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

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 to150), 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 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.