IMMUNOHISTOCHEMICAL STAINING FOR GLUTATHIONE-S-TRANSFERASE PREDICTS RESPONSE TO PLATINUM-BASED CHEMOTHERAPY IN HEAD AND NECK-CANCER

The glutathione S-transferases (GSTs) play an important role in the ce ll's defense against toxic substances, The GSTs are a family of enzyme s produced by several genes that interact with distinct but overlappin g substrates and that may play a role in resistance of tumor cells to several chemotherapeutic agents,We examined the correlation between ex pression of GSTs determined by immunohistochemistry and clinical respo nse to platinum-based chemotherapy in 51 patients with head and neck c ancer, who received a total of 56 courses of chemotherapy, The overall response rate for the 56 chemotherapy treatment courses was 48%, The overall response rate (complete response + partial response) for patie nts with low GST scores was 88% (21 of 24), whereas among the patients with high GST scores, the overall response rate was 19% (6 of 32; P = 0.001), Patients with a low GST score were 4.7 times more likely to r espond to chemotherapy than patients with high GST scores, GST scores corresponded to response in 84% of cases, Among 23 patients treated wi th neoadjuvant chemotherapy, the overall response rate for patients wi th low GST scores was 100% (14 of 14), whereas among the patients with high GST scores, the overall response rate was 44% (4 of 9; P = 0.002 ), Among 33 patients treated with chemotherapy for relapsed disease, t he overall response rate for patients with low GST scores was 70% (7 o f 10), whereas among the patients with high GST scores, the overall re sponse rate was 8.6% (2 of 23; P < 0.001), We conclude that GST expres sion correlates well with response to platinum-based chemotherapy in h ead and neck cancer.