We evaluated the rate at which family cancer history changes over time with respect to indicating the need for earlier or intensified screening for colorectal, breast, and prostate cancer. Although family history of cancer was based on self-report, other groups have confirmed the high quality of self-reported data.16
Participants with incomplete family history information (such as unknown age of cancer diagnosis for a relative) were included, as would be the case in the clinical setting, where determination of the need for cancer screening is based on information provided by the patient. However, we acknowledge that participants with a cancer diagnosis may be more motivated to provide accurate family history in a study setting than in a clinic setting.
We used 2 complementary approaches with distinct sets of family history data obtained within the same study population: retrospectively, from birth to enrollment, and prospectively, from enrollment to last follow-up, in a large cohort of individuals followed up to 10 years. Both analyses demonstrate that clinically relevant family history changes substantially during early and middle adulthood, particularly for colorectal and breast cancer, for which the percentage recommended for high-risk screening increases 1.5- to 3-fold between ages 30 and 50 years. Results of the 2 prostate cancer analyses were not in complete agreement, possibly because of the limited data available, particularly for the prospective analysis.
We have taken several steps to design our analyses so the results could be applied to the general US population, although the CGN registry is underrepresented in participants from racial and ethnic minorities and estimates in these populations may differ. For these analyses, we included approximately two-thirds of the registrants who were ascertained via population-based tumor registries. To attenuate the influence of our higher-than-average-risk population, we excluded participants who had a diagnosis of the cancer of interest from the screening-specific analyses. Thus, by excluding these participants, who are more likely to have clinically relevant family history, our results may represent an underestimate of the true rate of change in family history; however, we cannot rule out that our results are overestimates due to the elevated cancer risk level inherent in our population. Scheuner et al5
found that the percentage of adult women who met criteria for genetic evaluation for hereditary breast cancer was similar but lower than ours (2%–4%), but this is not surprising given that their measure was indication for genetic evaluation as opposed to indication for MRI.
Other studies have documented that the majority of patients do not receive adequate familial cancer risk assessment in primary care settings.8,17–20
Family health history data are more likely to be collected at the initial clinic visit and are not adequately updated during follow- up visits.21
These analyses are relevant principally to primary care clinicians, who are often the first (or only) to initiate collection of family health history and are the main source of referral for cancer screening, although they are also relevant for other physicians who provide care to patients over many years. For this analysis, we only examined breast, colorectal, and prostate cancer status and age at diagnosis among first- and second-degree relatives. Subsequent updates require determining only whether there have been any new
diagnoses among living first- and second-degree relatives. These questions could be easily added to standard patient questionnaires filled out during routine physician visits. Electronic medical record systems could be designed to prompt physicians for periodic updates and alert them to patients who now meet criteria for high-risk screening.
In our study, we found a 5% chance that an individual’s colorectal cancer screening recommendation would change between ages 30 and 50 years based on family history and that 4% of women would become candidates for MRI screening. Although there is disagreement in the medical community regarding the merits of screening for prostate cancer, family history of prostate cancer also increased over these age ranges. If a patient’s family history is not updated during early and middle adulthood, the opportunity may be missed to intervene with earlier or more intensive screening that maximizes the likelihood of detecting cancer at an early, treatable stage.
Our study has several limitations. First, our determination of whether an individual would meet criteria that would represent an increased risk level and therefore would be recommended for earlier or intensive screening was based solely on reported changes in family history of cancer over time. We did not address how many additional cancers would be expected to be detected if appropriate screening based on the changing family history was performed. Factors such as an individual’s personal medical history or prior cancer screening results were not considered, and these issues also may change during adulthood and need to be assessed by clinicians. Second, our study did not evaluate indications for genetic risk assessment, although obtaining an accurate family history is also critical for identifying patients who merit further genetic evaluation to reduce cancer morbidity in their families. Third, our study did not assess whether participants who met criteria for high-risk screening based on family history and had recommendations for screening made by their physicians actually had additional screening performed.