Comorbidities related to metachronous recurrence for early gastric cancer in elderly patients.

INTRODUCTION
Stomach cancer ranks fifth in both incidence and mortality rates worldwide, with the highest rates observed in both men and women in Eastern Asia[1]. In 2022, approximately 0.97 million new cases of gastric cancer (GC) were diagnosed, 33.7% of which occurred in China[2]. A Markov model predicted that between 2021 and 2035, there will be 10.0 million new cases of GC and 5.6 million GC-related deaths. The model indicated that a significant proportion of these cases, ranging from 7.6% to 35.5%, and the related deaths, ranging from 6.9% to 44.5%, could be avoided through various prevention strategies[3]. Early GC (EGC), limited to the mucosa or submucosa regardless of lymph node metastasis, is known to have a favorable prognosis[4,5]. Recently, endoscopic resection (ER) has gained popularity as a standard, minimally invasive treatment for EGC. Metachronous GC (MGC) refers to a secondary carcinoma appearing in an area different from the primary lesion at least one year after curative ER[6]. The cumulative incidences of MGC at 5, 7, and 10 years were 9.5%, 13.1%, and 22.7%, respectively[7].
Population aging significantly contributes to the increasing burden of cancer[8]. The peak incidence and mortality of cancer occurs in individuals aged 60-79 years. Males experience higher years lived with disability owing to neoplasms, cardiovascular diseases, and diabetes, while females show higher rates related to musculoskeletal, mental, and neurological disorders starting in older age groups (≥ 60 years)[9]. The prevalence and incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) are rising worldwide; its overall prevalence is estimated to be 32.4% [95% confidence interval (CI): 29.9-34.9], while the overall incidence is approximately 4612.8 cases (95%CI: 3931.5-5294.2) per 100000 person-years[10], posing significant health and economic burdens on societies[11]. Some studies have reported an inverted U curve concerning the age-prevalence of MASLD, indicating a decrease in prevalence in individuals aged ≥ 65 years; nevertheless, MASLD gradually progresses to cancer over time[12,13]. MASLD was associated with an almost 1.8-fold increased risk of stomach cancer [pooled random-effects hazard ratio (HR) = 1.81, 95%CI: 1.19-2.75][14]. These findings suggest that MASLD increases the risk of developing MGC after ER.
Several studies have identified various risk factors for MGC, including age > 65 years, smoking, male sex, lower body mass index, Helicobacter pylori (H. pylori) infection, differentiated types, serum pepsinogen levels, and severe atrophic gastritis (AG)[7,15-22]. However, the correlation between comorbidities and the risk of MGC remains unclear.
Therefore, this study aimed to investigate the risk factors of MGC after curative endoscopic submucosal dissection (ESD), focusing on MASLD and other comorbidities in elderly patients.

MATERIALS AND METHODS

Study design and patient selection
This retrospective cohort study included 848 elderly patients aged ≥ 65 years who underwent curative ESD for EGC at the Affiliated Drum Tower Hospital of Nanjing University Medical School between January 2014 and June 2020. We excluded patients who did not meet the criteria for curative resection, those with an indefinite H. pylori infection status, those with a history of GC or gastrectomy, those who were scheduled for surgery within one year, those who had incomplete information, or those who had follow-up periods of < 12 months. In total, 653 eligible patients were included in the analysis.
Verbal informed consent was obtained from each patient; the requirement for written informed consent was waived owing to the study’s retrospective design. The study protocol was approved by the Human Ethics Review Committee of the Nanjing Drum Tower Hospital, No. 2024-395-01.

Independent variables
Demographic and clinical characteristics, including age, sex, lifestyle habits, comorbidities, and H. pylori infection status, were collected from the patients’ medical records. Diagnoses of MASLD, hypertension, diabetes, cardiovascular disease, and cerebrovascular disease were confirmed and validated based on international classification of diseases, tenth revision, clinical modification codes. A diagnosis of MASLD, excluding other causes of chronic liver disease, was based on ultrasonography or computed tomography performed by experienced radiologists during the preoperative examinations. Curative resection of EGC was performed according to Japanese gastric cancer treatment guidelines[23]. Two experienced gastrointestinal endoscopists and pathologists evaluated the endoscopic and histopathological features based on the World Health Organization classification of GC[24].

H. pylori infection and mucosal atrophy
The presence of H. pylori infection was determined using ¹³C-urea breath and fast urease tests, and a histological examination. Based on their H. pylori infection status, patients were categorized into the following three groups: (1) A negative group, consisting of patients without active H. pylori infection at the time of ESD and prior to ESD; (2) An eradicated group, indicating successful eradication of H. pylori; and (3) A persistent group, comprising patients who did not attempt or failed to eradicate H. pylori. Mucosal atrophy was classified into two grades according to the Kimura-Takemoto classification, namely, mild/moderate (C0-C3) and severe (O1-O3)[25,26].

