Adults with a bloodstream infection face an increased risk of developing colorectal cancer within 1 year, according to the results of a Canadian study.
The organisms associated with the highest risk of new colorectal cancer were Clostridium spp., the Bacteroides fragilis group, and other anaerobes, reported during a poster session at the meeting.
However, Streptococcus bovis, which has been proposed as a marker of colorectal malignancy, was not found to be associated with increased diagnoses of the condition.
“If patients have a bloodstream infection, particularly older patients, you should definitely be looking for signs of colorectal cancer,” said at the meeting, which was sponsored by the American Society for Microbiology. “We did not look at premalignant conditions such as polyps. If we did, I suspect that we would have had even stronger feelings.”
Who conducted the research during an infectious disease fellowship at the University of Calgary (Alta.), and her associates use a regional electronic surveillance system database to identify a cohort of Calgary area adults who had an incident bloodstream infection between 2000 and 2007. They used a computer program to match the patients to the Alberta Cancer Registry.
Over the 7-year period, 10,121 blood-stream infections occurred in 8,806 patients. The mean age of the patients was 62 years, and 54% were male. During the same time frame, 3,859 residents in the region were diagnosed with a colorectal cancer, of which 349 followed a bloodstream infection.
Colleagues found that 71 patients had a diagnosis of colorectal cancer made at the same time as or within 1 year following a bloodstream infection, for a standardized incidence ratio of 14.4 compared with the general population. Organisms associated with the highest risk of new colorectal cancer diagnosis were Clostridium spp. (standard incidence ratio, 115.39), the Bacteroides fragilis group (SIR, 77.2), and other gram-positive anaerobic organisms (Sir, 47.7)
Advancing age, male gender, liver disease, and a higher Charlson Index score were associated with bloodstream infections and a new diagnosis of colorectal cancer.
Currently, a medical microbiology registrar at St. Vincent’s Hospital, Fitzroy, Australia, said that she and her associates are conducting a further review of patients with a Streptococcus bovis bloodstream infection. They also hope to determine the percentage of patients who underwent a colonoscopy.
She acknowledged certain limitations of the study, including the potential for missed cases during database matching and the relatively small sample size of patients used in the final analysis.