Editor’s note:
Previous studies have indicated a close association between disseminated tumor cells (DTC) in the bone marrow and breast cancer recurrence. At the 2023 ESMO conference, data from the CLEVER study was presented, investigating the effects of hydroxychloroquine (HCQ) and the mTOR inhibitor everolimus (EVE) in treating DTC and preventing breast cancer recurrence. Oncology Frontier had the privilege of inviting Professor Feng Jin from the First Affiliated Hospital of China Medical University to provide an introduction and commentary.
Study Introduction
Background: Dormancy of tumor cells is a crucial factor in breast cancer recurrence, with the bone marrow being a common site for dormant tumor cell colonization. Previous research has shown a significant correlation between disseminated tumor cells (DTC) in the bone marrow and breast cancer recurrence. This study aims to explore the effects of the autophagy inhibitor hydroxychloroquine (HCQ) and the mTOR inhibitor everolimus (EVE) in treating DTC and preventing breast cancer recurrence.
Methods:
The CLEVER study (NCT03032406) is a Phase II randomized clinical trial that enrolled patients diagnosed with breast cancer within the past 5 years, having completed all treatments. This includes patients with triple-negative breast cancer (TNBC), ER-positive with lymph node metastasis and high-risk results on Oncotype or Mammaprint testing after neoadjuvant therapy, and HER2-positive with lymph node metastasis or residual lesions after neoadjuvant therapy. All patients underwent bone marrow aspiration, and DTC status was assessed using immunohistochemistry. DTC-positive (DTC+) breast cancer patients were randomly assigned to three groups: 1) HCQ group (600mg, twice daily), 2) EVE group (10mg, once daily), and 3) HCQ+EVE group (some patients allowed a 3-month observation period), all receiving a 6-cycle treatment (28 days/cycle). Patients remaining DTC+ after treatment continued to receive combined HCQ+EVE therapy for an additional 6 cycles. DTC testing was conducted at the 3rd, 6th, and 12th cycles, as well as six months after completing the entire treatment. Adverse reactions were assessed based on CTCAE 4.0. The primary endpoint was the feasibility of the treatment regimen, defined as a 75% proportion of patients completing the 6-cycle treatment without grade 3-4 adverse events. Secondary endpoints included safety, DTC response rate, and 3-year recurrence-free survival (RFS). Bayesian Poisson regression analysis was employed to assess the DTC response rate. (Figure 1)
Results: A total of 197 breast cancer patients were enrolled in this study, with 184 patients undergoing initial bone marrow aspiration. Among them, 55 patients (30%) were identified as DTC-positive. Fifty-three DTC-positive patients were randomly assigned to three groups, receiving treatment with HCQ (n=15), EVE (n=15), or HCQ+EVE (n=23), with 13 patients receiving HCQ+EVE treatment after a 3-month observation period. Among the 51 patients receiving treatment, all three treatment regimens achieved the primary endpoint of feasibility (HCQ group: 100%; EVE group: 87%; HCQ+EVE group: 76%).
In terms of safety, no grade 4-5 drug-related adverse events occurred in the enrolled patients during the treatment period, and no new safety issues were identified. In the HCQ group, the most common adverse reactions were gastrointestinal, but most patients experienced symptom relief after the first treatment cycle. Meanwhile, in the EVE group, two patients experienced moderate pneumonia (grade 2). The median follow-up time in this study was 42 months (range: 7–60 months). During the treatment period, one patient developed lung metastasis (after 2 cycles of EVE treatment), and another patient developed contralateral breast cancer. Compared to the observation group, three cycles of HCQ, EVE, and HCQ+EVE resulted in an approximately 80% reduction in DTC (HCQ group: 80%; EVE group: 78%; HCQ+EVE group: 87%). Statistical analysis showed posterior probabilities of 99.5%, 98.4%, and 99.9% for the three treatment groups, respectively (Figure 2).
Study Conclusion: The CLEVER study validates the feasibility of treating patients based on targeting DTC, and therapeutic interventions addressing the molecular mechanisms of DTC effectively reduce their presence. Further follow-up is needed to assess the recurrence and survival outcomes of enrolled patients.
Expert Commentary
The CLEVER study is the first clinical trial to demonstrate the feasibility of using autophagy-related drugs and mTOR inhibitors for the treatment of DTC, marking a significant breakthrough in preventing tumor recurrence related to DTC.
As is well-known, recurrence and metastasis are the leading causes of death in breast cancer patients. Studies have shown that nearly 30% of breast cancer patients experience disease recurrence even after receiving standard treatment. In recent years, extensive research has confirmed that DTC is one of the most critical factors leading to recurrence and metastasis in cancer patients. Since current widely used treatments such as chemotherapy, radiation therapy, and targeted therapy primarily target proliferating tumor cells, DTC can resist existing treatments and remain dormant in patients for an extended period. Therefore, treating DTC is a feasible approach to reducing recurrence and improving patient survival.
Although the role of DTC in patient recurrence and metastasis is well-established, clinical detection, drug intervention, and efficacy assessment are still in the exploratory stage, lacking standardized strategies and drugs within standard clinical treatments. Currently, there are three main strategies for DTC treatment: 1) maintaining the dormancy of DTC; 2) awakening dormant DTC to enhance the efficacy of radiation and chemotherapy; 3) eliminating or reducing DTC.
