Robotic gastrectomy (RG) has always been a hot topic in the field of minimally invasive surgery for gastric cancer. More and more studies have confirmed that short- and long-term outcomes of RG are similar to those of laparoscopic gastrectomy. Robotic surgical systems have more advantages in specific regional lymph node dissection. More delicate operation can reduce intraoperative blood loss and the incidence of postoperative complications. Robotic surgical systems are also more ergonomically designed. However, there are also some problems such as high surgical cost, lack of tactile feedback and prolonged total operation time. In the future, robotic surgical system may be further developed in the direction of miniaturization, intelligence and modularity. At the same time, the robotic surgical system deeply integrated with artificial intelligence technology may realize the automation of some operation steps to some extent.
Humans ; Robotic Surgical Procedures/adverse effects* ; Stomach Neoplasms/pathology* ; Artificial Intelligence ; Treatment Outcome ; Lymph Node Excision/adverse effects* ; Gastrectomy/adverse effects* ; Laparoscopy/adverse effects* ; Postoperative Complications/etiology* ; Retrospective Studies

Objective: To investigate the safety and efficacy of laparoscopic surgery in locally advanced gastric cancer patients with neoadjuvant SOX chemotherapy combined with PD-1 inhibitor immunotherapy. Methods: Between November 2020 and April 2021, patients with locally advanced gastric cancer who were admitted to the Union Hospital of Tongji Medical College of Huazhong University of Science and Technology were prospectively enrolled in this study. Inclusion criteria were: (1) patients who signed the informed consent form voluntarily before participating in the study; (2) age ranging from 18 to 75 years; (3) patients staged preoperatively as cT3-4N+M0 by the TNM staging system; (4) Eastern Collaborative Oncology Group score of 0-1; (5) estimated survival of more than 6 months, with the possibility of performing R0 resection for curative purposes; (6) sufficient organ and bone marrow function within 7 days before enrollment; and (7) complete gastric D2 radical surgery. Exclusion criteria were: (1) history of anti-PD-1 or PD-L1 antibody therapy and chemotherapy; (2) treatment with corticosteroids or other immunosuppre- ssants within 14 days before enrollment; (3) active period of autoimmune disease or interstitial pneumonia; (4) history of other malignant tumors; (5) surgery performed within 28 days before enrollment; and (6) allergy to the drug ingredients of the study. Follow-up was conducted by outpatient and telephone methods. During preoperative SOX chemotherapy combined with PD-1 inhibitor immunotherapy, follow-up was conducted every 3 weeks to understand the occurrence of adverse reactions of the patients; follow-up was conducted once after 1 month of surgical treatment to understand the adverse reactions and survival of patients. Observation indicators were: (1) condition of enrolled patients; (2) reassessment after preoperative therapy and operation received (3) postoperative conditions and pathological results. Evaluation criteria were: (1) tumor staged according to the 8th edition of the American Joint Committee on Cancer (AJCC) TNM staging system; (2) tumor regression grading (TRG) of pathological results were evaluated with reference to AJCC standards; (3) treatment-related adverse reactions were evaluated according to version 5.0 of the Common Terminology Criteria for Adverse Events; (4) tumor response was evaluated by CT before and after treatment with RECIST V1.1 criteria; and (5) Clavien-Dindo complication grading system was used for postoperative complications assessment. Results: A total of 30 eligible patients were included. There were 25 males and 5 females with a median age of 60.5 (35-74) years. The primary tumor was located in the gastroesophageal junction in 12 cases, in the upper stomach in 8, in the middle stomach in 7, and in the lower stomach in 3. The preoperative clinical stage of 30 cases was III. Twenty-one patients experienced adverse reactions during neoadjuvant chemotherapy combined with immunotherapy, including four cases of CTCAE grade 3-4 adverse reactions resulting in bone marrow suppression and thoracic aortic thrombosis. All cases of adverse reactions were alleviated or disappeared after active symptomatic treatment. Among the 30 patients who underwent surgery, the time from chemotherapy combined with immunotherapy to surgery was 