TY - JOUR
T1 - Free somatostatin receptor fraction predicts the antiproliferative effect of octreotide in a neuroendocrine tumor model
T2 - Implications for dose optimization
AU - Heidari, Pedram
AU - Wehrenberg-Klee, Eric
AU - Habibollahi, Peiman
AU - Yokell, Daniel
AU - Kulke, Matthew
AU - Mahmood, Umar
PY - 2013/12/1
Y1 - 2013/12/1
N2 - Somatostatin receptors (SSTR) are highly expressed in well-differentiated neuroendocrine tumors (NET). Octreotide, an SSTR agonist, has been used to suppress the production of vasoactive hormones and relieve symptoms of hormone hypersecretion with functional NETs. In a clinical trial, an empiric dose of octreotide treatment prolonged time to tumor progression in patients with small bowel neuroendocrine (carcinoid) tumors, irrespective of symptom status. However, there has yet to be a dose optimization study across the patient population, and methods are currently lacking to optimize dosing of octreotide therapy on an individual basis. Multiple factors such as total tumor burden, receptor expression levels, and nontarget organ metabolism/excretion may contribute to a variation in SSTR octreotide occupancy with a given dose among different patients. In this study, we report the development of an imaging method to measure surface SSTR expression and occupancy level using the PET radiotracer 68Ga-DOTATOC. In an animal model, SSTR occupancy by octreotide was assessed quantitatively with 68Ga-DOTATOC PET, with the finding that increased occupancy resulted in decreased tumor proliferation rate. The results suggested that quantitative SSTR imaging during octreotide therapy has the potential to determine the fractional receptor occupancy in NETs, thereby allowing octreotide dosing to be optimized readily in individual patients. Clinical trials validating this approach are warranted.
AB - Somatostatin receptors (SSTR) are highly expressed in well-differentiated neuroendocrine tumors (NET). Octreotide, an SSTR agonist, has been used to suppress the production of vasoactive hormones and relieve symptoms of hormone hypersecretion with functional NETs. In a clinical trial, an empiric dose of octreotide treatment prolonged time to tumor progression in patients with small bowel neuroendocrine (carcinoid) tumors, irrespective of symptom status. However, there has yet to be a dose optimization study across the patient population, and methods are currently lacking to optimize dosing of octreotide therapy on an individual basis. Multiple factors such as total tumor burden, receptor expression levels, and nontarget organ metabolism/excretion may contribute to a variation in SSTR octreotide occupancy with a given dose among different patients. In this study, we report the development of an imaging method to measure surface SSTR expression and occupancy level using the PET radiotracer 68Ga-DOTATOC. In an animal model, SSTR occupancy by octreotide was assessed quantitatively with 68Ga-DOTATOC PET, with the finding that increased occupancy resulted in decreased tumor proliferation rate. The results suggested that quantitative SSTR imaging during octreotide therapy has the potential to determine the fractional receptor occupancy in NETs, thereby allowing octreotide dosing to be optimized readily in individual patients. Clinical trials validating this approach are warranted.
UR - http://www.scopus.com/inward/record.url?scp=84890280115&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84890280115&partnerID=8YFLogxK
U2 - 10.1158/0008-5472.CAN-13-1199
DO - 10.1158/0008-5472.CAN-13-1199
M3 - Article
C2 - 24080280
AN - SCOPUS:84890280115
SN - 0008-5472
VL - 73
SP - 6865
EP - 6873
JO - Cancer research
JF - Cancer research
IS - 23
ER -