6 Survival Benefit of Eribulin, But Not Capecitabine, for Metastatic Breast Cancer Is Associated With Baseline Absolute Lymphocyte Count in Peripheral Blood

Ayako Ueno¹; Reina Maeda¹; Takanori Kin¹; Mitsuya Ito¹; Kensuke Kawasaki¹; Shoichiro Ohtani¹

¹Hiroshima City Hiroshima Citizens Hospital, Hiroshima, Japan.

Background

Eribulin and capecitabine are thought to be equally effective for metastatic breast cancer (mBC). Recently, growing evidence suggests that absolute lymphocyte count (ALC) in peripheral blood affects the efficacy of eribulin for mBC. The association between ALC and the efficacy of capecitabine is less studied. Here, we investigated how the efficacy balance between eribulin and capecitabine is influenced by baseline ALC.

Materials and Methods

We reviewed the medical records of 275 patients receiving eribulin (n = 125) or capecitabine (n = 150) for mBC at Hiroshima City Hiroshima Citizens Hospital between July 2011 and April 2019. Progression-free survival (PFS) was compared between patients with high ALC (≥1500/μL) and those with low ALC (<1500/μL) in each treatment group. Then, we investigated the relationship between the hazard ratio (HR) for PFS (eribulin vs capecitabine), taking into account patients’ baseline ALC levels. We used the Cox proportional hazards model; included covariates were age, hormonal and HER2 status, presence or absence of liver and other visceral metastasis, the number of involved organs, and the number of previous chemotherapy regimens.

Results

Median (interquartile range) ALC levels at baseline were 1107 (733-1485)/μL in the eribulin group and 1425 (1014-1773)/μL in the capecitabine group (P < .001). In the eribulin group, high ALC at baseline was significantly associated with longer PFS (adjusted HR, 0.50; 95% CI, 0.29-0.85; P = .010). On the other hand, in the capecitabine group, baseline ALC was not significantly associated with PFS (adjusted HR, 0.86; 95% CI, 0.58-1.28; P = .456). In the whole cohort, treatment with eribulin was significantly associated with worse PFS (adjusted HR, 1.44; 95% CI, 1.08-1.91). However, in patients with high ALC, PFS was similar or improved in the eribulin group. For patients with ALC ≥1500/μL, ALC ≥1900/μL, and ALC ≥2200/μL, adjusted HRs were 1.07 (95% CI, 0.64-1.82), 0.79 (95% CI, 0.29-2.11), and 0.67 (95% CI, 0.18-2.41), respectively.

Conclusions

Baseline ALC was significantly associated with PFS in the eribulin group, but not in the capecitabine group. This study suggested the potential role of ALC as a biomarker to predict the efficacy balance between eribulin and capecitabine in the treatment of mBC.

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