To the best of our knowledge, this is the only one retrospective study ever conducted in a tertiary hospital in China that summarize the experience of diagnosis and treatment of AIP, which specifically focus on the management of relapse and side effects. We found the misdiagnosis rates of AIP is very high, so it is very important to improve the accurate diagnosis rate of AIP. There was no significant difference between prednisolone and prednisolone plus cyclophosphamide in the treatment of type Ⅰ AIP. Increasing the dose of steroid can be effective on therapy relapse patients. Low dose steroid and symptomatic treatment should be performed when side effects arise from a high dose of steroid.
AIP is an enigmatic disease and sometimes difficult to diagnose [30]. The clinical manifestations of AIP are complex, in particular, focal AIP is very similar to pancreatic cancer in imaging manifestation, so it is difficult to distinguish focal AIP from pancreatic cancer. But AIP is sensitive to hormone therapy and does not need surgical treatment, whereas pancreatic cancer requires surgical treatment. Therefore, the differential diagnosis between AIP and pancreatic cancer is great importance. AIP has a variety of diagnostic criteria, and the applicable conditions and methods of each criterion are different, so the AIP diagnosed in different countries may sometimes differ [16]. In 2011, Shimosegawa et al first proposed the International Consensus of Diagnostic Criteria (ICDC) of AIP, and divided the AIP into Type I and Type II, which is the most widely accepted diagnostic criteria [10]. The AIP in China is mainly type I, that is, IgG4-related diseases affect the pancreas, most of them onset in the elderly, and about 70% of cases can be diagnosed in experienced treatment centers without the pathological specimens [17].
Elevated gamma globulinemia and immunoglobulin IgG, especially elevated IgG4, have been considered as characteristic indicator of AIP [18]. As many as 94% of AIP patients have elevated IgG4 levels [31], and IgG4 levels are closely related to disease activity [32]. Van Heerde et al. [33] studied the serum IgG4 and CA19-9 in patients with AIP and pancreatic cancer found that the sensitivity and specificity for diagnosis of AIP was 73% and 74% respectively with CA19-9 < 74 kU/L as the cut-off value. with IgG4 > 2.6 g/L as the threshold, the sensitivity of IgG4 for diagnosis of AIP was 70%, and the specificity was 100%. The sensitivity and specificity of diagnosis of AIP with combined CA19-9 < 74 kU/L and IgG4 > 1.0 g/L was 94% and 100% respectively. Therefore, simultaneous detect IgG4 levels and CA19-9 can improve the differential diagnosis rate between AIP and pancreatic cancer. The results of this study were basically consistent with the report. 72 patients were tested for IgG and 62 patients (86.1%) were elevated; IgG4 was detected in 62 cases, and 56 cases (90.3%) were positive.
Chari et al. [12] reported that 30% of AIP patients needed steroid experimental therapy, needle biopsy and surgical resection to make a definite diagnosis. In this study, 16 cases (19.5%) were misdiagnosed as pancreatic cholangiocarcinoma and were diagnosed as AIP after surgery. Focal mass AIP is difficult to be diagnosed by imaging examination and endoscopic ultrasound biopsy [34], and endoscopic ultrasound biopsy is not available in some hospitals, so biopsy of the involved organs is helpful for diagnosis. In this study, 44 patients (53.7%) underwent tissue biopsy. The results showed that biopsy of involved organs is beneficial to the diagnosis of AIP. If cholangitis is combined, do ERCP and duodenal papillary biopsy can help to exclude pancreatic cancer and cholangiocarcinoma. When the differential diagnosis is not clear, steroid experimental therapy is helpful to diagnose AIP, but in order to avoid delay in the treatment of malignant tumors, imaging examination have performed 2 to 4 weeks after hormone therapy, the mass must be nearly completely relieved, any no relief of the mass must do exploratory surgery [35].
The first goal of therapy in type I AIP is to induce remission. Response to steroid therapy in patients with AIP is dramatic and consistently leads to clinical improvement regardless of the subtypes [19, 36]. As a result, steroids have become the standard therapy for inducing remission in AIP [37, 38]. In the ICDC the starting dose of steroid for remission induction is defined as 0.6–1 mg/kg per day [10]. Hart et al. [39] suggested the usefulness of a step-up approach to treating AIP with azathioprine, 6-mercaptopurine, mycophenolate mofetil, cyclophosphamide or rituximab. Treatment with prednisolone plus cyclophosphamide has not been explored in AIP. In our study we use initial prednisolone fixed-dose (30mg/d) or prednisolone (30mg/d) plus cyclophosphamide (100 mg/d) regimen. We found that the effective rate of prednisolone and prednisolone plus cyclophosphamide was no significant difference [37/40 (92.5%) vs 22/24 (91.7%), P = 0.904].
Although steroid therapy is effective, but the type I AIP has a high RRs, ranging from 24–63% [19–22]. The Japanese consensus guidelines for AIP recommend re-administration or dose-up of steroid in patients who relapse after successful remission induced by initial steroid therapy [20]. Kazuichi Okazaki et al. [40] reported that most relapsed AIP cases, remission can be achieved with the same prednisolone dose as the initial dose, although it may be necessary to taper more gradually. In our study the relapsed patients achieved the same prednisolone or prednisolone plus cyclophosphamide dose as the initial dose, and most of the patients who relapsed had good results.
Current guidelines recommend low-dose (5 mg/day) maintenance steroid treatment (MST) for 2–3 years to reduce the relapse rate (< 30%) [41]. However, steroid side effects are inevitable, the risk of corticosteroid-associated side effects, as well as the lifetime cumulative steroid dose, must be considered, the short- and long-term corticosteroid treatment may induce side effects, including chronic glycometabolism, obesity, an immunocompromised status against infection, cataracts, glaucoma, osteoporosis, and myopathy [42]. The majority of side effects, including secondary diabetes mellitus and osteoporosis, are treatable and/or preventable. Severe side effects, such as infection, bone fracture, femoral head necrosis and cardiovascular diseases, are life-threatening and should be avoided [41]. In this research the side effects of the 64 medications treatment patients were DM in 8 cases (12.5%); central obesity or moon face in 10 cases (15.6%); hyperlipidemia in 12 cases (18.8%); gastric ulcer in 4 cases (6.3%); osteoporosis in 6 case (9.4%); bone fracture in 1 case (1.6%). For these patients we reduce the dose of prednisolone, and low dose maintenance treatment was performed, furthermore, oral hypoglycemic drugs for DM patients, oral statins for central obesity or moonface and hyperlipidemia patients, oral proton pump inhibitors (PPIs) and gastric mucosal protection drugs for gastric ulcer patients, and oral calcium supplements for osteoporotic patients. For the fracture patient we withdrew prednisolone and operated on fracture, but AIP recurred three months later, and we performed low dose prednisolone maintenance treatment, the effect is also very good.
We acknowledge the study has several limitations. This study is a retrospective study, retrospective analysis may lead to some bias. Additionally, some patients with incomplete information are excluded, which may have some influence on the results. Lastly, China as a high incidence of type Ⅰ AIP countries, the number of cases is not enough, so there may be partial bias. Further multicenter, prospective original studies would provide more precise data to reduce potential confounding results.