Circulating CgA is considered important in indicating tumor recurrence in most radically operated midgut carcinoid tumor patients. Therefore, we wanted to evaluate the significance of CgA protein expression levels on PFS and RFS in our patient biological activity material. The median level of circulating CgA in 36 patients with primary tumors was mainly within the same reference range with CgA <4.0 ng/ml, as shown in Table 2. The Cox regression modeling as explained in Material and Methods revealed that anti-Ma2 titer is more predictive of patient outcome than CgA concentration. The statistical analysis of PFS showed that Cox proportional hazard for the progression time in function of anti-Ma2 + CgA properly fits; p value=0.0192. Clear effect of anti-Ma2 titer was found (coefficient=0.000409 and p-value=0.
013), whereas no significant effect of CgA was found (coefficient=0.141492, p-value=0.087). Similar analysis of RFS showed that Cox proportional hazard for the recurrence time in function of anti-Ma2 + CgA fits with p-value=0.0222. Clear effect of anti-Ma2 titer was shown (coefficient=0.000397, p-value=0.015); whereas no significant effect of CgA was found (coefficient=0.140190, p-value=0.089). We observed that in the group of 19 patients with Ma2 autoantibody titer < cutoff only 4 patients had tumor recurrence during the follow-up. 2 of these 4 patients had increased CgA levels. Furthermore, in the group of 17 patients with Ma2 autoantibody titer > cutoff 13 patients presented tumor recurrence. CgA levels increased in only one out of these 13 patients.
Our study clearly shows by Cox modeling that CgA is not predictive of PFS and RFS. Circulating Ma2 autoantibody levels and Ma2 expression in SI-NET patients Matched blood samples and formalin-fixed paraffin-embedded tumor material from 20 untreated SI-NET patients at different stage of disease with primary tumors (P), lymph node metastasis (LNM) and liver metastasis (LM) were analyzed to detect a possible correlation between the serum titer of Ma2 autoantibodies and the tumor expression of Ma2 antigen. Patients are described in Table S1. We evaluated serum samples by ELISA and the expression of Ma2 by immunohistochemistry (IHC) analysis. The ELISA results found that 12 patients out of 20 expressed Ma2 autoantibodies with titer higher than the cutoff, whereas 8 patients out of 20 expressed Ma2 autoantibodies with titer lower than the cutoff.
The results are summarized in Table S1. We confirmed that our commercial rabbit antibody specifically detects Ma2 antigen (Figure S1) Ma2 immunohistochemistry was then performed on primary Cilengitide tumors and metastases from the same patients. The results showed that all 12 patients who expressed Ma2 autoantibodies with titer higher than the cutoff were positive for Ma2 in the tumors.