Anti‐Helicobacter pylori therapy in localized gastric mucosa‐associated lymphoid tissue lymphoma: A prospective, nationwide, multicenter study in Japan

Abstract Background Helicobacter pylori eradication therapy was approved in Japan for the first‐line, standard treatment of H. pylori‐positive gastric mucosa‐associated lymphoid tissue (MALT) lymphoma. Although several retrospective studies or small‐scale single‐center studies have been reported, a prospective, large‐scale, nationwide, multicenter study has not been reported from Japan. Materials and Methods We conducted a prospective, nationwide, multicenter study to evaluate the clinical efficacy of rabeprazole‐based triple H. pylori eradication therapy for patients with localized gastric MALT lymphoma in practice‐based clinical trial. A total of 108 H. pylori‐positive patients with stage I/II 1 gastric MALT lymphoma underwent H. pylori eradication therapy. The primary endpoints were complete remission (CR) rate and the rate of transfer to secondary treatment. The secondary endpoints were CR maintenance duration and overall survival (OS). Results CR of lymphoma was achieved in 84 of 97 patients (86.6%), during the period 2.0‐44.7 months (median, 5.3 months) after starting H. pylori eradication treatment. CR was maintained in 77 of 81 patients (95.1%) for 0.4‐53.2 months (median, 33.1 months). Secondary treatments (radiotherapy, rituximab, or gastrectomy) for gastric MALT lymphoma were needed in 10 of the 97 patients (10.31%). During follow‐up, OS rate was 96.9% (94/97) and the causes of 3 deaths were not related to lymphoma. Conclusions Rabeprazole‐based H. pylori eradication therapy demonstrated a high CR rate, long CR maintenance, and a good OS for patients with localized gastric MALT lymphoma in this prospective, practice‐based, multicenter study.

lymphoma, and Helicobacter pylori eradication induces clinical and histological regression of the disease in the majority of cases, as first reported by Wotherspoon et al. 3 Approximately 60%-80% of H. pylori-positive gastric MALT lymphomas achieve complete histological response after H. pylori eradication. [3][4][5] H. pylori eradication therapy is currently recommended as the first-line treatment for all patients with gastric MALT lymphoma, as described in guidelines from the United States, Europe, and Japan. [6][7][8][9][10][11] In Japan, H. pylori eradication therapy was approved for the treatment of H. pylori-positive gastric MALT lymphoma in 2010, based on single-center retrospective studies. 12,13 To date, however, no well-controlled, prospective, multicenter studies have been reported from Japan. We therefore conducted a prospective, nationwide, multicenter study to confirm the efficacy and safety of this treatment in Japan.

| Subjects and study design
This prospective, multicenter trial (ClinicalTrials.gov, NCT01264822) was conducted at 34 hospitals in Japan from December 2010 to February 2016. Subjects were patients with H. pylori-positive gastric MALT lymphoma in stage I or II 1 , as determined by the Lugano staging system. 14  H. pylori status was determined according to histology, culture, rapid urease test, 13 C urea breath test (UBT), H. pylori stool antigen test (HpSA), and/or serology. H. pylori infection was judged as positive if at least one of the tests yielded a positive result, and as negative when all tests were negative. The endoscopic type of MALT lymphoma was classified as superficial, ulcerative, elevated, or other. 15 Endoscopic ultrasound (EUS) was performed to evaluate the depth of tumor invasion and degree of perigastric lymphadenopathy. 15 The status of t(11;18)(q21;q21)/API2-MALT1 was investigated by reverse-transcription polymerase chain reaction and/or fluorescence in situ hybridization (FISH). 15 All patients underwent H. pylori eradication with rabeprazole (RPZ)-based triple therapy (RPZ 10 mg + amoxicillin 750 mg + clarithromycin [CAM] 200 or 400 mg, or metronidazole [MNZ] 250 mg) twice a day for 7 days, as a regimen approved by the Japanese governmental healthcare system. Successful eradication was basically evaluated using the UBT or HpSA according to the Maastricht IV consensus. 10 After successful eradication, the follow-up observation was started from the first day of successful H. pylori eradication, and the related parameters including histopathology and transition to secondary treatment for MALT lymphoma were evaluated. The follow-up period after eradication therapy in each patient was basically set to ≥24 months.
This study was designed as a prospective, practice-based, observation study and conducted in compliance with Good Postmarketing Study Practice (GPSP), a ministerial ordinance of the Ministry of Health, Labour and Welfare of Japan. Patient consent was therefore not sought, but the right to opt out was explained by survey physicians according to the Japanese Ethical Rule for clinical observation studies. All the data collection and analyses were performed at Eisai Co., Ltd. (Tokyo Japan).

