Objective: To assess the overall survival (OS) and progression-free survival (PFS) of peptide receptor radionuclide therapy (PRRT) in neuroendocrine neoplasms (NENs).

Methods:

Out of 2294 NEN patients screened since 2004 by Ga-68 somatostatin receptor (SSTR) PET/CT, 1048 received at least one PRRT cycle. OS and PFS (RECIST and on Ga-68 SSTR PET/CT) were analyzed.

Results:

OS (median) of all patients was 51 months (mo.), range 47-54.9 mo. Patients younger than 40 years, and those treated with a combination of ⁹⁰Y and ¹⁷⁷Lu PRRT (64 months 51.7-64.3 95% CI), as well as those with grade 1 tumors (88 months 69.3-106.6 95% CI) and of small intestinal origin (69 months 53.7-84.2 95% CI) had a better survival. Patients with grade 3 carcinomas (23 months 10.8-35.2 95% CI) and those treated with exclusively ⁹⁰Y-based PRRT (24 months 17.4-30.6 95% CI) had a worse survival. PFS of all patients was 19 months and was significantly worse in patients treated with exclusively ⁹⁰Y-based PRRT (13 months 9.8-16.1 95% CI), grade 3 tumors (7 months 5-8.9 95% CI), lung carcinoids (11 months 6.3-15.6 95% CI) and tumors of unknown origin (13 months 9.5-16.4 95% CI). There was no difference in PFS of grade 1 and 2 tumors as well as those of small intestinal and pancreatic origin. PFS after initial progression and first and second reinstallation of PRRT after therapy-free intervals of 6 months, were 11 months and 8 months, respectively.

Conclusions:

Peptide receptor radionuclide therapy is effective and provides survival benefit depending on the radionuclide, grade and origin of NENs. The benefit in OS is not reflected accurately by the relatively shorter PFS on Ga-68 SSTR PET/CT. This is most probably due to the very high sensitivity of PET/CT in detecting progression - the prognostic significance needs to be addressed in future studies.