Reviewer's report
Title:Consumption of Coffee Reduces Risk for Liver Cancer: A Meta-Analysis
Version: 3Date:24 December 2012
Reviewer: Susan Stewart
Reviewer's report:
The authors have responded to the reviews and made several improvements,
resulting in a much more polished manuscript.
Major compulsory revisions: Unfortunately, they have added two sentences to
their conclusions that are unwarranted. 1) A negative association between coffee
consumption and liver cancer incidence found in observational studies is
insufficient basis for suggesting that coffee could be used as an adjunct in liver
cancer management. 2) Although additional cohort studies could provide a more
precise estimate of relative risk, and extend the geographical area covered,
conducting more observational studies is likely to be of limited value in
understanding this association and elucidating the biological mechanisms by
which coffee may reduce the risk of liver cancer.
Minor essential revisions:
1. The authors revised their analysis to include the most extreme comparison in
the Inoue (2005) study, overall (figure 2) and in the analyses stratified by study
type (figure 4). However, it appears that the analyses by study region (figure 5)
were not updated. Also, the results given in the abstract were not updated. The
authors need to update all places in the manuscript affected by the risk estimate
for the Inoue (2005) study (and to verify that the most extreme comparisons for
this study were used in the gender-specific analyses).
2. Materials and methods
a. Search strategy: A key word is missing at the end of the first list of key words:
“lifestyle OR)”.
b. Statistical analysis: The text should say, “Otherwise” (rather than “In addition”)
“a random effects model was used.”
3. Discussion: Regarding the meta-analyses of Bravi et al. and Larsson & Wolk
(“Susanna” should be changed to “Larsson”), the authors do not go far enough in
describing the overlap: it should be noted that all of the studies in these two
articles are included in the authors’ analysis. Also the statements about the
results of the two articles are not quite correct. Bravi et al. found a relative risk of
0.45 (55% reduction) for high consumption vs. non-drinkers. Larsson & Wolk
found a risk reduction of 43% per 2 cups of coffee per day increment.
4. The format for references 29-31 should be made consistent with that of the
other references.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
Reviewer's report
Title:Consumption of Coffee Reduces Risk for Liver Cancer: A Meta-Analysis
Version: 3Date:24 December 2012
Reviewer: Susan Stewart
Reviewer's report:
The authors have responded to the reviews and made several improvements,
resulting in a much more polished manuscript.
Major compulsory revisions: Unfortunately, they have added two sentences to
their conclusions that are unwarranted. 1) A negative association between coffee
consumption and liver cancer incidence found in observational studies is
insufficient basis for suggesting that coffee could be used as an adjunct in liver
cancer management. 2) Although additional cohort studies could provide a more
precise estimate of relative risk, and extend the geographical area covered,
conducting more observational studies is likely to be of limited value in
understanding this association and elucidating the biological mechanisms by
which coffee may reduce the risk of liver cancer.
Minor essential revisions:
1. The authors revised their analysis to include the most extreme comparison in
the Inoue (2005) study, overall (figure 2) and in the analyses stratified by study
type (figure 4). However, it appears that the analyses by study region (figure 5)
were not updated. Also, the results given in the abstract were not updated. The
authors need to update all places in the manuscript affected by the risk estimate
for the Inoue (2005) study (and to verify that the most extreme comparisons for
this study were used in the gender-specific analyses).
2. Materials and methods
a. Search strategy: A key word is missing at the end of the first list of key words:
“lifestyle OR)”.
b. Statistical analysis: The text should say, “Otherwise” (rather than “In addition”)
“a random effects model was used.”
3. Discussion: Regarding the meta-analyses of Bravi et al. and Larsson & Wolk
(“Susanna” should be changed to “Larsson”), the authors do not go far enough in
describing the overlap: it should be noted that all of the studies in these two
articles are included in the authors’ analysis. Also the statements about the
results of the two articles are not quite correct. Bravi et al. found a relative risk of
0.45 (55% reduction) for high consumption vs. non-drinkers. Larsson & Wolk
found a risk reduction of 43% per 2 cups of coffee per day increment.
4. The format for references 29-31 should be made consistent with that of the
other references.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
Please review this paper.
user
Reviewer's report
Title:Consumption of Coffee Reduces Risk for Liver Cancer: A Meta-Analysis
Version: 3Date:24 December 2012
Reviewer: Susan Stewart
Reviewer's report:
The authors have responded to the reviews and made several improvements,
resulting in a much more polished manuscript.
Major compulsory revisions: Unfortunately, they have added two sentences to
their conclusions that are unwarranted. 1) A negative association between coffee
consumption and liver cancer incidence found in observational studies is
insufficient basis for suggesting that coffee could be used as an adjunct in liver
cancer management. 2) Although additional cohort studies could provide a more
precise estimate of relative risk, and extend the geographical area covered,
conducting more observational studies is likely to be of limited value in
understanding this association and elucidating the biological mechanisms by
which coffee may reduce the risk of liver cancer.
Minor essential revisions:
1. The authors revised their analysis to include the most extreme comparison in
the Inoue (2005) study, overall (figure 2) and in the analyses stratified by study
type (figure 4). However, it appears that the analyses by study region (figure 5)
were not updated. Also, the results given in the abstract were not updated. The
authors need to update all places in the manuscript affected by the risk estimate
for the Inoue (2005) study (and to verify that the most extreme comparisons for
this study were used in the gender-specific analyses).
2. Materials and methods
a. Search strategy: A key word is missing at the end of the first list of key words:
“lifestyle OR)”.
b. Statistical analysis: The text should say, “Otherwise” (rather than “In addition”)
“a random effects model was used.”
3. Discussion: Regarding the meta-analyses of Bravi et al. and Larsson & Wolk
(“Susanna” should be changed to “Larsson”), the authors do not go far enough in
describing the overlap: it should be noted that all of the studies in these two
articles are included in the authors’ analysis. Also the statements about the
results of the two articles are not quite correct. Bravi et al. found a relative risk of
0.45 (55% reduction) for high consumption vs. non-drinkers. Larsson & Wolk
found a risk reduction of 43% per 2 cups of coffee per day increment.
4. The format for references 29-31 should be made consistent with that of the
other references.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
assistant