| Histological evaluation
Histological diagnosis of MALT lymphoma was performed from biopsy specimens by pathologists in each participating hospital. When a definitive diagnosis of MALT lymphoma could not be confirmed in the hospital, the central pathologist (T.Y.) reviewed the cases. Biopsy specimens after H. pylori eradication were also evaluated by pathologists in each the hospital, while relapsed cases and suspicious cases were reviewed by the central pathologist (T.Y.). Histopathological evaluation after treatment was carried out using the Groupe d'Etude des Lymphomes de l'Adulte (GELA) histological grading system, with classification as either complete histological response (ChR), probable minimal residual disease (pMRD), responding residual disease (rRD) or no change (NC) 8,16 or Wotherspoon's histological score (0-5). 3 Complete remission (CR) of lymphoma was defined as ChR or pMRD in the GELA system, or grades 0 or 1 in Wotherspoon's score, with non-CR defined as any other category. Histopathological examinations were performed every 3 months until 1 year after successful eradication, and every 6 months thereafter. Treatment failure was defined as relapse after CR or progressive disease (PD) including transformation into DLBCL, or non-CR after successful H. pylori eradication.

| Secondary treatment for patients with treatment failure
When a lymphoma was judged by a physician as not responsive to eradication treatment, the patients underwent other oncological treatments (radiotherapy, chemotherapy, rituximab, or surgical resection). They were defined as in transition to secondary treatment.
The timing of transfer to secondary treatment was judged by the physician, because this trial was not an interventional study, but an observation study, as defined in the Japanese Ethical Rule for clinical observation studies.

| Endpoints and statistical analysis
Primary endpoints were CR rate by H. pylori eradication therapy alone and the rate of transfer to secondary treatment. CR rate was calculated as the proportion of patients in the efficacy analysis set who responded to H. pylori eradication therapy alone (ChR or pMRD in the GELA system, or Wotherspoon score 0 or 1). In this analysis, patients who achieved CR after secondary treatment were not regarded as achieving CR by H. pylori eradication therapy. Secondary endpoints were the rate of CR maintenance and overall survival (OS), as well as rates of successful H. pylori eradication and adverse reactions to RPZ-based triple therapy. The 95% confidence intervals (CIs) were calculated with F-distribution. Subgroup analyses were performed for response rate and background factors by Fisher's exact probability test or the chi-square test, with a two-tailed significance level of 5%. Probabilities of CR maintenance, secondary treatment transfer, and OS were analyzed by the Kaplan-Meier method.

| Clinical features of patients
Among the 108 registered patients, one was excluded for a registration violation and 107 were included in the safety analysis set.
Among the 107 patients in the safety analysis set, 10 patients were excluded for either a lack of efficacy evaluation (n = 4), using a regimen unapproved in Japan (n = 4), or lacking confirmed histological evidence of MALT lymphoma (n = 2). The remaining 97 patients were included in the efficacy analysis set.
As shown in Table 1

| Response to Helicobacter pylori eradication therapy
Clinical course and outcomes in the efficacy analysis set of 97 patients are shown in Figure 1. CR was achieved in 86.6% of patients (84/97) using H. pylori eradication treatment alone. The median interval to CR after the start of the successful eradication treatment was 5.3 months (range, 2.0-44.7 months), and 61.9% of CR patients (52/84) achieved CR within 6 months after starting successful eradication treatment.
The clinical characteristics and CR rates in the 97 patients are shown in Table 1. Cases with superficial type on endoscopy showed a significantly higher CR rate than cases with other type (P = .016).

