Poster Presentation Asia Pacific Neuroendocrine Tumour Society 2018

Peptide receptor radionuclide therapy (PRRT), a promising therapy in adrenocorticotropic hormone (ACTH) producing metastatic neuroendocrine tumour (NET). (#109)

Lih Kin Khor 1 , Te-Jui (Terry) Hung 2 , Rod Hicks 2 , Grace Kong 2
  1. Advanced Medicine Imaging, Biopolis, Singapore
  2. Peter McCallum Cancer Centre, Center of Cancer Imaging, Melbourne, VIC, Australia

Background

Ectopic adrenocorticotropic hormone (ACTH) producing neuroendocrine tumours (NETs) are a rare entity, with a reported incidence of approximately 3%. Detection and excision of isolated primary tumours is the mainstay of treatment. In metastatic disease, patients who progress despite medical therapy or those with intractable Cushing’s syndrome would usually succumb to bilateral adrenalectomy. There is an increasing role of peptide receptor radionuclide therapy (PRRT) in NETs due to its favourable safety profile and treatment outcomes. There is limited literature describing the utility of PRRT in hormonal and tumour control in ACTH-producing NETs.  

 

Methods

Outcome of 3 consecutive patients with ectopic ACTH secreting metastatic NETs treated with PRRT at PMCC were retrospectively reviewed.

 

Results

Patients one (2 mitosis/10 hpf) and two (Ki-67 15%) had metastatic gastrinoma, patient three had metastatic rectal NET (Ki-67 >95%). Patient 1 required bilateral adrenalectomy, followed by PRRT due to persisting hormone secretion, which resulted in biochemical and complete imaging response sustained nine years following the last cycle. Patient 2 received PRRT with concurrent Metapyrone blockade; the 1st cycle was complicated by tumour lysis and transient biochemical deterioration with subsequent cycles better tolerated, and resulted in sustained biochemical and near-complete imaging response of 27 months duration, avoiding adrenalectomy. Patient 3 was referred with progressive high grade metastatic rectal NET, despite two lines of chemotherapy. He received 2 cycles of PRRT with adrenal blockade which conferred a short interval of biochemical and disease response, however the disease rapidly progressed with spatial discordance (FDG +ve / SSTR –ve), with the patient deceased 3 months after commencement of PRRT.     

 

Conclusion

This small series highlights the potential role of PRRT in biochemical and tumour control in ACTH-secreting NETs with ongoing response seen in two of three patients with high SSTR-expressing tumours.