Erschienen in:
09.11.2017 | Clinical trial
Serial immunological parameters in a phase II trial of exemestane and low-dose oral cyclophosphamide in advanced hormone receptor-positive breast cancer
verfasst von:
Maryann Kwa, Xiaochun Li, Yelena Novik, Ruth Oratz, Komal Jhaveri, Jennifer Wu, Ping Gu, Marleen Meyers, Franco Muggia, James Speyer, Alyssa Iwano, Maryam Bonakdar, Lina Kozhaya, Ece Tavukcuoglu, Bahar Budan, Roy Raad, Judith D. Goldberg, Derya Unutmaz, Sylvia Adams
Erschienen in:
Breast Cancer Research and Treatment
|
Ausgabe 1/2018
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Abstract
Background and purpose
Resistance to endocrine therapies in hormone receptor (HR)-positive breast cancer is a significant challenge. Prior studies have shown that low-dose oral cyclophosphamide can transiently deplete regulatory T cells (Tregs) and improve anti-tumor immunity. We investigated the combination of exemestane with cyclophosphamide in patients with advanced HR-positive breast cancer and assessed changes in circulating immune cell subsets.
Methods
This was a single-arm phase II trial of exemestane with cyclophosphamide in patients with metastatic HR-positive/HER2-negative breast cancer who had progressed on prior endocrine therapy (ClinicalTrials.gov: NCT01963481). Primary endpoint was progression-free survival (PFS) at 3 months (RECIST 1.1). Secondary objectives included median PFS, objective response rate, duration of response, and safety. Circulating Tregs (FOXP3+Helios+) and other immune cell subsets were monitored during treatment and compared with healthy controls.
Results
Twenty-three patients were enrolled. Treatment was well tolerated, without grade 4/5 toxicities. Objective responses were seen in 6/23 patients (26.1%; 95% CI 10.2–48.4%) and were durable (median 11.6 months). Three-month PFS rate was 50.1% (95% CI 33.0–76.0%); median PFS was 4.23 months (95% CI 2.8–11.7). No treatment-related decrease in Tregs was observed. However, elevated baseline levels of Naïve Tregs [greater than 2.5 (the median of the naïve Tregs)] were associated with relative risk of disease progression or death [hazard ratio 11.46 (95% CI 2.32–56.5)]. In addition, the baseline levels of Naïve Tregs (adj-p = 0.04), Memory Tregs (adj-p = 0.003), CD4 + Central Memory T cells (adj-p = 0.0004), PD-1 + CD4 + Central Memory T cells (adj-p = 0.008), and PD-1 + CD4 + Effector Memory T cells (adj-p = 0.009) were significantly greater in the patients than in the healthy controls; the baseline levels of %CD4 + Naïve T cells (adj-p = 0.0004) were significantly lower in patients compared with healthy controls (n = 40).
Conclusion
Treg depletion was not observed with low-dose cyclophosphamide when assessed by the specific marker FOXP3 + Helios +; however, baseline naïve Tregs were associated with 3-month PFS. Exemestane/cyclophosphamide combination had favorable safety profile with evidence of clinical activity in heavily pretreated patients.