We assessed the accuracy of reported family history of breast, colorectal, prostate, and lung cancers. Overall, specificity and NPV were high, whereas sensitivity and PPV were low to moderate. One or more of the measures of accuracy was affected by cancer type and by degree of relatedness to the respondents. Breast cancer reports had the highest sensitivity and PPV, whereas colorectal cancer had the lowest sensitivity and PPV. Except for prostate cancer, PPV was statistically significantly higher for reports on FDR than for those on SDR. In general, cancer history obtained on relatives with a completed living relative/proxy interview had higher measures of accuracy.
The sensitivity of family history reports for the four adult cancers in our study was lower than previously reported by other studies, particularly for colorectal and prostate cancers. In one review (23
), sensitivity of family history reports ranged from 72% to 95% for breast cancer, 30% to 90% for colorectal cancer, and 47% to 79% for prostate cancer (23
). The lower sensitivity observed in the Connecticut FHS could be because of its population-based design. Many previous estimates of family cancer history reporting accuracy used information collected in specialty clinics or from respondents who themselves had cancer, who were perhaps more knowledgeable about their family cancer history than the general population. No differences in reporting sensitivity by respondents’ personal cancer history were observed in the Connecticut FHS (data not shown), but the number of cancer-affected respondents was small, and most of the cancers were nonmelanoma skin cancer. We defined false negative as a report of no cancer for a relative found to have cancer by any of the confirmation sources; an accurate report of other cancers for relatives with more than one cancer diagnosis, but the cancer of interest was not mentioned; or a report of cancer at a different site. Overall, the numbers of reports of inaccurate cancer type were small, and some of the sites named were within the same system or anatomical region or could represent a metastasis. Prostate cancer had the most false-negative reports classified as “no cancer reports”. Perhaps prostate cancer is less openly discussed in families, and men are generally less willing to discuss health issues or disseminate health information (9
), leading to low awareness among relatives of this cancer diagnosis.
Overall, PPV was low, ranging from 40% (lung cancer) to 61.3% (breast cancer). Higher PPV has been reported previously, particularly for breast cancer (24
). Potential reasons for false-positive reports include a misunderstanding of the benign vs malignant nature of the tumor (eg, fibroadenoma reported as breast cancer) and confusion between primary and metastatic site (eg, lung metastasis vs primary lung cancer). Because family history can affect the recommendations for breast and colorectal cancer screening (5
), a low PPV could lead to overscreening. Furthermore, family history is essential in cancer risk estimation (25
) and evaluation for hereditary cancer syndromes (27
); consequently, inaccurate family history reports could lead to inappropriate risk management recommendations or unnecessary referral for genetic evaluation. Thus, there is a need to promote family cancer history awareness and to find better tools to capture it accurately, to ensure that appropriate risk assessment and clinical care recommendations can be made. One potential approach to improving family cancer history awareness, and consequently, family history report accuracy, is to raise general knowledge of cancers within the community. Improved knowledge about cancer might encourage people to be more willing to communicate about it with others, either when sharing information about their own diagnoses or when asking for information about their relatives’ diagnoses.
Specificity and NPV were very high for all four cancers. Cancer diagnoses were rare among relatives in this study; thus, this finding is not surprising. Furthermore, our confirmation sources might have missed some cancer diagnoses. Consequently, some of the actual false-negative reports might have been misclassified as true negative because they were never confirmed.
We observed that accuracy varied by cancer type, with breast cancer reports being the most accurate, consistent with prior literature (24
), which presumably reflects different levels of respondent awareness by cancer types. Women in general are more likely to be the family disseminator of health information (9
) and thus might be more likely to share information about their own breast cancer diagnosis. Within families, some cancers, such as colorectal (14
), might be less openly discussed, leading to decreased awareness and inaccurate reports.
Our results showed greater, although non-statistically significant, sensitivity and PPV for reported family history of breast, prostate, and lung cancers by female respondents. The association between respondents’ sex and accuracy of reported family cancer history has been inconsistent, with some studies showing no differences (15
) and others showing more accurate reports by women (31
). We found that measures of accuracy were associated with degree of relatedness, as previously reported (24
). Closely related relatives are more likely to share information. In addition, SDR include grandparents, who might be deceased, making their health information less readily available.
