Long-term efficacy and safety of addition of carboplatin with or without veliparib to standard neoadjuvant chemotherapy in triple-negative breast cancer: 4-year follow-up data from BrighTNess, a randomized phase III trial.

BACKGROUND: Primary analyses of the phase III BrighTNess trial showed addition of carboplatin with/without veliparib to neoadjuvant chemotherapy significantly improved pathological complete response (pCR) rates with manageable acute toxicity in patients with triple-negative breast cancer (TNBC). Here, we report 4.5-year follow-up data from the trial. PATIENTS AND METHODS: Women with untreated stage II-III TNBC were randomized (2 : 1 : 1) to paclitaxel (weekly for 12 doses) plus: (i) carboplatin (every 3 weeks for four cycles) plus veliparib (twice daily); (ii) carboplatin plus veliparib placebo; or (iii) carboplatin placebo plus veliparib placebo. All patients then received doxorubicin and cyclophosphamide every 2-3 weeks for four cycles. The primary endpoint was pCR. Secondary endpoints included event-free survival (EFS), overall survival (OS), and safety. Since the co-primary endpoint of increased pCR with carboplatin plus veliparib with paclitaxel versus carboplatin with paclitaxel was not met, secondary analyses are descriptive. RESULTS: Of 634 patients, 316 were randomized to carboplatin plus veliparib with paclitaxel, 160 to carboplatin with paclitaxel, and 158 to paclitaxel. With median follow-up of 4.5 years, the hazard ratio for EFS for carboplatin plus veliparib with paclitaxel versus paclitaxel was 0.63 [95% confidence interval (CI) 0.43-0.92, P = 0.02], but 1.12 (95% CI 0.72-1.72, P = 0.62) for carboplatin plus veliparib with paclitaxel versus carboplatin with paclitaxel. In post hoc analysis, the hazard ratio for EFS was 0.57 (95% CI 0.36-0.91, P = 0.02) for carboplatin with paclitaxel versus paclitaxel. OS did not differ significantly between treatment arms, nor did rates of myelodysplastic syndromes, acute myeloid leukemia, or other secondary malignancies. CONCLUSIONS: Improvement in pCR with the addition of carboplatin was associated with long-term EFS benefit with a manageable safety profile, and without increasing the risk of second malignancies, whereas adding veliparib did not impact EFS. These findings support the addition of carboplatin to weekly paclitaxel followed by doxorubicin and cyclophosphamide neoadjuvant chemotherapy for early-stage TNBC.

Veliparib monotherapy following carboplatin/paclitaxel plus veliparib combination therapy in patients with germline BRCA-associated advanced breast cancer: results of exploratory analyses from the phase III BROCADE3 trial.

BACKGROUND: In the BROCADE3 trial, addition of the poly(ADP-ribose) polymerase inhibitor, veliparib, to carboplatin/paclitaxel improved progression-free survival (PFS) (hazard ratio 0.71, 95% confidence interval 0.57-0.88; P = 0.002) in patients with advanced human epidermal growth factor receptor 2-negative, germline BRCA1/2-mutated breast cancer. A subset of patients discontinued both carboplatin and paclitaxel before progression and continued on veliparib/placebo maintenance monotherapy until progression. Analyses in this patient subgroup are reported. PATIENTS AND METHODS: Patients were randomized 2 : 1 to veliparib plus carboplatin/paclitaxel or placebo plus carboplatin/paclitaxel. Veliparib (120 mg twice daily) or placebo was given on days -2 to 5, carboplatin (area under the curve 6 mg/ml) on day 1, and paclitaxel (80 mg/m2) on days 1, 8, and 15 of 21-day cycles. Patients who discontinued both carboplatin and paclitaxel before progression received blinded study drug monotherapy at an increased dose of 300-400 mg twice daily continuously. PFS was the primary endpoint. Exploratory analyses were carried out in the subgroup of patients who received blinded study drug as monotherapy. A time-varying Cox model including data from all patients was also used to evaluate treatment effect in the combination and monotherapy phases. RESULTS: A total of 136 of 337 patients randomized to veliparib plus carboplatin/paclitaxel and 58/172 patients randomized to placebo plus carboplatin/paclitaxel discontinued both carboplatin and paclitaxel before progression and continued on blinded veliparib or placebo monotherapy. In this blinded monotherapy subgroup, investigator-assessed median PFS from randomization was 25.7 months with veliparib versus 14.6 months with placebo. Hazard ratios from a time-varying Cox model favored veliparib during both combination therapy and monotherapy. Any-grade adverse events occurring in the monotherapy phase were primarily gastrointestinal. The most common grade ≥3 adverse events were neutropenia and anemia (4% each with veliparib; 5% and 2%, respectively, with placebo). CONCLUSIONS: Veliparib maintenance monotherapy had a tolerable safety profile and may extend PFS following combination chemotherapy.

Hepatitis C virus RNA-dependent RNA polymerase (NS5B) as a mediator of the antiviral activity of ribavirin.

Ribavirin is administered in combination with interferon-alpha for treatment of hepatitis C virus (HCV) infection. Recently, we demonstrated that the antiviral activity of ribavirin can result from the ability of a viral RNA polymerase to utilize ribavirin triphosphate and to incorporate this nucleotide with reduced specificity, thereby mutagenizing the genome and decreasing the yield of infectious virus (Crotty, S., Maag, D., Arnold, J. J., Zhong, W., Lau, J. Y., Hong, Z., Andino, R., and Cameron, C. E. (2000) Nat. Med. 6, 1375-1379). In this study, we performed a quantitative analysis of a novel HCV RNA polymerase derivative that is capable of utilizing stably annealed primer-template substrates and exploited this derivative to evaluate whether lethal mutagenesis of the HCV genome is a possible mechanism for the anti-HCV activity of ribavirin. These studies demonstrate HCV RNA polymerase-catalyzed incorporation of ribavirin opposite cytidine and uridine. In addition, we demonstrate that templates containing ribavirin support CMP and UMP incorporation with equivalent efficiency. Surprisingly, templates containing ribavirin can also cause a significant block to RNA elongation. Together, these data suggest that ribavirin can exert a direct effect on HCV replication, which is mediated by the HCV RNA polymerase. We discuss the implications of this work on the development of nucleoside analogs for treatment of HCV infection.

