Targeted Alpha Therapy Using Astatine (At-211) Against Differentiated Thyroid Cancer

Inclusion Criteria:

1. Patients with differentiated thyroid cancer (papillary cancer, follicular cancer)after total thyroidectomy who meet the following conditions (1) resistance tostandard treatment or (2) difficulty in continuing standard treatment (1) Patientswho are refractory to standard treatment such as 131I-NaI treatment Insufficienttherapeutic effect after 3 or more 131I-NaI treatments. 131I-NaI treatmentresistance and difficulty in performing or continuing tyrosine kinase inhibitor (TKI) treatment (2) Patients who have difficulty continuing standard treatment suchas 131I-NaI treatment Ablation for residual thyroid or 131I-NaI treatment forrelapsed / metastatic lesions has been performed, but relapsed / metastatic lesionswere observed at the time of participation in this study, and 131I-NaI is thestandard treatment. If it is difficult to continue treatment or if local radiationtherapy (including addition) is not indicated (if it is not 131I-NaI treatmentresistant, TKI treatment is not indicated).

2. Patients aged 18 years or older at the time of consent acquisition

3. Patients with stable general condition with PS (Performance status) of 0 to 2 inECOG (Eastern Cooperative Oncology Group)

4. Patients who can be expected to survive for 6 months or more, judging from clinicalsymptoms and medical examination findings

5. Patients with no or controlled brain metastases with symptoms

6. Patients with no clinically significant abnormal findings in electrocardiogram,respiratory rate, and blood oxygen saturation within 30 days before registration

7. Patients whose laboratory values within 30days before the enrollment are within therange specified in the protocol

8. Patients who thoroughly listened to the explanation of the clinical trial, agreed tothe examination, visit during the observation period and follow-up survey,contraception during the clinical trial period, etc. according to the clinical trialprotocol, and signed the consent document.

Exclusion Criteria:

1. Patients who need fertility preservation

2. Pregnant or potentially pregnant women, lactating patients

3. Patients with active double cancer (simultaneous double cancer and ectopic doublecancer with a disease-free period of 5 years or less)

4. Patients who received other investigational or unapproved drugs within 5 weeks priorto enrollment

5. Patients who received chemotherapy, immunotherapy or radiation therapy within 8weeks prior to enrollment in this study

6. Patients with uncontrollable active infections

7. HBsAg positive, HCV antibody positive or HIV antibody positive patients

8. Patients with mental illness or psychiatric symptoms who are judged to be difficultto participate in clinical trials

9. Other patients who are judged to be inappropriate by the investigator, etc.