The CLEVER study focuses on the strategy of eliminating or reducing DTC. The primary drugs used in this study, hydroxychloroquine and everolimus, to some extent, fall under the category of repurposing existing drugs. Hydroxychloroquine, approved by the FDA since 1955, is widely used to treat various immune-related diseases, including rheumatoid arthritis, systemic lupus erythematosus, and Sjögren’s syndrome. However, recent research has found that hydroxychloroquine can inhibit autophagy and enhance the sensitivity of radiotherapy and chemotherapy through this mechanism. Building on this, the current study further demonstrates the significant value of hydroxychloroquine in preventing recurrence and metastasis in high-risk breast cancer patients. Everolimus is an mTOR inhibitor primarily used for hormone receptor-positive, HER2-negative advanced breast cancer. This study takes a novel approach, targeting DTC based on the crucial role of mTOR inhibitors in tumor autophagy, discovering that everolimus still holds exploratory value in treating high-risk recurrent breast cancer. In terms of trial design, this study is based on existing risk assessment systems in clinical diagnosis and treatment and bone marrow aspiration testing, screening out breast cancer patients at high risk of recurrence and metastasis with DTC+.
Triple-negative breast cancer (TNBC) is characterized by a higher risk of early recurrence and relatively poorer prognosis, with early TNBC treatment primarily relying on chemotherapy. Looking back at previous studies, TNBC has the highest recurrence rate within 10 years among all molecular subtypes, with an average recurrence time of only 19–40 months. In this study, with a median follow-up time of 42 months, only 2 cases (3.8%) experienced recurrence or metastasis. Although there was no control group, the preliminary results of the study confirm the efficacy of an intensified treatment strategy targeting DTC in high-risk breast cancer patients, aiming to further reduce early recurrence.
Furthermore, the CLEVER study found that hydroxychloroquine and everolimus could reduce DTC in the bone marrow of high-risk breast cancer patients who had already received adjuvant therapy by approximately 80%, suggesting the potential application of this treatment strategy in the adjuvant reinforcement therapy of high-risk breast cancer and providing new ideas for exploring intensified treatment models. In this study, monotherapy with hydroxychloroquine was superior to everolimus in terms of safety and efficacy, and the combination of the two drugs further increased the DTC clearance rate while maintaining manageable safety. Based on the current research results, we look forward to the CLEVER study not only proving that targeting DTC can reduce the risk of patient recurrence and metastasis, improving patient survival but also exploring more efficient and less toxic treatment regimens.
As the crucial role of DTC in tumors is revealed, in addition to the CLEVER study, several clinical trials focusing on DTC treatment in breast cancer are currently underway. These include the c-TRAK study (NCT03145961), which uses ctDNA monitoring to assess the risk of recurrence and metastasis in TNBC patients after standard treatment and surgery; the GMI1359 study (NCT04197999), targeting E-Sel and CXCR4 to mobilize DTC in the bone marrow; and other clinical studies (NCT02732171) screening for effective treatment strategies in DTC+ breast cancer patients. The encouraging results of the CLEVER study, combined with ongoing advancements in DTC detection technology and the deepening understanding of tumor cell dormancy mechanisms, will likely lead to more innovative research in the future.
In summary, the CLEVER study successfully explores the repurposing of existing drugs, uncovering the therapeutic potential of hydroxychloroquine and everolimus in high-risk breast cancer patients. We will continue to follow clinical studies targeting DTC, including CLEVER, with the hope of further optimizing intensified treatment models for high-risk breast cancer patients and benefiting more patients.
Reference:
1.Cheun，J.H.，et al.，Locoregional Recurrence Patterns in Patients With Different Molecular Subtypes of Breast Cancer.JAMA Surg，2023.158(8):p.841-852.
2.Yin，L.，et al.，Triple-negative breast cancer molecular subtyping and treatment progress.Breast Cancer Res，2020.22(1):p.61.
Professor, Chief Physician, Doctoral Supervisor
Director of Breast Surgery, The First Affiliated Hospital of China Medical University
Chairman of the Breast Cancer Professional Committee, Liaoning Anti-Cancer Association
Chairman of the Breast Surgery Branch, Liaoning Medical Association
Deputy Director of the Breast Tumor Group, Oncology Branch, Chinese Medical Association
Deputy Chairman of the Breast Cancer Professional Committee, China Anti-Cancer Association
Executive Committee Member of CSCO-BC, Chinese Society of Clinical Oncology
Committee Member of Breast Surgery, Surgical Branch, Chinese Medical Association
Deputy Chairman of the Breast Cancer Subcommittee, China Gerontological Society
Deputy Chairman of the Surgical Special Committee on Breast Diseases, Beijing Breast Disease Prevention and Control Society
Chairman of the Breast Surgery Group, Surgical Branch, Liaoning Medical Association
Lecturer
Department of Breast Surgery, The First Affiliated Hospital of China Medical University
Ph.D. in Oncology, China Medical University
Postdoctoral Fellow in Biology, China Medical University
Principal Investigator of one National Natural Science Foundation of China (NSFC) Young Scientist Project
Author of 5 SCI publications related to breast tumors
