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Improved Survival With Higher TIL Values in Advanced HER2-Positive Breast Cancer

Baseline stromal tumor–infiltrating lymphocyte level was associated with overall survival in patients with advanced HER2-positive breast cancer receiving trastuzumab/docetaxel plus pertuzumab or placebo, according to the findings from a retrospective analysis of the phase III CLEOPATRA trial. Moreover, each 10% increase in tumor-infiltrating lymphocyte level was associated with an 11% reduction in the risk of death.

To investigate the prognostic role of host antitumor immunity in the setting of advanced disease, the investigators evaluated stromal tumor–infiltrating lymphocytes in both archival and fresh tissue. Tumor samples from 678 of 808 participants (84%) were evaluable for stromal tumor–infiltrating lymphocytes, including 519 archival samples (77%) and 155 freshly obtained samples (23%) collected ≤ 45 days before randomization. 

Progression-free survival did not appear to be associated with stromal tumor–infiltrating lymphocytes (adjusted hazard ratio [HR] = 0.95, P = .063), but each 10% increase in stromal tumor–infiltrating lymphocytes was significantly associated with longer overall survival (adjusted HR = 0.89, P = .0014).

The treatment effect of pertuzumab did not differ significantly by stromal tumor–infiltrating lymphocyte value for either progression-free survival (adjusted HRs = 0.94 for pertuzumab and 0.99 for placebo for each 10% increment; P = .23 for interaction) or overall survival (adjusted HRs = 0.89 for pertuzumab and 0.95 for placebo for each 10% increment; P = .21 for interaction).

The authors’ interpretation of these findings led them to suggest that, “Future clinical studies in this cancer subtype should consider tumor-infiltrating lymphocytes as a stratification factor and investigate whether therapies that can augment immunity could potentially further improve survival.”

Editor’s note: A meta-analysis of neoadjuvant trials reported at the 2016 San Antonio Breast Cancer Symposium also noted that tumor-infiltrating lymphocyte levels were a strong predictor of pathologic complete response in all breast cancer subtypes and were associated with a survival benefit in HER2-positive and triple-negative disease (Denkert C, et al: Abstract S1-09).