Validity of Danish Breast Cancer Group (DBCG) registry data used in the predictors of breast cancer recurrence (ProBeCaRe) premenopausal breast cancer cohort study

Abstract

Background: Validation studies of the Danish Breast Cancer Group (DBCG) registry show good agreement with medical records for adjuvant treatment data, but inconsistent recurrence information. No studies have validated changes in menopausal status or endocrine therapy during follow-up. In a longitudinal study, we validated DBCG data using medical records as the gold standard.

Material and methods: From a cohort of 5959 premenopausal women diagnosed during 2002–2010 with stage I–III breast cancer, we selected 151 patients – 77 estrogen-receptor-positive and 74 estrogen-receptor-negative – from three hospitals. We assessed the validity of DBCG registry data on patient, tumor, and treatment factors, and follow-up information on menopausal transition, changes in endocrine therapy, and recurrence. We computed positive predictive values (PPVs) with 95% confidence intervals (95%CI).

Results: Agreement was near perfect for tumor size, lymph node involvement, receptor status, surgery type, and receipt of radiotherapy, chemotherapy, or tamoxifen treatment. The PPV for a change in endocrine therapy in the DBCG was 96% (95%CI = 83, 100). The PPV for menopausal transition was 61% (95%CI = 42, 77). The PPV for DBCG-recorded recurrence was 100%. However, of 19 patients who had a recurrence documented in their medical record, 13 had the recurrence registered in DBCG.

Conclusions: DBCG data are valid for most epidemiological studies of breast cancer treatment. Data on menopausal transition may be less valid, though this interpretation depends on the suitability of medical records for making this assessment. Although recurrence is missing for some, this would not bias most ratio measures of association.

Acknowledgments

The authors thank the Danish Breast Cancer Group for preparation of the initial dataset, and Henriette Kristoffersen and Hanne M. Madsen for reviewing medical records.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The study was supported by grants from the US National Institutes of Health, National Cancer Institute (R01CA166825) (T.L.L.), the Program for Clinical Research Infrastructure (PROCRIN), established by the Lundbeck Foundation and the Novo Nordisk Foundation (H.T.S.), and the Lundbeck Foundation (R167-2013-15861) (D.C.F.), and Susan G. Komen for the Cure (CCR13264024) (T.P.A.). The funding agencies had no role in the design of the study; the collection, analysis, and interpretation of the data; the writing of the article; or the decision to submit the article for publication.