Critical Analysis: Coffee, Tea, Endometrial Cancer Risk - RPCI Study

This report presents a critical analysis of a hospital-based case-control study investigating the relationship between coffee and tea consumption and the risk of endometrial cancer. The study, conducted at Roswell Park Cancer Institute (RPCI), examined the dietary habits of women diagnosed with endometrial cancer and a control group. The analysis focuses on the methodology, including data collection via questionnaires and statistical approaches used to determine associations between beverage consumption and cancer risk. The report assesses the study's strengths, such as its efforts to minimize bias, and weaknesses, like the potential for inaccurate consumption measurements and limitations in dietary assessment. It also explores the study's findings, which suggest an inverse relationship between regular coffee and tea intake and endometrial cancer risk, and discusses the study's contribution to existing literature on diet and cancer, as well as its limitations in establishing causality, considering factors like the timing of dietary influences and potential biases in study design. The analysis evaluates the internal validity of the study, considering potential biases related to dietary assessment and the challenges in establishing causal relationships between diet and chronic diseases, and also appraises the study's ability to infer causality using Bradford Hill's criteria. The report concludes by summarizing the study's contribution to the understanding of the relationship between coffee, tea, and endometrial cancer, and highlighting areas for further research.

Running Head: CRITICAL ANALYSIS 1
Critical Analysis: Higher Regular Coffee and Tea Consumption is Associated with Reduced
Endometrial Cancer Risk
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CRITICAL ANALYSIS 2
Critical Analysis: Higher Regular Coffee and Tea Consumption is Associated with Reduced
Endometrial Cancer Risk
There are many studies that have sought to find the link that exists between diet and
particular diseases and conditions. According to the recommendations made by the experts, it is
possible to prevent death and disability from some nutrition-related diseases through physical
activity and proper dieting (World Health Organization, 2003). For this reason, diet and the
mitigation or reduction of diseases has always been an issue that is taken seriously over the
years. In the current study, Susan et al (2009) focus on the connection between coffee and tea
and their impact on endometrial cancer. The research relied on a hospital-based approach of
examining women at Roswell Park Cancer Institute (McCann, Yeh, Rodabaugh, & Moysich,
2009). The research monitors the women’s consumption of black tea, coffee, and decaffeinated
coffee in a span of 6 years before their final diagnosis and the information is constantly collected
through questionnaires. Through this approach, it is possible for the researchers to study the
connection between regular consumption of coffee and exposure to endometrial cancer
(McCann, 2009). This critical appraisal will rely on Bradford Hill’s causality principles as well
as the Strobe guidelines in its quest to understand the validity of this study.
Overview of the study
The author’s state the purpose of this study in a clear way at the end of their introduction
(McCann, 2009).. Their aim was to examine the association that exists between the consumption
of tea, coffee and endometrial cancer through a hospice based-case study that was undertaken at
Roswell Park Cancer institute. However, there are several other aspects that the article overlooks
that would have been useful in making the introductory part of the study more focused and
complete. To begin with, the study lacks a clear statement of its objectives and hypotheses.

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Without these critical tenets, the research lacks pointers to the overall direction of the study.
Moreover, the study does not state or clearly describe its study design or provide adequate
information on how the study would meet its objectives (McCann, 2009).. Despite these
deficiencies, I consider this research strong with useful insights into the relationship between
exposure to coffee and tea and their impact on this form of cancer.
Methodology
The data that was used for analysis in this study was collected with the help of Roswell’s
Patient Epidemiologic Data System (McCann, 2009).. The period for the study was between
1982 and 1998 under the approval of the Institutional review board. The patients who visited the
RPCI for cancer treatment of diagnosis were given a detailed epidemiologic questionnaire and
541 participants managed to return the forms. A larger number of the individuals took 2 months
from their day of diagnosis to participate in the study. Only 541 women who had their uteruses in
healthy condition served as the controls. These women were randomly selected from a pool of
5650 candidates who were eligible for the process and only had a scare of neoplastic disease but
were not found to have any dangerous conditions (McCann, 2009).. According to Keeble, Law,
Barber, and Baxter (2015), selection bias is an important aspect of consideration in
epidemiological studies because it can affect results and lead to compromised conclusions.
Therefore it is essential that selection bias is minimized in order to promote consistency across
different studies and eventually save on time and resources that would have been otherwise
consumed in repeating the research. In this aspect, the study minimized selection bias which
would have compromised its findings. In case- control studies, such as the current one, a bias can
always arise when trying to determine whether an individual is a “case” or not” (Pearce, 2016).
The study does excellently in classifying a participant as a case in an objective manner making

