Direct Measurement of Gastroesophageal Reflux Episodes in Patients With Squamous Cell Carcinoma by 24-h pH-Impedance Monitoring Kaname Uno et al Am J Gastroenterol, 20 September 2011
Esophageal cancer is one of the most lethal diseases in the world. • Heavy alcohol drinking and smoking are two main risk factors for esophageal squamous cell carcinoma (ESCC) . • Some clinical studies demonstrated a possible relationship between gastric atrophy and ESCC risk. However, it remains unclear whether this relationship between gastric atrophy and ESCC risk is a causal factor or a result from confounding factors due to alcohol drinking or smoking.
From the point of view of pathogenesis, we assumed that gastroesophageal reflux (GER), as another risk factor, might have a key role in the carcinogenesis of ESCC. However, no report has focused on the direct measurement of the characteristics of GER in patients with ESCC. • To test our hypothesis that the contents of GER concomitant with gastric atrophy might participate in the development of ESCC, we directly measured the characteristics of GER using a portable 24-h multichannel intraluminal impedance monitoring in conjunction with a pH sensor (MII-pH) in a case–control study.
METHODS • From July 2008 to May 2010, 14 consecutive patients (14 men; median age, 70.5 (61–83) years) with superficial ESCCs who were scheduled for endoscopic mucosal resection (EMR) were prospectively enrolled in this study. • In the same period, 14 age- and sex-matched patients (14 men; median age, 69.9 (58–81) years) scheduled for EMR for superficial differentiated early gastric cancer (EGC) were selected as controls (non-ESCC group). • In the non-ESCC group, the concomitant presence of esophageal dysplastic lesions was strictly excluded by 1.5% iodine solution spray as described below . • Cancer lesions were successfully treated with EMR and were finally confirmed histologically by the obtained specimens in both groups.
All subjects underwent biochemistry test for pepsinogen and anti-Helicobacter pylori antibody. • In each participant, portable 24-h MII-pH monitoring was then performed a few days before EMR treatment under a hospitalized condition. • Smoking status, alcohol consumption, and gastroesophageal reflux disease (GERD) symptoms, such as heart burn and acid regurgitation, were assessed. • Alcohol consumption was classified into two categories: heavy drinkers defined as taking >75 ml ethanol per day and others. • GERD symptoms were regarded as positive if subjects complained of the symptom more than once per month. • We excluded the individuals with a history of GI surgery or EMR for upper GI malignancies, previous H. pylori eradication therapy, serious systemic disease, and those taking anticoagulation drugs, medication known to influence esophageal motor function or anti-secretory .
Endoscopic findings • All patients underwent esophagogastroduodenoscopy with 1.5% iodine solution spray. • All digital endoscopic images were independently and retrospectively reviewed by two trained endoscopists to assess the endoscopic findings, including other lesions of gastric or esophageal neoplasia, reflux esophagitis, and hiatus hernia. • The endoscopic findings of EGC and ESCC were recorded according to the Japanese Classification of Gastric Carcinoma and the Japanese Classification of Esophageal Cancer , respectively. • Anatomical subsites of the ESCC were classified according to the location of the major lesion in the upper, middle, or lower third of the esophagus. • Hiatus hernia was diagnosed when the distance between the esophagogastric junction and the diaphragmatic hiatus was ≥2 cm.
Measurement of serum pepsinogen I and II • Gastric atrophy was evaluated serologically by measuring the serum pepsinogen I concentration and pepsinogen I/II ratio. A fasting blood sample was obtained from each patient, and the serum was separated and stored at −20 °C. • A value of serum pepsinogen I <25 ng/ml or pepsinogen I/II ratio <2.0 was considered to indicate serological fundic atrophy.
Evaluation of H. pylori infection • Serum IgG antibodies against H. pylori were measured by enzyme-linked immunosorbent assay. Patients were considered to be infected with H. pylori if their serum tests were positive.
MII-pH catheter characteristics and placement • The data of intraluminal electrical impedance were recorded with electrodes spaced at 2-cm intervals. • Each pair of electrodes formed a measuring segment, corresponding to one recording channel. • The signals from 6 impedance channels and 2 pH channels were recorded at 50 samples per second. • The esophageal pH level and gastric pH level were measured using an antimony pH electrode. pH electrodes were calibrated using pH 4.0 and pH 7.0 buffer solutions before beginning the recording.
