Kümler I, et al. - Two open-label, single-arm phase II studies including HER2 positive and negative patients was conducted by the researchers to investigate whether gene copy number of the topoisomerase 1 gene was predictive of response to the topoisomerase inhibitor irinotecan. Three patients achieved partial remission and while two patients had SD. However, the trials failed to include the planned number of patients. Furthermore, no association between gene copy number of the topoisomerase 1 gene and response to irinotecan could be concluded. In 5/12 patients and in 2/3 patients with HER2 positive disease from each trial, clinical benefit was found.