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Jiang et al. Hepatoma Res 2020;6:52 I http://dx.doi.org/10.20517/2394-5079.2020.47 Page 9 of 13

of patients who have been hospitalized, which reflects the service’s capacity and treatment effects in a
particular department. For example, using follow-up data in a hospital’s registry, a study in Qidong of
[55]
Jiangsu Province from China calculated the 5-year observed survival rate of patients with liver cancer
from 2002 to 2016 to be 14.6% [Supplementary Table 3], which was higher than the population-based OSR
of 8.9% reported in the general population of Qidong during 2001-2007. For hospital-based survival, the
follow-up time starts from the first hospitalization date, while the population-based cancer registry starts
from the date of diagnosis of cancer. However, according to the data in China, the survival rates of PLC
in the more developed areas such as Shanghai and Zhejiang were higher than that of other areas and the
national average during the similar period, and studies have additionally supported the observation that
the survival rates of PLC in urban areas were higher than that in the rural areas for the same period.

A common reason to study population-based cancer survival is to estimate the net survival, a measure of
[56]
patient survival following primary cancer in the absence of other causes of death , which can be obtained
by calculating disease-specific survival. Since the estimation of net survival must rely on complete and
accurate information on the cause of death, which is often difficult to obtain, an alternative indicator -
[5]
RSR - can be used. RSR is defined as the ratio of the observed survival rate (where all causes of deaths are
considered as events) to the expected survival rate (which is estimated from national population life tables
stratified by sex, age, and calendar period) in the general population with the same distribution of key
demographic factors (sex, age, calendar, period, and country). It provides a measure of the excess mortality
hazard experienced by cancer patients, irrespective of whether the excess mortality is directly or indirectly
[56]
attributable to the cancer and enables direct comparison of survival rates between different populations
or regions by eliminating the effects of age, gender, ethnicity, and calendar period on cancer survival to
some extent. In addition, to further eliminate the effect of age structure, international comparisons of RSRs
ought to use age-standardized relative survival .
[57]

It is apparent from our review then that the prognosis of PLC has shown continuous improvement
overtime, whether in China or around the world. Over the past decades, numerous changes in clinical
practice, public health, and social economy may affect the survival of PLC. For instance, advances
in imaging diagnosis, clinical treatment such as chemoembolization, ablation, and surgical resection
techniques, increased surveillance and screening for early-stage disease and anti-cancer health education,
the improvement of socio-economic status (SES) and the transformation of peoples’ health consciousness
and lifestyles [39,58,59] . However, it is these factors that can improve survival rates that may lead to regional
disparity in survival rates of PLC as well, because of their varying degrees of development between different
regions. Globally, the 5-year RSRs in Africa such as Eastern Libya and Uganda Kampala are much poorer
than in the countries of Europe and North America during the same time period, and 5-year RSRs of
PLC were also varied across regions in Europe. Studies have shown that people from the highest SES have
better survival outcomes compared to those in the lowest SES [60-62] . The low SES and the attendant delayed
diagnosis and treatment, unfair distribution of medical resources, incomplete medical insurance systems,
lack of health education, and other factors will all affect cancer survival.

The data we have summarized from the literature implied that there are gender and age disparities in liver
cancer survival. For example, in the majority of countries and regions, the prognosis of liver cancer in
women was better than men, although the situation was not systematic. Therefore, it is inappropriate to
draw the conclusion that the prognosis of women with PLC is better than men. Gender-specific distinctions
in the survival rate of PLC require more population-based follow-up studies. In terms of the age at
diagnosis, survival was highest among patients in the 35-44 age group, followed by the 45-54 age group,
and lowest for the 75 or older age group. This might have been due to the presence of comorbidities and
various chronic diseases in the aged patients that reduced their tolerance of cancer treatments or affected
physicians’ decisions for treatment options, as compared to younger patients [63-65] . In addition, studies have