Dr Hastings may be correct in his observation that we found no colon cancers in our study group using the HO test because none was present.
We have analyzed the death rates in Oregon from colo-rectal cancer, the available cancer incidence data, and reports from our tumor registries in the state. On the basis of these data we have predicted that at least two cases of colon cancer were present in our group at the time of our study. We detected none.
One woman, aged 66 years, had a large obstructing carcinoma of the ascending colon and cecum 16 months after she participated in our study. (Her three HO tests were negative.) As Dr Hastings suggests, follow-up of at least two years is essential. This follow-up period has been completed in most but not all of our population.
Dr Hastings calls attention to the new modification of the