Impact of Tumour Infiltrating Lymphocytes on the Recurrence Free Survival of Breast Cancer Patients; a Cohort Study

Abstract

Breast cancer(BC) is the most common cancer in Sri Lanka since the year 2000. It is a heterogeneous disease with many biologically distinct subtypes. Tumour infiltrating lymphocytes (TIL) is a new prognostic biomarker for BC. The current study intended to assess the effect of TIL on the recurrence free survival (RFS) of a cohort of BC patients. Data of consecutive BC patients were retrieved based on inclusion and exclusion criteria, from the department survival database, which included BC patients who sought immunohistochemical assessment from 2006 to 2015, from the immunohistochemistry laboratory of the Department of Pathology, Faculty of Medicine, University of Ruhuna. TIL was semi-quantitatively assessed according to TILs Working Group 2014 guidelines. TILs of all BCs were categorized as low (TIL 0-10%), intermediate (TIL-20-40%), and high grade(TIL–50-90%). Kaplan-Meier model with log-rank test was used for survival analysis. A total of 284 patients were included. Low stromal-TIL was present in 73.9% (n=210) while 13.78% (n=39) had intermediate and 12.3%(n=35) had high stromal-TIL. Stromal-TIL grade and Nottingham grade of BC (p<0.001), ER(estrogen receptor) expression (p=0.002), PR(progesterone receptor) expression (p=0.005) and molecular subtype (p=0.007) had a significant association. High-TIL was more commonly seen among BCs with no ER and PR expression (p=0.002,0.005), than those with hormone expression and in triple-negative BCs 9p=0.007). There was no significant difference in RFS (p=0.297) between the three TIL groups. Even the RFS (p=0.573) of the low stromal TIL against the high stromal-TIL group did not have a significant difference. High stromal-TIL is present in the subsets of BCs which are ER, PR negative, and triple negative. However, the presence of high stromal TIL has not imparted an RFS benefit to the BC patients in the study group which comprised all molecular subsets. It is recommended to assess the effect of TIL in a triple-negative subset of patients than in a heterogeneous group of BC patients.