28 (23-49) days. All 30 patients underwent laparoscopic radical gastrectomy, of which 20 patients underwent laparoscopic-assisted radical gastric cancer resection; 10 patients underwent total gastrectomy for gastric cancer, combined with splenectomy in 1 case and cholecystectomy in 1 case. The surgery time was (239.9±67.0) min, intraoperative blood loss was 84 (10-400) ml, and the length of the incision was 7 (3-12) cm. The degree of adenocarcinoma was poorly differentiated in 18 cases, moderately differentiated in 12 cases, nerve invasion in 11 cases, and vascular invasion in 6 cases. The number lymph nodes that underwent dissection was 30 (17-58). The first of gas passage, the first postoperative defecation time, the postoperative liquid diet time, and the postoperative hospitalization time of 30 patients was 3 (2-6) d, 3 (2-13) d, 5 (3-12) d, and 10 (7-27) d, respectively. Postoperative complications occurred in 23 of 30 patients, including 7 cases of complications of Clavien-Dindo grade IIIa or above. Six patients improved after treatment and were discharged from hospital, while 1 patient died 27 days after surgery due to granulocyte deficiency, anemia, bilateral lung infection, and respiratory distress syndrome. The remaining 29 patients had no surgery-related morbidity or mortality within 30 days of discharge. Postoperative pathological examination showed TRG grades 0, 1, 2, and 3 in 8, 9, 4, and 9 cases, respectively, and the number of postoperative pathological TNM stages 0, I, II, and III was 8, 7, 8, and 7 cases, respectively. The pCR rate was 25.0% (8/32). Conclusion: Laparoscopic surgery after neoadjuvant SOX chemotherapy combined with PD-1 inhibitor immunotherapy for locally advanced gastric cancer is safe and feasible, with satisfactory short-term efficacy. Early detection and timely treatment of related complications are important.
Male ; Female ; Humans ; Middle Aged ; Aged ; Adolescent ; Young Adult ; Adult ; Stomach Neoplasms/pathology* ; Neoadjuvant Therapy ; Immune Checkpoint Inhibitors ; Gastrectomy/methods* ; Esophagogastric Junction/pathology* ; Laparoscopy ; Immunotherapy ; Postoperative Complications ; Retrospective Studies ; Treatment Outcome

Radical gastrectomy combined with perioperative comprehensive treatment is the main curable strategy for gastric cancer patients, and postoperative complications are the issue that gastric surgeons have to face. Complications not only affect the short-term postoperative recovery, but also facilitate tumor recurrence or metastasis, thus resulting in poor prognosis. Therefore, unifying the diagnostic criteria for postoperative complications, bringing the surgeons' attention to complications, and understanding the potential mechanism of complications undermining long-term survival, will be helpful to the future improvement of the clinical diagnosis and treatment as well as prognosis for gastric cancer patients in China. Meanwhile, surgeons should constantly hone their operative skills, improve their sense of responsibility and empathy, and administer individualized perioperative management based on patients' general conditions, so as to minimize the occurrence of postoperative complications and their influence on prognosis.
Humans ; Stomach Neoplasms/pathology* ; Empathy ; Neoplasm Recurrence, Local/surgery* ; Prognosis ; Gastrectomy/methods* ; Postoperative Complications/etiology* ; Surgeons ; Retrospective Studies

Radical gastrectomy for gastric cancer results in various post-operative complications, and the influencing factors are complicated. The diagnosis, treatment and prevention of common complications have been reported in many literatures. However, there are few reports on the prevention and treatment of rare complications. Rare complications after radical gastrectomy are often overlooked due to their low incidence. In addition, there are few guidelines and expert consensus regarding to the rare complications. Therefore, clinicians may lack experience in the diagnosis, treatment and prevention of rare complications after radical gastrectomy. Based on the literature review and the author's experience, this article systematically reviews seven rare complications after radical gastrectomy (duodenal stump fistula, pancreatic fistula, chyle leakage, esophagomediastinal fistula, internal hernia, gastroparesis, and intussusception). This article aims to provide a comprehensive reference for the diagnosis, treatment and prevention of rare complications after radical gastrectomy for gastric cancer patients.
