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 Colonoscopy is the most commonly used screening test for colorectal
cancers, but it’s invasive, costly and inconvenient. A growing
number of patients are instead using screening kits known as fecal
immunochemical tests (FIT) that can detect tiny amounts of blood in
the stool that might indicate cancer. Positive FIT results require a
follow-up colonoscopy to find any tumors and assess their severity.
For the study, researchers examined data on how long more than
70,000 patients with positive FIT results waited to get follow-up
colonoscopies. When they waited no more than one month, 30 cases out
of every 1,000 colonoscopies confirmed cancer and 8 cases per 1,000
showed advanced tumors. Results were similar for patients who waited
up to nine months.
But when patients got colonoscopies 10 to 12 months after positive
FIT results, there were 49 cases of cancer confirmed for every 1,000
colonoscopies, or 48 percent higher odds than waiting no more than
one month. The odds of advanced cancer were roughly doubled, with 19
cases per 1,000 colonoscopies.
“Colonoscopy can be a complicated test to schedule, requiring time
off from work and someone to accompany the patient home,” said lead
study author Dr. Douglas Corley of Kaiser Permanente Division of
Research in Oakland, California.
“This study suggests patients have a little time to make
arrangements for the exam around their work or personal schedules,”
Corley said by email. “These data confirm that colorectal cancers
progress fairly slowly and that it is feasible to get large numbers
of patients in for follow-up fairly rapidly.”
Half of the patients in the study had colonoscopies within 37 days
of a positive FIT result, the researchers report in JAMA.
Almost two-thirds of patients with positive FIT results got
follow-up colonoscopies within two months, and 81 percent of them
had a colonoscopy within six months, the study found.
Patients ranged in age from 50 to 75 years old, and half of them
were at least 61.
Overall, there were 2,191 cases of any colorectal cancer and 601
cases of advanced disease diagnosed.
Compared to people who got colonoscopies within a month, patients
who waited a year or more had more than triple the odds of having
advanced malignancies at the time of diagnosis.
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The study isn’t a randomized experiment designed to prove whether or
how the time between FIT results and a colonoscopy directly
influences the risk of cancer or of advanced tumors, the authors
note. It’s also possible the study might not have detected
differences between patients who got colonoscopies sooner and people
who waited longer for follow-up tests.
“It could be that people who return for colonoscopy several months
after a positive screening test are returning because they have
symptoms and so are more likely to have cancer detected,” said
Carolyn Rutter, a senior statistician at RAND Corporation in Santa
Monica, California, and co-author of an accompanying editorial.
Symptoms can include diarrhea, constipation, rectal bleeding,
cramping, fatigue or weight loss - all of which could also be due to
conditions other than cancer.
“Fecal-based tests are a very effective, inexpensive, and
non-invasive approach to screening for colorectal cancer,” Rutter
said by email. “But they can only detect cancer when positive tests
are followed by colonoscopy, and because they are most sensitive for
detection of preclinical cancer, fecal-based tests need to be
repeated annually.”
While it’s not ok to skip that follow-up colonoscopy, the study
results suggest it’s fine for patients to wait a little bit to
schedule the exam at a time that works best with everything else
they have going on in their lives, Rutter said.
SOURCE: http://bit.ly/2pw1rLO and http://bit.ly/2peyvVL JAMA, online
April 25, 2017.
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