Dacomitinib as first-line treatment in patients with clinically or molecularly selected advanced non-small-cell lung cancer: a multicentre, open-label, phase 2 trial.

BACKGROUND: Patients with EGFR-mutant non-small-cell lung cancer generally have a progression-free survival of 9-13 months while being treated with the EGFR tyrosine-kinase inhibitors gefitinib or erlotinib. However, resistance inevitably develops, and more effective EGFR inhibitors are needed. Dacomitinib is a covalent pan-HER inhibitor that has shown clinical activity in patients previously treated with gefitinib or erlotinib. We did a trial of dacomitinib as initial systemic therapy in clinically and molecularly selected patients with advanced non-small-cell lung cancer. METHODS: In this open-label, multicentre, phase 2 trial, we enrolled treatment-naive patients with advanced lung cancer who had clinical (never-smokers [<100 cigarettes per lifetime] or former light smokers [<10 pack-years per lifetime] and ≥15 years since last cigarette) or molecular (EGFR mutation, regardless of smoking status) characteristics associated with response to EGFR inhibitors. We gave dacomitinib orally once daily (45 mg or 30 mg) until progressive disease, unacceptable toxicity, or patient withdrawal. We used Response Evaluation Criteria in Solid Tumors criteria (version 1.0) to investigate the activity of dacomitinib in all patients with a baseline scan and at least one post-treatment scan, with investigator assessment of response and progression. The primary endpoint was progression-free survival at 4 months in the as-enrolled population, with a null hypothesis of progression-free survival at 4 months of 50% or less. The study is registered with ClinicalTrials.gov, number NCT00818441, and is no longer accruing patients. FINDINGS: Between March 11, 2009, and April 1, 2011, we enrolled 89 patients from 25 centres, including 45 (51%) with EGFR-activating mutations in exon 19 (n=25) or exon 21 (n=20). Progression-free survival at 4 months was 76·8% (95% CI 66·4-84·4) in the as-enrolled population, and was 95·5% (95% CI 83·2-98·9) in the EGFR-mutant population. The most common all-grade treatment-related adverse events were diarrhoea in 83 (93%) patients, dermatitis acneiform in 69 (78%) patients, dry skin in 39 (44%) patients, and stomatitis in 36 (40%) patients. Two patients (2%) had grade 4 treatment-related events (one with hypokalaemia and one with dyspnoea). No grade 5 toxicities were recorded. INTERPRETATION: Dacomitinib had encouraging clinical activity as initial systemic treatment in clinically or molecularly selected patients with advanced non-small-cell lung cancer. FUNDING: Pfizer.

Dacomitinib versus erlotinib in patients with advanced-stage, previously treated non-small-cell lung cancer (ARCHER 1009): a randomised, double-blind, phase 3 trial.

BACKGROUND: Dacomitinib is an irreversible pan-EGFR family tyrosine kinase inhibitor. Findings from a phase 2 study in non-small cell lung cancer showed favourable efficacy for dacomitinib compared with erlotinib. We aimed to compare dacomitinib with erlotinib in a phase 3 study. METHODS: In a randomised, multicentre, double-blind phase 3 trial in 134 centres in 23 countries, we enrolled patients who had locally advanced or metastatic non-small-cell lung cancer, progression after one or two previous regimens of chemotherapy, Eastern Cooperative Oncology Group (ECOG) performance status of 0-2, and presence of measurable disease. We randomly assigned patients in a 1:1 ratio to dacomitinib (45 mg/day) or erlotinib (150 mg/day) with matching placebo. Treatment allocation was masked to the investigator, patient, and study funder. Randomisation was stratified by histology (adenocarcinoma vs non-adenocarcinoma), ethnic origin (Asian vs non-Asian and Indian sub-continent), performance status (0-1 vs 2), and smoking status (never-smoker vs ever-smoker). The coprimary endpoints were progression-free survival per independent review for all randomly assigned patients, and for all randomly assigned patients with KRAS wild-type tumours. The study has completed accrual and is registered with ClinicalTrials.gov, number NCT01360554. FINDINGS: Between June 22, 2011, and March 12, 2013, we enrolled 878 patients and randomly assigned 439 to dacomitinib (256 KRAS wild type) and 439 (263 KRAS wild type) to erlotinib. Median progression-free survival was 2·6 months (95% CI 1·9-2·8) in both the dacomitinib group and the erlotinib group (stratified hazard ratio [HR] 0·941, 95% CI 0·802-1·104, one-sided log-rank p=0·229). For patients with wild-type KRAS, median progression-free survival was 2·6 months for dacomitinib (95% CI 1·9-2·9) and erlotinib (95% CI 1·9-3·0; stratified HR 1·022, 95% CI 0·834-1·253, one-sided p=0·587). In patients who received at least one dose of study drug, the most frequent grade 3-4 adverse events were diarrhoea (47 [11%] patients in the dacomitinib group vs ten [2%] patients in the erlotinib group), rash (29 [7%] vs 12 [3%]), and stomatitis (15 [3%] vs two [<1%]). Serious adverse events were reported in 52 (12%) patients receiving dacomitinib and 40 (9%) patients receiving erlotinib. INTERPRETATION: Irreversible EGFR inhibition with dacomitinib was not superior to erlotinib in an unselected patient population with advanced non-small-cell lung cancer or in patients with KRAS wild-type tumours. Further study of irreversible EGFR inhibitors should be restricted to patients with activating EGFR mutations. FUNDING: Pfizer.