Humans ; Stomach Neoplasms/complications* ; Gastrectomy/methods* ; Postoperative Complications/etiology* ; Duodenal Diseases ; Laparoscopy/adverse effects* ; Retrospective Studies

Surgical resection plays pivotal role in the treatment of gastric cancer. Adequate preoperative evaluation, precise intraoperative maneuver and delicate postoperative management lay the foundation for successful gastrectomy. The aim of preoperative evaluation is to stage tumor and identify potential risk factors (including preoperative factors like age, ASA status, body mass index, comorbidity, hypoalbuminemia, and intraoperative factors like blood loss and combined resection) which could lead to postoperative complication. With the management of prehabilitation, adequate medical decision could be made and patient's fast recovery could be ensured. With the rapid adoption of ERAS concept, there is increasing attention to prehabilitation which focus on optimization of cardio-pulmonary capacity and muscular-skeletal capacity. Despite of the efficacy of prehabilitation demonstrated by randomized controlled trials, consensus has yet to be reached on the following items: specific intervention, optimal measurement, candidate population and optimal timing for intervention. Balancing the efficiency and safety, preoperative evaluation could be put into clinical practice smoothly.
Humans ; Stomach Neoplasms/complications* ; Preoperative Care/adverse effects* ; Postoperative Complications/etiology* ; Gastrectomy/adverse effects* ; Risk Factors

The postoperative 30-day mortality and morbidity of gastric cancer surgery has markedly improved over the past years due to minimally invasive techniques, perioperative rehabilitation programs and centralization of care. However, there is still need for improvement as postoperative complications may have a serious negative impact on the efficacy of surgical treatment of gastric cancer. High-quality clinical research is a very important tool to analyze treatment outcomes and evaluate new treatment strategies. The meticulous registration of gastric cancer patient data is the basis of high-quality surgical research. In the past 11 years, the Dutch upper gastrointestinal cancer audit (DUCA) database has vast experience in data registration and maintenance of patients with upper gastrointestinal cancer. The effective measures it has taken in data registration, data quality control, data application and use, and data security have maintained quality at a high level. These data has been used for medical care quality monitoring and scientific research leading to a positive impact on the postoperative short-term outcomes of patients with upper gastrointestinal cancer. The work of DUCA may be a good incentive for the setup of population-based databases and clinical research in other countries.
Humans ; Stomach Neoplasms/surgery* ; Digestive System Surgical Procedures ; Treatment Outcome ; Postoperative Complications

Objective: To compare the effectiveness of total laparoscopic versus laparoscopic-assisted distal gastrectomy and investigate the safety and replicability of total laparoscopic distal gastrectomy in older patients. Methods: This was a retrospective cohort study. The inclusion criteria were as follows: (1) age ≥65 years; (2) malignant gastric tumor diagnosed pathologically preoperatively; (3) Eastern Cooperative Oncology Group performance status score 0-1; (4) Grade I-III American Society of Anesthesiologists physical status; (5) preoperative clinical tumor stage I-III; (6) total laparoscopic or laparoscopic-assisted distal gastrectomy performed; and (7) gastrointestinal tract reconstruction using uncut Roux-en-Y or Billroth-II+Braun procedure. Patients who had received neoadjuvant therapy, undergone conversion to open surgery, or had serious comorbidities or incomplete data were excluded. The clinical data of 129 patients who met the above criteria and had undergone laparoscopic surgery for gastric cancer from January 2012 to December 2021 in the Gastrointestinal Cancer Center in the Beijing Cancer Hospital were analyzed. According to the operation method, the patients were divided into total laparoscopic group and laparoscopic-assisted group. Variables studied comprised: (1) surgical procedure and postoperative recovery; (2) postoperative pathological findings; and (3) postoperative complications. Measurement data with skewed distribution are represented as mean(quartile 1, quartile 3). Comparisons between groups were evaluated using the Mann-Whitney U test. Results: After propensity score matching in a 1:1 ratio, there were 40 patients in