Researchers from the USA determined the incidence of second primary colorectal cancer after treatment for localized colon cancer. They also compared this incidence with that of first primary colorectal cancer in both the general population and high-risk patients.
A total of 3278 patients with resected stage II and stage III colon carcinomas were included in the study.
Individuals were given adjuvant 5-fluorouracil-based chemotherapy for localized disease.
The occurrence of endoscopic or radiologic colon surveillance and incidence of second primary colorectal cancer were measured.
| Incidence rate of second primary colon cancer: 274 per 100,000 person-years.
|Annals of Internal Medicine |
Some 42 cases of second primary invasive colon cancer were found over 15,345 person-years of follow-up. This yielded an incidence rate of 274 per 100,000 person-years and a cumulative incidence of 1.5% at 5 years.
This rate was compared with rates of first colon cancer in two reference groups.
The two groups were the general population, and patients who had undergone frequent colonoscopy and polypectomy because of a history of adenomatous polyps. The respective standardized incidence ratios were found to be 1.6 and 6.8.
Dr Robert J. Green, of the Helen and Harry Gray Cancer Institute, West Palm Beach, Florida, concluded on behalf of his colleagues, "The incidence of second primary colorectal cancer remains high, despite intensive surveillance strategies."