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The Quarterly Journal of Nuclear Medicine 1999 September;43(3):268-80


language: English

Diagnostic applications of radiolabeled peptides in nuclear endocrinology

Behr T. M., Béhé M., Becker W.

From the Department of Nuclear Medicine Georg-August-University of Göttingen, Germany


Regulatory pep­tides are ­small, read­i­ly dif­fus­able and ­potent nat­u­ral sub­stanc­es ­with a ­wide spec­trum of recep­tor-medi­at­ed ­actions in ­humans. High affin­ity recep­tors for ­these pep­tides are (­over-) ­expressed in ­many neo­plasms, and ­these recep­tors may rep­re­sent, there­fore, new molec­u­lar tar­gets for can­cer diag­no­sis and ther­a­py. This ­review ­intends to ­give an over­view of the pep­tide-­based radio­phar­ma­ceu­ti­cals ­which are pres­ent­ly ­already com­mer­cial­ly avail­able or ­which are in ­advanced stag­es of ­their clin­i­cal test­ing so ­that ­their broad­er avail­abil­ity is antic­i­pat­ed ­soon. Physiologically, ­these pep­tides ­bind to and act ­through G pro­tein-cou­pled recep­tors in the ­cell mem­brane. Historically, som­a­tos­ta­tin ana­logs are the ­first ­class of recep­tor bind­ing pep­tides hav­ing ­gained clin­i­cal appli­ca­tion. 111In-­DTPA-[D-Phe1]-octre­o­tide is the ­first and ­only radio­pep­tide ­which has ­obtained reg­u­la­to­ry approv­al in Europe and the United States to ­date. Extensive clin­i­cal stud­ies involv­ing sev­er­al thou­sands of ­patients ­have ­shown ­that the ­major clin­i­cal appli­ca­tion of som­a­tos­ta­tin recep­tor scin­tig­ra­phy is the det­e­c­tion and the stag­ing of gas­troen­te­rop­an­creat­ic neu­ro­en­do­crine ­tumors (car­ci­noids). In ­these ­tumors, octre­o­tide scin­tig­ra­phy is super­i­or to any oth­er stag­ing meth­od. However, its sen­si­tiv­ity and accu­ra­cy in oth­er, ­more fre­quent neo­plasms is lim­it­ed. Radiolabeled vasoac­tive intes­ti­nal pep­tide (VIP) has ­been ­shown to vis­u­al­ize the major­ity of gas­troin­tes­ti­nal aden­o­car­cin­o­mas, as ­well as ­some neu­ro­en­do­crine ­tumors, includ­ing insu­lin­o­mas (the lat­ter ­being ­often ­missed by som­a­tos­ta­tin recep­tor scin­tig­ra­phy). Due to the out­stand­ing diag­nos­tic accu­ra­cy of the pen­ta­gas­trin ­test in detect­ing the pres­ence, per­sis­tence, or recur­rence of medul­lary thy­roid can­cer (MTC), we pos­tu­lat­ed the expres­sion of the cor­re­spond­ing [i.e., chol­e­cys­tok­i­nin (CCK-) -B] recep­tor ­type in ­human MTC. This recep­tor is ­also wide­ly ­expressed on ­human ­small-­cell ­lung can­cer. Indeed, 111In-­labeled ­DTPA deriv­a­tives of gas­trin ­showed excel­lent tar­get­ing of CCK-B recep­tor express­ing tis­sues in ani­mals and ­patients. A varie­ty of fur­ther pep­tide-­based radio­lig­ands is cur­rent­ly ­under devel­op­ment. Summarizing, radio­lab­eled reg­u­la­to­ry pep­tides ­have ­opened new hori­zons in nucle­ar oncol­o­gy for diag­no­sis (and poten­tial inter­nal radio­nu­clide ther­a­py). Future ­work ­will prob­ably ­reveal a mul­ti­tude of nov­el poten­tial­ly clin­i­cal­ly use­ful pep­tide-­based radio­lig­ands.

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