Trends and Outcomes of Catheter Ablation for Ventricular Tachycardia in a Community Cohort.

OBJECTIVES: This study examined the trend in growth of catheter ablation for ventricular tachycardia (VT) performed in the United States with analysis of rates and predictors of major adverse events. BACKGROUND: Sustained VT is a significant cause of sudden death, heart failure (HF), and recurrent shocks in implantable cardioverter-defibrillator (ICD) recipients. Catheter ablation for VT reduces arrhythmia recurrence. Limited data are available regarding the use, safety, and long-term outcomes after VT ablation. METHODS: Using the U.S. Medicare database linked to the Social Security Death Index, we examined the annual use of VT ablation in 21,073 patients over 12 years, with 30-day risk of mortality, nonfatal major adverse events (MAEs), 1-year risk of mortality, re-hospitalization, repeat ablation, and factors associated with adverse outcomes. RESULTS: Among 21,073 patients (age 70 ± 9 years; 77% men; 90% white), there were 1,581 (7.5%) non-fatal MAEs within 30 days. There were 963 (4.6%) vascular complications, 485 (2.3%) pericardial complications, and 201 (1%) strokes and/or transient ischemic attacks. Mechanical circulatory support use was infrequent (2.3%). The 30-day and 1-year mortality rates were 4.2% and 15.0%, respectively. The 1-year incidence of repeat ablation was 10.2 per 100 person-years and re-hospitalization for HF or VT was 15.4 per 100 person-years and 18 per 100 person-years, respectively. Patients with an ICD had increased 30-day (4.9% vs. 0.86%) and 1-year mortality (17.5% vs. 2.54% [22.9 per 100 person-years vs. 3.1 per 100 person-years]; hazard ratio [HR]: 2.93; 95% confidence interval [CI]: 2.21 to 3.88). Rates of hospitalization for HF (18 per 100 person-years vs. 1.8 per 100 person-years; HR: 4.00; 95% CI: 2.78 to 5.78) or VT recurrence (22.7 per 100 person-years vs. 2.1 per 100 person-years; HR: 5.70; 95% CI: 4.09 to 7.96) were also higher at 1 year. Between 2000 and 2012, annual VT ablation volumes increased >4-fold. CONCLUSIONS: Catheter ablation for VT is frequently performed. Short-term MAEs and 1-year mortality is significant and is highest in patients with an ICD. These findings may provide greater insight of outcomes in an unselected real-world population undergoing VT ablation.

Association Between Changes in CMS Reimbursement Policy and Drug Labels for Erythrocyte-Stimulating Agents With Outcomes for Older Patients Undergoing Hemodialysis Covered by Fee-for-Service Medicare.

IMPORTANCE: In 2011, the US Centers for Medicare & Medicaid Services (CMS) changed its reimbursement policy for hemodialysis to a bundled comprehensive payment system that included the cost of erythrocyte-stimulating agents (ESAs). Also in 2011, the US Food and Drug Administration revised the drug label for ESAs, recommending more conservative dosing in patients with chronic kidney disease. In response to concerns that these measures could have adverse effects on patient care and outcomes, the CMS and the FDA initiated a collaboration to assess the effect. OBJECTIVE: To assess the effects of the changes in reimbursement policy and the ESA drug label on patients who underwent incident hemodialysis. DESIGN, SETTING, AND PARTICIPANTS: For this retrospective cohort study, patients 66 years or older who had undergone incident hemodialysis, and were enrolled in Medicare parts A, B, or D for at least 12 months prior to hemodialysis initiation between January 1, 2008, and December 31, 2013, were recruited from hemodialysis centers across the United States. Patients were divided into 2 cohorts based on their date of hemodialysis initiation and followed: January 1, 2008, to December 31, 2009, for the prepolicy cohort and July 1, 2011, to June 30, 2013, for the postpolicy cohort, with the exclusion of January 1, 2010, to June 30, 2011, as a transition period. INTERVENTIONS: Changes in CMS reimbursement policy for dialysis and the FDA label for ESAs. MAIN OUTCOMES AND MEASURES: Major adverse cardiovascular events (MACEs), including acute myocardial infarction (AMI), stroke, and all-cause mortality; hospitalized congestive heart failure (H-CHF); venous thromboembolism; and red blood cell transfusions. Secondary outcomes included evaluating effects on black and other patient subgroups. RESULTS: Baseline characteristics of the 69 718 incident hemodialysis patients were similar between cohorts. Compared with the prepolicy period, the risk of MACE, death, H-CHF, and venous thromboembolism were similar in the postpolicy period, and the risk of stroke decreased (hazard ratio [HR], 0.77; 95% CI, 0.64-0.93; P = .01); the use of ESAs also decreased, and the rate of blood transfusions increased (HR, 1.09; 95% CI, 1.07-1.12; P < .001). In the post-postpolicy period, black patients had a significant reduction in risk of MACE (HR, 0.82; 95% CI, 0.73-0.92; P < .001) and all-cause mortality (HR, 0.82; 95% CI, 0.73-0.93; P = .002). CONCLUSIONS AND RELEVANCE: After the bundling policy and ESA labeling changes in 2011, the risks of MACE and death for patients 66 years or older and covered by fee-for-service Medicare who had undergone incident hemodialysis did not change; the risk of stroke was reduced, and the rate of blood transfusions modestly increased. Black patients had substantial reductions in the risks of MACE and death.

Oxygen levels do not determine radiation survival of breast cancer stem cells.

