Background
In Japan, gastric cancer is characterized by increased rate of early-stage disease and occurrence in elderly patients [
1,
2]. Early gastric cancer is only curable by local treatment, and cause of death is mostly other than gastric cancer [
3,
4]. In the elderly population, pneumonia is one of the most frequent causes of death [
5]. Thus, pneumonia in the long-term period after gastrectomy could decrease overall survival in patients with early gastric cancer, which is a serious threat, especially for elderly patients.
Pneumonia in the elderly population is associated with frailty caused by muscle depletion [
6]. On the other hand, many physicians reported that gastrectomy easily causes body weight loss and muscle loss after surgery [
7,
8]. Furthermore, total gastrectomy can cause reflux and aspiration which are risk factors for pneumonia [
9]. Accordingly, elderly patients are considered to have a very high risk of developing pneumonia in the long-term period after gastrectomy. To separate the term of perioperative pneumonia, we called this pneumonia developing in the long-term period after gastrectomy “long-term postoperative pneumonia (LTPP)” in the present study.
There have been no reports focusing on LTPP in elderly patients. Its incidence and risk factors remain unclear. Physicians may select endoscopic treatment instead of gastrectomy, even in cases that endoscopic treatment is not oncologically justified, if the frequency of LTPP is high or if physicians can identify patients who are at high risk for LTPP.
In this background, we investigated the frequency of LTPP in the elderly patients who received gastrectomy and were diagnosed with stage I gastric cancer and its risk factors.
Discussion
In the present study, we called the pneumonia shadow found in the long-term period after gastrectomy “LTPP” and examined its incidence and risk factors in elderly patients who received curative gastrectomy and who were diagnosed with early gastric cancer. We firstly clarified that more than one quarter of the elderly patients developed LTPP within 2 years after gastrectomy. This high incidence must impact the decision on whether the patient should receive surgery or not. Moreover, preoperative sarcopenia was the only significant risk factor for LTPP. After gastrectomy, special care through the long-term period is required for elderly patients, especially with sarcopenia.
In this study, LTPP was observed in 26% of elderly patients. There are no reports on the frequency of LTPP in any age group. On the other hand, the incidence of hospitalized community-acquired pneumonia in the elderly was reported to be approximately 2% in the United States [
18]. Kaplan et al. also reported that its incidence was 8.4 per 1000 in individuals of aged 65–69 years of age and 48.5 per 1000 in individuals of ≥ 90 years of age [
19]. Although our results showed a higher incidence in comparison to the above reports, the incidence in our study would be overestimated. In this study, LTPP was diagnosed based on chest CT images, by which even minimal changes of pneumonia shadow can be detected [
20]. Therefore, this study included cases of asymptomatic pneumonia or pneumonia that did not require medical treatment. Even if the incidence in our study was overestimated, the very high incidence of LTPP is a serious issue, because early gastric cancer is mostly curable and pneumonia is a major cause of death in the elderly population.
Aging is associated with loss of muscle mass and physical function, that often leads to progressive disability [
21]. The amount of muscle begins to decrease after the age of 50, and approximately 50% are lost until the age of 80 [
22]. Sarcopenia has been defined as the loss of muscle mass and strength that occurs with aging [
23,
24]. In the present study, sarcopenia was observed in 70% of the elderly patients who had early gastric cancer, that seemed to be higher than general elderly people. Approximately 22% of men and women aged 75–79 years old and 32.4% of men and 47.7% of women aged 80 years and older [
25]. As definition of sarcopenia would be different, it is unclear whether elderly patients who developed gastric cancer have high risk of sarcopenia.
Several studies have shown that gastric cancer patients with sarcopenia at the time of surgery experienced worse long-term outcomes than non-sarcopenic patients [
26‐
30]. Pneumonia in the elderly population is associated with frailty caused by muscle depletion [
6]. Altuna-Venegas et al. reported that sarcopenia was a risk factor for the onset of pneumonia [
31]. In the present study, more than 90% of the elderly patients who developed LTPP had sarcopenia. Thus, preoperative sarcopenia would have high risk of LTPP for elderly patients who received gastrectomy for gastric cancer. Moreover, gastrectomy itself frequently induces loss of body weight and muscle, which would be severe especially in patients with preoperative sarcopenia. Thus, progressive sarcopenia and frailty would closely associated with LTPP in the elderly patients who received gastrectomy.
Originally, diagnosis of sarcopenia required low muscle mass plus either low muscle strength or low physical performance and the diagnosis criteria was defined for aging patients [
23,
24]. However, many studies have performed CT-based body composition measurement and muscle area from CT has been used to define sarcopenia. Since CT is taken for staging in almost all cases, the indirect CT method is readily applicable. It is of note that the cutoff value to define sarcopenia differs in each study and has not yet been standardized [
32]. One reason is that differences in the nutritional status among cancer patients are actually very large. Another reason in sarcopenia studies is the difficulty of obtaining normal CT values from areas of muscle mass in a healthy cohort. In the present study, the cut-off values of preoperative sarcopenia for males and females were 49.2 and 35.7 cm
2/m
2, respectively. They were similar to the previous reports examining the preoperative sarcopenia of gastric cancer patients, in which the cut-off values for males and females were 40.8–55 and 34.9–41 cm
2/m
2, respectively [
26‐
29].
Previously, surgical procedure, comorbidity, and preoperative respiratory function have been reported as risk factors for perioperative pneumonia [
33‐
37], while age, gender and comorbidity have been reported as risk factors for community-acquired pneumonia [
19,
38,
39]. In this study, age, comorbidity, the preoperative respiratory function, and the type of gastrectomy were not significant risk factors for LTPP. Thus, risk factors for LTPP after gastrectomy might be different from those of perioperative pneumonia or community-acquired pneumonia. On the other hand, the type of gastrectomy was not associated with LTPP. Notably, the risk of LTPP was similar irrespective of the loss of the cardia, suggesting that reflux was not a major determinant for LTPP. Previously, Marumo et al. reported that reflux and aspiration after total gastrectomy was related to pneumonia [
9]. On the other hand, Jackson et al. reported that a poor functional status and recent weight loss were major risk factors for community-acquired pneumonia in the elderly [
38]. Gastrectomy easily causes body weight loss, and muscle loss which would decrease activity of daily life, especially in elderly patients. Thus, it would be possible that gastrectomy itself is a risk factor for pneumonia in elderly patients.
The present study was associated with some limitations. First, this was a retrospective single-center study. Our results should be further validated in a multicenter study. Second, the frequency of LTPP may be underestimated because our hospital specializes in oncology and often performs surgery for patients with few comorbidities. In the community hospital setting, where surgeons operate on elderly patients with severe comorbidities, LTPP would be more frequent because such patients would be sarcopenic.
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