In a recent study published in the British Journal of Cancer, a group of researchers investigated the association between pre-diagnosis tea and coffee consumption and survival rates in women diagnosed with ovarian cancer (Cancer originating in the ovaries).
Study: Pre-diagnosis tea and coffee consumption and survival after a diagnosis of ovarian cancer: results from the Ovarian Cancer Association Consortium. Image Credit: andriano.cz/Shutterstock.com
Background
Ovarian cancer, the seventh leading cause of cancer death among women globally, has a 5-year survival rate below 50%. Tea and coffee, widely consumed beverages, contain compounds that may influence ovarian cancer risk and survival.
Green tea, rich in bioactive polyphenols like epigallocatechin-3-gallate (EGCG), shows potential anti-cancer effects, including antioxidant activity, inhibition of angiogenesis, and apoptosis stimulation.
Meta-analyses suggest an inverse relationship between green tea consumption and ovarian cancer risk, while no strong link is found with coffee or caffeine. Limited data suggest green tea may benefit survival after an ovarian cancer diagnosis. Further research is needed to confirm these potential benefits and explore the mechanisms.
About the study
Researchers analyzed data from one cohort, one case-only, and eight case-control studies of ovarian cancer from the Ovarian Cancer Association Consortium (OCAC), providing dietary information through the Multidisciplinary Ovarian Cancer Outcomes Group (MOCOG).
After excluding women missing dietary or follow-up information, those with more than two years between diagnosis and interview, and 240 women who died, the analysis included 5,724 women.
The Queensland Institute of Medical Research (QIMR) Berghofer Medical Research Institute pooled and harmonized dietary data. All studies received institutional review board approval, and participants provided informed consent.
Tea and coffee consumption before diagnosis was assessed and categorized using food frequency questionnaires (FFQ), with study-specific quartiles created for caffeine intake.
Covariate information included age, education, body mass index (BMI), race/ethnicity, smoking status, physical activity, and menopausal hormone therapy use. Clinical information covered histotype, tumor stage, and residual disease after surgery.
Survival time was calculated from diagnosis to death or last follow-up. Cox proportional hazards regression estimated hazard ratios (HR) and 95% confidence intervals (CI) for survival associations, adjusted for age and stratified by tumor stage, study, and histotype, with additional adjustments for race, BMI, education, smoking status, and physical activity.
Associations were also analyzed based on stage of disease, race, residual disease, histotype, menopausal status, BMI, smoking, or physical inactivity. Analyses were conducted using SAS version 9.4 and STATA version 13.
Study results
The study included women with an average diagnosis age of 57 years, mostly diagnosed with advanced high-grade serous carcinoma (HGSC), a highly aggressive ovarian cancer type.
As expected, advanced disease, older age, HGSC, residual disease after surgery, obesity (BMI > 30), and smoking were linked to worse survival outcomes.
No link was found between coffee, herbal tea, black tea, or caffeine consumption before diagnosis and overall survival. However, drinking one or more cups of green tea daily was significantly associated with better survival, with a fully adjusted hazard ratio (HR) of 0.84.
There was no significant variation among the five studies analyzed for green tea consumption. The effect estimate was below 1.0 in four studies, with one study showing a non-significant positive association.
When individual studies were excluded, pooled estimates ranged from 0.79 to 0.87.
No significant differences were found in survival based on the stage of disease, BMI, smoking status, physical activity, menopausal status, cancer histotype, residual disease, or study site.
The only significant variation was seen with black tea, which was linked to worse survival among pre-menopausal women, and herbal tea, which was linked to worse survival among former smokers and pre-menopausal women in two studies. However, these results were based on small numbers, likely due to chance.
Sensitivity analyses showed similar results, even when including women who died within the first year and truncating survival at five years after diagnosis. The results were consistent when considering death from ovarian cancer specifically, with an HR of 0.81 for those who drank at least one cup of green tea daily.
Conclusions
To summarize, this study supports the hypothesis that higher green tea consumption is associated with better survival among women with ovarian cancer. No consistent associations were found between other types of tea, coffee, or caffeine intake and overall survival. Variations between sub-groups are likely due to chance.
Previous studies have shown mixed results, with one Australian study finding no significant association and another reporting a comparable estimate for green tea.
However, a study in China found an inverse association between green tea and ovarian cancer-specific survival. The potential benefits of green tea are attributed to EGCG, which affects tumorigenesis-related pathways.
Recent studies underscore the importance of diet for the prevention of cancer