RT Journal Article
SR Electronic
T1 Effects of Repeated <sup>131</sup>I-<em>Meta-</em>Iodobenzylguanidine Radiotherapy on Tumor Size and Tumor Metabolic Activity in Patients with Metastatic Neuroendocrine Tumors
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 685
OP 694
DO 10.2967/jnumed.120.250803
VO 62
IS 5
A1 Keiichiro Yoshinaga
A1 Takashige Abe
A1 Shozo Okamoto
A1 Yuko Uchiyama
A1 Osamu Manabe
A1 Yoichi M. Ito
A1 Naomi Tamura
A1 Natsue Ito
A1 Naho Yoshioka
A1 Komei Washino
A1 Nobuo Shinohara
A1 Nagara Tamaki
A1 Tohru Shiga
YR 2021
UL http://jnm.snmjournals.org/content/62/5/685.abstract
AB 131I-meta-iodobenzylguanidine (131I-MIBG) radiotherapy has shown some survival benefits in metastatic neuroendocrine tumors (NETs). European Association of Nuclear Medicine clinical guidelines for 131I-MIBG radiotherapy suggest a repeated treatment protocol, although none currently exists. The existing single-high-dose 131I-MIBG radiotherapy (444 MBq/kg) has been shown to have some benefits for patients with metastatic NETs. However, this protocol increases adverse effects and requires alternative therapeutic approaches. Therefore, the aim of this study was to evaluate the effects of repeated 131I-MIBG therapy on tumor size and tumor metabolic response in patients with metastatic NETs. Methods: Eleven patients with metastatic NETs (aged 49.2 ± 16.3 y) prospectively received repeated 5,550-MBq doses of 131I-MIBG therapy at 6-mo intervals. In total, 31 treatments were performed. The mean number of treatments was 2.8 ± 0.4, and the cumulative 131I-MIBG dose was 15,640.9 ± 2,245.1 MBq (286.01 MBq/kg). Tumor response was observed by CT and 18F-FDG PET or by 18F-FDG PET/CT before and 3–6 mo after the final 131I-MIBG treatment. Results: On the basis of the CT findings with RECIST, 3 patients showed a partial response and 6 patients showed stable disease. The remaining 2 patients showed progressive disease. Although there were 2 progressive-disease patients, analysis of all patients showed no increase in summed length diameter (median, 228.7 mm [interquartile range (IQR), 37.0–336.0 mm] to 171.0 mm [IQR, 38.0–270.0 mm]; P = 0.563). In tumor region–based analysis with partial-response and stable-disease patients (n = 9), 131I-MIBG therapy significantly reduced tumor diameter (79 lesions; median, 16 mm [IQR, 12–22 mm] to 11 mm [IQR, 6–16 mm]; P &lt; 0.001). Among 5 patients with hypertension, there was a strong trend toward systolic blood pressure reduction (P = 0.058), and diastolic blood pressure was significantly reduced (P = 0.006). Conclusion: Eighty-two percent of metastatic NET patients effectively achieved inhibition of disease progression, with reduced tumor size and reduced metabolic activity, through repeated 131I-MIBG therapy. Therefore, this relatively short-term repeated 131I-MIBG treatment may have potential as one option in the therapeutic protocol for metastatic NETs. Larger prospective studies with control groups are warranted.