Phase I Study and Cell-Free DNA Analysis of T-DM1 and Metronomic Temozolomide for Secondary Prevention of HER2-Positive Breast Cancer Brain Metastases.

PURPOSE: Preclinical data showed that prophylactic, low-dose temozolomide (TMZ) significantly prevented breast cancer brain metastasis. We present results of a phase I trial combining T-DM1 with TMZ for the prevention of additional brain metastases after previous occurrence and local treatment in patients with HER2+ breast cancer. PATIENTS AND METHODS: Eligible patients had HER2+ breast cancer with brain metastases and were within 12 weeks of whole brain radiation therapy (WBRT), stereotactic radiosurgery, and/or surgery. Standard doses of T-DM1 were administered intravenously every 21 days (3.6 mg/kg) and TMZ was given orally daily in a 3+3 phase I dose escalation design at 30, 40, or 50 mg/m2, continuously. DLT period was one 21-day cycle. Primary endpoint was safety and recommended phase II dose. Symptom questionnaires, brain MRI, and systemic CT scans were performed every 6 weeks. Cell-free DNA sequencing was performed on patients' plasma and CSF. RESULTS: Twelve women enrolled, nine (75%) with prior SRS therapy and three (25%) with prior WBRT. Grade 3 or 4 AEs included thrombocytopenia (1/12), neutropenia (1/12), lymphopenia (6/12), and decreased CD4 (6/12), requiring pentamidine for Pneumocystis jirovecii pneumonia prophylaxis. No DLT was observed. Four patients on the highest TMZ dose underwent dose reductions. At trial entry, 6 of 12 patients had tumor mutations in CSF, indicating ongoing metastatic colonization despite a clear MRI. Median follow-up on study was 9.6 m (2.8-33.9); only 2 patients developed new parenchymal brain metastases. Tumor mutations varied with patient outcome. CONCLUSIONS: Metronomic TMZ in combination with standard dose T-DM1 shows low-grade toxicity and potential activity in secondary prevention of HER2+ brain metastases.

Temozolomide in secondary prevention of HER2-positive breast cancer brain metastases.

Brain metastases occur in up to 25-55% of patients with metastatic HER2-positive breast cancer. Standard treatment has high rates of recurrence or progression, limiting survival and quality of life in most patients. Temozolomide (TMZ) is known to penetrate the blood-brain barrier and is US FDA approved for treatment of glioblastoma. Our group has demonstrated that low doses of TMZ administered in a prophylactic, metronomic fashion can significantly prevent development of brain metastases in murine models of breast cancer. Based on these findings, we initiated a secondary-prevention clinical trial with oral TMZ given to HER2-positive breast cancer patients with brain metastases after recent local treatment in combination with T-DM1 for systemic control of disease. Primary end point is freedom from new brain metastases at 1 year. (NCT03190967).

Radiation-induced astrocyte senescence is rescued by Δ133p53.

BACKGROUND: Cellular senescence and the senescence-associated secretory phenotype (SASP) may contribute to the development of radiation therapy-associated side effects in the lung and blood vessels by promoting chronic inflammation. In the brain, inflammation contributes to the development of neurologic disease, including Alzheimer's disease. In this study, we investigated the roles of cellular senescence and Δ133p53, an inhibitory isoform of p53, in radiation-induced brain injury. METHODS: Senescent cell types in irradiated human brain were identified with immunohistochemical labeling of senescence-associated proteins p16INK4A and heterochromatin protein Hp1γ in 13 patient cases, including 7 irradiated samples. To investigate the impact of radiation on astrocytes specifically, primary human astrocytes were irradiated and examined for expression of Δ133p53 and induction of SASP. Lentiviral expression of ∆133p53 was performed to investigate its role in regulating radiation-induced cellular senescence and astrocyte-mediated neuroinflammation. RESULTS: Astrocytes expressing p16INK4A and Hp1γ were identified in all irradiated tissues, were increased in number in irradiated compared with untreated cancer patient tissues, and had higher labeling intensity in irradiated tissues compared with age-matched controls. Human astrocytes irradiated in vitro also experience induction of cellular senescence, have diminished Δ133p53, and adopt a neurotoxic phenotype as demonstrated by increased senescence-associated beta-galactosidase activity, p16INK4A, and interleukin (IL)-6. In human astrocytes, Δ133p53 inhibits radiation-induced senescence, promotes DNA double-strand break repair, and prevents astrocyte-mediated neuroinflammation and neurotoxicity. CONCLUSIONS: Restoring expression of the endogenous p53 isoform, ∆133p53, protects astrocytes from radiation-induced senescence, promotes DNA repair, and inhibits astrocyte-mediated neuroinflammation.

Correction to expert consensus on re-irradiation for recurrent glioma.

In the original publication [1] two author names were missing the middle names. The corrected versions can be found in this Erratum.

Re-irradiation for recurrent glioma- the NCI experience in tumor control, OAR toxicity and proposal of a novel prognostic scoring system.

