Clinical trial design in brain metastasis: approaches for a unique patient population

Meaningful prevention of breast cancer metastasis: candidate therapeutics, preclinical validation, and clinical trial concerns

The development of drugs to treat breast and other cancers proceeds through phase I dose finding, phase II efficacy, and phase III comparative studies in the metastatic setting, only then asking if metastasis can be prevented in adjuvant trials. Compounds without overt cytotoxic activity, such as those developed to inhibit metastatic colonization, will likely fail to shrink established lesions in the metastatic setting and never be tested in a metastasis prevention scenario where they were preclinically validated. We and others have proposed phase II primary and secondary metastasis prevention studies to address this need. Herein, we have asked whether preclinical metastasis prevention data agrees with the positive adjuvant setting trials. The data are limited but complimentary. We also review fundamental pathways involved in metastasis, including Src, integrins, focal adhesion kinase (FAK), and fibrosis, for their clinical progress to date and potential for metastasis prevention. Issues of inadequate preclinical validation and clinical toxicity profiles are discussed.

Vorinostat as a radiosensitizer for brain metastasis: a phase I clinical trial

Perform a phase I study to evaluate the safety, and tolerability of vorinostat, an HDAC inhibitor, when combined with whole brain radiation treatment (WBRT) in patients with brain metastasis. A multi-institutional phase I clinical trial enrolled patients with a histological diagnosis of malignancy and radiographic evidence of brain metastasis. WBRT was 37.5 Gy in 2.5 Gy fractions delivered over 3 weeks. Vorinostat was administrated by mouth, once daily, Monday through Friday, concurrently with radiation treatment. The vorinostat dose was escalated from 200 to 400 mg daily using a 3+3 trial design. Seventeen patients were enrolled, 4 patients were excluded from the analysis due to either incorrect radiation dose (n = 1), or early treatment termination due to disease progression (n = 3). There were no treatment related grade 3 or higher toxicities in the 200 and 300 mg dose levels. In the 400 mg cohort there was a grade 3 pulmonary embolus and one death within 30 days of treatment. Both events were most likely related to disease progression rather than treatment; nonetheless, we conservatively classified the death as a dose limiting toxicity. We found Vorinostat administered with concurrent WBRT to be well tolerated to a dose of 300 mg once daily. This is the recommended dose for phase II study.

Targeted therapy in brain metastasis

PURPOSE OF REVIEW

To review the state of the art and new developments in the field of targeted agents for brain metastases.

RECENT FINDINGS

The huge amount of information on new molecular compounds and the advances in understanding the molecular pathways that mediate brain colonization have led to an increase of interest in preclinical and clinical investigations in the field of brain metastases. Targeted therapies can be employed either on established brain metastases or in a prevention setting. Targeting angiogenesis is an attractive approach. Up to date, large clinical trial datasets have shown that antiangiogenic agents do not increase the risk of bleeding into the brain. Bevacizumab (an anti-VEGF agent) is undergoing investigation in clinical trials on brain metastases from non-small cell lung cancer (NSCLC), breast cancer and melanoma. Sunitinib, a multitarget small molecule tyrosine kinase inhibitor (TKI), is a promising agent in brain metastases from renal cell cancer. The EGFR inhibitors gefitinib and erlotinib have a definite activity in brain metastases from NSCLC with activating EGFR mutations. Regarding HER2-positive breast cancer patients with established brain metastases, lapatinib (small molecule TKI) seems particularly active in association with capecitabine. Lapatinib alone is attractive in the prevention setting. Brain metastases from melanoma with BRAF V600E mutations respond to a specific inhibitor, such as vemurafenib. The immunomodulator ipilimumab is also active on brain metastases from melanoma.

SUMMARY

The use of targeted agents in brain metastases from solid tumors is promising. The setting of prevention will be probably expanded in the next years. Well designed clinical trials with proper endpoints are needed.