This study characterized the completeness and coherence of family cancer history reports ascertained in a general population sample. Only 6.1% of relatives had a completely unknown cancer history and there was little evidence of over-reporting of other conditions as cancer. Eighty three percent of respondents reported a positive history of cancer in at least one relative. However, only 79% of reports describing types of cancer diagnosed in relatives were judged to be fully coherent, based on the dual criteria of consistency with malignancy and site-specificity. Coherence of reports varied significantly in association with a number of covariates, discussed in greater detail below. These findings suggest that family history data may be sufficiently detailed to provide useful risk assessment in the primary care setting or to monitor familial risk patterns in population surveys. However, risk assessment may be hampered by ambiguous cancer site information in approximately one fifth of reported diagnoses.
Since the study questionnaire used an open-ended format to ascertain type of cancer, the responses were distributed across a qualitative continuum. There were three intermediate categories of reports in between the 79% fully coherent reports and the 1% indicative of indeterminate disease. The ill-defined reports mentioned body regions or several distinct organs, reflecting respondent uncertainty about the exact diagnosis. The unspecified reports lacked information about any possible site of origin, suggesting wider gaps in respondent knowledge, or perhaps some cases with disseminated disease at diagnosis where site of origin was not determined. Given that family history reports must be interpretable in the context of disease risk in order to have clinical utility (32
), such reports would generally have little use in the clinical setting, where familial risk patterns are evaluated based on the specific cancer sites involved. The third intermediate category contained reports of non-malignant diseases, indicating that some respondents held imprecise beliefs about what constitutes cancer. Although contradictory, these reports can still be useful for ruling out cancer.
Not surprisingly, both the coherence and completeness of family history reports, and respondent awareness that their relatives did or did not have cancer, varied by kinship and other factors that influence communication within families. A much greater percentage of ambiguous cancer reports concerned SDR, who also had more unknown cancer histories than FDR. Given that SDR outnumber FDR in almost all families (24
) and information about them is generally of lower quality, the cost vs. benefit of collecting SDR data warrants consideration in settings where its value may be limited. One consequence of not seeking SDR information is that cancer patterns suggesting an underlying hereditary susceptibility may be missed in small families with few at-risk FDRs (33
). For example, in some families, it may be difficult to recognize paternally transmitted breast-ovarian cancer syndrome without SDR information. Thus, the decision of whether or not to seek information about SDR may vary, depending on the cancer site of interest and what is known regarding its genetics.
Besides kinship, vital status of the relative was the only variable consistently associated with both ill-defined or unspecified cancer reports and unknown cancer history. After adjustment for vital status, unknown cancer history among SDR was further associated with older generations, and with parental separation during the respondent’s childhood. Encouraging individuals to communicate with “family gatekeepers” who possess detailed information about the larger pedigree may improve family history ascertainment for deceased or older generations of SDR. Our findings support the need for initiatives, such as the Surgeon General’s Family History Initiative (13
) to encourage people to learn more about, and maintain records of, their family health history.
Demographic characteristics of respondents were another major source of variation in the coherence and completeness of family history of cancer reports. Lower educational attainment was positively associated with ill-defined or unspecified cancer reports in relatives, and with unknown cancer history in each kinship group, suggesting less awareness or perceived benefit of family history information among respondents from lower socioeconomic subgroups. Male gender of the respondent was also associated with ill-defined or unspecified cancer reports, and unknown cancer history, but only among SDR. Other studies have found underreporting of family history of common cancers by men (34
), possibly attributable to cultural practices favoring women as family gatekeepers. Our data suggest that men may provide coherent family history of cancer information for their closest relatives.
After adjustment for education and all other factors, African-Americans were more likely to report ill-defined or unspecified cancers than whites, although these estimates were unstable due to small sample size. This may partly reflect limited cancer information-sharing within families (34
), fewer inquiries about family history from health care providers (38
), or less awareness of paternal family history (39
). Findings that coherence and completeness of reports vary significantly by demographic features of respondents suggest that interventions to promote family history-taking should be tailored to the educational and cultural characteristics of population subgroups (40
In this study, 8.3% of respondents reported a personal history of any cancer, including non-melanoma skin cancer. This was higher than a published national estimate of 4.8% from the NHIS that excluded non-melanoma skin cancers (42
). We used 2001 NHIS data (14
) to obtain an estimate that, like our survey, restricted respondent ages to 25–64 years and included all skin cancers. The resulting estimate of 5.1% was still lower than 8.3%, perhaps reflecting true differences between CT and the U.S. overall, or reporting errors in both surveys. Unexpectedly, unknown cancer among SDR was significantly higher if respondents reported a personal history of cancer, and a non-significant increase was also observed among FDR. We would expect respondents with a personal history to have greater awareness of relatives’ diagnoses, or to have a similar awareness as those without a personal history if their diagnosis was simply non-melanoma skin cancer. This counter-intuitive finding may be partly explained by misclassification of respondents with regard to their personal cancer history. For example, family history knowledgeable- respondents may have underreported their personal history, and also, 7 of the 96 who did report a personal history actually mentioned non-malignant diagnoses. Awareness may have been further tempered by the fact that 25 of them only reported non-melanoma skin cancers.
