Breast carcinoma in situ: Risk factors and screening patterns

Background: Risk factors associated with invasive breast cancer are well do cumented, but those associated with breast carcinoma in situ are not well d efined. Methods: We conducted a population-based, case-control study among female residents of Connecticut to identify risk factors for breast carcino ma in situ. Case patients, diagnosed with ductal carcinoma in situ (DCIS) ( n = 875) or lobular carcinoma in situ (LCIS) (n = 123), were matched by 5-y ear age groups with control subjects (n = 999). Case patients were diagnose d between September 15, 1994, through March 14, 1998, and all subjects were between the ages of 20 and 79 years. Information on risk factors and cance r-screening history was collected by telephone interviews. Conditional logi stic regression was used to determine odds ratios (ORs) for the association of these factors with the risk of DCIS and LCIS. Results: Case patients wi th DCIS were more likely than control subjects to report a family history o f breast cancer (OR 1.48; 95% confidence interval [CI] 1.19 to 1.85) or pre vious breast biopsy (OR = 3.56; 95% CI = 2.86 to 4.43). They also had fewer full-term pregnancies (OR = 0.86; 95% CI = 0.80 to 0.93) and were older at first full-term pregnancy (OR for being 20-29 years old relative to being < 20 years old = 1.68; 95% CI = 1.17 to 2.43) and at menopause (OR for bein g greater than or equal to 55 years old relative to being < 45 years old = 1.71; 95% CI = 1.05 to 2.77). DCIS case patients were more likely than cont rol subjects to have had a mammographic examination (OR = 2.46; 95% CI = 1. 78 to 3.40) or an annual clinical breast examination (OR = 1.83; 95% CI = 1 .48 to 2.26). DCIS patients and control subjects did not differ with respec t to oral contraceptive use, hormone replacement therapy, alcohol consumpti on or smoking history, or breast self-examination. Associations for LCIS we re similar. Conclusions: The risk factors associated with DCIS and LCIS are similar to those associated with invasive breast cancer. Diagnosis of DCIS is associated with increased mammography screening.