Iatrogenic tumour seeding not a risk factor for metachronous CRC

In patients with colorectal cancer (CRC), biopsy of nontumour sites after biopsy of the primary cancer is unlikely to cause metachronous cancers, a study reports.

The study used data from a large community-based healthcare organization and identified adult patients with an initial CRC diagnosed by colonoscopy who then underwent curative resection. Those who developed a second primary (metachronous) CRC diagnosed within 6 months to 4 years of the initial CRC (case patients) were matched by age, sex, diagnosis of inflammatory bowel disease, race, and ethnicity with up to five control patients without a second CRC diagnosis.

Researchers applied conditional logistic regression to examine whether biopsy in the colonic segment of the metachronous CRC (or corresponding segment) after tumour biopsy was associated with the metachronous CRC itself.

A total of 14,119 patients were diagnosed with an initial CRC during colonoscopy, of which 107 received a second CRC diagnosis. After exclusions for recurrent or synchronous CRC, 45 case and 212 control patients were included in the analysis.

Multivariable logistic regression showed that biopsy of nontumour sites after initial CRC biopsy did not contribute to an increase in the risk of metachronous CRC in the segment of the additional biopsy site (adjusted odds ratio, 2.29, 95 percent confidence interval, 0.77–6.81).

Even though the sample size does not allow definite exclusion of any association, the present data provide evidence to support that iatrogenic tumour seeding is not a risk factor for metachronous CRC.