Peptide Receptor Radionuclide Therapy (PRRT) with radiolabelled
somatostatin analogues is a promising treatment option for patients with inoperable or metastasised neuroendocrine tumours. Symptomatic improvement may occur with all of the various (111)In, (90)Y, or (177)Lu-labelled
somatostatin analogues that have been used. Since tumour size reduction was seldom achieved with (111)
Indium labelled
somatostatin analogues, radiolabelled
somatostatin analogues with beta-emitting
isotopes like (90)Y and (177)Lu were developed. Reported anti-tumour effects of [(90)
Y-DOTA(0),
Tyr(3)]octreotide vary considerably between various studies: Tumour regression of 50% or more was achieved in 9 to 33% (mean 22%). With [(177)Lu-
DOTA(0),
Tyr(3)]octreotate treatments, tumour regression of 50% or more was achieved in 28% of patients and tumour regression of 25 to 50% in 19% of patients, stable disease was demonstrated in 35% and progressive disease in 18%. Predictive factors for tumour remission were high tumour uptake on
somatostatin receptor scintigraphy and limited amount of liver
metastases. The side-effects of PRRT are few and mostly mild, certainly when using renal
protective agents: Serious side-effects like
myelodysplastic syndrome or
renal failure are rare. The median duration of the
therapy response for [(90)
Y-DOTA(0),
Tyr(3)]octreotide and [(177)Lu-
DOTA(0),
Tyr(3)]octreotate is 30 months and more than 36 months respectively. Lastly, quality of life improves significantly
after treatment with [(177)Lu-
DOTA(0),
Tyr(3)]octreotate. These data compare favourably with the limited number of alternative treatment approaches, like
chemotherapy. If more widespread use of PRRT is possible, such
therapy might become the
therapy of first choice in patients with metastasised or inoperable gastroenteropancreatic neuroendocrine tumours. Also the role in
somatostatin receptor expressing non-GEP tumours, like metastasised
paraganglioma/
pheochromocytoma and non-radioiodine-avid differentiated
thyroid carcinoma might become more important.