the total laparoscopic distal gastrectomy group and 40 in the laparoscopic-assisted distal gastrectomy group. Baseline characteristics did not differ significantly between the two groups (all P>0.05).Compared with the laparoscopic-assisted group, the total laparoscopic group had shorter main incisions (4.1±1.0 cm vs. 8.5±2.8 cm, t=9.375, P<0.001), time to fluid intake [4.0 (3.0, 4.8) days vs. 5.0 (4.0, 6.0) days, Z=2.167, P=0.030], and duration of indwelling abdominal drainage catheter [6.0 (6.0, 7.0) days vs. 7.0 (6.0, 8.0) days, Z=2.323, P=0.020]. Numerical Rating Scale scores on postoperative days 1 and 2 were higher in the total laparoscopic than the laparoscopic-assisted group [2.5 (1.0, 3.0) vs. 1.5 (1.0, 2.0), Z=1.980, P=0.048; 2.0 (1.0, 3.0) vs. 1.0 (1.0, 2.0), Z=2.334, P=0.020, respectively]. However, there were no significant differences between the groups in operation time, intraoperative blood loss, white blood cell count, hemoglobin concentration, or albumin concentration on postoperative day 1, time to ambulation, mean time to bowel movement, postoperative admission to the intensive care unit, length of postoperative hospital stay, or Numerical Rating Scale scores on postoperative day 3 (all P>0.05). There were also no significant differences between the two groups in maximum tumor diameter, pathological tumor type, total number of lymph nodes dissected, or total number of positive lymph nodes (all P>0.05). The incidence of postoperative complications was 15.0% (6/40) in the total laparoscopic group and the laparoscopic-assisted group; these differences are not significant (χ²<0.001, P>0.999). Conclusions: Compared with laparoscopic-assisted radical gastrectomy for distal gastric cancer, total laparoscopic surgery has the advantages of shorter incision, shorter time to fluid intake, and shorter duration of indwelling abdominal drainage catheter in older patients (age ≥65 years). Total laparoscopic radical gastrectomy for distal gastric cancer does not increase the risk of postoperative complications and could therefore be performed more frequently.
Aged ; Humans ; Gastrectomy/methods* ; Laparoscopy/methods* ; Postoperative Complications ; Retrospective Studies ; Stomach Neoplasms/pathology* ; Surgical Wound ; Treatment Outcome

Objective: To assess the effect of jejunal feeding tube placement on early complications of laparoscopic radical gastrectomy in patients with incomplete pyloric obstruction by gastric cancer. Methods: This was a retrospective cohort study. Perioperative clinical data of 151 patients with gastric antrum cancer complicated by incomplete pyloric obstruction who had undergone laparoscopic distal radical gastrectomy from May 2020 to May 2022 in the First Affiliated Hospital of Nanchang University were collected. Intraoperative jejunal feeding tubes had been inserted in 69 patients (nutrition tube group) and not in the remaining 82 patients (conventional group). There were no statistically significant differences in baseline characteristics between the two groups (all P>0.05). The operating time, intraoperative bleeding, time to first intake of solid food, time to passing first flatus, time to drainage tube removal, and postoperative hospital stay, and early postoperative complications (occurded within 30 days after surgery) were compared between the two groups. Results: Patients in both groups completed the surgery successfully and there were no deaths in the perioperative period. The operative time was longer in the nutritional tube group than in the conventional group [(209.2±4.7) minutes vs. (188.5±5.7) minutes, t=2.737, P=0.007], whereas the time to first postoperative intake of food [(2.7±0.1) days vs. (4.1±0.4) days, t=3.535, P<0.001], time to passing first flatus [(2.3±0.1) days vs. (2.8±0.1) days, t=3.999, P<0.001], time to drainage tube removal [(6.3±0.2) days vs. (6.9±0.2) days, t=2.123, P=0.035], and postoperative hospital stay [(7.8±0.2) days vs. (9.7±0.5) days, t=3.282, P=0.001] were shorter in the nutritional tube group than in the conventional group. There was no significant difference between the two groups in intraoperative bleeding [(101.1±9.0) mL vs. (111.4±8.7) mL, t=0.826, P=0.410]. The overall incidence of short-term postoperative complications was 16.6% (25/151). Postoperative complications did not differ significantly between the two groups (all P>0.05). Conclusion: It is safe and feasible to insert a jejunal feeding tube in patients with incomplete outlet obstruction by gastric antrum cancer during laparoscopic radical gastrectomy. Such tubes confer some advantages in postoperative recovery.
