Table 16. Summary of Prospective Studies Evaluating Participation in Genetic Counseling and Testing for Hereditary Colorectal Cancer (CRC)a,b,c continued...
In a study of cancer-affected and cancer-unaffected persons who fulfilled clinical criteria for LS, 92% reported having had a colonoscopy and/or flexible sigmoidoscopy at least once before genetic testing. Another study of unaffected individuals presenting for genetic risk assessment and possible consideration of LS, FAP, or APCI1307K genetic testing reported that 77% had undergone at least one screening exam (either colonoscopy, flexible sigmoidoscopy, or barium enema).
Three studies determined whether cancer-unaffected persons adhered to LS colonoscopy screening recommendations before genetic testing, and reported adherence rates of 10%, 28%, and 47%.
Several longitudinal studies examined the use of screening colonoscopy by cancer-unaffected persons after undergoing testing for a known LS mutation.[57,74,75,76] These studies compared colonoscopy use before LS genetic testing with colonoscopy use within 1 year after disclosure of test results. One study reported that LS mutation carriers were more likely to have a colonoscopy than were noncarriers and those who declined testing (73% vs. 16% vs. 22%) and that colonoscopy use increased among carriers (36% vs. 73%) in the year after disclosure of results. Two other studies reported that carriers' colonoscopy rates at 1 year after disclosure of results (71% and 53%) were not significantly different from rates before testing,[74,76] though noncarriers' colonoscopy rates decreased in the same time period. Factors associated with colonoscopy use at 1 year after results disclosure included carrying a LS-predisposing mutation,[74,75,76] older age, and greater perceived control over CRC. These findings suggest that colonoscopy rates increase or are maintained among mutation carriers within the year after disclosure of results and that rates decrease among noncarriers. Data from a longitudinal study including 134 MMR mutation carriers with and without a prior LS-related cancer diagnosis found that those who did not undergo colonoscopy for surveillance within 6 months after receiving genetic test results were six times more likely to report clinically significant depressive symptoms as measured by the Center for Epidemiological Studies-Depression (CES-D) scale (OR, 6.06; 95% confidence interval [CI], 2.09–17.59). Higher levels of CRC worry measured prior to genetic testing also were associated with clinically significant depressive symptoms (OR, 1.53; 95% CI, 1.19–1.97).
Two studies examined the level of adherence to published screening guidelines after LS genetic testing, based on mutation status. One study reported a colonoscopy adherence rate of 100% among mutation carriers. Another study found that 35% of mutation carriers and 13% of noncarriers did not adhere to published guidelines for appropriate CRC screening; in both groups, about one-half screened more frequently than published guidelines recommend, and one-half screened less frequently.
The longitudinal studies described above examined colorectal screening behavior within a relatively short period of time (1 year) after receiving genetic test results, and less is known about longer-term use of screening behaviors. A longitudinal study (N = 73) that examined psychological and behavioral outcomes among cancer-unaffected persons at 3 years following disclosure of genetic test results found that all carriers (n = 19) had undergone at least one colonoscopy between 1 and 3 years postdisclosure. Ninety-four percent of carriers in one study stated an intention to have annual or biannual colonoscopy in the future; among noncarriers, 64% did not intend to have colonoscopy in the future or were unsure, and 33% intended to have colonoscopy at 5- to 6-year intervals or less frequently. A cross-sectional study conducted in the Netherlands examined the use of flexible sigmoidoscopy or colonoscopy among persons with CRC, endometrial cancer, or a clinical or genetic diagnosis of LS during a time that ranged from 2 years to 18 years after risk assessment and counseling. Eighty-six percent of LS mutation carriers, 68% of those who did not test or who had an uninformative LS genetic test result, and 73% of those with a clinical LS diagnosis were considered adherent with screening recommendations, based on data obtained from medical records. Participants also answered questions regarding screening adherence, and 16% of the overall sample reported that they had undergone screening less frequently than recommended. For the overall sample, greater perceived barriers to screening were associated with screening nonadherence as determined through medical record review, and embarrassment with screening procedures was associated with self-reported nonadherence. A second cross-sectional study, also conducted in the Netherlands, surveyed cancer-unaffected LS mutation carriers (n = 42) regarding their colorectal screening behaviors after learning their mutation status (range, 6 months–8.5 years). Thirty-one percent of respondents reported that they had undergone annual colonoscopy prior to LS genetic testing, and 88% reported that they had undergone colonoscopy since their genetic diagnosis (P < .001).