2007Mar20 1

Journal Club for Analysis of Complex Datasets

Cui Y, Shu X-O, Gao Y-T, Cai H, Tao M-H, Zheng W. Assocation of ginseng use with survival and quality of

life among breast cancer patients. Am J Epidemiol 2006; 163: 645-653.

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Summary

• Objective: evaluate effects of ginseng use on breast cancer survival & survivors’ QOL.

• Design: cohort study.• Setting: Shanghai Breast Cancer Study.

– Population-based case-control study.

• Subjects: women aged 25-64 years w/ newly diagnoses breast cancer Aug1996 – Mar1998 (N=1455).– Cases from Shanghai Study.– Followed through Dec2002.

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Summary (2)• In-person interviews conducted ~66 days post-dx.• Exposure: ginseng use.

– Type, duration, & frequency of use.

• Outcome:– Overall survival.– Disease-free survival.– QOL.

• Assessed during in-person follow-up interviews for 1065 of 1248 surviving patients.

• Sociodemographic, medical, & other CAM info collected as well.

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Analysis

• Overall survival & disease-free survival:– Kaplan-Meier plots & log-rank tests.– Proportional hazards regression.

• Adjusted for age, education, income, stage of disease, estrogen & progesterone receptor status, & std cancer tx’s.

• QOL:– Linear regression.

• Adjusted for age, marital status, education, income, menopausal status, recurrence of disase, time since cancer dx, & use of other CAM.

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Results: survival

• Ginseng use:– 398 (27.4%) regular use.– 1057 (72.6%) nonusers (never used before

cancer dx).– All ginseng users received 1+ mainstream

tx.

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Results: QOL

• Ginseng use:– Before/after dx:

• Never use before or after.• Use before but not after.• Use after but not before.• Use both before & after.

– Ever/current use after dx.– Cumulative use by current users.

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Strengths

• Large population-based sample.• Excellent participation rate.• All ginseng users received mainstream tx:

– provides well-defined sample to evaluate ginseng as complementary rather than alternative therapy.

• Differentiate between types of ginseng & use:– Red (hot) used for short periods.– White Asian & American (cold) used for longer

periods.

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Strengths (2)

• QOL:– Assessed timing of ginseng use (before/after dx).– Assessed ever/current use:

• Ever users quit using ginseng?• Placebo/healthy user effect for current users?

– Assessed dose-response.• “…caution is required in interpreting the results…

findings need to be confirmed in more rigorous and randomized clinical trials.”

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Limitations

• Lack of info on ginseng use after dx for patients who died before follow-up interview.

• Unable to exclude confounding by other CAM.

• Self-reported data: potential recall & self-report bias.

• Could not evalute methods of ginseng use.

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Suggestions: Survival

• Adjusted survival curves.

• Time-dependent ginseng use (eg, QOL analysis).

• Account for timing of cancer tx.

• Adjustment for other “healthy patient” factors possibly associated with ginseng?

2007Mar20 15

Suggestions: QOL

• “…lack of ginseng’s effect on physical well-being obsrved in this study may be due to the fact that patients had already fully recovered physically by the time the survey was conducted.”– Time-dependent analysis of ginseng use &

physical state.– Authors state need to further study effect of

ginseng on physical well-being at earlier time points.

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Sensitivity analysis

• Lin DY, Psaty BM, Kronmal RA. Assessing the sensitivity of regression results to unmeasured confounders in observational studies. Biometrics 1998; 54: 948-963.

• Assess effect of unmeasured binary or normal confounder.– For binary confounder, effect is function of

prevalence & effect among E+/E- groups.

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Example from Lin et al. (1998)