Lymphocyte infiltration in histologic subtypes of epithelial ovarian carcinoma and its effect on survival (229)

Abstract

Objectives: The purpose of the study was to examine the degree of T and B cell infiltration in four subtypes of epithelial ovarian cancer and understand how it affects overall survival. Methods: A total of 432 patients with high-grade serous (HGS) histology, 67 patients with clear cell (CC) histology, 16 patients with mucinous histology, and 28 patients with endometrioid histology were analyzed using multiplex immunohistochemistry. All patients included were treatment naïve. The tissue microarrays of each of the samples were analyzed for the percent infiltration of lymphocytes. Total T cells were identified with CD3+, helper T cells with CD3+/CD4+, and cytotoxic T cells with CD3+/CD8+. Similarly, total B cells were identified with CD20+ and plasma cells with CD19+/CD138+. The location of the infiltrating lymphocytes was also noted and designated as “Total,” “Intraepithelial,” and “Stroma.” Kaplan-Meier survival curves were created to evaluate the association of the percent infiltration of the lymphocytes (greater than the median vs less than the median) and the patient’s survival in months. Results: Tissue microarrays of 572 ovarian carcinomas from different locations in the United States comprising high-grade serous, mucinous, clear cell, and endometrioid histologies were examined. T cell and B cell infiltration in the intraepithelial and intratumoral compartments were examined. High-grade serous (HGS) ovarian cancer had the highest percent infiltration of all T cell subtypes (CD3+, CD4+, CD8+). Compared to HGS, endometrioid tumors had a significantly lower percentage of total CD3+ T cell infiltration, while mucinous and CC tumors showed significantly lower CD8+ cytotoxic T cells infiltration. Denser intratumoral T cell infiltrates in HGS, and denser intraepithelial T cell infiltrates in CC were associated with improved survival. HGS tumors also exhibited significantly denser CD20+ B cell infiltrates compared to other histological subtypes of epithelial ovarian cancer. Infiltration of tumor islets by CD19+/CD138+ and CD20+ B cells, but not their presence in the tumor stroma, was associated with better outcomes in HGS ovarian cancer. No other histological subtype of ovarian cancer showed any significant association or trend with regards to survival in association with B cell infiltration. Conclusions: Our results suggest that the most immunogenic histologic subtype of this disease is HGS. The degree of T cell infiltration is similar in HGS and clear cell tumors, with greater intra-epithelial T cell infiltration also predicting the patients’ outcome in clear cell ovarian cancer. These findings could suggest a basis for why immune checkpoint blockade, which relies on T cell modulation, has not been as successful in epithelial ovarian malignancies as has been seen in other solid tumors. T cell infiltration in endometrioid and mucinous tumors is not only low but also is not associated with differences in survival. Furthermore, B cell infiltration appears to only be associated with improved survival in HGS. These findings suggest that future treatments of epithelial ovarian cancer may need to rely on different strategies of immunotherapy in order for them to be more successful at improving survival. Objectives: The purpose of the study was to examine the degree of T and B cell infiltration in four subtypes of epithelial ovarian cancer and understand how it affects overall survival. Methods: A total of 432 patients with high-grade serous (HGS) histology, 67 patients with clear cell (CC) histology, 16 patients with mucinous histology, and 28 patients with endometrioid histology were analyzed using multiplex immunohistochemistry. All patients included were treatment naïve. The tissue microarrays of each of the samples were analyzed for the percent infiltration of lymphocytes. Total T cells were identified with CD3+, helper T cells with CD3+/CD4+, and cytotoxic T cells with CD3+/CD8+. Similarly, total B cells were identified with CD20+ and plasma cells with CD19+/CD138+. The location of the infiltrating lymphocytes was also noted and designated as “Total,” “Intraepithelial,” and “Stroma.” Kaplan-Meier survival curves were created to evaluate the association of the percent infiltration of the lymphocytes (greater than the median vs less than the median) and the patient’s survival in months. Results: Tissue microarrays of 572 ovarian carcinomas from different locations in the United States comprising high-grade serous, mucinous, clear cell, and endometrioid histologies were examined. T cell and B cell infiltration in the intraepithelial and intratumoral compartments were examined. High-grade serous (HGS) ovarian cancer had the highest percent infiltration of all T cell subtypes (CD3+, CD4+, CD8+). Compared to HGS, endometrioid tumors had a significantly lower percentage of total CD3+ T cell infiltration, while mucinous and CC tumors showed significantly lower CD8+ cytotoxic T cells infiltration. Denser intratumoral T cell infiltrates in HGS, and denser intraepithelial T cell infiltrates in CC were associated with improved survival. HGS tumors also exhibited significantly denser CD20+ B cell infiltrates compared to other histological subtypes of epithelial ovarian cancer. Infiltration of tumor islets by CD19+/CD138+ and CD20+ B cells, but not their presence in the tumor stroma, was associated with better outcomes in HGS ovarian cancer. No other histological subtype of ovarian cancer showed any significant association or trend with regards to survival in association with B cell infiltration. Conclusions: Our results suggest that the most immunogenic histologic subtype of this disease is HGS. The degree of T cell infiltration is similar in HGS and clear cell tumors, with greater intra-epithelial T cell infiltration also predicting the patients’ outcome in clear cell ovarian cancer. These findings could suggest a basis for why immune checkpoint blockade, which relies on T cell modulation, has not been as successful in epithelial ovarian malignancies as has been seen in other solid tumors. T cell infiltration in endometrioid and mucinous tumors is not only low but also is not associated with differences in survival. Furthermore, B cell infiltration appears to only be associated with improved survival in HGS. These findings suggest that future treatments of epithelial ovarian cancer may need to rely on different strategies of immunotherapy in order for them to be more successful at improving survival.