Patients and controls were studied after an overnight fast of at least 10 h. • After stationary esophageal manometry to locate the lower esophageal sphincter (LES), the combined pH-impedance assembly was passed through the nose and positioned with the pH electrodes at 5 cm above the proximal border of the LES and 10 cm below the LES. In this position, impedance was measured at 3, 5, 7, 9, 15, and 17 cm proximal to the LES. • During 24 h of hospital stay, all subjects were in the upright position during daytime and were allowed free movement and one recumbent period. • All subjects had 3 standardized meals, at fixed times during the measurement period. All events during testing, including meals, medication, symptoms, and body position (upright/recumbent), were entered by the patient directly into the monitor.
MII-pH interpretation • The data were visually analyzed with the assistance of dedicated software. Each recording was manually reviewed, edited, and analyzed by two authors independently. Discordant readings were reviewed until agreement was reached. • Reflux episodes consisting of only gaseous reflux were excluded. • Reflux events were divided into two subcategories based on the pH level at the point of reflux, including acid reflux (AR: reflux episodes which reduce the pH of the esophagus to below 4 or which occur when esophageal pH is already below 4) and non-AR (NAR: an impedance-detected reflux event occurring when esophageal pH was >4). • Meal periods (3 periods of ~20 min each) were excluded from the analysis.
For each reflux episode detected by impedance, the bolus exposure at 5 cm above LES was calculated as the time (seconds) between the 50% drop in impedance until the 50% recovery of the impedance baseline and lasting for at least 5 s. • The total bolus exposure time (%) was obtained by adding the bolus exposures of all individual reflux episodes divided by the time of monitoring. • Esophageal acid exposure (%) was defined as the total time when the pH was below 4 divided by the time of monitoring. • The average bolus clearance time (seconds) was defined as total bolus exposure time (seconds) divided by the number of reflux episodes during the 24-h recording.
Statistical analysis • Parametric data were expressed as mean±s.d. and non-parametric data as median (interquartile range). The frequencies of different impedance/pH patterns of reflux in each group were analyzed and compared using Mann–Whitney U-test. Correlations among intragastric pH levels and the numbers of total reflux events, AR, and NAR, were analyzed by Spearman’s rank correlation. Fisher’s exact test was used to compare differences between proportions. A P value of <0.05 was considered to be significant. Analyses were carried out using Statview 5.0 (SAS Institute, Cary, NC).
RESULTS • In the ESCC group, all lesions were superficial cancers located in the middle or lower part of the esophagus, and 6 of 14 (42.9%) were concomitant with superficial EGC. This observation is consistent with previous reports. • All EGC lesions detected in both groups were non-cardiac differentiated adenocarcinomas. • There were no subjects with any endoscopic findings of reflux esophagitis or GERD symptoms defined above. • The endoscopic prevalence of hiatus hernia was similar in the two groups (7.1% in the ESCC group vs. 7.1% in the non-ESCC group). • There were no significant differences in body mass index, prevalence of H. pylori infection. • The prevalence of serological gastric atrophy was similarly high in the two groups and the difference between them was not significant. • The total recording time was similar in the two groups (23.8 (22.7–24.5) h in the ESCC group vs. 23.7 (22.6–24.5) h in the non-ESCC group).
pH probe findings • There was a trend of a higher intragastric pH level in the ESCC group than in the non-ESCC group, but the difference was not significant (P=0.085). • The differences in the intraesophageal pH level and the percentage of time with a pH <4 were also not significant (P=0.535 and P=0.369, respectively)
Impedance findings 5 cm above LES • We studied the numbers and duration of bolus exposures during liquid GER events at an anatomical point 5 cm above the LES. The numbers of total GER and NAR episodes in the ESCC group were significantly greater than those in the non-ESCC group, although those of AR episodes were similar in the two groups. • The bolus exposure time of total reflux and NAR in the ESCC group were significantly longer than that in the non-ESCC group, although that of AR was not significantly different between two groups. • With regard to the median bolus clearance time, there was no significant difference between the ESCC group and the non-ESCC group.
After excluding six patients with concomitant EGC lesions from the initial ESCC group, there was the same tendency toward more frequent and longer total reflux in the ESCC group than in the non-ESCC group, although the difference did not reach statistical significance because of the limited numbers of subjects .
With regard to the correlation between the pH level and the numbers of GER episodes, we revealed that the median number of NAR was significantly proportional to the intragastric pH level (r=0.457, P=0.0129).
