RADIOPHARMACOLOGY 

The Quarterly Journal of Nuclear Medicine 2001 June;45(2):174-8

Copyright © 2009 EDIZIONI MINERVA MEDICA

language: English

Evaluation of alternative approaches for imaging cellular growth

Krohn K. A.

From the Division of Nuclear Medicine, University of Washington, Seattle, USA

Uncontrolled ­growth is a char­ac­ter­is­tic of malig­nant ­tumors. Histochemical tech­niques to meas­ure ­tumor ­growth ­rate in tis­sue spec­i­mens ­have ­proved use­ful, but are lim­it­ed ­because of sam­pling and the dif­fi­cul­ty of fol­low­ing ­response to ther­a­py. PET imag­ing ­offers the oppor­tu­nity to meas­ure ­tumor ­growth non-inva­sive­ly and repeat­ed­ly as an ear­ly assess­ment of ­response to ther­a­py. Measuring cel­lu­lar ­growth ­instead of ener­gy metab­olism ­offers sig­nif­i­cant advan­tag­es in eval­u­at­ing ther­a­py. The ratio­nale is ­that a ­cell’s bio­syn­thet­ic machin­ery, rath­er ­than its fuel­ing pro­cess, is ­more sus­cep­ti­ble to can­cer ther­a­py. Cytostatic ­agents may not ­reduce the quan­tity of ­viable ­tumor; so imag­ing a ­change in cel­lu­lar pro­life­ra­tion may be the ­only effec­tive way to ­assess the ­response to ther­a­py. Radiopharmaceuticals to ­image ­growth ­include ­labeled ami­no ­acids, lip­id pre­cur­sors, and nucle­osides. The bio­chem­i­cal char­ac­ter­is­tic ­that ­most unique­ly dis­tin­guish­es suc­cess­ful­ly treat­ed can­cer ­cells is ­that ­they no long­er syn­the­size DNA and no long­er ­divide. Thus imag­ing ­with ­labeled thy­mi­dine, ­which is incor­po­rat­ed ­into DNA but not ­into RNA, pro­vides defin­i­tive evi­dence of a ­cell ­that is pro­life­rat­ing and, there­fore, wheth­er it has respond­ed to treat­ment.