General characteristics of the study population
The study population is made up of 51 patients with a mean follow-up time of 12.6 years. Characteristics of study participants are shown in table 1.
|
Total
|
I131 treatment
|
Controls
|
p
|
Nº patients
|
51
|
40
|
11
|
|
Initial age a
Years (mean ± SD)
Range
|
30.8 ± 8.3
15.4 - 44.9
|
29.6 ± 8.2
15.4 - 44.9
|
35.2 ± 7.9
22.1 - 44.4
|
0.048
|
Final age b
Years (mean ± SD)
Range
|
43.5 ± 9.2
24.3 - 65.3
|
39.7 ± 6.8
24.3 - 65.3
|
42.7 ± 5.5
29.7 - 55.6
|
0.856
|
Follow up period
Years (mean ± SD)
Median
Range
|
12.6 ± 9.8
12.5
0.5 - 36.8
|
13.7 ± 9.7
14.3
0.6 - 36.8
|
8.7 ± 9.7
4.3
0.5 - 25.6
|
0.135
|
Microcarcinoma (< 1 cm) c
|
12/47 (25.5%)
|
4/36 (11.1%)
|
8/11 (72.7%)
|
0.000
|
Low Risk (ATA) d
|
34/51 (66.7%)
|
23/40 (57.5%)
|
11/11 (100.0%)
|
0.009
|
BRAF +
|
11/20 (55.0%)
|
10/18 (55.6%)
|
1/2 (50.0%)
|
-
|
KRAS +
|
1/3 (33.3%)
|
1/3 (33.3%)
|
0/0 (0.0%)
|
-
|
Table 1. Characteristics of study participants: age at diagnosis and age at the study, follow-up time and tumour characteristics. aAge at diagnosis and start treatment. bAge at the time of present study. cIn 4 cases we do not know the tumour size. dATA (American Thyroid Association) risk classification.
As we see, women who have received iodine treatment are significantly younger at the time of initial diagnosis and treatment. As expected, they have larger tumours and are at higher risk according to the ATA (American Thyroid Association) classification.
Inside the group of women who were only treated with surgery, all had histological diagnosis of papillary thyroid carcinoma and all of them were classified as low-risk patients. There were microcarcinomas in 72.7% of the cases. In the group of I131 exposed patients, 57.5% are considered of low risk, 37.5% intermediate risk and 5% high risk, one of the cases due to the presence of lung metastases and the other due to extensive local extension. There are 37 papillary carcinomas (92.5%) and 3 follicular carcinomas (7.5%). Regarding the size of the tumors, only 4 (11.1%) are microcarcinomas.
The study of genetic mutations reveals a positivity of 50-55% for the BRAF mutation in papillary carcinomas and 33.3% in follicular carcinomas.
When we study the dose used to treat DTC, almost 70% of women receive high doses of iodine (> 100 mCi). Only 15% of patients received less than 50 mCi.
Menopause age
Women undergoing hysterectomy are excluded from the analysis (four in the group exposed to radioactive iodine and one in the control group).
Eleven women (23.9%) showed menopause. The frequency of menopausal cases distributed according to age is shown in Table 2.
|
I131 treatment
|
Controls
|
p
|
Spontaneous Menopause N (%)
|
10/36 (27.8%)
|
1/10 (10%)
|
0.400
|
Menopause mean age
|
44.6 ± 1.857
|
49
|
-
|
Early menopause (< 45 years old) N (%)
|
4/10 (40%)
|
0/1
|
1.000
|
Table 2. Cases of women with menopause classified by age of onset before or after 45 years.
When comparing the frequency of spontaneous menopause between both groups, there are no significant differences between the women exposed to iodine and their controls. Similarly, given the scarcity of cases, we cannot speak of statistically significant differences in the appearance of early menopause in our series of patients. However, there seems to be a trend towards early menopause in women exposed to I131(Figure 1).
AMH alteration
When we compare mean AMH level in the radioiodine group and the control group, regardless of the age, there are no significant differences (Table 3).
|
I131 treatment
|
Controls
|
p
|
AMH (ng/ml)
|
1.18 ± 1.2
|
1.24 ± 1.0
|
0.692
|
AMH < P5
|
11/30 (36.7%)
|
2/10 (20%)
|
0.451
|
Table 3. Summary of results of the AMH levels study.
Once deeply studied the AMH level behaviour, we see there is always a negative correlation between age and AMH level (Figure 2).
The relationship is statistically significant for both groups, exposed women (p = 0.001) and the control group (p-value = 0.002). What varies is the strength of the association, in the control group, Spearman’s Rho statistic is -0.851 (strong association) and in the group of exposed women, Spearman's Rho is -0.582 (moderate association).
When comparing the individual AMH values with the proposed nomogram of La Marca et al.17 it is obtained that there are 13 patients whose value is below the 5th percentile. Eleven of those women with low ovarian reserve belong to the iodine exposure group. Only 2 patients with decreased AMH values have not been treated with radioactive iodine (Table 3).
The measure of the association between decreased AMH and I131 exposure gives an Odds Ratio of 2.3158. However, it does not turn out to be statistically significant (CI: 0.4514 - 12.9097).
Impairment of fertility
Among women in our study, 8 expressed to have failed to fulfil their reproductive desire. This represents 16% of the sample. One of the women who considered their fertility to be affected belongs to the control group, while the remaining 7 women were exposed to radioactive iodine.
The woman who belongs to the control group, prior to the diagnosis of thyroid carcinoma, had already consulted for sterility, therefore we cannot implicate the carcinoma in the impairment of fertility in this case. This means that there are 7/40 women whose fertility was affected after the diagnosis, and all of them were exposed to I131, or what is the same, 17.5% of the women who were treated with I131 consider to have not achieved their reproductive desire.
The difference in frequency of fertility impairment according to I131 exposure was not statistically significant. The same as the association measure (OR) calculation whose confidence interval is 0.239 - 19.987.