Impact of histological response after neoadjuvant therapy on podocalyxin as a prognostic marker in pancreatic cancer

Abstract

Podocalyxin overexpression associates with poor survival in pancreatic cancer (PDAC). We investigated whether podocalyxin expression correlates with treatment response or survival in neoadjuvant-treated PDAC. Through immunohistochemistry, we evaluated podocalyxin expression in 88 neoadjuvant and 143 upfront surgery patients using two antibodies. We developed a six-tier grading scheme for neoadjuvant responses evaluating the remaining tumor cells in surgical specimens. Strong podocalyxin immunopositivity associated with poor survival in the patients responding poorly to the neoadjuvant treatment (HR 4.16, 95% CI 1.56-11.01, p = 0.004), although neoadjuvant patients exhibited generally low podocalyxin expression (p = 0.017). Strong podocalyxin expression associated with perineural invasion (p = 0.003) and lack of radiation (p = 0.036). Two patients exhibited a complete neoadjuvant response, while a strong neoadjuvant response (≤ 5% of residual tumor cells) significantly associated with lower stage, pT-class and grade, less spread to the regional lymph nodes, less perineural invasion, and podocalyxin negativity (p < 0.05, respectively). A strong response predicted better survival (HR 0.28, 95% CI 0.09-0.94, p = 0.039). In conclusion, strong podocalyxin expression associates with poor survival among poorly responding neoadjuvant patients. A good response associates with podocalyxin negativity. A strong response associates with better outcome.

Figure 1

Immunohistochemical staining pattern of podocalyxin in neoadjuvant treated pancreatic ductal adenocarcinoma. Staining pattern of podocalyxin in neoadjuvant treated pancreatic ductal adenocarcinoma using monoclonal antibody, HES9 (1A-1D) and polyclonal antibody, HPA2110 (2A-2D). Representative images of podocalyxin expressions using HES9: (1A) negative expression with positivity in blood vessels, (1B) weak cytoplasmic positivity, (1C) moderate cytoplasmic positivity, and (1D) strong cytoplasmic positivity. Representative images of podocalyxin expression using HPA2110: (2A) negative expression with positivity in blood vessels, (2B) weak cytoplasmic positivity, (2C) moderate cytoplasmic positivity, and (2D) strong cytoplasmic positivity. Magnification is x200.

Figure 2

Frequencies of the different neoadjuvant responses and the percentage of viable residual tumor cells.

Figure 3

Kaplan–Meier and Aalen-Johansen survival by podocalyxin immunoexpression. (a) The association of disease-specific survival (DSS) and podocalyxin immunoexpression based on polyclonal (pAb), HPA2110 and monoclonal antibodies (mAb), HES9 combined among non-responders. A categorization for podocalyxin expression with three groups was created as follows: 1, strong staining for both pAb and mAb (both scored 3); 2, either exhibiting strong staining (either scored 3); and 3, both staining weakly (both scored 0–2), corresponding to strong, moderate, and weak, respectively. Non-responders were defined as a class 4 or 5 response corresponding to > 50% residual tumor cells. Kaplan–Meier analysis. Log-rank test was used for statistical significance. (b) The association of progression-free survival (PFS) and podocalyxin immunoexpression based on polyclonal (pAb) and monoclonal antibodies (mAb) combined among non-responders. A categorization for podocalyxin expression with three groups was created as follows: 1, strong staining for both pAb and mAb (both scored 3); 2, either exhibiting strong staining (either scored 3); and 3, both staining weakly (both scored 0–2), corresponding to strong, moderate, and weak, respectively. Non-responders were defined as a class 4 or 5 response corresponding to > 50% residual tumor cells. Death from any cause (overall survival, OS) was used as a competing event. Aalen-Johansen analysis. Gray's test was used for statistical significance. (c) The association of progression-free survival (PFS) and podocalyxin immunoexpression with polyclonal antibody HPA2110, (pAb) in the upfront surgery group. Podocalyxin expressions were grouped as follows: 1, strong staining for pAb (scored 3); and 2, moderate, weak or negative staining for pAb (scored 0–2) corresponding to strong and weak, respectively. Upfront surgery patients included for the analysis. Aalen-Johansen analysis. Death from any cause (overall survival, OS) was used as a competing event. Grays' test was used for statistical significance. (d) The association of progression-free survival (PFS) and podocalyxin immunoexpression with monoclonal antibody HES9, (mAb) in the upfront surgery group. Podocalyxin expressions were grouped as follows: 1, strong staining for mAb (scored 3); and 2, moderate, weak or negative staining for mAb (scored 0–2) corresponding to strong and weak, respectively. Upfront surgery patients included for the analysis. Aalen-Johansen analysis. Death from any cause (overall survival, OS) was used as a competing event. Grays' test was used for statistical significance.

Figure 4

Kaplan–Meier and Aalen-Johansen survival by neoadjuvant therapy (NAT) response. (a) The association between NAT response and disease-specific survival (DSS). NAT responses were grouped as follows: a strong response as class 0 or 1 response, corresponding to ≤ 5% residual tumor cells (RTCs) and a poor response as class 2–5 response corresponding to > 5% RTCs. Kaplan–Meier analysis. Log-rank test was used for statistical significance. (b) The association between NAT response and progression-free survival (PFS). NAT responses were grouped as follows: a strong response as class 0 or 1 response, corresponding to ≤ 5% residual tumor cells (RTCs) and a poor response as class 2–5 response corresponding to > 5% RTCs Death from any cause (overall survival, OS) was used as a competing event. Aalen-Johansen analysis. Gray's test was used for statistical significance.