Retrospective clinical case studies in recent years have shown that most cases of lung cancer and abdominal aortic aneurysm (AAA) are detected at the same time and that there is a wide variation in the prevalence of AAA in patients with primary lung cancer reported in the literature, with some papers suggesting as high as 11%, suggesting that there may be a relationship between the prevalence of the two diseases. However, its exact incidence and mechanism are unknown. Accurate prevention of AAA in patients with primary lung cancer requires more in-depth studies. To solve the above problems, a multi-center prospective epidemiological investigation and mechanism study on the association of AAA in primary lung cancer combined has become particularly urgent. The results of the study will be of great significance for the follow-up treatment and prognosis of lung cancer patients as well as the improvement of long-term survival rate of lung cancer patients, and will also provide scientific basis and clinical guidance for the screening and prevention of AAA in lung cancer patients.

1. research purpose： This study collected detailed basic information, lifestyle habits, past medical history, and laboratory indicators from 2000-3000 outpatient patients with primary lung cancer for data analysis and long-term follow-up. The study analyzed the related factors of lung cancer complicated with AAA, providing direct scientific evidence to better guide lung cancer patients in screening for AAA, identifying common high-risk factors for lung cancer patients complicated with AAA, providing clinical guidance for the prevention of AAA, and reducing the risk of AAA rupture. The research results are of great significance for the subsequent treatment and prognosis of lung cancer patients, as well as improving the long-term survival rate of lung cancer patients. They will also provide scientific basis and clinical guidance for the screening and prevention of AAA in lung cancer patients. Early detection and treatment of AAA can reduce the risk of AAA rupture, greatly improve the prognosis of lung cancer patients with AAA, and enhance their quality of life.
2. research population： The research subjects are patients diagnosed with primary lung cancer at the Third Affiliated Hospital of Kunming Medical University and the First Affiliated Hospital of Kunming Medical University from 1st October 2022 to 30 st April 2025. The expected sample size is about 2000 people, and the age of patients is 20-90 years old. Collect detailed epidemiological data and long-term follow-up data, conduct statistical analysis, and conduct epidemiological investigations.
3. Epidemiological data collection:

3.1 Basic Information: name, gender, ethnicity, age, height, weight, hometown, occupation, education level, ID card, phone number, and medical record number.

3.2 Behavioral Life Information：Whether smoking, smoking index, alcohol consumption, alcohol content and quantity consumed, history of exposure to asbestos products, dietary habits, and history of dust exposure.

3.3 Past medical history and family genetic history: Presence of hypertension, degree of hypertension, blood pressure control medications, and blood pressure control; diabetes mellitus, blood glucose control medications, and blood glucose control; hyperlipidemia, elevated lipid composition, lipid control medications, and lipid control; urologic disorders; family history of vascular disorders; and family history of oncologic disorders.

3.4 Laboratory information: Blood pressure, fasting blood glucose, glycosylated hemoglobin Total cholesterol (TC), triglyceride (TG), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C).

3.5 Follow-up information:

1. Information related to primary lung cancer: types of lung tumors (squamous cell carcinoma, adenocarcinoma, small cell/neuroendocrine/other); Staging of lung tumors (stages I, II, III, IV); CNM staging; Differentiation results of lung tumors; Immunohistochemical staining results; Tumor markers (outliers); Tumor genes (outliers); The treatment methods for lung tumors (surgery, radiotherapy, chemotherapy, molecular targeting, immunity, biological therapy, neoadjuvant chemotherapy); Surgical time and bleeding volume.
2. Information related to abdominal aortic aneurysm: whether it is complicated with abdominal aortic aneurysm; Is there a concomitant iliac artery aneurysm; Whether to undergo surgical treatment; Surgical treatment methods (endovascular repair of abdominal aortic aneurysm, open surgery); Surgical time and bleeding volume.
3. Patient prognosis: last follow-up time, time of lung tumor recurrence, whether death occurred, and cause of death.

4.Data entry and analysis At the Department of Thoracic Surgery of the First Affiliated Hospital of Kunming Medical University and the Department of Thoracic Surgery of the Third Affiliated Hospital of Kunming Medical University, patient basic information, laboratory tests, and treatment plans are obtained and filled out from the hospital's medical record system. Epidemiological survey questions are collected at the patient's bedside using a question and answer format to ensure the accuracy and reliability of the epidemiological survey information. All collected data is organized and encoded using REDCap（ https://www.wcrcnet.cn/redcap/ ）Perform data entry. IBM SPSS Statistics 22 will be used to analyze the entered data and identify the risk factors for primary lung cancer combined with AAA.

Inclusion Criteria:

• Patients diagnosed with primary lung cancer through clinical or pathological examination

Exclusion Criteria:

• Patients diagnosed with primary lung cancer who refuse to undergo abdominal aortic imaging screening.

The selected subjects for the study were all patients diagnosed with primary lung cancer at the First Affiliated Hospital of Kunming Medical University and the Third Affiliated Hospital of Kunming Medical University from 1st October 2022 to 30 st April 2025, with an estimated sample size of about 2000 people. Detailed epidemiological data and long-term follow-up data were collected and analyzed, and epidemiological investigations were conducted.

If necessary, upload to make individual participant data (IPD) available to other researchers after the research is completed