Table 4.

Difference in marker expression (worst minus best tissue specimens)

Histology difference*Marker expression
EGFR overexpression
HER-2 overexpression
n− (%)+/− (%)−/+ (%)+/+ (%)n− (%)+/− (%)−/+ (%)+/+ (%)
  • Abbreviations: −, best and worst samples both negative (no overexpression of receptor); +/−, best sample positive (overexpression of receptor) and worst sample negative; −/+, best sample negative and worst sample positive; +/+, both samples positive.

  • * Difference between numeric histologic identifiers for worst and best biopsies in each subject.

  • Values for marker expression are percentage of samples with particular receptor expression pattern (i.e., +/−, −/+, etc.) within each histologic difference group.

  • P values for testing linear trend in the (−/+) with increasing histology difference. Test is adjusted for within-subject average histology (average of the best and worst histologies). A significant P value implies the absence of a field effect (i.e., a significant P value implies that the difference in marker expression is related to difference in histology). If marker expression is elevated across the entire lung, then there would be no difference between worst and best samples; in particular, the difference would not change with increasing difference in histology between best and worst samples.