CRITICAL ANALYSIS 4
sure that the bias is eliminated completely (McCann, 2009). The cases were matched against the
controls across a period of five years.
The 16- page PEDS questionnaires used in this study was self-administered by the
participants. It covered information on consumption of alcohol, their history of cancer, exposures
to cancer at work or their environment, consumption of alcohol, medical and reproductive
histories, diet, and the use of vitamins or medication (McCann, 2009). The 44- item food
frequency questionnaire was used to query the diet the participants had a few years prior to the
diagnosis. However, the category of beverages was questioned in a separate avenue from the
food frequency questionnaire and it involved questions on the number of cups of coffee,
decaffeinated coffee, and black tea that the participants took on a daily basis. According to
Edwards (2010), self-administered questionnaires are desirable in such studies because they
allow the interviewee to answer the questions at their own pace and limit the involvement of the
investigator ensuring that there is little vulnerability to information bias and other interviewer
effects. For this reason, the decision by the researchers to rely on self- administered
questionnaires is important because it guarantees the credibility of the feedback considering the
some of the issues the participants were required to respond to are sensitive.
Data Analysis and Results
In this study, only participants that had complete data on their use of tea and coffee were
considered in the analyses (McCann, 2009).. The SAS for windows 9.1 version of Statistical
Analysis System was used to carry out all the two-sided analyses with at p<0.05 significance. In
Analyzing continuous variables, the authors used t-tests while the chi-square was used to
investigate the categorical variables. These statistical approaches were useful in determining the
differences that exist in descriptive characteristics between the controls and the cases. Because of

CRITICAL ANALYSIS 5
the nature of the multivariate factors under consideration in this study, the decision to use the t-
tests and chi-square for two continuous and categorical variables is appropriate (Chatfield, 2018).
To determine the link that exists between the consumption of beverages and endometrial cancer,
the authors grouped each beverage into three; more than 2 cups daily, 1-2 cups daily, half a cup
daily, and none (McCann, 2009). The combined consumption of tea and coffee was categorized
into: more than 4 cups daily, 2.5- 4 cups daily, 1-2 cups daily, and 0.5 cups daily. The measure
of the link between the exposure and outcome for each category, in reference to the nondrinkers,
was carried out with concurrent logistic regression adjustments for endometrial risk factors and
age was conducted at 95 percent confidence intervals.
The overall result indicated that the negative link with risk to endometrial cancer was
negligible for women who consumed more than 2 mugs of coffee on a regular basis compared to
the nondrinkers (McCann, 2009). Equally, the results showed a major inverse link between risk
to endometrial cancer and consumption of more than 2 mugs of black tea on a regular basis.
Finally, there was an inverse association between the consumption of more than 4 cups of coffee
and tea and risk to endometrial cancer. The study does well in accounting for all the variables
with all the basic date described in an adequate manner. All the results are presented clearly in
tabular format and there are sufficient details provided to help the reader make personal
conclusions on the subjects. In the analysis of the results, the study uses appropriate and well-
known statistical methods (McCann, 2009). For instance, the use of confidence intervals in this
case is important is quantifying the uncertainty that exists within a measurement (Bland, 2015).
With the use of the right statistical tools and approaches, the researchers present information that
is credible and reliable.

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Discussion
In the discussion, the study points out that there are limited studies on the topic and they
all point to an inverse connection between endometrial cancer and frequent intake of tea and
coffee (McCann, 2009). The authors provide context to their findings and provide more details
on the trends that were evident from the study. They reflect on the calculated statistics and try to
give scientific reasons as to why coffee and tea mitigate endometrial cancer. In addition, the
authors point out the strengths and weaknesses of their study. First, they assert that the trends and
results indicated that there was no selection bias in their study. For the limitation, they make it
clear that miscalculation could arise due to the fact that they did not have a standard size of cup
for all the participants. Thus, measuring consumption through the “number of cups” might have
been inaccurate in some sense contributing to the inaccuracy of the findings. Furthermore, the
questionnaire that was used in this study to investigate frequency of food intake had not been
validated in the study but they made up for this by having standardized questions on the
consumption of tea and coffee. Finally, the authors note that the control women were patients at
the hospital and there might have been a possibility of altering their diets before getting
admission to hospital (McCann, 2009). This would have been the same for women with
endometrial cancer and this might have led to a weakening of the observed results.
Appraisal of Internal Validity
In an overall sense, this is a well-timed study that contributes to an area that is lacking in
knowledge (McCann, 2009). It adds to the little pool of knowledge that exists on the link
between the frequent intake of coffee and tea and the risk of endometrial cancer. It is worth
noting that he validity and reliability of the various approaches used to justify this research are
appropriate and this makes it credible to a greater sense. However, there are some aspects of the

