February 22, 2012 — Colonoscopic polypectomy has the potential to slash the colorectal cancer mortality rate in half, but screening compliance is very low, according to 2 studies published in the February 23 issue of the New England Journal of Medicine.
In the first study, a team led by Ann G. Zauber, PhD, from the Memorial Sloan-Kettering Cancer Center in New York City, performed a retrospective analysis showing that removal of adenomatous polyps decreased colorectal cancer mortality by 53% over a mean of 15.8 years.
Although mortality rates remained low for the first 10 years, during which screening measures were strict, the reduced effect that followed the cessation of surveillance emphasizes the need for long-term screening.
Unfortunately, real-world screening rates remain low, according to the results of the second study, a large randomized controlled trial conducted by Enrique Quintero, MD, PhD, from the Department of Gastroenterology, Hospital Universitario de Canarias, Tenerife, Spain, and colleagues.
Researchers found that only 24.6% of recruited individuals 50 to 69 years of age accepted once-only screening with colonoscopy. Although 34.2% agreed to the first of 5 biennial fecal immunochemical screenings, compliance is expected to decrease over time.
Both methods were equally effective for identifying colorectal cancer, but colonoscopy was associated with significantly increased detection and diagnostic yield with respect to adenomas, which represent a strong predictor of cancer risk.
Colonoscopic Polypectomy Halves Colorectal Cancer Mortality Rate
In the first study, investigators conducted a long-term follow-up (up to 23 years; mean, 15.8 years) of patients in the National Polyp Study to determine the effects of polyp removal on colorectal cancer mortality.
Data from the National Death Index were used to identify deaths and cause of mortality; a reference group was established from the Surveillance, Epidemiology, and End Results (SEER) program.
Among 2602 patients with adenomas, there were 1246 deaths (48%) — 12.0 from colorectal cancer. In the general population, there would be 25.4 expected deaths from the disease, representing a 53% reduction in mortality overall (standardized incidence-based mortality ratio [SMR], 0.47; 95% confidence interval [CI], 0.26 to 0.80; P = .008).
Although colorectal cancer mortality rates in the adenoma cohort were similar to those in the nonadenoma cohort for the first 10 years (0.19% vs 0.15%; relative risk, 1.2; 95% CI, 0.1 to 10.6, P = 1.00), the mortality rate increased upon discontinuation of strict surveillance strategies.
Four deaths were reported in patients with adenoma during the first 10 years, representing a 56% reduction, compared with the general population (SMR, 0.44; 95% CI, 0.14 to 1.06; P = .09). Over the next 10 years, 8 deaths were reported, for a reduction in the mortality rate of only 51% (SMR, 0.49; 95% CI, 0.23 to 0.93; P = .04).
"This highlights the importance of long-term surveillance for patients after the initial removal of adenomas," write Michael Bretthauer, MD, PhD, and Mette Kalager, MD, from the National Institutes of Health in Bethesda, Maryland, in an accompanying editorial.
"Adenoma status at baseline screening...is a strong predictor of the risk of colorectal cancer, and the study by Zauber and colleagues confirms that this risk can be reduced by strict surveillance after the removal of adenomas," they add.
Colonoscopy May Be a Better Screening Tool for Cancer Than FIT
In the second study, investigators compared colorectal cancer mortality rates after either once-only screening with colonoscopy (n = 26,703) or biennial fecal immunochemical testing (FIT) for 10 years (n = 26,599) in patients 50 to 69 years of age at baseline.
They found that compliance with screening was low in both groups (24.6% vs 34.2%), and the apparent increased use of FIT represents only 1 round of 5.
"Compliance with fecal screening has been shown to decrease over time," note the editorialists.
Both methods were equally effective for identifying colorectal cancer, with colonoscopy identifying 30 patients and FIT identifying 33 patients (0.1% vs 0.1%; odds ratio [OR], 0.99; 95% CI, 0.61 to 1.64; P = .99).
However, colonoscopy identified significantly more cancers per screening, including advanced adenomas (493 vs 252; OR, 4.32; 95% CI, 3.69 to 5.07; P < .001), advanced neoplasias (520 vs 288; OR, 4.01; 95% CI, 3.45 to 4.67; P < .001), and nonadvanced neoplasias (1116 vs 112; OR, 25.98; 95% CI, 21.27 to 31.74; P < .001).
The higher detection rate and diagnostic yield of colonoscopy with respect to adenomas is of particular importance, the authors note.
Because "advanced adenomas are usually considered a surrogate marker for colorectal cancer, the superiority of colonoscopy for detecting such lesions should be considered a potential advantage of this strategy in terms of reducing not only the rate of death from colorectal cancer, but also the incidence of disease," write Dr. Quintero and colleagues.
Colonoscopy as a Triage Screening Test
Adenoma status at baseline is a strong predictor of colorectal cancer risk, which can be reduced with strict surveillance and removal of adenomas. The issue of poor compliance could be grounded in false assumptions about the magnitude of testing discomfort.
How, then, should colonoscopy be encouraged?
"An appealing concept would be to use colonoscopy as a triage screening, offering it once for everybody at 60 years of age and using the results to classify persons as having a low risk of colorectal cancer (no adenomas detected) or a high risk (adenomas detected, particularly advanced ones), with strict surveillance for the latter group but no further screening for the former, suggest the editorialists.
The study by Dr. Zauber and colleagues was supported by grants from the National Cancer Institute and by funding from the Society of the Memorial Sloan-Kettering Cancer Center, the Tavel-Reznik Fund, and the Cantor Colon Cancer Fund. The study by Dr. Quintero and colleagues was supported by grants from the Asociación Española contra el Cáncer (Fundación Científica and Junta de Barcelona), Instituto de Salud Carlos III (PI08/90717), FEDER funds, and Agència de Gestió d'Ajuts Universitaris i de Recerca (2009SGR849). Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd) is funded by Instituto de Salud Carlos III. In the Basque Country, the study received additional grants from Obra Social de Kutxa, Diputación Foral de Gipuzkoa (DFG 07/5), Departamento de Sanidad del Gobierno Vasco, EITB-Maratoia (BIO 07/ CA/19), and Acción Transversal contra el Cáncer del CIBERehd (2008). In Galicia, this work was supported by Dirección Xeral de Innovación e Xestión da Saúde Pública, Conselleria de Sanidade, and Xunta de Galicia. Eiken Chemical of Japan and its Spanish representatives, Palex Medical and Biogen Diagnóstica, donated supplies and automated analyzers used for FIT.
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου