Estimation of life expectancy of patients diagnosed with the most common cancers in the Valparaiso Region, Chile

Background The 1000s of people who die from cancer each year have become one of the leading causes of death among the Chilean population, placing it as the second cause of death in the region of Valparaiso between 1997 and 2003. Statistics have provided different measures regarding the life expectancy of cancer patients which have resulted in being useful to establish courses of action for prevention and treatment plans to follow. Methods Data was extracted from the cancer module of the Epidemiology Assistance System (SADEPI for its initials in Spanish) which stores information about cancer cases in the provinces of Valparaiso and Petorca. The survival period is defined as the difference in days between the date of occurrence and the date of death of the patient by separating the data into quartiles. Results The more frequent cancers in the region of Valparaiso behave similarly to global behaviours of the disease. The majority of affected patients are around 65 years of age which progressively lowers its occurrence in younger adults under the age of 45. Conclusions Further efforts are required for early detection and timely access to treatment for cancer patients. Statistics are an important support in achieving this.


Introduction
The changing lifestyle of the population and exposure to risk factors has led to the emergence and increasing cases of chronic, noncommunicable diseases such as cancer.
In most developed countries, cancer is the second cause of death after circulatory diseases [1][2][3]. Because of population growth and ageing, it is estimated that global cancer mortality will increase by 45% by the year 2030, and the number of new cases will go from 11.3 million in 2007 to 15.5 million in 2030.
In Chile, according to several studies conducted since the end of the last century, malignant tumours are the second leading cause of death. Published data on the occurrence of malignant tumours in the last two decades of the 20th century in Chile, revealed an increase in mortality rates from 98-118 per 100,000 population [5]. These mortality rates have continued to increase up to 133 and 135.3 deaths in 2009 and 2010 respectively [6][7]. The publication "Cancer Status in Chile 2000-10" reveals that the Valparaiso Region is the most affected area. In this study 13 out of 16 types of analysed cancers presented rates higher than the national average rates [7]. This fact suggests that continuous studies on cancer prevalence in the Valparaiso Region are still needed to develop appropriate prevention policies.
Statistics have provided various measures regarding the life expectancy of cancer patients [8][9]. For example, according to the National Cancer Institute of the United States (NCI), the index of relative five year survival for women diagnosed with breast cancer during the period 2001-7 was 89% and for patients diagnosed with lung cancer during the same period was 16% [10]. Therefore only 16% of patients diagnosed with lung cancer survived more than five years in relation to people without cancer. This displays the application of statistical methods to analyse the prognosis of a patient in a standard way.
Historically, such detailed analysis of life expectancy of cancer patients in Chile has not been possible. The National Health System in Chile did not record statistical data that would allow them to be carried out until recently. The regional computer platforms for recording cancer data have just been implemented. The registration of data in these computer platforms has made possible studies of obesity as a risk factor for the development of certain types of cancer [6], and the trend of cancer mortality according to the educational level of the adult population [11]. Similarly, the recoded data on cancer patients has made possible the analysis of the epidemiological transition of cancer, the global burden of cancer, and trends in cancer mortality, and its occurrence in Chile [12].
Since statistics are based on large groups of people, we cannot predict what will happen with a particular patient. This is because of personal differences, differences in treatment, and the patients' response to it. Nevertheless, statistical measures are useful to establish courses of action in prevention and planning of treatment plans to follow.
A key factor in cancer treatment is early detection because many times cases are detected in advanced phases, when organ function is compromised and cancer cells have spread in the body. Therefore, the detection of cancer in early stages is critical in order to design a treatment plan that will greatly increase the chances of it being effective.
The objective of this study is to analyse the occurrence of cancer in the Valparaiso Region thereby further identifying the survival period. This period is the time elapsing from the date of occurrence to the date of death of a patient who suffers from some type of cancer, and it is registered in the cancer module of the Epidemiology Assistance System (SADEPI for its initials in Spanish).
We are also seeking to identify the occurrences and subsequent death for certain types of cancers in a given region and the age groups associated with it.

Data
The data used was extracted from the SADEPI database, specifically from the Cancer Module, which stores information regarding cancer cases in the provinces of Valparaiso and Petorca and from the Causes of Death module. www.ecancer.org ecancer 2017, 11:713 The criterion for choosing the set of cancers to be used in the study is based on the locations of the cancers with higher mortality [5] in the region of Valparaiso and the highest number of cases in the Cancer Module. Thus six different cancers were selected (Table 1) and these included malignant stomach tumour, malignant colon tumour, malignant gallbladder tumour, others and unspecified, malignant neoplasm of the pancreas, malignant neoplasm of the trachea, bronchi, and lung, malignant breast tumour. All these together caused 49 % of all cancer deaths between 2010 and 2011. Table 2 shows that the occurrence distribution of four of these six cancers is not statistically different (by using a χ 2 test of identity of distribution) from those observed worldwide (p = 0.05).
The results of the relationship between the date of occurrence of cancer cases and the date of death of the patients using statistical techniques are presented here. The six types of cancers which are studied are among the mostly frequently occurring in the population and for which there are registries of the patient's cases, including information regarding the date of occurrence and date of death.
For age analysis at the time of the patient's occurrence and death date, cases where the date of birth was known were considered.
For each cancer case the survival period was calculated as the difference in days between the date of occurrence and the date of death of the investigated patients suffering from different types of cancers. Once this data was obtained, it was separated into quartiles to facilitate the analysis.