Humans ; Stomach Neoplasms/etiology* ; Pyloric Antrum ; Retrospective Studies ; Flatulence/surgery* ; Treatment Outcome ; Postoperative Complications/etiology* ; Laparoscopy ; Gastrectomy/adverse effects* ; Length of Stay ; Pyloric Stenosis/surgery*

Objective: To evaluate the effects on short-term clinical outcomes and long-term quality of life of laparoscopic-assisted radical proximal gastrectomy with esophageal gastric tube anastomosis versus total gastrectomy with Roux-en-Y anastomosis for adenocarcinoma of the esophagogastric junction. Methods: This was a propensity score matching, retrospective, cohort study. Clinicopathological data of 184 patients with adenocarcinoma of the esophagogastric junction admitted to two medical centers in China from January 2016 to January 2021 were collected (147 in the First Affiliated Hospital of Xiamen University and 37 in the Affiliated Hospital of Qinghai University). All patients had undergone laparoscopic-assisted radical gastrectomy. They were divided into two groups based on the extent of tumor resection and technique used for digestive tract reconstruction. A proximal gastrectomy with reconstruction by esophageal gastric tube anastomosis group comprised 82 patients and a total gastrectomy with reconstruction by Roux-en-Y anastomosis group comprised 102 patients. These groups differed significantly in the following baseline characteristics: age, preoperative hemoglobin, preoperative albumin, tumor length, tumor differentiation, and tumor TNM stage (all P<0.05). To eliminate potential bias caused by unequal distribution between the two groups, 1∶1 matching was performed by the nearest neighbor matching method. The 13 matched variables comprised sex, age, height, body mass, body mass index, preoperative glucose, preoperative hemoglobin, preoperative total protein, preoperative albumin, neoadjuvant radiotherapy, tumor length, degree of differentiation, and pathological TNM stage. Postoperative complications, postoperative nutritional status, incidence of reflux esophagitis 1 year after surgery, and quality of life were compared between the two groups. Results: After propensity score matching, 60 patients each were enrolled in the proximal gastrectomy with esophageal gastric tube anastomosis and total gastrectomy with Roux-en-Y anastomosis groups. The baseline characteristics were comparable between these groups (all P>0.05). There were no significant differences between the two groups in operative time, intraoperative bleeding, time to semifluid diet, postoperative hospital days, tumor length, and total hospital costs (P>0.05). Patients in the proximal gastrectomy with esophageal gastric tube anastomosis group had earlier postoperative gastric tube and abdominal drainage tube removal time than those in the total gastrectomy with Roux-en-Y anastomosis group (t=-2.183, P=0.023 and t=-4.073, P<0.001, respectively). In contrast, significantly fewer lymph nodes were cleared and significantly fewer lymph nodes were positive in the proximal gastrectomy with esophageal gastric tube anastomosis group than in the total gastrectomy with Roux-en-Y anastomosis group (t=-5.754, P<0.001 and t=-2.575, P=0.031, respectively). The incidence of early postoperative complications was 43.3% (26/60) in the total gastrectomy with Roux-en-Y anastomosis group; this is not significantly higher than the 26.7% (16/60) in the proximal gastrectomy with esophageal gastric tube anastomosis group (χ²=3.663，P=0.056). The incidences of pulmonary infection (31.7%, 19/60) and pleural effusion (30.0%, 18/60) were significantly higher in the total gastrectomy with Roux-en-Y anastomosis group than in the proximal gastrectomy with esophageal gastric tube anastomosis group (13.3%, 8/60 and 8.3%, 5/60, respectively); these differences are significant (χ²=8.711, P=0.003 and χ²=11.368, P=0.001, respectively). All early complications were successfully treated before discharge. The incidence of long-term postoperative complications was 20.0% (12/60) in the total gastrectomy with Roux-en-Y anastomosis group and 35.0% (21/60) in the proximal gastrectomy with esophageal gastric tube anastomosis group; this difference is not significant (χ²=3.386，P=0.066). The incidence of reflux esophagitis was 23.3% (14/60) in the proximal gastrectomy with esophageal gastric tube anastomosis group; this is significantly higher than the 1.7% (1/60) in the total gastrectomy with Roux-en-Y anastomosis group (χ²=12.876, P<0.001). Body mass index had decreased significantly in both groups 1 year after surgery compared with preoperatively; however, the difference between the two groups was not significant (P>0.05). The differences in hemoglobin and albumin concentrations between 1 year postoperatively and preoperatively were not significant (both P>0.05). Quality of life was assessed using the Visick grade. Visick grade I dominated in both groups. The percentage of patients with Visick II and III in the total gastrectomy with Roux-en-Y anastomosis group was 11.7% (7/60), which is significantly lower than the 33.3% (20/60) in the proximal gastrectomy with esophageal gastric tube anastomosis group (χ²=8.076, P=0.004). No patients in either group had a grade IV quality of life. Conclusions: Both proximal gastrectomy with esophageal gastric tube anastomosis and total gastrectomy with Roux-en-Y anastomosis laparoscopic-assisted radical surgery for adenocarcinoma of the esophagogastric junction are safe and feasible. However, both procedures have their own advantages and disadvantages in terms of postoperative complications. The incidence of reflux esophagitis is higher after proximal gastrectomy with esophageal gastric tube anastomosis, whereas the long-term quality of life is lower than that of patients after total gastrectomy with Roux-en-Y anastomosis.
