Abstract :
[en] Background: Cancer outcome appears to be affected by circulating immune cells in several tumor types. The role of peripheral eosinophils was widely studied in melanoma, while less data are available for breast cancer (BC) so far. In a previous study, we showed an association between baseline relative eosinophil count (REC), pathological complete response and survival rate in triple negative and hormone receptor negative/HER2 positive breast cancer. In this retrospective study we analyzed the role of REC in all breast cancer subtypes at time of diagnosis and during follow-up.
Material and Methods: Stage I-III BC patients (pts) treated between 1999 and 2018 were included in the study. REC and relative lymphocyte count (RLC) at seven different timepoints were collected. The pts were divided into two groups according to REC, using 1.5% as threshold, and according to RLC, using 17.5% as threshold. The co-primary endpoints were the BC specific survival (BCSS) and the time to treatment failure (TTF) according to REC. The secondary endpoints were: BCSS and TTF according to RLC, the association between REC and RLC with relapse; the variation of REC during follow-up and at relapse. Statistical analysis was done with SPSS v25 software.
Results: Overall 930 early BC pts were included in the study. The median age of the whole cohort was 61 years (25–97). The pts were well balanced according to the TNM stage in the group REC-low (393 pts) and in the group REC-high (597 pts): 30.5% and 32.9% stage I; 45.3% and 45.1% stage II; 22.6% and 21.4% stage III respectively; 1.4% unknown. After a median follow-up of 91 months (range 1–245) we observed a benefit in TTF (HR 0.610–95% CI 0.458–0.812, p 0.001) and BCSS (HR 0.632–95%CI 0.433– 0.923, p 0.018) in REC-high vs REC-low group. A survival benefit was observed also in the RLC-high vs RLC-low group (TTF: HR 0.421–95% CI 0.262–0.677, p 0.001; BCSS: HR 0.350–95% CI 0.2–0.614, p 0.001). A lower rate of relapse was observed in the REC-high vs REC-low group (17.1% vs 24.7%, p 0.005) and in the RLC-high vs RLC-low group (19.4% vs 35.8%, p 0.004). We observed a lower median REC at baseline before surgery (1.8% and 1.4% in pts without and with relapse respectively), compared to the median value after surgery (2.7% and 2.5% respectively), that remain stable until 10 years of postsurgical follow up in cancer free pts. A decrease in median REC was detected at time of relapse (1.5%). All the differences observed in the groups of pts with and without tumor recurrence were statistically significant (p < 0.0001), suggesting a role of the presence of cancer in the modulation of eosinophil count.
Conclusions: REC could be a new promising, affordable and accessible predictive and prognostic biomarker in all BC subtypes. Mechanistic studies, ongoing in our laboratory, are needed to understand eosinophils’ physiopathological role.
