This study found that age, tumor stage, treatment were independent risk factors affecting survival time of patients. The survival time of patients aged over 75 years is significantly shorter than that of patients aged under 75 years old. Elderly patients are often accompanied by organ dysfunction, decreased immunity, and various chronic diseases. When clinicians choose treatment strategies according to pathological characteristics and clinical stages of tumors and so on, the basic physiological status of patients gave enough attention and the significance of different treatment methods to the prognosis, survival and quality of life of patients should also be considered. In the clinical treatment, it is common to choose relatively conservative treatment strategies when patients are too old, which may cause that some older patients do not receive more suitable treatment, thus affecting the survival time of patients. In this study, age is negatively correlated with survival time. Firstly, the patient's own physical condition is taken into account, and secondly, whether the choice of clinical treatment also affects the survival time of patients because they are too old.
The best treatment for elderly EC patients has always been controversial. Most scholars believe that surgery has great trauma to elderly patients and chemotherapy has many toxic and side effects, so radiotherapy is recommended for elderly patients with esophageal cancer [15, 16]. With the rapid development of minimally invasive surgical techniques and anesthesia techniques, the feasibility and safety of surgical treatment for elderly EC patients have been confirmed [17, 18]. Lymph node dissection is an important step in esophageal cancer surgery. Previous studies showed that the more lymph nodes dissected, the more accurate postoperative staging, and the better long-term prognosis of patients [19, 20]. However, extensive lymph node dissection lengthens the operative time and increases intraoperative bleeding, resulting in increased perioperative complications and mortality [21]. Elderly patients with esophageal cancer have short life expectancy, poor postoperative recovery ability and high risk of perioperative death [22]. Therefore, surgeons should consider the pros and cons of lymph node dissection in elderly patients.
Our study also suggests that surgery and combination therapy may have a significant survival benefit in elderly patients with esophageal cancer. A large number of studies have basically confirmed that surgically-based combination of radiotherapy and chemotherapy has significant efficacy for young patients with esophageal cancer or patients with good physical fitness [23, 24]. For advanced esophageal cancer, some studies have advocated the use of radiotherapy alone or combination of radiotherapy and chemotherapy [25]. However, for elderly advanced EC patients, the poor physical quality, declined organ function, reduced tolerance of treatment and late onset characteristics of esophageal cancer can affect the choice of treatment methods and treatment effect, which need more sample size and the research of higher quality to explore the suitable treatment methods in elderly EC patients.
The 5-year survival rate of early esophageal cancer is improved by more than 90% after the comprehensive therapy of surgery, radiotherapy and chemotherapy, but the 5-year survival rate of middle and advanced esophageal cancer is not optimistic. Esophageal cancer in the elderly is mostly in the middle and late stage, with many complications, poor physique and poor efficacy. Most patients seek medical treatment after obvious symptoms. After comprehensive treatment, the efficacy is also poor, and most patients die within 1 year. In this way, it is expected to strengthen the elderly tumor survey work in the future, early detection, early diagnosis, early reasonable treatment, in order to improve the survival period of the elderly esophageal cancer.
In our study, it was found that the 5-year survival rate of elderly patients with EC stage I was 53.4%, and the median survival time was 64 months while the 5-year survival rate of EC stage Ⅳ was 26.5%, and the median survival time was 22 months. TNM staging of esophageal cancer is a general comprehensive judgment of the stage in the development of esophageal cancer, which integrates three indicators (Tumor size, lymph node, metastasis) that have an important impact on the prognosis of EC patients, so it is an important factor affecting the treatment and prognosis of patients with EC [5, 26]. The earlier the tumor stage, the higher the surgical resection rate, the better the treatment effect. Therefore, early detection, early surgical resection and comprehensive treatment are the main measures to improve the prognosis of esophageal carcinoma. The prognosis of esophageal cancer is highly correlated with tumor stage, which suggests the importance of early detection of esophageal cancer with lower stage and early diagnosis and treatment to prolong the survival time.
The occurrence of esophageal cancer is related to environment, diet and lifestyle, poverty. Low income, high-temperature drinks and food can increase the incidence of esophageal cancer [27-31], and smoking and excessive drinking are also one of the important risk factors of esophageal cancer [32, 33]. The occurrence of esophageal cancer is also related to the polymorphism of genetic loci and thus EC has genetic susceptibility [34]. Esophageal cancer in China has obvious regional distribution characteristics of high incidence, mainly distributed in Taihang Mountain system, Qinling Mountain system and Huaihe River system, followed by Guangdong and Fujian coastal areas [35, 36]. The experience in the prevention and treatment of EC shows that the key strategy to EC prevention and treatment is early detection, early diagnosis and early treatment. The combined operation techniques of endoscopic screening, iodine staining of esophageal mucosa and indicative biopsy are the most practical and effective methods at present [37]. Wei et al.[38] conducted a 10-year follow-up study on the study cohort of more than 45,000 people in Cixian County, Hebei province, a high-incidence site of esophageal cancer, and found that endoscopy as an early screening method for esophageal cancer can effectively reduce the morbidity and mortality of esophageal squamous cell carcinoma. Since 2005, China's Ministry of Health has launched a population-based endoscopic screening program in 11 high-risk areas, which has been expanded to cover more than 110 cities and counties in 29 provinces in China. The implementation results of the program show that esophageal cancer screening has a high detection rate, early diagnosis rate and treatment rate, with good performance [37]. It is expected to strengthen the elderly tumor survey work in the future, early detection, early diagnosis, early reasonable treatment, in order to improve the survival period of the elderly esophageal cancer. Therefore, it is very necessary to strengthen the early detection, early diagnosis and early reasonable treatment of esophageal cancer, in order to improve the survival period of esophageal cancer in the elderly, especially on elderly population.
However, our study also had some limitations. Firstly, in the study, different levels of diagnostic evaluation and treatment in different hospitals may have influenced the results. In future studies, we will investigate more cases in city and county hospitals. Secondly, smoking, alcohol consumption status and other variables associated with EC are self-reported, which led to recall bias. As a result, people who have never smoked may be misclassified, especially those who have been ever smokers and stopped smoking for less than 15 years. In addition, the proportion of the missing data of some variables such as differentiation status was relatively high, but our previous study had verified that it was within a reasonable range [14]. Further more detailed data are required to increase the precision of the effect for these exposures and explored more factors related to EC survival.