Impedance findings 15 cm above LES • The proximal reflux events of total reflux, those of AR, and those of NAR that reached to 15 cm above the LES in the ESCC group were 17.0 (10–23), 1.0 (0–9), and 13.5 (9–17), respectively ( Table 3). In contrast, those in the non-ESCC group were 10.0 (4–21), 4.0 (3–7), and 5.5 (1–11), respectively. • At the most proximal impedance segment, differences in the characteristics of the GER episodes between those in the ESCC group and in the non-ESCC group were not significant, although there was a trend for higher numbers of NAR episodes in the ESCC group than those in the non-ESCC group.
DISCUSSION • Although previous studies have suggested a possible linkage between gastric atrophy and ESCC risk, the pathogenic factors in this causal relationship between the two adjacent organs have been unclear. • We demonstrated for the first time that patients with ESCC located in the middle or lower esophagus were more frequently exposed to GER, especially NAR, than were those without any esophageal dysplastic lesions. • Therefore, NAR may be a key factor that links gastric atrophy to the development of ESCC.
We showed that the intragastric pH level in the ESCC group was similar to that in EGC patients who tend to have profound gastric atrophy . • Moreover, intragastric pH levels in the ESCC group of this study were comparable to those in patients with atrophic gastritis of the corpus induced by H. pylori infection , implying the existence of hypochlorhydria in the present ESCC patients. • These data agreed with our previous achievements that gastric atrophy or related hypochlorhydria was an independent risk factor for ESCC in case–control studies in Japanese subjects . In relation to lower intragastric acidity, NAR was the predominant pattern of GER in both groups.
There has been no report that directly analyzed the characteristics of GER in patients with ESCC. The conventional pH monitoring would have been of no use to evaluate GER in ESCC patients, as such subjects showed NAR as a predominant pattern of GER, most of which were undetectable by the conventional method. • Indeed, the intraesophageal pH levels in the ESCC group were similar to those in the non-ESCC group in this study. Alternatively, using portable 24-h MII-pH monitoring, which could detect all reflux events regardless of the pH level , we could successfully demonstrate that the total numbers and duration of GER in the ESCC group were significantly higher than those in the non-ESCC group and that most of those reflux episodes in the ESCC group were NAR. • The frequency of reflux episodes in the non-ESCC group of this study seemed similar to those in healthy volunteers of several populations reported in previous reports
Interestingly, compared with the impedance findings at 15 cm above the LES, the differences in those at 5 cm above the LES were more prominent between the ESCC and non-ESCC groups. These findings suggested that NAR in the lower or middle thoracic esophagus might be more clinically important than that in the upper thoracic esophagus in the pathogenesis of ESCC, . • Further studies in patients with ESCC arising from proximal portion are required to clarify the possible contribution of the proximal extent of GER to carcinogenesis in the proximal esophagus.
The carcinogenic process of ESCC is multi-factorial, in which susceptibility to the disease can be affected by other factors including environmental exposure to alcohol drinking or smoking, and genetic predisposition . Particularly in Orientals, genetic polymorphism of aldehydedehydrogenase 2, a major enzyme responsible for the elimination of acetaldehyde, is also an important determinant for ESCC . Therefore, we speculate that NAR could exert carcinogenic effects on the esophageal epithelium in conjunction with other carcinogenic factors, which sometimes lead to a multicentric pattern of neoplastic transformation as field carcinogenesis
On the other hand, the difficulty in choosing appropriate clinical controls could be a potential limitation of this study. In this study, we set up age- and sex-matched control subjects not among healthy volunteers, but among patients without esophageal dysplastic lesions who were hospitalized for EMR of small lesions of EGC, as it was difficult to enroll healthy volunteers of the same age as those of the ESCC group. • Although EGC usually develops in the context of hypochlorhydria , there has been no report that showed any direct association between motility disorder and the pathogenesis of gastric cancer. • In addition, a recent study using an impedance technique revealed that profound acid suppression with PPI did not alter the total numbers of reflux episodes, although the treatment shifted the component of reflux from acid to non-acid , suggesting that hypochlorhydria did not exert any effect on the frequency of GER. Therefore, it could be reasonable to regard the ECG patient group as a control in this study. In fact, the total numbers of reflux episodes in the present non-ESCC group were similar to those in healthy volunteers from several populations .
Summary • 24-h MII-pH technology was a useful tool for investigating the actual conditions of GER episodes in hypochlorhydric patients. • Using this new technology, we successfully revealed that the numbers and duration of total GER episodes, especially NAR, were significantly higher in ESCC patients than in age- and sex-matched controls without any dysplastic lesions of the esophagus, suggesting a pivotal role of non-acid refluxate in the pathogenesis of ESCC. Further studies are required to clarify the mechanisms by which the components of non-acid refluxate facilitate the development of ESCC.