Cancer history information obtained on relatives for whom a living relative/proxy interview was also completed had higher measures of accuracy, which could be an artifact of verification method. Because the living relative/proxy interview served as a cancer confirmation source, positive reports on these relatives would be more likely to be confirmed. However, the ability to obtain consent for the interview might be an indication that the respondent kept close contact with the relative and thus was more knowledgeable about the relative’s health history.
Our study has several strengths. First, this was a population-based survey in which we attempted to confirm all cancers reported on a randomly selected sample of relatives. The respondents in this study were more representative of the population seen in primary care clinics, where initial cancer risk assessment usually takes place, and of population control subjects randomly sampled into case–control studies. Therefore, our observation of low to moderate sensitivity and PPV for family cancer history may have important implications regarding the potential extent of reporting error in population surveillance, risk assessment, and risk estimation. Second, a large percentage of the sampled relatives reported living all their lives in Connecticut. As a result, we were able to effectively use the CTR as the main confirmation source. In addition, a small but important number lived in nearby states with long-standing tumor registries. Finally, this study focused on the four major adult cancers most common in the United States and whose risk has been shown to be affected by a positive family history.
There were also some limitations to this study. We were not able to obtain pathology report–based cancer registry data (the “gold standard” for assessing accuracy of cancer history reports) for all sampled relatives because of missing SSN or other critical personal identifiers or lack of a participating tumor registry where the relative resided. In addition, there were variations in matching methods, percentage of pathology-confirmed cancers, and start date across state registries. The methods used in this study have been used as the standard in several prior studies and represent the best confirmation sources available (23
). Except for cancer registries, all the other confirmation sources have limitations. When cancer is the direct cause of death, death certificates are accurate and can serve as an adequate source of cancer confirmation (33
), but when cancer is unrelated to the immediate cause of death, a cancer history would not necessarily be recorded. For example, in the US Radiologic Technologists Study, death certificates did not identify 35.2% of cancer patients identified by cancer registries (35
). Consequently, using death certificates as the only source of cancer confirmation can potentially result in an overestimation of false-positive reports (ie, falsely low PPV). Alternatively, data abstracted from Medicare claims databases are sensitive for cancer diagnoses (36
) but might include other diagnoses or procedures coded as cancers (38
), resulting in a falsely low sensitivity. Furthermore, self-reported cancers or cancers reported by proxies might not be accurate because one cancer can often be mistaken for another, depending on the location and nature of the disease. In this study, for the subset of relatives who lived only in Connecticut, there were cancers identified in at least one of the other sources, specifically by the Centers for Medicare and Medicaid Services, which were not recorded in the CTR (data not shown). It is unclear to what extent cancer diagnoses were overreported by administrative claims databases and might have contributed to the observed low sensitivity.
Alternatively, it is inevitable that some of the cancer reports were accurate but were not confirmed by any of the sources available and thus were classified as false positives. It is unclear how much of an impact this classification might have had on the results; however, we made every attempt to match the relatives with all of the confirmation sources available.
Although the study was population based, the participants were not strictly representative of Connecticut or the United States overall (18
), with individuals of minority and low socioeconomic status being underrepresented. Thus, our results are most generalizable to the non-Hispanic white population of Connecticut and similar populations. In addition, because the eligibility criteria restricted the respondents to age 25–64, the results might not be generalizable outside of this age range. Furthermore, the interview data are approximately 10 years old; however, we are not aware of any data suggesting that accuracy of family cancer reports has markedly changed in recent years. Finally, although respondents were not asked to prepare for the first interview, some may have chosen to gather family history information anyway, thus increasing reporting accuracy and limiting extrapolation of our findings to primary care or research settings that lack opportunities for advance ascertainment.
In summary, the sensitivity and PPV of a reported family history of lung, colorectal, breast, and prostate cancers in this population-based survey were low to moderate, especially among SDR, but the specificity and NPV were high. Given that the population from which we sampled is similar to primary care populations, the results of this study suggest that family cancer history collected in the primary care setting might be useful as an initial screening tool, and, if positive, confirmation of the reported cancers is needed for the purpose of making cancer screening recommendations or referral to a specialty clinic. Verification of family cancer history can be cumbersome, given the lack of a readily available electronically linkable source. Promoting awareness, encouraging people to ask questions about cancer in their family, and using pre-visit information collection tools such as that proposed in the Surgeon General’s Family Health History Initiative might help improve family cancer history report accuracy.