TILs linked to HER2-positive breast cancer treatment outcomes
medwireNews: Tumour-infiltrating lymphocytes (TILs) could serve as a prognostic marker in patients with early-stage HER2-positive breast cancer being treated with chemotherapy plus trastuzumab, indicates an analysis of the ShortHER trial comparing 9 weeks of trastuzumab with the standard 1-year regimen.
Among 866 trial participants who were evaluable for TILs, higher levels were associated with significantly better distant disease-free survival (DDFS), such that the hazard ratio (HR) was 0.76 for each 10% increment in TIL levels.
The relationship held true after accounting for age, stage, histological grade, and hormone receptor status, which gave a significant HR of 0.73 per 10% increment in TILs.
Of note, although the primary analysis of the trial did not demonstrate noninferiority of the 9-week regimen, the current study found a significant interaction between TIL levels and treatment. Specifically, DDFS was significantly worse with the 9-week than 1-year regimen among participants with TIL levels below 20%, with 5-year rates of 88.8% and 93.3%, and an HR of 1.75.
By contrast, DDFS did not differ significantly between the 9-week and 1-year schedules for patients with TIL levels of 20% or more; the corresponding 5-year DDFS rates were 97.6% and 93.7%.
These findings indicate that “higher TILs may discriminate patients at good prognosis who may be optimally treated with shorter trastuzumab”, say Pier Franco Conte, from the University of Padova in Italy, and co-authors.
“If further validated in other studies, this may represent the first evidence of potential clinical utility in this setting”, they write in the Annals of Oncology.
The study authors caution, however, that the 20% cutoff value was chosen arbitrarily and therefore the analyses using the cutoff “should be considered as exploratory.”
And they stress the need for individual pooled analyses of large studies “in order to draw definitive conclusions on the potential clinical utility of TILs in selecting patients for deescalated therapies.”
The team concludes: “Although general TILs evaluation does not allow to capture the complexity of the tumor immune milieu, it constitutes a simple, inexpensive and reproducible biomarker able to discriminate patients at different prognosis independently from classic clinicopathological features.”
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