Breast carcinoma tumour-infiltrating lymphocytes in pre- and post-systemic therapy in HIV-positive and HIV-negative women.

Background: HIV-positive women with breast cancer do not exhibit significant differences in tumour characteristics when compared to their HIV-negative counterparts. Stromal tumour-infiltrating lymphocytes (TILs) serve as an important indicator of the host's capacity to combat malignancy, particularly during the early stages of tumour progression. Objectives: The objective of this study was to assess and compare the pathological characteristics of breast carcinomas, specifically focusing on TILs in histological specimens obtained before and after systemic therapy, between HIV-positive and HIV-negative patient groups at a public hospital in the Western Cape province. Additionally, the study aimed to determine whether a higher percentage of TILs was associated with a favourable treatment response. Method: A retrospective cohort study was conducted, incorporating a negative control group matched for histological subtype, and intrinsic subtypes among patients diagnosed between January 2017 and December 2018. Results: There was no significant difference in TILs before and after treatment, nor was there a difference between patients treated with neoadjuvant chemotherapy (NACT) compared to those receiving endocrine therapy (ET) within both groups. A complete pathological response was achieved in four HIV-positive patients (14%) and one HIV-negative patient (2%). An inversely proportional relationship was noted between TILs and CD4 counts prior to treatment. Conclusion: This study found no significant differences in TILs between HIV-positive and HIV-negative women with breast cancer. There is a need for further research on the prognostic value of TILs, especially for guiding additional treatment options including the use of immune checkpoint inhibitors.