CRITICAL ANALYSIS 7
study that fall into the trap similar studies have encountered and this compromises on some
aspects of its validity. The upside of this study is that, the authors have made a mention of most
of these challenges in the discussion section of their research (McCann, 2009). Commenting on
similar studies, Delgado-Rodrigous and Llorca (2004) present various issues that could affect
their internal validity. To begin with, the fact that the relationship between diet and chronic
diseases are different from that between deficiency or acute disease and diet is the first challenge
that the study seems to assume (Oria & Suitor, 2007). The problem with this approach is that, the
techniques that are available for evaluation do not reflect on this and it results in a bias or
inaccurate conclusion of such studies. Parekh et al (2007) add to this study by saying that factors
such as the complex and slow nature of development of chronic diseases, the timing of dietary
influences, and bias due to inherent study designs leads to wrong conclusions.
Equally, the diet-time relationship is another aspect that affects the internal validity of the
study. This is because the time at which the diet is measured can have more of an influence on
the accuracy of the estimate than the method that is used to measure the diet and this can lead to
a bias (Quatromoni et al., 2002). The best way out of this problem is to get multiple estimates of
the dietary intake over a period of time so as to have a true reflection on the disease under study
(Hoffman et al., 2002). Moreover, the change in diet over a period of time can bring in other
aspects of uncertainties (Byers, 1987). This was proved by Moeller and coworkers (2006) in their
study to collect data in two separate periods.
Appraisal of Causality Inference
As is admitted by the authors, the current study on the connection between the ingesting
of coffee and tea and endometrial cancer is confirmatory in nature (McCann, 2009). There have
been various studies that have been conducted over the years, albeit in different locations, that

CRITICAL ANALYSIS 8
make similar conclusions about the topic (Je & Giovannucci, 2012, Shimizu et al., 2008. Friberg
et al., 2009). Going by Hill’s criteria, the consistency on replication under similar circumstances
showed by these results point to causality of the variables under study (Goodman, 2014).
However, all these studies explain the inverse association in diverse ways taking away the
specificity of coffee and tea as mitigators of endometrial cancer. Particularly, studies such as
those by Friberg et al (2009) explain that the link coffee has with endometrial cancer is strictly
for women that do not have a track record of using any form of hormone therapy and their
evidence shows that such links are stronger in overweight and obese individuals as compared to
the leaner participants.
Appraisal of External Validity
The authors do not make a mention of whether the findings of the study can apply to the
general population (McCann, 2009). However, similar studies conducted in different locations
indicate that replicable results can be obtained if the study is repeated in other areas. According
to Giri et al (2011) there is a “plausible biological evidence” as well as sufficient epidemiologic
evidence to indicate that the consumption of coffee leads to a consequent decrease in the risk of
endometrial cancer. Other studies indicate that the compounds that are present in coffee play the
crucial role of eliminating carcinogenic elements within the body (Lukic et al., 2018, Yang et al.,
2018, Crous-Bou et al., 2016). This is an indication that the findings of this study can be
generalized and still be applicable in a wide range of situations, places, and periods.
Conclusion
Apart from the various aspects that might have compromised the accuracy of this study
such as study lacks a clear statement of its objectives and hypotheses or a clear description of the
study designs and main objectives, the findings are crucial additions to the existing body of

CRITICAL ANALYSIS 9
knowledge on the association between the consumption of tea and coffee and endometrial
cancer. The results revealed that there was a significant inverse association of consuming either
>2 cups of regular coffee and >4 cups of combined tea and coffee in reducing endometrial cancer
risk in comparison to nondrinkers. When compared to the findings from other studies, it is clear
that these findings are consistent and bring in an added explanation on the link that might exist
between endometrial cancer, coffee and tea. Furthermore, the findings from this study are
impressive because they add a new perspective and explanation on the inverse association
between coffee, tea, and endometrial cancer in a pool that has many possible explanations for the
situation.

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References
Bland, M. (2015). An introduction to medical statistics. Oxford University Press (UK).
Byers, T., Marshall, J., Anthony, E., FIEDLER, R., & Zielezny, M. (1987). The reliability of
dietary history from the distant past. American Journal of Epidemiology, 125(6), 999-
1011.
Chatfield, C. (2018). Introduction to multivariate analysis. Routledge.
Crous-Bou, M., De Vivo, I., & Epidemiology of Endometrial Cancer Consortium. (2016). Coffee
and tea intake and risk of endometrial cancer in the Epidemiology of Endometrial Cancer
Consortium (E2C2). Cancer Research, 76(14), 1751-175. http://dx.doi.org/10.1158/1538-
7445.AM2016-1751
Delgado-Rodrigous M, Llorca J (2004). Bias. Epidemiol Community Health
Edwards, P. (2010). Questionnaires in clinical trials: Guidelines for optimal design and
administration. Trials, 11(1), 2. https://doi.org/10.1186/1745-6215-11-2
Friberg, E., Orsini, N., Mantzoros, C. S., & Wolk, A. (2009). Coffee drinking and risk of
endometrial cancer—a population‐based cohort study. International Journal of
Cancer, 125(10), 2413-2417. https://doi.org/10.1002/ijc.24543
Giri, A., Sturgeon, S. R., Luisi, N., Bertone-Johnson, E., Balasubramanian, R., & Reeves, K. W.
(2011). Caffeinated coffee, decaffeinated coffee and endometrial cancer risk: a
prospective cohort study among US postmenopausal women. Nutrients, 3(11), 937-950.
https://doi.org/10.3390/nu3110937
Goodman, K. J., & Phillips, C. V. (2014). Hill's criteria of causation. Wiley StatsRef: Statistics
Reference Online.

