid gland before and after treatment (0.444 ± 0.113, 0.447 ± 0.120, P = 0.753), no significant difference in secretion index of the left submandibular gland before and after treatment (0.318 ± 0.108, 0.331 ± 0.096, P = 0.150), no significant difference in secretion index of the right submandibular gland before and after treatment (0.276 ± 0.592, 0.326 ± 0.088, P = 0.210).