Making Sense of Cancer Risk Calculators on the Web

Objective

Cancer risk calculators on the internet have the potential to provide users with valuable information about their individual cancer risk. However, the lack of oversight of these sites raises concerns about low quality and inconsistent information. These concerns led us to evaluate internet cancer risk calculators.

Design

After a systematic search to find all cancer risk calculators on the internet, we reviewed the content of each site for information that users should seek to evaluate the quality of a website. We then examined the consistency of the breast cancer risk calculators by having 27 women complete 10 of the breast cancer risk calculators for themselves. We also completed the breast cancer risk calculators for a hypothetical high- and low-risk woman, and compared the output to Surveillance Epidemiology and End Results estimates for the average same-age and same-race woman.

Results

Nineteen sites were found, 13 of which calculate breast cancer risk. Most sites do not provide the information users need to evaluate the legitimacy of a website. The breast cancer calculator sites vary in the risk factors they assess to calculate breast cancer risk, how they operationalize each risk factor and in the risk estimate they provide for the same individual.

Conclusions

Internet cancer risk calculators have the potential to provide a public health benefit by educating individuals about their risks and potentially encouraging preventive health behaviors. However, our evaluation of internet calculators revealed several problems that call into question the accuracy of the information that they provide. This may lead the users of these sites to make inappropriate medical decisions on the basis of misinformation.

Appendices

Appendix 1: Risk factors of the hypothetical high and low breast cancer risk women

The high-risk patient is a 55-year-old, 5′2″, 150-lb Jewish woman who smokes. Her mother had breast and ovarian cancer, and two sisters had breast cancer, one of whom also had ovarian cancer. She has no personal history of cancer and no other family history of cancer. She has no significant medical history except for benign breast disease and two negative breast biopsies. She had no pregnancies, no live births, began menstruating at age 11, reached menopause at age 53, and did not have a hysterectomy. She took oral contraceptives for 10 years and stopped 10 years ago. She did not take hormone replacement therapy. She does not have annual mammograms or conduct regular self breast exams. She has poor nutrition and exercise habits (the worst option in response to questions assessing these two risk factors was entered on each site).

The low-risk patient is a 55-year-old, 5′5″, 115-lb African-American woman who does not smoke. She has no family history of any cancer and no personal history of cancer. She has had no biopsies and has not been diagnosed with benign breast disease and no other significant medical history. She has had 3 pregnancies, which all resulted in live births, breast fed for a total of 2 years, and had her first child at age 24. Menstruation began at age 14; she reached menopause at age 47 and has not had a hysterectomy. She never took oral contraceptives or hormone replacement therapy. She has annual mammograms and conducts regular self breast exams. She has good nutrition and exercise habits (the best option in response to questions assessing these two risk factors was entered on each site).

Other risk factor questions were either answered as “unknown/not sure” or were answered randomly and recorded.

Appendix 2: Risk factors for sample subjects presented in Table 4

Risk factor	Subject 16	Subject 1	Subject 37	Subject 31
First period before age 12?	No*	No*	Yes†	No*
First child after age 30?	No*	No*	No*	No*
Childless?	Yes*	Yes*	Yes*	No†
Mother had/has breast cancer?	No*	Yes†	No*	No*
Sisters had/has breast cancer?	No†	No†	No†	No†
Daughters had/has breast cancer?	No†	No†	No†	No†
Ever had breast biopsy?	No†	No†	No†	Yes*
Doctor ever tell you biopsy showed premalignant or precancerous condition?	No†	No†	No†	No†
Doctor ever tell you that one of your biopsies showed early cancer that had not spread yet?	No†	No†	No†	No†
Have you ever used birth control pills?	No*	No*	No*	No*
Ashkenazi Jewish?	No†	No†	No†	No†

1. *Status of this risk factor is risk increasing (e.g., is Ashkenazi Jewish).^†Status of this risk factor is risk decreasing (e.g., is not Ashkenazi Jewish).