For more than a century oxygen has been known to be one of the most powerful radiosensitizers. However, despite decades of preclinical and clinical research aimed at overcoming tumor hypoxia, little clinical progress has been made so far. Ionizing radiation damages DNA through generation of free radicals. In the presence of oxygen these lesions are chemically modified, and thus harder to repair while hypoxia protects cells from radiation (Oxygen enhancement ratio (OER)). Breast cancer stem cells (BSCSs) are protected from radiation by high levels of free radical scavengers even in the presence of oxygen. This led us to hypothesize that BCSCs exhibit an OER of 1. Using four established breast cancer cell lines (MCF-7, T47D, MDA-MB-231, SUM159PT) and primary breast cancer samples, we determined the number of BCSCs using cancer stem cell markers (ALDH1, low proteasome activity), compared radiation clonogenic survival and mammosphere formation under normoxic and hypoxic conditions, and correlated these results to the expression levels of key members of the free radical scavenging systems. The number of BCSCs increased with increased aggressiveness of the cancer. This correlated with increased radioresistance (SF(8Gy)), and decreasing OERs. When cultured as mammospheres, breast cancer cell lines and primary samples were highly radioresistant and not further protected by hypoxia (OER∼1).We conclude that because BCSCs are protected from radiation through high expression levels of free radical scavengers, hypoxia does not lead to additional radioprotection of BCSCs.

Radiation-induced reprogramming of breast cancer cells.

Breast cancers are thought to be organized hierarchically with a small number of breast cancer stem cells (BCSCs) able to regrow a tumor while their progeny lack this ability. Recently, several groups reported enrichment for BCSCs when breast cancers were subjected to classic anticancer treatment. However, the underlying mechanisms leading to this enrichment are incompletely understood. Using non-BCSCs sorted from patient samples, we found that ionizing radiation reprogrammed differentiated breast cancer cells into induced BCSCs (iBCSCs). iBCSCs showed increased mammosphere formation, increased tumorigenicity, and expressed the same stemness-related genes as BCSCs from nonirradiated samples. Reprogramming occurred in a polyploid subpopulation of cells, coincided with re-expression of the transcription factors Oct4, sex determining region Y-box 2, Nanog, and Klf4, and could be partially prevented by Notch inhibition. We conclude that radiation may induce a BCSC phenotype in differentiated breast cancer cells and that this mechanism contributes to increased BCSC numbers seen after classic anticancer treatment.

Metabolic state of glioma stem cells and nontumorigenic cells.

Gliomas contain a small number of treatment-resistant glioma stem cells (GSCs), and it is thought that tumor regrowth originates from GSCs, thus rendering GSCs an attractive target for novel treatment approaches. Cancer cells rely more on glycolysis than on oxidative phosphorylation for glucose metabolism, a phenomenon used in 2-[(18)F]fluoro-2-deoxy-D-glucose positron emission tomography imaging of solid cancers, and targeting metabolic pathways in cancer cells has become a topic of considerable interest. However, if GSCs are indeed important for tumor control, knowledge of the metabolic state of GSCs is needed. We hypothesized that the metabolism of GSCs differs from that of their progeny. Using a unique imaging system for GSCs, we assessed the oxygen consumption rate, extracellular acidification rate, intracellular ATP levels, glucose uptake, lactate production, PKM1 and PKM2 expression, radiation sensitivity, and cell cycle duration of GSCs and their progeny in a panel of glioma cell lines. We found GSCs and progenitor cells to be less glycolytic than differentiated glioma cells. GSCs consumed less glucose and produced less lactate while maintaining higher ATP levels than their differentiated progeny. Compared with differentiated cells, GSCs were radioresistant, and this correlated with a higher mitochondrial reserve capacity. Glioma cells expressed both isoforms of pyruvate kinase, and inhibition of either glycolysis or oxidative phosphorylation had minimal effect on energy production in GSCs and progenitor cells. We conclude that GSCs rely mainly on oxidative phosphorylation. However, if challenged, they can use additional metabolic pathways. Therefore, targeting glycolysis in glioma may spare GSCs.

Survival and self-renewing capacity of breast cancer initiating cells during fractionated radiation treatment.

INTRODUCTION: Recent data indicate a hierarchical organization of many solid cancers, including breast cancer, with a small number of cancer initiating cells (CICs) that have the ability to self-renew and exhibit multi-lineage potency. We, and others, have demonstrated that CICs in breast cancer and glioma are relatively resistant to ionizing radiation if compared to their non-tumorigenic counterparts. However, the extent of the remaining self-renewing capacity of CICs after fractions of radiation is currently unknown. We hypothesized that CICs, in contrast to their non-tumorigenic counterparts, not only survive fractions of ionizing radiation but also retain the CIC phenotype as defined by operational means. METHODS: We used two marker systems to identify breast CICs (CD24-/low/CD44high, or lack of proteasome activity) and performed sphere-forming assays after multiple clinical fractions of radiation. Lineage tracking was performed by membrane staining. Cell cycle distribution and RNA content were assessed by flow cytometry and senescence was assessed via beta-galactosidase staining. RESULTS: We demonstrated that irradiated CICs survived and retained their self-renewal capacity for at least four generations. We show that fractionated radiation not only spared CICs but also mobilized them from a quiescent/G0 phase of the cell cycle into actively cycling cells, while the surviving non-tumorigenic cells were driven into senescence. CONCLUSIONS: The breast CIC population retains increased self-renewal capacity over several generations and therefore, we conclude that increases in the number of CICs after sublethal doses of radiation have potential clinical importance. Prevention of this process may lead to improved clinical outcome.