Humans ; Anastomosis, Roux-en-Y ; Retrospective Studies ; Cohort Studies ; Esophagitis, Peptic ; Quality of Life ; Propensity Score ; Gastrectomy/methods* ; Esophagogastric Junction/surgery* ; Anastomosis, Surgical/methods* ; Adenocarcinoma/pathology* ; Stomach Neoplasms/pathology* ; Postoperative Complications ; Treatment Outcome

Objective: To analyze the factors associated with readmission within three months of surgery for gastric cancer and the impact of readmission on patients' long-term nutritional status and quality of life. Methods: This was a prospective cohort study comprising patients who underwent radical gastrectomy in the Department of Pancreatic and Gastric Surgery, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences from October 2018 to August 2019. Patients who failed to complete postoperative follow-up, whose body mass index (BMI) could not be accurately estimated, or who were unable to complete a quality-of-life questionnaire were excluded. The patients were followed up for 12 months. Time to, cause(s) of, and outcomes of readmission were followed up 1, 2 and 3 months postoperatively. BMI was followed up 1, 3, 6 and 12 months postoperatively. Results of blood tests were collected and patients' nutritional status and quality of life were assessed 12 months postoperatively. Nutritional status was evaluated by BMI, hemoglobin, albumin, and total lymphocyte count. Quality of life was evaluated using the European Organization for Research in the Treatment of Cancer (EORTC) Quality of Life scale. The higher the scores for global health and functional domains, the better the quality of life, whereas the higher the score in the symptom domain, the worse the quality of life. Results: The study cohort comprised 259 patients with gastric cancer, all of whom were followed up for 3 months and 236 of whom were followed up for 12 months. Forty-four (17.0%) patients were readmitted within 3 months. The commonest reasons for readmission were gastrointestinal dysfunction (16 cases, 36.3%), intestinal obstruction (8 cases, 18.2%), and anastomotic stenosis (8 cases, 18.2%). Logistic regression analysis showed that preoperative Patient-Generated Subjective Global Assessment score ≥ 4 points (OR=1.481, 95% CI: 1.028‒2.132), postoperative complications (OR=3.298, 95%CI:1.416‒7.684) and resection range (OR=1.582, 95% CI:1.057‒2.369) were risk factors for readmission within 3 months of surgery. Compared with patients who had not been readmitted 12 months after surgery, patients who were readmitted within 3 months of surgery tended to have greater decreases in their BMI [-2.36 (-5.13,-0.42) kg/m² vs. -1.73 (-3.33,-0.33) kg/m², Z=1.850, P=0.065), significantly lower hemoglobin and albumin concentrations [(122.1±16.6) g/L vs. (129.8±18.4) g/L, t=2.400, P=0.017]; [(40.9±5.0) g/L vs. (43.4±3.3) g/L, t=3.950, P<0.001], and significantly decreased global health scores in the quality of life assessment [83 (67, 100) vs. 100 (83, 100), Z=2.890,P=0.004]. Conclusion: Preoperative nutritional risk, total or proximal radical gastrectomy, and complications during hospitalization are risk factors for readmission within 3 months of surgery for gastric cancer. Perioperative management and postoperative follow-up should be more rigorous. Readmission within 3 months after surgery may be associated with a decline in long-term nutritional status and quality of life. Achieving improvement in long-term nutritional status and quality of life requires tracking of nutritional status, timely evaluation, and appropriate interventions in patients who need readmission.
Humans ; Nutritional Status ; Quality of Life ; Patient Readmission ; Stomach Neoplasms/complications* ; Prospective Studies ; Postoperative Complications/etiology* ; Gastrectomy/adverse effects* ; Retrospective Studies