Background and aims
Functioning and symptomatic disease resistant to conventional therapies constitutes a subset amongst neuroendocrine tumors (NETs) that are commonly considered for peptide receptor radionuclide therapy (PRRT). The aim of this study was to evaluate the efficacy of 177Lu-DOTATATE PRRT in this group with objective assessment criteria.
Materials and methods
A total of 46 patients with refractory or progressive symptomatic GEP-NETs (previously treated at various stages with long-acting octreotide, chemotherapy, multikinase inhibitors, etc.) who had undergone treatment with PRRT were retrospectively analyzed. These patients were evaluated for response on three scales: clinical, biochemical parameters (tumor marker levels), and imaging (functional molecular and contrast enhanced anatomic). They were classified as complete remission (CR), partial remission (PR), stable disease (SD), and progressive disease (PD) on each scale. Furthermore, the patients were classified as (a) those who gained benefit from PRRT and (b) those who were nonresponders using predefined criteria.
Ninety-one percent of the patient population had liver metastases, with a mean serum chromograninA level of 3307 U/ml, consistent with high volume tumor burden and refractory symptoms. Clinical symptomatic response on an analogue scale showed 54% CR, 35% PR, and 6% SD, whereas 4% showed worsening of symptoms. Biochemically, 17% CR, 28% PR, and 28% SD were observed, whereas 12% showed PD. On evaluation by imaging (PERCIST and RECIST 1.1 criteria), we observed 4% CR, 39% PR, and 36% SD, whereas 19% showed PD. The clinical scale showed the highest overall benefit of 95.6% in the population studied.
The data support the evidence that PRRT could be potentially beneficial in resistant, refractory, and progressive symptomatic groups of GEP-NETs with functional disease burden. The use of a multidimensional response evaluation should be adopted (rather than only anatomical–functional imaging) and needs to be considered while managing this subset of patients.