PRRT Shows Long-Term Effectiveness in Malignant Neuroendocrine Tumors
A 12-year retrospective clinical study of patients who received peptide receptor radionuclide therapy (PRRT) for malignant neuroendocrine tumors demonstrated the long-term effectiveness of this treatment, which also allows patients to maintain a high quality of life. The study was published by Gabriel et al in The Journal of Nuclear Medicine.
PRRT
While PRRT has been used for more than 20 years to treat patients with inoperable or metastatic somatostatin receptor–positive tumors, knowledge of long-term outcomes has been limited. A number of clinical studies have demonstrated PRRT’s efficacy, and the overall response rate (including complete response, partial response, minor response, and stable disease) is about 70% to 80% for the most commonly used radiopharmaceuticals: yttrium-90 (90Y)-DOTATOC (best suited for treating larger tumors) and lutetium Lu-177 dotatate (preferred for smaller tumors). For patients who respond to PRRT, the prognosis is generally favorable, with a median time to disease progression of 3 to 4 years.
Study Details and Results
This study included 44 patients (27 men and 17 women) with advanced tumors and enhanced somatostatin receptor expression. Mean age at initial diagnosis was 60 years (range = 40–84). Median follow-up was 80 months. For Lu-177 dotatate, the mean number of cycles administered was 5.3 ± 2.5; for 90-Y PRRT, the mean number of cycles administered was 5.5 ± 2.6.
Median overall survival was 79 months, but 32% of the patients (14 of the 44 patients; 6 men and 8 women) were still alive more than 12 years after starting PRRT. Twenty-one (77.8%) of the 27 men and 9 (52.9%) of the 17 women had died 12 years after commencement of PRRT. The shortest duration of illness was 8 months and the longest was 155 months. Progressive disease occurring early after therapy began resulted in a poor prognosis, while women and patients with no more than two tumor sites seemed to benefit the most from PRRT.
Grade 3 and 4 side effects were seen in 9 of the 14 patients still alive. Chronic kidney disease in combination with anemia was the most common finding in the 9 patients with severe side effects.
“This study clearly demonstrates the long-term efficacy of PRRT over more than a decade in patients with metastatic tumor disease of neuroendocrine origin,” explained study authors Michael Gabriel, MD, and Irene J. Virgolini, MD, of the Department of Nuclear Medicine at the Medical University of Innsbruck in Austria. “PRRT can be repeatedly used with limited side effects. From this perspective, a relatively stable tumor situation can be achieved over many years in a large number of patients. None of the patients who were still alive at the end of the observation period were dialysis-dependent, and most of the patients showed a still very high key performance indicator, which underlines the positive effect of PRRT in terms of the quality of life,” they added.
Drs. Gabriel and Virgolini also pointed out the value of molecular imaging in therapeutic decision-making and, looking ahead, recommended “new prospective studies combining the nuclear medicine therapy approach with other therapeutic modalities to further increase efficiency.”
Disclosure: For full disclosures of the study authors, visit jnm.snmjournals.org.
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