Dependency of the remnant 131I-NaI biokinetics on the administered activity in patients with differentiated thyroid cancer.

PURPOSE: To study the dependency of the effective half-life on the administered activity and the correlation between the time-integrated activity and the remnant uptake at 2d and 7d in patients treated for DTC with 1.11 GBq, 3.7 GBq or 5.55 GBq of 131I-NaI. METHODS: Ninety-two patients undergoing total thyroidectomy and lymph node removal were included. If cancer had not spread to lymph nodes, patients received 1.11 GBq of 131I-NaI when the lesion maximal diameter was smaller than 4 cm, and 3.7 GBq for bigger sizes. If cancer had spread to lymph nodes patients received 5.55 GBq. There were 30, 49 and 13 patients respectively treated with 1.11 GBq(Group 1), 3.7 GBq(Group 2) and 5.55 GBq(Group 3). Two SPECT/CT scans were performed at 2d and 7d after radioiodine administration for each patient to determine the thyroid remnant activities and effective half-lives of the radioiodine. RESULTS: Statistical analysis showed significant differences (p < 0.05) in the effective half-life among patients treated with 1.11 GBq, 3.7 GBq and 5.55 GBq. A high positive correlation (ρ > 0.95) was found between the time-integrated activity and the remnant activity at 2d for the three groups of patients. CONCLUSIONS: There were significant differences in the effective half-life of the radioiodine in remnants of patients treated with activities of 1.11 GBq, 3.7 GBq or 5.55 GBq. The high positive linear correlation found between the time-integrated activity and the remnant activity at 2d for the three groups of patients indicate that the time-integrated activity could be estimated from one time-point.

Analysis of activity uptake, effective half-life and time-integrated activity for low- and high-risk papillary thyroid cancer patients treated with 1.11 GBq and 3.7 GBq of 131I-NaI respectively.

PURPOSE: To analyse the activity uptakes, effective half-lives and time-integrated activities, of relevance for remnant dosimetry, for patients treated for papillary thyroid cancer (PTC) with a different amount of activity of 131I-NaI. METHODS: Fifty patients were included. Of those, 18 patients had low-risk PTC and were treated with 1.11 GBq of 131I-NaI (Group 1), and 32 patients had high-risk PTC and were treated with 3.7 GBq (Group 2). Radioiodine was administered after total thyroidectomy and rhTSH stimulation. Two SPECT/CT scans were performed for each patient to determine the remnant activities and effective half-lives. RESULTS: Significantly higher values (p < 0.05) were obtained for Group 1 for the remnant activity at 7 d (medians 1.4 MBq vs 0.27 MBq), the remnant activity per administered activity at 2 d (0.35% vs 0.09%) and at 7 d (0.13% vs 0.007%), and the effective half-life (93 h vs 40 h). Likewise, the time-integrated activity coefficient was significantly higher for Group 1. The time-integrated activity did not differ significantly between the two groups (p > 0.05). CONCLUSIONS: We found a significant difference in the remnant activity per administered activity, the rate of washout from thyroid remnants, and the time-integrated activity coefficient between low-risk PTC patients treated with 1.11 GBq and high-risk PTC patients treated with 3.7 GBq. On the contrary, there was no such difference in the time-integrated activity. If remnant masses were also not statistically different (reasonable assumption for this monocentric study) no difference in time-integrated activity would imply no difference in remnant absorbed dose, of relevance for treatment efficacy and the risks of stochastic effects.

Ultrasound-guided core-needle biopsy in thyroid nodules. A study of 676 consecutive cases with surgical correlation.

OBJECTIVES: To analyze the diagnostic accuracy of ultrasound-guided core-needle biopsy (CNB) of thyroid nodules. METHODS: Of 3517 CNBs performed using an 18G spring-loaded device in one institution, we retrospectively reviewed 676 nodules in 629 consecutive patients who underwent surgery. CNB and pathological examination were compared. CNB diagnosis was standardized in four categories: insufficient (I), benign (B), follicular lesion (FOL), and malignant (M). Main outcome measures were predictive positive values (PPV), false positives (FP), and false negatives (FN). RESULTS: CNB showed a low rate of insufficient and FOL diagnoses (5.8 % and 4.5 %). On surgery, there were eight FNs in 374 benign CNBs and three FPs in 148 malignant CNBs. The 154 nodules classified as FOL in CNB included, at surgery, 122 neoplasms; 28 of them malignant. PPV for malignancy of a malignant CNB was 98 %, and for a CNB diagnosis of FOL 18.2 %. Sensitivity for malignancy if CNB of FOL and M are considered positive was 95.6. Only one major complication was observed. CONCLUSIONS: CNB is reliable, safe, and accurate to evaluate thyroid nodules and can be an alternative technique to FNA. It has low rate of non-diagnostic and undetermined cases, with high sensitivity and PPV. KEY POINTS: Thyroid core-needle biopsy (CNB) has high sensitivity and PPV. Pitfalls of CNB are rare. Pitfalls are due to cystic cancer, histological heterogeneity, and mistakes in analysis. CNB is a reliable, safe, and accurate method to approach thyroid nodules. CNB can be used primarily or after insufficient or indeterminate FNA.