Predictive and Prognostic Role of Tumor-Infiltrating Lymphocytes for Early Breast Cancer According to Disease Subtypes: Sensitivity Analysis of Randomized Trials in Adjuvant and Neoadjuvant Setting

Background: The role of tumor-infiltrating lymphocytes (TILs) in breast cancer (BC) is still an issue for clinical research. Toward this end, a sensitivity analysis of neoadjuvant and adjuvant randomized clinical trials was performed according to disease subtypes.

Methods: Pathological complete responses (pCRs) after neoadjuvant treatment according to the presence or absence of lymphocyte-predominant BC (LPBC) were extracted and cumulated as odds ratios (ORs) by adopting a random-effects model by subtype. Overall survival hazard ratios as a function of 10% incremental values of stromal TILs (sTILs) in adjuvant trials were extracted. The interaction test was adopted to determine the differential effect according to the subtype.

Results: Eight trials (5,514 patients) were identified. With regard to neoadjuvant setting (4 studies), a significant interaction (p < .0001) according to LPBC was found. The presence of LPBC was associated with a 29.5% increase in pCR rate compared with non-LPBC (p < .0001). The pCR rate was significantly higher in patients with LPBC in triple-negative BC (TNBC) and HER2-positive BC settings, with an absolute difference of 15.7% (95% confidence interval [CI], 4.9%-26.2%) and 33.3% (95% CI, 23.6%-42.7%), respectively. With respect to the adjuvant setting (4 studies), a significant interaction (p < .0001) according to sTILs was found. A survival benefit was more likely to be determined for HER2-positive BC (p = .025) and TNBC (p < .0001), with no statistically significant difference for estrogen receptor-positive/HER2-negative disease.

Conclusion: Despite the retrospective nature of this analysis, the presence of TILs may represent a robust predictive and prognostic marker for BC, particularly for TNBC and HER2-positive disease.