The duodenal papilla is located at the opening where the pancreatic-bile ducts merge into the duodenum [1, 2]. Tumors growing in this region can present with progressive and painless jaundice at an early stage, offering the possibility of early diagnosis [3, 24]. Compared to distal cholangiocarcinoma and pancreatic head adenocarcinoma, DPC has a higher resection rate and a better long-term prognosis, with a five-year survival rate of up to 50% [3]. PD is by far the preferred strategy for radical resection of DPC, however, even after radical resection, some patients are prone to relapse. In this study, we integrated four independent prognostic factors for DPC to develop and validate a series of nomograms to predict ER and long-term survival for DPC after PD. Both the DPC-ER and DPC-OS nomogram showed higher predictive accuracy and net benefit than single variable (including tumor size, perineural invasion, lymph node metastasis, and tumor differentiation status).
Early tumor recurrence is a common and fatal condition in various malignancies, including DPC, and often indicates a poor prognosis [2, 25, 26]. Although DPC has a better long-term prognosis compared with pancreatic head adenocarcinoma and distal cholangiocarcinoma, 30% of patients will relapse within 2 years after surgery [3]. Thus, screening for independent prognostic factors associated with tumor recurrence may help guide further treatment of these patients and improve their overall prognosis [12]. Previous studies have shown that tumor size, lymph node metastasis, tumor differentiation status, and TNM stage are important prognostic factors affecting the recurrence and long-term survival of DPC after resection [3]. Consistent with previous studies, in the present study, multivariate logistic regression analysis revealed that tumor size, peripheral nerve invasion, lymph node metastasis, and tumor differentiation status were also independent prognostic factors for ER of DPC.
Yoen et al. [27] analyzed preoperative imaging findings of ampullary or papilla carcinoma and found that tumor size was an independent prognostic factor affecting OS and disease-free survival (DFS). Park et al. [28] also indicated that tumor recurrence was significantly affected by tumor diameter. Larger tumor diameters often indicate that the tumor was detected later and has a broader invasion area [27, 28]. Several studies have shown that lymph node metastasis and perineural invasion are the major factors affecting the recurrence and long-term survival of DPC after surgery. de Castro et al. [29] demonstrated that the long-term prognosis of patients was negatively correlated with the number of lymph node metastases. Sakata et al. [30] also found that the number, not the location, of positive regional lymph nodes independently affects long-term survival after resection in patients with ampullary carcinoma. These findings suggest that standardized lymph node dissection may be important in improving long-term outcomes in these patients. Although the incidence of perineural invasion in DPC is lower, perineural invasion often indicates tumor progression and a poorer prognosis [31]. Junrungsee et al. [24] retrospectively analyzed the clinicopathological data of 72 patients with carcinoma of the ampulla of vater (CAV) treated by PD and found that tumor differentiation status was also an important prognostic factor affecting the long-term survival of these patients. Tumor differentiation status is also an important prognostic factor for ER and long-term survival in patients with DPC. Poor tumor differentiation often indicates strong invasion ability and early metastasis [24, 29, 31].
In the present study, we not only demonstrated the value of these four factors in predicting long-term survival outcomes for DPC, but for the first time integrated these four independent prognostic factors to develop the DPC-ER and DPC-OS models for predicting ER and OS for DPC following radical resection. The results indicated that the prediction models exhibited satisfactory prediction performance in both the training and validation cohorts. The DPC nomogram models were more accurate in predicting ER and long-term survival compared to a single variable. In addition, patients were further divided into different risk subgroups according to the DPC-ER nomogram score (high-risk group: nomogram score > 63; low-risk group: nomogram score ≤ 63). The results showed that patients in the high-risk group had significantly higher ER rates than those in the low-risk group, and that patients in the low-risk group had significantly better RFS and OS than those in the high-risk group. Thus, with the DPC predictive models, we can screen high-risk patients for tumor recurrence at an early stage and recommend them for closer post-operative follow-up and timely adjuvant therapy to prolong survival. In addition, we further transform the series nomogram into an online calculator so that it can be used in real-time to provide predictive capabilities in computers or mobile terminals, thus generating a high level of clinical utility [32].
Although the DPC prediction models constructed in this study can effectively screen ER patients and accurately predict their long-term survival after radical resection, several limitations need to be clarified. First, this study is a retrospective study conducted from a single center, and inherent biases are inevitable. In the future, multicenter and prospective studies are needed to validate the predictive power of the web-based calculators. Second, the sample size of this study is relatively small and we will further collect relevant patients in the future to provide more convincing validation results. Third, pathology classification of DPC was not performed in this study due to constraints from existing pathology diagnosis results. Finally, given the fact that the specific adjuvant therapy and outcomes were unknown, further exploration of the clinical efficacy of adjuvant therapy and different adjuvant therapies in patients in high-risk and low-risk subgroups is warranted in the future.