Validity and Representativity in the Danish Breast Cancer Cooperative Group

Jensen, Annette Østergaard; Storm, Hans H.; Møller, Susanne; Overgaard, Jens

doi:10.1080/02841860310000737

Cited by 32 publications

(15 citation statements)

References 9 publications

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“…Use of the DBCG and Danish registries ensured high quality data on breast cancer diagnosis, treatment, and recurrence, and virtually complete follow-up. 37 Due to the comprehensive registry network, a strength of our study was the possibility of adjusting for several potential confounders. However, as our crude estimates were similar to the adjusted estimates, there was little evidence of confounding.…”

Section: Discussionmentioning

confidence: 99%

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Low-dose Aspirin, Nonsteroidal Anti-inflammatory Drugs, Selective COX-2 Inhibitors and Breast Cancer Recurrence

et al. 2016

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Background Aspirin, non-steroidal anti-inflammatory drugs (NSAIDs), and selective COX-2 inhibitors may improve outcomes in breast cancer patients. We investigated the association of aspirin, NSAIDs, and use of selective COX-2 inhibitors with breast cancer recurrence. Methods We identified incident stage I–III Danish breast cancer patients in the Danish Breast Cancer Cooperative Group registry, who were diagnosed during 1996–2008. Prescriptions for aspirin (>99% low-dose aspirin), NSAIDs, and selective COX-2 inhibitors were ascertained from the National Prescription Registry (NPR). Follow-up began on the date of breast cancer primary surgery and continued until the first of recurrence, death, emigration, or 01/01/2013. We used Cox regression models to compute hazard ratios (HR) and corresponding 95% confidence intervals (95%CI) associating prescriptions with recurrence, adjusting for confounders. Results We identified 34,188 breast cancer patients with 233,130 person-years of follow-up. Median follow-up was 7.1 years; 5,325 patients developed recurrent disease. Use of aspirin, NSAIDs, or selective COX-2 inhibitors was not associated with the rate of recurrence (HRadjusted aspirin=1.0, 95% CI=0.90, 1.1; NSAIDs=0.99, 95% CI=0.92, 1.1; selective COX-2 inhibitors=1.1, 95% CI=0.98, 1.2), relative to non-use. Pre-diagnostic use of the exposure drugs was associated with reduced recurrence rates (HRaspirin=0.92, 95%CI=0.82, 1.0; HRNSAIDs=0.86, 95%CI=0.81, 0.91; HRsCOX-2inhibitors=0.88, 95%CI=0.83, 0.95). Conclusions This prospective cohort study suggests that post-diagnostic prescriptions for aspirin, NSAIDs, and selective COX-2 inhibitors have little or no association with the rate of breast cancer recurrence. Pre-diagnostic use of the drugs was, however, associated with a reduced rate of breast cancer recurrence.

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Section: Discussionmentioning

confidence: 99%

“…Since its establishment in 1976 the DBCG has registered most cases of invasive breast cancer in Denmark. 37 Registration completeness has increased over time from 87% in 1986 to 96% in 1997. 38,39 Pre-specified data on tumor, treatment, and patient characteristics are prospectively obtained from treating physicians.…”

Section: Methodsmentioning

confidence: 99%

Low-dose Aspirin, Nonsteroidal Anti-inflammatory Drugs, Selective COX-2 Inhibitors and Breast Cancer Recurrence

et al. 2016

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“…Use of tamoxifen was determined from the assigned treatment protocol for each patient collected from the DBCG database [28]. Tamoxifen exposure was defined for this study by the assigned treatment protocol for each patient to reduce confounding by non-compliance and other factors.…”

Section: Methodsmentioning

confidence: 99%

Risk of Parkinson's disease after tamoxifen treatment

et al. 2010

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BackgroundWomen have a reduced risk of developing Parkinson's disease (PD) compared with age-matched men. Neuro-protective effects of estrogen potentially explain this difference. Tamoxifen, commonly used in breast cancer treatment, may interfere with the protective effects of estrogen and increase risk of PD. We compared the rate of PD in Danish breast cancer patients treated with tamoxifen to the rate among those not treated with tamoxifen.MethodsA cohort of 15,419 breast cancer patients identified from the Danish Breast Cancer Collaborative Group database was linked to the National Registry of Patients to identify PD diagnoses. Overall risk and rate of PD following identification into the study was compared between patients treated with tamoxifen as adjuvant hormonal therapy and patients not receiving tamoxifen. Time-dependent effects of tamoxifen treatment on PD rate were examined to estimate the likely induction period for tamoxifen.ResultsIn total, 35 cases of PD were identified among the 15,419 breast cancer patients. No overall effect of tamoxifen on rate of PD was observed (HR = 1.3, 95% CI: 0.64-2.5), but a PD hazard ratio of 5.1 (95% CI: 1.0-25) was seen four to six years following initiation of tamoxifen treatment.ConclusionsThese results provide evidence that the neuro-protective properties of estrogen against PD occurrence may be disrupted by tamoxifen therapy. Tamoxifen treatments may be associated with an increased rate of PD; however these effects act after four years, are of limited duration, and the adverse effect is overwhelmed by the protection against breast recurrence conferred by tamoxifen therapy.

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“…A new comparison in 2006 showed the same tendency (Figure 2). Data quality and completeness was investigated in patients diagnosed between 1983 and 1989 in one county (n 01765) comparing DBCG recordings with a complete population-based database holding detailed information on patient characteristics, treatment and outcome [31]. The DBGC hold highquality data for the patients registered (83%), however, a substantial subset of patients (17%) were not recorded to DBCG, and for those the stage distribution was poorer and the life expectation was lower.…”

Section: Quality Controlmentioning

confidence: 99%