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Evaluation of Tumor-infiltrating Leukocyte Subsets in a Subcutaneous Tumor Model
Published on: April 13, 2015
Association of Tumor-Infiltrating Lymphocytes (TILs) With Pathological Complete Response to Neoadjuvant Therapy
Noor Ul Ain1, Sara Ishaq2, Muhammad Khurrum Islam3
1Oncology, King Edward Medical College, Lahore, Lahore, PAK.
Background:
Breast cancer remains a major global health challenge, with tumor-infiltrating lymphocytes (TILs) emerging as a potential biomarker of response to neoadjuvant therapy. This study aimed to evaluate the association between stromal TILs and pathological complete response (pCR) across different molecular subtypes of breast cancer within a South Asian population.
Materials And Methods:
A cross-sectional analytical study was conducted at the Department of Oncology, Sindh Medical College, Karachi, from February 15, 2025, to August 15, 2025. A total of 110 female patients with histologically confirmed breast cancer who received standard neoadjuvant therapy and subsequently underwent surgery were included. The cohort comprised all major molecular subtypes (Luminal A, Luminal B, HER2-positive, and triple-negative). HER2-positive patients received anti-HER2-targeted therapy (trastuzumab ± pertuzumab), while triple-negative patients received standard chemotherapy. Stromal TILs were evaluated on pre-treatment biopsy specimens stained with hematoxylin and eosin (H&E), following the International Immuno-Oncology Biomarker Working Group guidelines. A pre-specified cut-off of 20% was used to categorize TILs as low or high, consistent with prior studies and regional validation protocols. Statistical analyses included chi-square tests and multivariate logistic regression to identify independent predictors of pCR.
Results:
The mean age of participants was 48.6 ± 10.2 years, and 58 (52.7%) were postmenopausal. Overall, 40 (36.4%) patients achieved pCR. High TILs were observed in 50 (45.5%) cases and were significantly associated with higher pCR rates compared to those with low TILs (28/50, 56.0% vs. 12/60, 20.0%; p < 0.001). In multivariate analysis, high TILs (adjusted OR 5.25; 95% CI 2.10-13.1; p < 0.001), HER2-positive subtype (adjusted OR 2.10; 95% CI 0.90-4.92; p = 0.08), and triple-negative subtype (adjusted OR 1.75; 95% CI 0.65-4.72; p = 0.27) independently predicted higher pCR rates.
Conclusion:
High stromal TILs were strongly associated with improved pathological complete response following neoadjuvant therapy, particularly in HER2-positive and triple-negative breast cancer subtypes. Routine TIL assessment offers a simple, cost-effective, and clinically meaningful biomarker for predicting therapeutic response and guiding individualized treatment strategies, especially within resource-limited regional settings.
