Table 2.
Women's perceptions of benefits and harms of screening
| No (%) of patients | |
|---|---|
| Perceptions of harms | |
| Do you agree that “if a woman getting mammograms turns out not to have breast cancer, she may have been harmed by the mammograms”? | 38 (8) |
| False positives | |
| “Imagine a typical, healthy 60 year old woman. Assume that you know nothing else about her. Suppose that this 60 year old woman has yearly mammograms for the next 10 years and she does not have breast cancer. What is the chance that she will have a ‘false alarm’ where one of her mammograms will look like she has cancer even though she doesn't?” | Median 20/100, 25th percentile=10%, 75th percentile=48% |
| “Is information about false alarms something you want to factor into your decision about getting a mammogram?”* | 182 (38) |
| Non-progressive cancer | |
| Do you agree that “some types of breast cancer grow so slowly that even without treatment they would not affect a woman's health”? | 34 (7) |
| Presentation of ductal carcinoma in situ (DCIS) information†: “Have you heard about DCIS before this survey?”* | 29 (6) |
| “Is information about DCIS something you want to factor into your decision about getting a mammogram?”* | 287 (60) |
| Perceptions of benefits | |
| Do you agree that “if a woman getting mammograms turns out to have breast cancer, she may have benefited from the mammograms”? | 450 (94) |
| Sensitivity of mammography | |
| “Imagine a typical, healthy 60 year old woman. Assume that you know nothing else about her. Now imagine this 60 year old woman has breast cancer but no obvious symptoms. What is the chance a mammogram will find the cancer?” | Median 73/100, 25th percentile=50%, 75th percentile=86% |
| Magnitude of benefit | |
| “All things being equal, if this 60 year old woman got yearly mammograms for the next 10 years, she would have . . .” | |
| A higher or unchanged chance of dying of breast cancer | 34 (7) |
| A lower chance of dying of breast cancer: | |
| By one fifth to one tenth | 62 (13) |
| By one third | 120 (25) |
| By a half | 263 (55) |
| Reduced to zero | 0 (0) |
95% confidence intervals ranged from 4% to 6% in either direction for all percentages. Questions preceded by ‘do you agree’ used a five point Likert scale (strongly agree to strongly disagree); the proportion agreeing is those who answered “strongly agree” or “agree.”
*
Percentage of women answering “yes.”
†
Women were given a brief explanation of ductal carcinoma in situ as a lesion that does not always progress to invasive cancer.