Patients with cancer had a lower rate of clinical cure (79.2%) than patients without cancer (88.6%; P < .001; Table 1). Consistent with the lower response rate, patients with cancer as a group had longer TTROD (Fig 2A; log-rank P < .001). Median TTROD was nearly doubled in patients with cancer (100 hours; 95% CI, 71 to 119 hours) versus those without cancer (55 hours; 95% CI, 53 to 58 hours; Appendix Table A2, online only). There was little effect of malignancy on recurrence; 21.4% of patients with cancer and 20.0% of patients without cancer had recurrence of CDAD (P = .693). Patients with cancer had a lower sustained response rate at 28 days after completing therapy (62.3% v 70.9%; P = .020). Although there were differences in response rates according to type of cancer (solid or hematologic) or whether patients received chemotherapy, sample sizes were too small to draw conclusions.