| Secondary treatment for non-responders and relapsed cases
Among the 97 patients in the efficacy analysis set, 10 (10.3%) were transferred to secondary treatments. These 10 patients included 3 of the 4 relapsed patients who had initially achieved CR, and 7 of the 13 patients who did not achieve CR after successful H. pylori eradication.
Secondary treatments included radiotherapy in 7 patients, rituximab monotherapy in 1 patient, radiotherapy combined with rituximab in 1 patient, and surgical resection in 1 patient with concomitant gastrointestinal stromal tumor of the stomach. Six of the 13 patients who did not achieve CR after successful H. pylori eradication therapy were followed up under a watch-and-wait strategy. The median interval to secondary treatment of MALT lymphoma was 12.3 months (range, 2.8-29.3 months). Kaplan-Meier estimates for the cumulative probability of secondary treatment transfer were 5.4% (95%CI, 2.3%-12.6%) at 12 months, 10.1% (95%CI, 5.4%-18.5%) at 24 months, and 11.5% (95%CI, 6.3%-20.4%) at 36 months and at 48 months. The median interval to CR after secondary treatment was 2.1 months (range, 1.5-12.9 months). Seventeen patients had shown treatment failures (4 patients relapsed after CR, 13 patients were non-CR) (Figure 1).

| Other cancers
Other cancers detected after the start of eradication therapy were observed in 5 of 97 patients (5.2%), comprising 2 gastric cancers, 1 brain tumor, 1 esophageal cancer, and 1 pancreatic cancer. The interval from start of successful eradication treatment until detection of other cancer was 1.9 months and 5.9 months for the two gastric cancers, 10.2 months for the brain tumor, 27.5 months for the pancreatic cancer, and 41.5 months for the esophageal cancer.

| Safety
Adverse reactions for H. pylori eradication were recorded in 3 of 107 patients (2.8%), comprising rash in 1 case, drug eruption in 1 case, and diarrhea and dysgeusia in 1 case. Apart from drug eruption, these reactions resolved spontaneously after the completion of eradication therapy. Only 1 patient developed a serious adverse reaction, the drug eruption, who was needed intravenous administration of prednisolone, and the reaction was attributed to penicillin allergy. Because gastric MALT lymphoma shows a slow progression and an excellent prognosis generally, one option is to adopt a watch-andwait approach using endoscopy and suitable histopathology, as long as no deterioration of any remaining lymphoma is recognized. 34 The National Comprehensive Cancer Network guideline recommends adopting a watch-and-wait strategy for 6 months after successful eradication in symptom-free cases, even if lymphoma remains. 6  No .
a Relapse, progressive disease, and/or non-CR at 6 months after eradication. and followed using a watch-and-wait strategy obtained a second CR during the follow-up period, while 6 of 13 non-CR patients were followed up using a watch-and-wait strategy, but did not achieved PD without secondary therapy. The duration of watch-and-wait before transfer to secondary treatment was >6 months in 80% (8/10) and ≥1 year in 50% (5/10) in this study.
Several limitations must be considered in the present study.

ACK N OWLED G M ENTS
We wish to thank all the staff at the following 34 Japanese medical centers who cooperated with this study and provided valuable data: We also wish to thank Seiichiro Hojo (Eisai Co., Ltd., Tokyo, Japan) and Saori Katata (EPS Corporation, Tokyo, Japan) for their advice on statistical analysis. This study was funded in full by Eisai Co., Ltd.  (14) CR, complete remission. a Relapse, progressive disease, and/or non-CR at 6 months after eradication.

CO N FLI C T O F I NTE R E S T
Otsuka Pharmaceutical Co., Ltd. Yasuhiko Kitadai, Ichiro Oda, Shotaro Nakamura, and Tadashi Yoshino have nothing to declare.

AUTH O R CO NTR I B UTI O N S
Guarantor of the article: Toshiro Sugiyama Katsuya Sugizaki, as the sponsor's (Eisai Co., Ltd.) employee in charge of this study, was involved in protocol planning, data interpretation, writing the first draft of the manuscript, and revising its final version. Akira Tari and Shotaro Nakamura were involved in protocol planning, patient recruitment, and data interpretation. Yasuhiko Kitadai and Ichiro Oda were involved in patient recruitment. Tadashi Yoshino was involved in protocol planning and data interpretation.
Toshiro Sugiyama, as the principal investigator, had overall responsibility of the study and was involved in protocol planning, data interpretation, and revising final version of the manuscript. All authors approved the final version of the manuscript.