Risk of breast cancer in symptomatic women in primary care: a case-control study using electronic records

Abstract

Background: Breast cancer is the most common cancer in the UK. GPs are encouraged to refer all women whose symptoms may represent cancer, rather than selecting those at highest risk.

Aim: To identify and quantify features of breast cancer in primary care.

Design and setting: A UK case-control study using the Clinical Practice Research Database (CPRD).

Method: Possible features of breast cancer were identified in the year before diagnosis, and odds ratios calculated using conditional logistic regression. Positive predictive values (PPVs) were estimated for consulting women.

Results: A total of 3994 women aged ≥40 years with breast cancer between 2000 and 2009, and 16 873 age-, sex-, and practice-matched controls were studied. Median age at diagnosis was 63 years (interquartile range 55-74 years). Four features were significantly associated with breast cancer: breast lump (odds ratio [OR] 110; 95% confidence interval [CI] = I88 to 150), breast pain (OR = 4.2; 95% CI = 3.0 to 6.0), nipple retraction (OR = 26; 95% CI = 10 to 64), nipple discharge (OR = 19; 95% CI = 8.6 to 41): all P-values <0.01. In the year before diagnosis, 1762 (44%) of cases had a breast lump compared with 132 (0.8%) controls. The PPV of breast cancer with a breast lump was 4.8% in women aged 40-49 years, rising to 48% in women aged >70 years. PPVs were lower in women who also reported breast pain.

Conclusion: Generally, the figures support current referral practice. However, the low likelihood of cancer for all the non-lump symptoms means that the current guidance recommends investigation for possible cancer at a more liberal risk threshold than for other cancers. Although supported by patients, this may not meet current NHS criteria for cost-benefit.

Keywords: breast cancer; diagnosis; primary health care.

Figure 1.

Application of exclusion criteria for cases and matched controls.

Figure 1.

Positive predictive value (PPV) for breast cancer for women reporting features of the cancer to primary care (aged ≥40 years). 1) The top figure in each cell is the PPV when the feature is present. The two smaller figures represent the 95% CIs for the PPV. These have not been calculated when any cell in the 2×2 table was < 5 (invariably this was because too few controls had the feature). 2) The yellow shading is for symptoms with a PPV > 1.0%; the orange shading is when the PPV is >2.0%; and the red shading is for PPVs >5.0%. 3) The breast lump/pain column is the PPV when a woman has reported both a breast lump and breast pain at least once each during the year before the index date. ^aNipple retraction was only reported by 4 cases and 0 controls aged 40–49 years. Thus no PPV can be calculated, although it is likely to be high. ^bBreast lump and breast pain were reported by 8 cases and 0 controls. Again, no PPV can be calculated, but given the relatively large number of cases with this combination, it has been estimated as >5%.