Outcome measurement
MGC was defined as a secondary carcinoma detected in areas other than the primary carcinoma > 12 months following the index ESD[6]. Confirmation of MGC relied on a histological examination of biopsy, ER, or gastrectomy specimens. Follow-up esophagogastroduodenoscopy was conducted periodically after the index ESD, every 3 months for the first 12 months, and annually thereafter, as part of the MGC surveillance protocols. The follow-up period was defined as the time interval from the index ESD to either histological confirmation of MGC or the last follow-up visit.

Statistical analysis
Univariate and multivariate Cox proportional hazard regression analyses were performed to identify the independent risk factors for MGC. Covariates with clinical or statistical significance (P < 0.1) in the univariate analysis were included in the multivariate analysis. The cumulative probabilities of developing MGC were calculated using the Kaplan-Meier method and assessed using a log-rank test. Continuous variables were compared using t- or Mann-Whitney U tests, and were reported as mean ± SD for parametrically distributed data, or as median interquartile range (IQR) for nonparametrically distributed data. Categorical data were compared using Pearson’s χ2 or Fisher’s exact tests. All statistical tests were two-sided, with P < 0.05 considered statistically significant. Statistical product and service solutions version 26.0 (IBM Corp., Armonk, NY, United States) and R version 4.0.5 (R Foundation for Statistical Computing, Vienna, Austria) software programs were used for analysis.

RESULTS

The socio-demographic profile of the elderly patients
In accordance with the inclusion and exclusion criteria, 653 patients aged ≥ 65 years were eligible for the retrospective analysis (Figure 1). In our study, 46 patients (7.0%, 20.46/1000 person-years) developed MGC during a median follow-up period of 38 months (IQR: 25-55). The cumulative incidences of MGC in the elderly patients at 2, 3, and 5 years were 3.3%, 5.3%, and 11.5%, respectively. The HRs for the cumulative incidence of MGC based on age at initial ESD are shown in Supplementary Figure 1, according to the EGC database at our hospital. The baseline and clinicopathological characteristics of the included study patients were compared based on the presence or absence of MGC (Table 1). The median age at the time of the index ESD was 70 years (IQR: 67-74 years; males, 71.2%). The incidence of MASLD was 9.6% (n = 63) at the time of the index ESD. The status of H. pylori infection (P < 0.001), baseline mucosal atrophy (P = 0.031), differentiation (P = 0.047), and median follow-up time (P < 0.001) differed significantly between the MGC and non-MGC groups.

Risk factors associated with MGC
Demographic and clinical characteristics including age, sex, lifestyle habits, and comorbidities, H. pylori infection, and endoscopic and histological features were analyzed using univariate Cox regression analyses (Table 2). The results indicated that MASLD (P < 0.001), cerebrovascular disease (P = 0.034), persistent H. pylori infection (P < 0.001), severe mucosal atrophy (P = 0.002), and well/moderately differentiated (WD/MD) tumors (P = 0.039) increased the likelihood of developing MGC. Multivariate Cox regression analysis identified MASLD (HR = 2.44, 95%CI: 1.15-5.17), persistent H. pylori infection (HR = 10.38, 95%CI: 3.36-32.07), severe mucosal atrophy (HR = 2.71, 95%CI: 1.45-5.08), and WD/MD differentiation (HR = 10.18, 95%CI: 1.30-79.65) as independent risk factors for MGC. No notable differences were observed in the initial multiplicity (HR = 1.79, 95%CI: 0.90-3.56, P = 0.096) in the multivariate Cox regression analysis. The cumulative incidences of MGC after curative ESD among the different subgroups of MASLD, H. pylori infection, baseline mucosal atrophy, and differentiation are illustrated in Figure 2, all showing statistical significance.

Subgroup analyses based on MASLD and severe AG
In the MASLD group, 10 patients (15.9%, 53.76/1000 person-years) developed MGC compared with 36 patients (6.1%, 17.45/1000 person-years) in the non-MASLD group (Figure 2). The cumulative incidences of MGC in the MASLD group at 2, 3, and 5 years were 8.8%, 16.9%, and 31.8%, respectively, whereas those in the non-MASLD group were 2.7%, 4.2%, and 9.7%, respectively. We performed subgroup analyses to evaluate the influence of MASLD on MGC development (Figure 3). MASLD was associated with a high incidence of MGC, which was consistent across various lifestyle factors, other comorbidities, and the negative and eradicated status of H. pylori infection subgroups (all P values < 0.05).
Severe AG was also associated with high incidence of MGC (Supplementary Figure 2). In the subgroup analyses based on sex, male sex was associated with a higher risk of MGC (P = 0.006) in the severe AG group. Factors such as alcohol consumption or smoking history (P = 0.005), absence of MASLD (P = 0.007), hypertension (P = 0.001), and diabetes (P = 0.002) showed a close association between severe AG and MGC. No interactions were found between severe AG and the aforementioned variables in the subgroup analyses (all P values for interactions, > 0.05). Additional subgroup analyses based on the differentiation between WD/MD and persistent H. pylori infection are shown in Supplementary Table 1 and Supplementary Figure 3.

