Outcome of ablation of thyroid remnants with 100 mCi (3.7 GBq) iodine-131 in patients with thyroid cancer.

A retrospective study was conducted on 186 patients with differentiated thyroid cancer without metastases who received an ablative dose of 100 mCi (3.7 GBq) iodine-131 after total thyroidectomy. Six months to one year after ablation, 155/186 patients (83%) had a negative scan. Diagnostic scanning with 5 mCi (185 MBq) performed 72 h or 3 months before ablation did not interfere with treatment success compared to patients not submitted to pre-therapy scanning. Pre-ablation cervical uptake values < 2% were associated with a higher ablation efficacy (94%), from 2 to 5% showed 80% success and values > 5%, 60% (p < 0.05). There were no significant differences between the responsive and no responsive groups in terms of age, sex, histological type or size of the primary tumor. 11% of the patients with low stimulated Tg (< 2 ng/ml) presented discrete thyroid bed uptake on follow-up diagnostic scan (< 0.5%) without definitive residual disease and 89% had negative uptake on scan. The patients with Tg > 2 ng/ml presented thyroid bed (10/12) or ectopic (2/12) uptake on follow-up diagnostic scan. An ablative dose of 100 mCi shows a high rate of efficacy, especially when cervical uptake is < 2%; no difference was noted between patients assessed by scan within 72 h or 3 months before treatment and those not scanned; follow-up diagnostic scan can be avoided in low risk patients with stimulated Tg < 2 ng/ml.

5mCi pretreatment scanning does not cause stunning when the ablative dose is administered within 72 hours

OBJETIVO: Determinar a interferência de uma dose traçadora de 5mCi de 131I. PACIENTES E MÉTODO: Nós analisamos retrospectivamente 145 pacientes que receberam o primeiro tratamento ablativo em nosso serviço. Eles foram divididos de acordo com o estadio da doença determinado pelo rastreamento pós-terapêutico (101 pacientes com remanescentes tireoidianos e 44 com metástases pulmonares) e scanning de corpo inteiro antes da ablação (realizada em 69 indivíduos). Todos os pacientes com remanescentes tireoidianos foram tratados com uma dose ablativa de 100mCi e aqueles com metástases receberam 200mCi. RESULTADOS: Nos pacientes com remanescentes apenas (n= 41) ou metastases (n= 28) submetidos ao scanning diagnóstico, a captação encontrava-se aparentemente aumentada na maioria dos patientscasos (71 e 73%, respectivamente) 7 dias após a terapia, enquanto captação reduzida (visual) não foi observada em nenhum paciente. A eficácia da ablação foi similar nos grupos submetidos ou não ao rastreamento diagnóstico: 71 e 80% em pacientes sem metástases (p= 0,28), respectivamente, e 43 e 50% naqueles com envolvimento pulmonar (p= 0,64). CONCLUSAO: Esses resultados indicam que o rastreamento diagnóstico usando uma dose de 5mCi de 131I não interefere com a captação da dose ablativa ou com a eficácia do tratamento quando a ablação é realizada dentro de 72h.

Ablative treatment of thyroid cancer with high doses of 131I without pre-therapy scanning.

OBJECTIVE: To determine the success of ablative treatment using fixed high doses of 131I in patients with thyroid cancer. METHODS: A retrospective study was conducted on 274 patients who received ablative treatment without previous scanning, with the dose being based on surgical staging: stage I patients (tumour restricted to the thyroid) received 3.7 GBq, and stage II (lymph node metastases) and stage III patients (extra-thyroid invasion) were treated with 5.5 GBq. Successful treatment was defined as a negative control scan. RESULTS: One hundred and sixty patients were classified as stage I and 114 as stages II or III. Forty-six patients presented ectopic uptake on post-therapy scans (10% in stage I and 26% in stage II or III). Among stage I patients, the efficacy of treatment was 78.7%. A 47% failure rate was associated with metastases, and among patients without metastases who did not respond to treatment, thyroid bed uptake >5% on post-therapy scans was observed in 61%. Patients with stage II or III showed 62.2% efficacy. Twenty-three of the 43 (53%) unsuccessfully treated patients in this group had metastases and of the 20 patients without metastases, 14 (70%) presented thyroid bed uptake >5%. There were no differences between the responsive and non-responsive groups in terms of age, gender, histological type or size of the primary tumour. CONCLUSION: Empirical treatment presented 72% efficacy (higher in stage I) and failure was associated with the presence of metastases and large thyroid remnants; factors that can be evaluated by pre-therapy whole-body scanning.

5 mCi pretreatment scanning does not cause stunning when the ablative dose is administered within 72 hours.

OBJECTIVE: To determine the stunning effect of a tracer dose of 5 mCi iodine-131. PATIENTS AND METHODS: We retrospectively analyzed 145 patients who received the first ablative treatment at our service. Patients were divided according to disease status determined upon post-treatment scanning (101 patients with thyroid remnants and 44 with pulmonary metastases) and whole-body scanning before ablation (performed on 69 individuals). All patients with thyroid remnants were treated with an ablative dose of 100 mCi and those with metastases received 200 mCi. RESULTS: In patients with remnants only (n= 41) or metastases (n= 28) submitted to diagnostic scanning, uptake was found to be apparently increased in most patients cases (71 and 73%, respectively) 7 days after therapy, while reduced uptake (visual) was not observed in any patient. The efficacy of ablation was similar in the groups submitted or not to diagnostic scanning: 71 and 80% in patients without metastases (p= 0.28), respectively, and 43 and 50% in those with pulmonary involvement (p= 0.64). CONCLUSION: The present results indicate that diagnostic scanning using a 5 mCi iodine-131 dose does not interfere with uptake of the ablative dose or with treatment efficacy when ablation is performed within 72 h.

Efficacy of low and high 131I doses for thyroid remnant ablation in patients with differentiated thyroid carcinoma based on post-operative cervical uptake.

OBJECTIVE: The aim of this study was to determine the efficacy of low (1110 MBq (30 mCi)) and high (3700 MBq (100 mCi)) 131I doses on the ablation of post-surgical remnants in patients with thyroid cancer based on the measurement of post-operative cervical uptake. METHODS: The study was conducted on 155 patients without metastases after thyroidectomy who received a 1110 or 3700 MBq ablative dose and who were assessed by pre-therapy cervical uptake. The patients were divided into six groups according to the uptake result and the dose received. Successful therapy was defined as a negative scan 6 months to 1 year after ablation. RESULTS: Ablative therapy was successful in 90% of patients with uptake <2% who received the 1110 MBq dose (n=30) and in 92.5% of patients who received the 3700 MBq dose (n=40), P=0.95. In the group with uptakes ranging from 2% to 5%, successful therapy was observed in 65% of patients receiving 1110 MBq (n=20) and in 86.6% of patients receiving 3700 MBq (n=30), P=0.14. In patients with uptake >5%, a 46.6% success rate was obtained for the 1110 MBq dose (n=15), while efficacy was 70% in patients receiving 3700 MBq (n=20), P=0.16. CONCLUSION: This study demonstrated the efficacy of low doses in patients with lower remnants after surgery (uptake <2%), the inverse correlation between uptake and ablation efficacy with low and high doses, and the usefulness of the measurement of cervical uptake for the definition of the ablative 131I dose.