The broad-spectrum antiviral ribonucleoside ribavirin is an RNA virus mutagen.

The ribonucleoside analog ribavirin (1-beta-D-ribofuranosyl-1,2, 4-triazole-3-carboxamide) shows antiviral activity against a variety of RNA viruses and is used in combination with interferon-alpha to treat hepatitis C virus infection. Here we show in vitro use of ribavirin triphosphate by a model viral RNA polymerase, poliovirus 3Dpol. Ribavirin incorporation is mutagenic, as it templates incorporation of cytidine and uridine with equal efficiency. Ribavirin reduces infectious poliovirus production to as little as 0. 00001% in cell culture. The antiviral activity of ribavirin correlates directly with its mutagenic activity. These data indicate that ribavirin forces the virus into 'error catastrophe'. Thus, mutagenic ribonucleosides may represent an important class of anti-RNA virus agents.

Template/primer requirements and single nucleotide incorporation by hepatitis C virus nonstructural protein 5B polymerase.

Nonstructural protein 5B (NS5B) of hepatitis C virus (HCV) possesses an RNA-dependent RNA polymerase activity responsible for viral genome RNA replication. Despite several reports on the characterization of this essential viral enzyme, little is known about the reaction pathway of NS5B-catalyzed nucleotide incorporation due to the lack of a kinetic system offering efficient assembly of a catalytically competent polymerase/template/primer/nucleotide quaternary complex. In this report, specific template/primer requirements for efficient RNA synthesis by HCV NS5B were investigated. For intramolecular copy-back RNA synthesis, NS5B utilizes templates with an unstable stem-loop at the 3' terminus which exists as a single-stranded molecule in solution. A template with a stable tetraloop at the 3' terminus failed to support RNA synthesis by HCV NS5B. Based on these observations, a number of single-stranded RNA templates were synthesized and tested along with short RNA primers ranging from two to five nucleotides. It was found that HCV NS5B utilized di- or trinucleotides efficiently to initiate RNA replication. Furthermore, the polymerase, template, and primer assembled initiation-competent complexes at the 3' terminus of the template RNA where the template and primer base paired within the active site cavity of the polymerase. The minimum length of the template is five nucleotides, consistent with a structural model of the NS5B/RNA complex in which a pentanucleotide single-stranded RNA template occupies a groove located along the fingers subdomain of the polymerase. This observation suggests that the initial docking of RNA on NS5B polymerase requires a single-stranded RNA molecule. A unique beta-hairpin loop in the thumb subdomain may play an important role in properly positioning the single-stranded template for initiation of RNA synthesis. Identification of the template/primer requirements will facilitate the mechanistic characterization of HCV NS5B and its inhibitors.

Commissioning and periodic quality assurance of a clinical electronic portal imaging device.

PURPOSE: An electronic portal imaging device (EPID) was recently installed on our dual-energy linear accelerator. Commissioning and quality assurance techniques were developed for the EPID. METHODS AND MATERIALS: A commissioning procedure was developed consisting of five parts: (a) physical operation and safety; (b) image acquisition, resolution, and sensitivity calibration; (c) image storage, analysis, and handling; (d) reference image acquisition; and (e) clinical operations. RESULTS: The physical operation and safety tests relate to the motions of the unit, stability of the unit supports, safety interlocks, and interlock overrides. Imager contrast and spatial resolutions are monitored by imaging a contrast-detail phantom. The imager calibration procedure consists of a no-radiation image to compensate for signal offsets, as well as a "flat-field image." The flat-field image is taken with 5.0 cm of homogeneous phantom material placed at isocenter to provide some photon scatter and to approximate the presence of a patient. Daily quality assurance procedures consists of safety tests and the acquisition and inspection of images of the contrast-detail phantom. After 1 year, the frequency of the daily procedure was reduced to weekly. Quarterly QA procedures are conducted by the physicist and consist of the same procedures conducted in the weekly test. The annual QA procedure consists of a duplication of the commissioning procedure. CONCLUSION: The procedures discussed in this article were applied to an ionization-chamber device. They have been useful in identifying difficulties with the EPID operation, including the need for recalibrating and monitoring the accelerator output stability.

A quality assurance program for ancillary high technology devices on a dual-energy accelerator.

Our facility has added high-technology ancillary devices to our dual-energy linear accelerator. After commissioning and acceptance testing of dual asymmetric jaws, dynamic wedge, portal imaging, and multileaf collimation (MLC), quality assurance programs were instituted. The programs were designed to be both periodic and patient specific when required. In addition, when dosimetric aspects were affected by these technologies, additional quality assurance checks were added. Positional accuracy checks (light and radiation) are done for both asymmetric jaws and MLC. Each patient MLC field is checked against the original simulation or digitally reconstructed radiographs. Off-axis factors and output checks are performed for asymmetric fields. Dynamic wedge transmission factors and profiles are checked periodically, and a patient diode check is performed for every new dynamic wedge portal. On-line imaging checks encompass safety checks along with periodic measurement of contrast and spatial resolution. The most important quality assurance activity is the annual review of proper operation and procedures for each device. Our programs have been successful in avoiding patient-related errors or device malfunctions. The programs are a team effort involving physicists, maintenance engineers, and therapists.