CRITICAL ANALYSIS 11
Hoffmann, K., Boeing, H., Dufour, A., Volatier, J. L., Telman, J., Virtanen, M., ... & De
Henauw, S. (2002). Estimating the distribution of usual dietary intake by short-term
measurements. European Journal of Clinical Nutrition, 56(S2), S53.
https://doi.org/10.1038/sj.ejcn.1601429
Je, Y., & Giovannucci, E. (2012). Coffee consumption and risk of endometrial cancer: Findings
from a large up‐to‐date meta‐analysis. International Journal of Cancer, 131(7), 1700-
1710. https://doi.org/10.1002/ijc.27408
Keeble, C., Law, G. R., Barber, S., & Baxter, P. D. (2015). Choosing a method to reduce
selection bias: A tool for researchers. Open Journal of Epidemiology, 5(3), 155-162.
http://dx.doi.org/10.4236/ojepi.2015.53020
Lukic, M., Guha, N., Licaj, I., van den Brandt, P. A., Stayner, L. T., Tavani, A., & Weiderpass,
E. (2018). Coffee drinking and the risk of endometrial cancer: An updated meta-analysis
of observational studies. Nutrition and Cancer, 70(4), 513-528.
https://doi.org/10.1080/01635581.2018.1460681
Moeller, S. M., Parekh, N., Tinker, L., Ritenbaugh, C., Blodi, B., Wallace, R. B., & Mares, J. A.
(2006). Associations between intermediate age-related macular degeneration and lutein
and zeaxanthin in the Carotenoids in Age-related Eye Disease Study (CAREDS):
ancillary study of the Women's Health Initiative. Archives of Ophthalmology, 124(8),
1151-1162. https://doi.org/10.1001/archopht.124.8.1151
McCann, S. E., Yeh, M., Rodabaugh, K., & Moysich, K. B. (2009). Higher regular coffee and tea
consumption is associated with reduced endometrial cancer risk. International Journal of
Cancer, 124(7), 1650-1653. doi:10.1002/ijc.24125.

CRITICAL ANALYSIS 12
Oria, M., Yaktine, A., & Suitor, C. W. (Eds.). (2007). Nutritional Risk Assessment: Perspectives,
Methods, and Data Challenges: Workshop Summary. National Academies Press.
Parekh, N., Chappell, R. J., Millen, A. E., Albert, D. M., & Mares, J. A. (2007). Association
between vitamin D and age-related macular degeneration in the Third National Health
and Nutrition Examination Survey, 1988 through 1994. Archives of
Ophthalmology, 125(5), 661-669. https://doi.org/10.1001/archopht.125.5.661
Pearce, N. (2016). Analysis of matched case-control studies. British Medical Journal, 352, i969.
https://doi.org/10.1136/bmj.i969
Quatromoni, P. A., Copenhafer, D. L., Demissie, S., D'agostino, R. B., O'horo, C. E., Nam, B.
H., & Millen, B. E. (2002). The internal validity of a dietary pattern analysis. The
Framingham Nutrition Studies. Journal of Epidemiology & Community Health, 56(5),
381-388. https://dx.doi.org/10.1136%2Fjech.56.5.381
Shimazu, T., Inoue, M., Sasazuki, S., Iwasaki, M., Kurahashi, N., Yamaji, T., & Tsugane, S.
(2008). Coffee consumption and risk of endometrial cancer: a prospective study in
Japan. International Journal of Cancer, 123(10), 2406-2410. doi:10.1002/ijc.23760.
World Health Organization. (2003). Diet, nutrition, and the prevention of chronic diseases:
report of a joint WHO/FAO expert consultation (Vol. 916). World Health Organization.
Yang, T. O., Crowe, F., Cairns, B. J., Reeves, G. K., & Beral, V. (2015). Tea and coffee and risk
of endometrial cancer: cohort study and meta-analysis. The American Journal of Clinical
Nutrition, 101(3), 570-578. doi:10.3945/ajcn.113.081836.