UC Irvine

To the Editor: Since our group first reported on the potential clinical applications of the human tumor stem-cell, or clonogenic, assay in the Journal,1 we think some comment from us is warranted regarding the recent article by Selby et al.2 and the editorial by Von Hoff.3 We clearly agree that it is important to plate good single-cell suspensions, that drug-sensitivity criteria are still in the developmental stages,4 that some drugs may require the evaluation of various exposure times, that inappropriate drug concentrations may be misleading, that drugs requiring bioactivation present special problems, that radiation-survival curves with plateaus at. © 1983, Massachusetts Medical Society. All rights reserved.