Uniform spatial distribution of the cellular response to cisplatin and docetaxel in HNSCC

LB-182 Background: Using biopsy material to predict the efficacy of non-surgical treatment for solid tumors leaves most of the tumor untested. Results may be dubious unless they are shown to be representative of the entire tumor. Methodology: After obtaining informed consent, 3 fragments were each excised from different areas of freshly resected head and neck squamous cell carcinomas (HNSCC) of 14 untreated patients. The specimens were weighed and studied by means of a colony formation assay starting with mincing followed by collagenase digestion for 16 hours. Digests were distributed to extracellular matrix-coated wells of microtiter plates containing graded concentrations of cisplatin or docetaxel which covered the range from 0.5 x to 32 x the tolerated plasma levels (TPL; cisplatin: 6.67 µM, docetaxel: 0.55 µM). Controls received solvent only. Internal standards: KB cells were exposed to fittingly graded concentrations made of the media and drug solutions from the colony formation test. After incubation for 72 hr, formed colonies were methanol-fixed and Giemsa stained, and KB cells were evaluated numerically. Numbers of epithelial cell colonies per well were determined by microscopy. Tests with average ≥ 2 such colonies per control well were included. Cut-off concentrations sufficient to suppress colony formation, and IC 50 values in both tumor tests and KB cell experiments were determined. Results: Twelve of the colony formation tests met inclusion criteria. Internal KB cell standards conformed to predetermined rated values. Sample wet weight averaged 146 ± 59 mg (range: 65 to 668 mg). Cisplatin: Throughout, hormesis was absent, and cut-off was reached. Inhibitory zones averaged 8.7 ± 3.8 µM (range: 4.2 to 16.3 µM). Cut-off concentrations were identical in 3 samples of 7 tumors, and in 2 of the samples of the remaining 5 tumors, with the 3 rd sample deviating by ± 1 gradient step. IC 50 values (n = 9) averaged 6.7 ± 3.1 µM (range: 3.9 to 16.6 µM). Intratumoral variability of IC 50 values missed statistical significance (p rd sample deviating by + 1 gradient step. IC 50 values averaged 1.7 ± 0.7 µM (range: 0.8 to 2.9 µM). Intratumoral variability of IC 50 values missed statistical significance (p Conclusions: The microheterogeneity was quantitated of the hormetic and/or inhibitory effects of cisplatin and docetaxel ex vivo. The inhibitory effects observed in separately processed samples taken from different areas of individual tumors were nearly identical. This suggests that the chemoresponse in a single biopsy sample represents that of the entire tumor.