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Page 10 of 13 Jiang et al. Hepatoma Res 2020;6:52 I http://dx.doi.org/10.20517/2394-5079.2020.47

suggested that the proportion of late-diagnosis of PLC in the older age group was higher, resulting in poor
[39]
long-term survival .

When comparing survival rates in different countries, times, or populations, etc., the following points need
to be considered. Firstly, the relative survival rate was the only indicator analyzed in this review. However,
descriptive indicators of cancer survival also include observed survival rate (all the OSRs collected
were showed in Supplementary Table 3), cause-specific survival, etc. The estimation methods and their
interpretations are completely different and cannot be substituted for each other. Next, close attention to
additional comorbidities or variables (such as age, gender, ethnicity, etc.) used in survival rate estimation
in the study is required. As in this review, some studies excluded patients aged under 15 or 20 during analy
sis [11,18,21,30,34,35,44,47] . Thirdly, it should be noted whether DCO cases or autopsy cases were excluded from the
analysis, which would affect outcomes.

In conclusion, we summarized one to five-years RSRs of liver cancer, which were markedly distinct between
different regions or periods in the same region. This implied that the region, period, and age might affect
the survival rate of PLC; however, whether gender is a relevant factor remains to be studied. Therefore,
more attention should be drawn to PLC prevention and screening, in particular, must be developed and
implemented. Epidemiological, basic, and clinical studies of PLC have a long way to go still.

DECLARATIONS
Authors’ contributions
Conducted the study and collected publications and abstract data and wrote the first draft: Jiang YF
Double check the collected publications and abstract data: Li ZY
Reviewed and approved the final version of the paper: Jiang YF, Li ZY, Ji XW, Shen QM, Tuo JY, Yuan HY,
Xiang YB
Primary responsibility for final content, designed the research study and obtained funding: Xiang YB

Availability of data and materials
Not applicable.

Financial support and sponsorship
This work was supported by the National Key Project of Research and Development Program of China
(No. 2016YFC1302503); the National Key Basic Research Program of China “973 Program” (No.
2015CB554000); the State Key Project Specialized for Infectious Diseases of China (No. 2008ZX10002-015
and No. 2012ZX10002008-002).

Conflicts of interest
All authors declared that there are no conflicts of interest.

Ethical approval and consent to participate
Not applicable.

Consent for publication
Not applicable.

Copyright
© The Author(s) 2020.