Risk stratification for MGC
After assigning weighted scores to the b regression coefficient (log HR) values, the variables MASLD, persistent H. pylori infection, severe mucosal atrophy, and differentiation of WD/MD tumors were assigned 1, 3, 1, and 3 points, respectively (Table 2). This risk stratification subsequently categorized patients into low (0-1 point), intermediate (2-3 points), and high (4-8 points) groups for MGC, with cumulative incidence rates of 12.3%, 21.6%, and 45%, respectively (Table 3). The risk stratification system highlighted significant differences in the cumulative incidence rates of MGC among the risk groups (Figure 4).

DISCUSSION
The development and utilization of endoscopic technology has drawn increased attention to the incidence of MGC following ER. Previous studies have indicated that older age (mean difference, 1.08 years; 95%CI: 0.21-1.96) is an independent risk factor for the increased incidence of MGC[27,28]. However, specific factors that contribute to the development of MGC in elderly individuals remain unclear. In this study, 46 patients (7.0%, 20.46/1000 person-years) developed MGC, with cumulative incidences of 3.3%, 5.3%, and 11.5% at 2, 3, and 5 years, respectively. Our findings indicated that MASLD, persistent H. pylori infection, and severe mucosal atrophy were independent risk factors for MGC in patients aged > 65 years.
Earlier studies have associated factors such as male sex [odds ratio (OR) = 1.43, 95%CI: 1.22-1.66], synchronous lesions (OR = 1.72, 95%CI: 1.30-2.28), severe gastric mucosal atrophy (OR = 2.77, 95%CI: 1.22-6.29), lower pepsinogen I/II ratio (mean difference -0.54, 95%CI: -0.86 to -0.22), current smoking (HR: 1.5, 95%CI: 1.03-2.16), and well-differentiated tumors (risk ratio = 4.02, 95%CI: 1.96-8.26) with a significantly increased risk of MGC post-ER[16,27,29]. Recent retrospective cohort studies and prospective randomized controlled trials have indicated that H. pylori infection is a significant risk factor for MGC development[15,20,30,31]. Elderly individuals with severe endoscopic atrophy in our study were at a substantially higher risk of developing MGC.
The subgroup analysis conducted in our study suggests a possible connection between MASLD and MGC in the elderly. Prior studies have indicated that MASLD is associated with an increased risk of developing GC (incidence rate ratio = 2.3, 95%CI: 1.3-4.1)[14,32]. MASLD has also been linked to a higher risk of metachronous colorectal neoplasia in both men (adjusted HR = 1.17, 95%CI: 1.06-1.29) and women (adjusted HR = 1.63, 95%CI: 1.27-2.07)[33]. Furthermore, bariatric surgery in patients with MASLD and severe obesity has shown significant risk reductions for GC (lower crude HR = 0.30, 95%CI: 0.02-1.70 and adjusted HR = 0.46, 95%CI: 0.03-2.44)[34]. Our findings showed a strong association between MASLD and a higher incidence of MGC in the elderly, consistent across various subgroups, including sex, smoking and drinking status, H. pylori eradication, family history of tumors, diabetes, hypertension, histological differentiation, and mild/moderate mucosal atrophy. However, future studies are needed to further investigate this association.
This study provides valuable insights into the development of MGC in elderly patients after ESD. The risk-scoring system had several advantages, particularly in assessing the effects of H. pylori infection status, gastric mucosal atrophy, and MASLD on MGC development. The link between MASLD and MGC has rarely been reported in previous studies. Additionally, we incorporated potential risk factors to establish a risk stratification for elderly patients with EGC post-ESD. This stratification can aid in determining the appropriate frequency of endoscopic surveillance for the different risk groups. For high-risk patients (total, 4-8 points), annual endoscopic surveillance is recommended for an extended period. Following the initial yearly surveillance, moderate-risk patients (total, 2-3 points) should be evaluated every other year. For low-risk patients (total, 0-1 points), the surveillance intervals can be extended appropriately. Consultation with healthcare professionals provides personalized medical advice and recommendations.
This study had several limitations. This was a retrospective, single-center study with a relatively small population size. We only gathered clinical characteristics and did not include laboratory tests for genetic and epigenetic markers and microsatellite instability. There was a time lag between the occurrence of MGC and availability of clinical follow-up records. The postoperative follow-up period was relatively short, limiting our ability to draw more accurate conclusions. In conclusion, this study underscores the need for further large-scale cohort studies and prospective randomized controlled trials to thoroughly evaluate risk factors associated with MGC.

CONCLUSION
Our findings suggest that MASLD, persistent H. pylori infection, and severe mucosal atrophy are associated with the development of MGC in elderly patients. These results provide valuable insights into management and surveillance strategies for this population. However, further studies are needed to confirm and expand upon these findings.