Pitfalls in the response evaluation after peptide receptor radionuclide therapy with [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotate

Peptide receptor radionuclide therapy (PRRT) with [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotate (¹⁷⁷Lu-DOTATATE) is a treatment with good results in patients with metastatic gastroenteropancreatic neuroendocrine tumours (GEPNETs). However, there are some pitfalls that should be taken into consideration when evaluating the treatment response after PRRT. 354 Dutch patients with GEPNETs who were treated with ¹⁷⁷Lu-DOTATATE between March 2000 and December 2011 were retrospectively selected. Liver function parameters and chromogranin A were measured before each therapy and in follow-up. Anatomical imaging was performed before therapy and in follow-up. An increase in aminotransferases by ≥20% compared to baseline was observed in 83 of 351 patients (24%). In patients with an objective response (OR) and stable disease (SD) this increase was observed in 71/297 (24%) and in patients with progressive disease (PD) it was observed in 12/54 patients (22%). An increase in chromogranin A by ≥20% compared to baseline was observed in 76 patients (29%). This was present in 34% of patients who eventually had PD and 27% of patients who had OR/SD. In 70% of patients this tumour marker returned to baseline levels after therapy. An increase in liver enzymes and chromogranin A is not uncommon after PRRT. In the vast majority of patients this will resolve in follow-up. Clinicians should be aware that these changes may occur due to radiation-induced inflammation or disease progression and that repeated measurements over time are necessary to differentiate between the two.