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Appendix of Randomized Controlled Trials

continued...

Ostergotland (County E of Two-County Trial), Sweden 1977[6,7,8]

Age at entry: 40 to 74 years.
Randomization: Geographic cluster, with stratification for residence (urban or rural), socioeconomic factors and size. Baseline breast cancer incidence and mortality were comparable between the randomly assigned geographic clusters. The study women were older than the control women, P < .0001, but this should not have had a major effect on the outcome of the trial.
Exclusions: Women with pre-existing breast cancer were excluded from both groups, but the numbers are reported differently in different publications. The Swedish meta-analysis excluded all women with a prior breast cancer diagnosis, regardless of group assignment.
Sample size: Variably reported, ranging from 38,405 to 39,034 in study and from 37,145 to 37,936 in control.
Consistency of reports: Variable.
Intervention: Three single-view MMGs every 2 years for women younger than 50 years and every 33 months for women 50 years and older.
Control: Usual care, with MMG at study end.
Compliance: 89% screened.
Contamination: 13% of women in the Two-County trial had MMG as part of routine care, mostly in 1983 and 1984.
Cause of death attribution: Determined by a team of local physicians. When results were recalculated in the Swedish meta-analysis, using data from the Swedish Cause of Death Registry, there was less benefit for screening than had been previously reported.
Analysis: Evaluation initially, with correction for delay in control group MMG. Follow-up analysis, as part of the Swedish meta-analysis.[5]
External audit: No. However, breast cancer cases and deaths were adjudicated by a Swedish panel that included the trial's investigators.[9]
Follow-up duration: 12 years.
Relative risk of breast cancer death, screening versus control (95% CI): 0.82 (0.64–1.05) Ostergotland.
Comments: Concerns were raised about the randomization methodology and the evaluation analysis, which required a correction for late performance of the control group MMG. The Swedish meta-analysis resolved these questions appropriately.

Kopparberg (County W of Two-County Trial), Sweden 1977 [6,7,8]

Age at entry: 40 to 74 years.
Randomization: Geographic cluster, with stratification for residence (urban or rural), socioeconomic factors and size. The process for randomization has not been described. The study women were older than the control women, P < .0001, but this should not have had a major effect on the outcome of the trial.
Exclusions: Women with pre-existing breast cancer were excluded from both groups, but the numbers are reported differently in different publications.
Sample size: Variably reported, ranging from 38,562 to 39,051 in intervention and from 18,478 to 18,846 in control.
Consistency of reports: Variable.
Intervention: Three single-view MMGs every 2 years for women younger than 50 years and every 33 months for women aged 50 years and older.
Control: Usual care, with MMG at study end.
Compliance: 89% participation.
Contamination: 13% of women in the Two-County trial had MMG as part of routine care, mostly between 1983 and 1984.
Cause of death attribution: Determined by a team of local physicians (see Ostergotland).
Analysis: Evaluation.
External audit: No. However, breast cancer cases and deaths were adjudicated by a Swedish panel that included the trial's investigators.[9]
Follow-up duration: 12 years.
Relative risk of breast cancer death, screening versus control (95% CI): 0.68 (0.52–0.89).
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