78P - Multiplex immunohistochemistry and digital pathology analysis examining the prevalence and prognostic value of tertiary lymphoid structures in early stage hormone positive, HER2 negative breast cancer

Background

Tertiary lymphoid structures (TLS) are ectopic lymphoid organs that arise in nonlymphoid tissue sites of chronic inflammation including tumours. The presence of TLS, has been associated with increased tumour antigen presentation and improved cytokine-mediated signalling activity against tumour cells. Due to this, TLS have been associated with favourable outcomes in a number of cancer types. There is limited data regarding the prevalence and prognostic implication of TLS in hormone positive, HER2-negative (ER+/HER2-) breast cancer.

Methods

Formalin-fixed paraffin embedded blocks from a cohort of 429 patients with early stage hormone positive/ HER2-negative breast cancer were used to construct a TMA with three x 1 mm cores per patient. Multiplex chromogenic immunohistochemistry staining was performed to stain for CD3+ T cells, CD20+ B cells and DCLamp + dendritic cells. Digital image analysis was performed using Qupath open source software.

Results

On the basis of staining with the TLS panel, samples could broadly be divided into three categories; immune cold with minimal immune infiltrate, T-cell only infiltrate and TLS defined by the presence of CD20+ B cells. TLS were seen in 14% (n=60) of patient samples which was similar to the rate of patients with a significant T-cell only immune infiltrate which was also 14% (n=60). The majority of samples had no infiltrate, comprising of 72% (n=312) of the cohort. The median CD3+ cells/mm² in the entire cohort was 295mm². When divided into these categories, there was no statistically significant difference in disease free survival (p value= 0.39) although there was a trend towards worse disease free survival in those with a high T-cell only infiltrate.

Conclusions

In contrast to other breast cancer subtypes, tumour infiltrating lymphocytes in ER+/HER2- breast cancer may be a poor prognositc feature. However this may be dependant on the subpopulation of immune infiltrate, with TLS presence perhaps differing from T-cell only infiltrate. Further research with larger cohorts would be required to investigate this further.

Legal entity responsible for the study

The authors.

Funding

Royal College of Surgeons Ireland (University) StAR MD programme.

Disclosure

All authors have declared no conflicts of interest.