Topoisomerase I expression correlates to response to neoadjuvant irinotecan-based chemoradiation in rectal cancer
Post S et al. - In a study to assess whether expression of topoisomerase I (Topo I) and thymidylate synthase (TS) helps predict treatment response in pts undergoing irinotecan and capecitabine-based chemoradiation, it was reported that Topo I expression in rectal tumour mucosa might serve as a predictor of response to neoadjuvant irinotecan-based chemoradiation, and might be a factor contributing to development of individualized treatment. Methods- Pts with rectal cancer (cT3/4Nx or Tx/N+) received neoadjuvant chemoradiotherapy within clinical studies with irinotecan and capecitabine.
- Samples of normal and tumour tissues were collected before start of treatment and during surgical resection.
- Topo I and TS were measured using real-time PCR.
Results- 38 pts were analysed, 18 of them were responders.
- Biopsies of untreated tumour tissue of responding pts showed a significant higher expression of Topo I vs nonresponding pts.
- Normal tissue did not show this difference.
- During chemoradiation, Topo I expression in tumour tissue of responders decreased significantly.
- TS did not show any differences between responders and nonresponders before treatment, but a significant decrease in the tumour tissue of responders was noted at the end of treatment.
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