We found that the factors independently prognostic of poor OS in patients with advanced SBA were absence of chemotherapy, no prior tumor resection, liver metastasis, and IALN metastasis. After adjustment of clinical factors using the IPTW method, chemotherapy status remained significantly associated with OS.
Of the four factors independently predictive of poor prognosis, three have previously been identified in patients with advanced SBA; these are absence of chemotherapy [7, 8], no prior tumor resection [8–11], and liver metastasis . The tumor burden of patients experiencing recurrence after curative resection, or metastasis after palliative resection has been regarded as lower than the burden in patients who did not undergo surgical resection. Although duodenal tumor location and peritoneal seeding have been reported to be predictive of poor prognosis in other series [7, 10–12], they were not statistically significant in our analysis.
In agreement with previous retrospective studies, our findings suggest that palliative chemotherapy may benefit patients with SBA [7, 9, 13–16]. As patients who did not receive chemotherapy showed the poorest prognosis, we sought to estimate the effects of chemotherapy. In principle, the best way to evaluate the efficacy of a treatment is to employ a prospective randomized comparison study, but this is near-impossible because of the rarity of SBA. Therefore, the clinical backgrounds of patients in each group were adjusted using propensity scoring, to minimize selection bias, and the survival of patients in the chemotherapy and non-chemotherapy groups was compared. As we could not perform analyses using score-matched pairs, because of the small sample size, we utilized the IPTW method to show that chemotherapy could significantly improve OS in patients with advanced SBA.
The response rate (11%) and survival outcome (median OS, 11.8 months) observed in patients receiving chemotherapy were comparable to those previously reported [9, 10, 12, 13, 15–18]. However, an optimal chemotherapy regimen remains to be defined. Chemotherapy in patients with SBA is guided primarily by the treatment of patients with colorectal or upper gastrointestinal tract cancers. FOLFOX has been shown to enhance both OS and PFS, compared with LV5FU2-cisplatin . A recent prospective Phase II trial of capecitabine-plus-oxaliplatin in patients with advanced SBA and ampullary adenocarcinoma yielded an overall RR of 50%, a median time-to-progression of 11.3 months, and a median OS of 20.4 months .
Our results should be interpreted with caution because this study had several limitations including its retrospective design and patients from a single institution, which could have selection biases. Bone and lung metastasis could be underestimated because bone scan and chest CT were not mandatory for the evaluation of disease extent. Furthermore, chemotherapy treatments were not homogeneous even though the majority of regimens consisted of fluoropyrimidine-based chemotherapy. Nonetheless, it should be considered that our cohort is one of the largest advanced SBA group evaluated to date.