Results
Survival Time (Table 3) The first quartile groups 25% of the patients who survived fewer days from the detection of their cancer. For this quartile the obtained results show that the malignant gallbladder tumour caused more rapid deaths from its detection in which patients  Table 3 and a comparison of the lifetime between the dates of occurrence to death divided by quartiles is shown in detail in Figure 1. Age at date of occurrence and date of death The age of death was divided into four ranges: 15-29 years of age, 30-44 years of age, 45-64 years of age, and 65 or older. The Figure  2 shows the occurrence of the six types of cancer under study according to the age ranges.

Gallbladder, other parts and non-specified parts of the bile duct (C23-C24) (Table 7)
In the year 2010, malignant tumours of the gallbladder, other parts, and non-specified bile duct registered a total of 173 deaths related to this type of cancer of which 65.9% corresponded to women and 34.1% to men. In 2011 these figures were steady at 66.0% for women and 34.0% for men. Regarding the age of occurrence 60.9 % of cases occur in or over age 65, followed by 32.6 % aged 45-64 years, and 6.5 % for patients aged 30-44 years.

Discussion
The short survival times from the occurrence of cancer to the death of the patient show that early detection plans, control, and monitoring of risk factors (where relevant) to improve the quality and life expectancy of the patients are necessary.
The results of the study show that one of the cancers with shortest survival time from occurrence is malignant tumour of the gallbladder which is present more frequently in countries of the Andean Zone [12] such as Chile. This cancer is usually detected when a person presents signs or symptoms which indicate that the illness is in its advanced stages. This contrasts with breast cancer which is one of the cancers with highest survival although considered to be one of the most frequent cancers and main causes of death in woman globally [13]. It multiplyiies several times the survival time obtained by malignant gallbladder tumours. Some epidemiological studies have already identified ethnic disparities like the high occurrence in American Indians who have malignant tumours of the gallbladder [14], showing in particular [15] high rates in Chilean Mapuche Indians [16]. www.ecancer.org ecancer 2017, 11:713 Contrary to the present study, these articles show that among Chilean women, gallbladder cancer is the first cause of cancer death, more frequent than breast, lung, and cervical cancers. We notice here that the gallbladder carcinoma is the second cause after the breast cancer and about the same statistical level than lung and stomach cancers. This high prevalence in women (not observed in men) is due probably to a combination of genetic factors, multiparity, or elevated BMI classically associated with a higher risk of developing gallbladder carcinoma [17].
As for the age of death and occurrence of malignant tumours of the stomach, colon as well as trachea, bronchus, and lung, the analysis shows that in Chile, as in other parts of the world [18][19][20], the majority of affected patients are around 65 years of age. The occurrence decreases in younger adults under 45 years of age [21][22][23] where cases in general are usually caused by a genetic predisposition.

Conclusion
The specificities of the cancer situation in Chile are related to the educational policy for cancer prevention, for which specific information, screening, and preventive therapies have been recommended: • Chile has implemented restrictions on tobacco availability to minors [24].
• Chile has launched screening programmes of early detection of cholelithiasis as this is found in approximately 85% of people with gallbladder cancer [25]. This has led to systematic cholecystectomy or ultrasonic therapy after a nationwide gallbladder cancer study [26][27] done by US NIH, Chilean Regional Hospitals of Antofagasta, Concepcion and Temuco, and the Hospital Sotero del Rio of Santiago. The study also showed that the risk populations in Chile all share a high prevalence of gallstones and/or Salmonella typhi infections favouring cholelithiasis. • Chile has improved the typhoid fever vaccination because it has been thought that typhoidic endemy during the 70s could have affected the occurrence of cancer of the gallbladder [28]. • Chile is edicting public health recommendations rules with specific food labelling indicating the danger of sugar and fat in processed food to prevent obesity, a disease frequently associated with cancer (see for example [29]).
These current and some other future efforts are required to promote prevention and early detection of cancers in order to allow both improvement of health education level, empowerment, and timely access to treatment by affected patients. www.ecancer.org ecancer 2017, 11:713