Hazard function analysis for development of second primary colorectal cancer after surgery for primary colorectal...

Although history of colorectal cancer (CRC) is a known risk factor for developing second CRC, the optimal surveillance protocol has not been established. Using hazard function analysis to evaluate changes in the hazard rate for the development of second primary CRCs or high-grade adenomas (HGAs), we aimed to clarify when and on whom to focus in order to effectively identify second primary colorectal neoplasms after initial surgery for CRC.

We retrospectively enrolled 1823 consecutive patients with stage 0-III CRCs who underwent radical surgery between 2004 and 2015, and subsequent colonoscopic surveillance after surgery. The time-course changes in the risk rates for developing metachronous CRC and HGA after surgery were assessed.

A peak was observed at 1.22 years after surgery in the hazard function curve for secondary colorectal neoplasms, which decreased until 4 years, then plateaued. Older patients were at higher risk than younger patients, both showing a peak at 1 year. Another peak at 6 to 8 years was observed in younger patients. Male patients showed a higher risk than female patients, and patients with synchronous lesions showed a markedly higher hazard rate than those without, with two distinct peaks around 1 and 9 years after surgery.

Intensive colonoscopic surveillance is recommended after surgery for CRC during the first 2 to 3 years, and if the patient is under 60 years old and has concomitant CRC or HGA, surveillance is also recommended at 6 to 8 years after surgery.