Respondents were able to provide a year or age of diagnosis for relatives’ cancers in a slim majority of cancer reports (54%). By further probing, using 10 year age-ranges, and where appropriate, about a diagnosis < or ≥age 50, we were able to estimate age for an additional 44% of relatives. This type of probing offers an easy, low-cost strategy to obtain an estimate of age at diagnosis for the cancer reports.
Specific strengths of this study include the population-based sample design that likely approximates primary care populations in demographics and the high prevalence of average to moderate cancer risk. Therefore, our results can shed light on potential barriers to and facilitators of family history ascertainment in primary care practice settings, where such information is of increasing interest for risk assessment and personalized preventive care (19
). The open-ended format of the family history questions in the survey instrument was an additional strength. Although this format is not necessarily cost-effective in studies seeking limited family history data, it enabled us to conduct a qualitative evaluation of the full range of verbatim responses. It is not well understood which if any kinds of family history questions or advance materials ultimately yield less ambiguous and more accurate responses.
There are several limitations to this study. First, the results may not be generalizable to ineligible subgroups of respondents, such as those under 25 or above 64 years old, or immigrants. In one national survey, the latter were one-third as likely to report any family history of cancer than U.S.-born respondents (44
), suggesting that our prevalence estimate of any family cancer history might have been substantially lower had immigrants been included. Furthermore, because the Connecticut sampling frame and study sample had greater proportions of whites and people with higher income and education than the U.S. population (24
), the coherence and completeness of family history reports may be overestimated relative to the U.S. overall or to populations with different demographic characteristics. The number of Hispanics and other minority groups was small, resulting in unstable estimates of ambiguous cancer reports and unknown cancer histories.” Pre-interview family history ascertainment by respondents whose households received advance recruitment materials, and inadvertent over-interpretation of verbatim reports by interviewers, may have also caused some overestimation. Also, this analysis used data from a follow-up interview (since respondent demographic data were not obtained in the baseline interview several weeks earlier), and it is possible that differential loss of respondents with less family history awareness introduced some bias.
An additional caveat is that study conclusions can only be drawn about the interpretive value of family history reports and not about their accuracy, as the latter was not evaluated in the present analysis and will be reported elsewhere. However, the distribution of reported cancers did show consistency with other studies: for example, four of the five most common cancers in family members (i.e., breast, lung, colorectal, and prostate) were also reported as the top four in a cancer screening trial of 149,332 participants in 10 U.S. locations (35
), and in the 2000 NHIS (17
). Although our survey was conducted in 2001, we are not aware of time trends that would render these results obsolete; in fact, our telephone response rates may have been higher than what could now be achieved (45
). Finally, the ability to draw conclusions about childhood cancers is somewhat limited since respondents’ grandchildren were excluded from ascertainment (although childhood cancers were ascertained from included relatives).
In primary care settings, recording and utilization of family health information may be limited by time or other considerations (18
). Therefore, data collection tools that enable patients to record family histories on their own time and transfer the information to their clinicians are potentially very useful. In recent years, a number of computerized tools have been developed to support family history ascertainment in broad populations (23
). Public use software, such as My Family Health Portrait, CDC Family Healthware™
, and others (47
) aim to promote and facilitate patient and consumer-based collection of family history information for risk assessment and health promotion purposes. Recent progress has been made toward standardizing core family history information to integrate into electronic health records (50
). The identification of five qualitative categories of cancer reports in this study provides a conceptual framework for designing such tools in ways that help shift the distribution of cancer responses towards consistency and site-specificity. For example, including definitions of cancer and site-specific descriptions (particularly for confusing sites like abdominal organs), or culturally sensitive suggestions regarding how to approach family members for information, may help reduce the percentage of ill-defined or inconsistent reports. However, additional research is needed to refine current family history data collection methods.