Relevance of Spatial Heterogeneity of Immune Infiltration for Predicting Risk of Recurrence After Endocrine Therapy of ER+ Breast Cancer

Abstract

Background: Despite increasing evidence supporting the clinical utility of immune infiltration in the estrogen receptor-negative (ER-) subtype, the prognostic value of immune infiltration for ER+ disease is not well defined.

Methods: Quantitative immune scores of cell abundance and spatial heterogeneity were computed using a fully automated hematoxylin and eosin-stained image analysis algorithm and spatial statistics for 1178 postmenopausal patients with ER+ breast cancer treated with five years' tamoxifen or anastrozole. The prognostic significance of immune scores was compared with Oncotype DX 21-gene recurrence score (RS), PAM50 risk of recurrence (ROR) score, IHC4, and clinical treatment score, available for 963 patients. Statistical tests were two-sided.

Results: Scores of immune cell abundance were not associated with recurrence-free survival. In contrast, high immune spatial scores indicating increased cell spatial clustering were associated with poor 10-year, early (0-5 years), and late (5-10 years) recurrence-free survival (Immune Hotspot: LR-χ2 = 14.06, P < .001, for 0-10 years; LR-χ2 = 6.24, P = .01, for 0-5 years; LR-χ2 = 7.89, P = .005, for 5-10 years). The prognostic value of spatial scores for late recurrence was similar to that of IHC4 and RS in both populations, but was not as strong as other tests in comparison for recurrence across 10 years.

Conclusions: These results provide a missing link between tumor immunity and disease outcome in ER+ disease by examining tumor spatial architecture. The association between spatial scores and late recurrence suggests a lasting memory of protumor immunity that may impact disease progression and evolution of endocrine treatment resistance, which may be exploited for therapeutic advances.

Figure 1. Consort diagram for the availability of samples for analysis from the ATAC (Arimidex, Tamoxifen Alone or Combined) trial.

ER, estrogen receptor; IHC, immunohistochemistry; PgR, progesterone receptor; ROR, Risk of Recurrence score; RS, recurrence score.

Figure 2. Illustration of the pipeline for identifying spatial hotspots with visual examples, and the Kaplan-Meier estimates for 10-year recurrence according to immune spatial scores in the validation set, split into two groups using cutoffs selected in the training set.

A) An example of TransATAC H&E image and corresponding map of identified cancer and immune cells. Scale bar illustrates 2.5mm. B-D) Visual examples of hotspots and Kaplan-Meier curves illustrating survival associations with immune spatial scores. Scale bar illustrates 35μm. Kaplan-Meier curves were calculated and tested for equality using the log-rank test. The numbers of patients at risk in each group at various time points are given below each graph. All statistical tests were two-sided. HR: hazard ratio (95% confidence interval).

Figure 3. Barplots of likelihood scores for immune spatial and prognostic scores as well as combination of IHC4 and each immune spatial score (IHC4+I) for 0-10 and 5-10 year time window in A) overall population and B) HER2-population.

Kaplan-Meier curves were calculated and tested for equality using the log-rank test. The numbers of patients at risk in each group at various time points are given below each graph. All statistical tests were two-sided.