PURPOSE/OBJECTIVES: Despite mounting evidence for the use of re-irradiation (re-RT) in recurrent high grade glioma, optimal patient selection criteria for re-RT remain unknown. We present a novel scoring system based on radiobiology principles including target independent factors, the likelihood of target control, and the anticipated organ at risk (OAR) toxicity to allow for proper patient selection in the setting of recurrent glioma. MATERIALS/METHODS: Thirty one patients with recurrent glioma who received re-RT (2008-2016) at NCI - NIH were included in the analysis. A novel scoring system for overall survival (OS) and progression free survival (PFS) was designed to include:1) target independent factors (age, KPS (Karnofsky Performance Status), histology, presence of symptoms), 2) target control, and 3) OAR toxicity risk. Normal tissue complication probability (NTCP) calculations were performed using the Lyman model. Kaplan-Meier analysis was performed for overall survival (OS) and progression free survival (PFS) for comparison amongst variables. RESULTS: No patient, including those who received dose to OAR above the published tolerance dose, experienced any treatment related grade 3-5 toxicity with a median PFS and OS from re-RT of 4 months (0.5-103) and 6 months (0.7-103) respectively. Based on cumulative maximum doses the average NTCP was 25% (0-99%) for the chiasm, 21% (0-99%) for the right optic nerve, 6% (0-92%) for the left optic nerve, and 59% (0-100%) for the brainstem. The independent factor and target control scores were each statistically significant for OS and the combination of independent factors plus target control was also significant for both OS (p = 0.02) and PFS (p = 0.006). The anticipated toxicity risk score was not statistically significant. CONCLUSION: Our scoring system may represent a novel approach to patient selection for re-RT in recurrent high grade glioma. Further validation in larger patient cohorts including compilation of doses to tumor and OAR may help refine this further for inclusion into clinical trials and general practice.

Expert consensus on re-irradiation for recurrent glioma.

PURPOSE: To investigate radiation oncologists' opinions on important considerations to offering re-irradiation (re-RT) as a treatment option for recurrent glioma. MATERIALS AND METHODS: A survey was conducted with 13 radiation oncologists involved in the care of central nervous system tumor patients. The survey was comprised of 49 questions divided into 2 domains: a demographic section (10 questions) and a case section (5 re-RT cases with 5 to 6 questions representing one or several re-RT treatment dilemmas as may be encountered in the clinic). Respondents were asked to rate the relevance of various factors to offering re-RT, respond to the cases with a decision to offer re-RT vs. not, volume to be treated, margins to be employed, dose/fractionation suggested and any additional comments with respect to rationale in each scenario. RESULTS: Sixty nine percent of responders have been practicing for greater than 10 years and 61% have re-RT 20 to 100 patients to date, with 54% seeing 2-5 re-RT cases per month and retreating 1-2 patients per month. Recurrent tumor volume, time since previous radiation therapy, previously administered dose to organs at risk and patient performance status were rated by the majority of responders (85%, 92%, 77%, and 69% respectively) as extremely relevant or very relevant to offering re-RT as an option. CONCLUSION: The experts' practice of re-RT is still heterogeneous, reflecting the paucity of high-quality prospective data available for decision-making. Nevertheless, practicing radiation oncologists can support own decisions by referring to the cases found suitable for re-RT in this survey.

Thioredoxin reductase as a novel molecular target for cancer therapy.

Tumor cell proliferation, de-differentiation, and progression depend on a complex combination of altered cell cycle regulation, excessive growth factor pathway activation, and decreased apoptosis. The understanding of these complex mechanisms should lead to the identification of potential targets for therapeutic intervention. Redox-sensitive signaling factors also regulate multiple cellular processes including proliferation, cell cycle, and pro-survival signaling cascades, suggesting their potential as molecular targets for anticancer agents. These observations suggest that redox-sensitive signaling factors may be potential novel molecular markers. We hypothesized that thioredoxin reductase-1 (TR), a component of several redox-regulated pathways, may represent a potential molecular target candidate in response to agents that induce oxidative stress. There have been numerous biological studies over the last decade investigating the cell biological, biochemical, and genetic properties of TR both in culture and in in vivo models. In addition, using a series of permanent cell lines that express either a wild-type TR or a dominant mutant TR gene or a chemical agent that inhibits TR we demonstrated that TR meets most criteria that would identify a molecular target. Based on these results we believe TR is a potential molecular target and discuss potential clinical possibilities.

The epigenome as a molecular marker and target.

Tumor cell proliferation, de-differentiation, and progression depend on a complex combination of altered cell cycle regulation, excessive growth factor pathway activation, and decreased apoptosis. The understanding of these complex mechanisms should lead to the identification of potential molecular markers, targets, and molecular profiles that should eventually expand and improve therapeutic intervention. It now appears clear that methylation plays a central role in transformation, both in vitro and in vivo. However, the exact targets and mechanism(s) are not yet fully understood. This is partly due to the significant number of genes altered by changes in intracellular methyltransferase activity and the chemical agents used to modulate gene expression. The complex nature of methylation's role in regulating gene expression suggests that in addition to investigating individual genes, researchers should develop more comprehensive methods to examine gene expression patterns and their predictive value as this will likely be necessary in the future. If methylation plays a role in transformation, then it seems logical that genes regulating intracellular methylation status may be used as molecular markers to profile tumors by any new methods currently being developed. Perhaps more noteworthy is that DNMT genes may be found to be novel molecular targets for new factor-specific anticancer agents. This idea will be addressed.