Dacomitinib compared with placebo in pretreated patients with advanced or metastatic non-small-cell lung cancer (NCIC CTG BR.26): a double-blind, randomised, phase 3 trial.

BACKGROUND: Dacomitinib is an irreversible pan-HER tyrosine-kinase inhibitor with preclinical and clinical evidence of activity in non-small-cell lung cancer. We designed BR.26 to assess whether dacomitinib improved overall survival in heavily pretreated patients with this disease. METHODS: In this double-blind, randomised, placebo-controlled, phase 3 trial, we enrolled adults (aged ≥18 years) with advanced or metastatic non-small-cell lung cancer from 75 centres in 12 countries. Eligible patients had received up to three previous lines of chemotherapy and either gefitinib or erlotinib, and had assessable disease (RECIST 1.1) and tumour tissue samples for translational studies. Patients were stratified according to centre, performance status, tobacco use, best response to previous EGFR tyrosine-kinase inhibitor, weight loss within the previous 3 months, and ethnicity, and were then randomly allocated 2:1 to oral dacomitinib 45 mg once-daily or matched placebo centrally via a web-based system. Treatment continued until disease progression or unacceptable toxicity. The primary outcome was overall survival in the intention-to-treat population; secondary outcomes included overall survival in predefined molecular subgroups, progression-free survival, the proportion of patients who achieved an objective response, safety, and quality of life. This study is completed, although follow-up is ongoing for patients on treatment. This study is registered with ClinicalTrials.gov, number NCT01000025. FINDINGS: Between Dec 23, 2009, and June 11, 2013, we randomly assigned 480 patients to dacomitinib and 240 patients to placebo. At the final analysis (January, 2014), median follow-up was 23·4 months (IQR 15·6-29·6) for patients in the dacomitinib group and 24·4 months (11·5-38·9) for those in the placebo group. Dacomitinib did not improve overall survival compared with placebo (median 6·83 months [95% CI 6·08-7·49] for dacomitinib vs 6·31 months [5·32-7·52] for placebo; hazard ratio [HR] 1·00 [95% CI 0·83-1·21]; p=0·506). However, patients in the dacomitinib group had longer progression-free survival than those in the placebo group (median 2·66 months [1·91-3·32] vs 1·38 months [0·99-1·74], respectively; HR 0·66 [95% CI 0·55-0·79]; p<0·0001), and a significantly greater proportion of patients in the dacomitinb group achieved an objective response than in the placebo group (34 [7%] of 480 patients vs three [1%] of 240 patients, respectively; p=0·001). Compared with placebo, the effect of dacomitinib on overall survival seemed similar in patients with EGFR-mutation-positive tumours (HR 0·98, 95% CI 0·67-1·44) and EGFR wild-type tumours (0·93, 0·71-1·21; pinteraction=0·69). However, we noted qualitative differences in the effect of dacomitinib on overall survival for patients with KRAS-mutation-positive tumours (2·10, 1·05-4·22) and patients with KRAS wild-type tumours (0·79, 0·61-1·03; pinteraction=0·08). Compared with placebo, patients allocated dacomitinib had significantly longer time to deterioration of cough (p<0·0001), dyspnoea (p=0·049), and pain (p=0·041). 185 (39%) of 477 patients who received dacomitinib and 86 (36%) of 239 patients who received placebo had serious adverse events. The most common grade 3-4 adverse events were diarrhoea (59 [12%] patients on dacomitinib vs no controls), acneiform rash (48 [10%] vs one [<1%]), oral mucositis (16 [3%] vs none), and fatigue (13 [3%] vs four [2%]). INTERPRETATION: Dacomitinib did not increase overall survival and cannot be recommended for treatment of patients with advanced non-small-cell lung cancer previously treated with chemotherapy and an EGFR tyrosine-kinase inhibitor. FUNDING: Canadian Cancer Society Research Institute and Pfizer.

Proteomic analysis of low dose arsenic and ionizing radiation exposure on keratinocytes.

Human exposure to arsenic and ionizing radiation (IR) occur environmentally at low levels. While the human health effects of arsenic and IR have been examined separately, there is little information regarding their combined effects at doses approaching environmental levels. Arsenic toxicity may be affected by concurrent IR especially given their known individual carcinogenic actions at higher doses. We found that keratinocytes responded to either low dose arsenic and/or low dose IR exposure, resulting in differential proteomic expression based on 2-DE, immunoblotting and statistical analysis. Seven proteins were identified that passed a rigorous statistical screen for differential expression in 2-DE and also passed a strict statistical screen for follow-up immunoblotting. These included: alpha-enolase, epidermal-fatty acid binding protein, heat shock protein 27, histidine triad nucleotide-binding protein 1, lactate dehydrogenase A, protein disulfide isomerase precursor, and S100A9. Four proteins had combined effects that were different than would be expected based on the response to either individual toxicant. These data demonstrate a possible reaction to the combined insult that is substantially different from that of either separate treatment. Several proteins had different responses than what has been seen from high dose exposures, adding to the growing literature suggesting that the cellular responses to low dose exposures are distinct.

Assessing probe-specific dye and slide biases in two-color microarray data.

BACKGROUND: A primary reason for using two-color microarrays is that the use of two samples labeled with different dyes on the same slide, that bind to probes on the same spot, is supposed to adjust for many factors that introduce noise and errors into the analysis. Most users assume that any differences between the dyes can be adjusted out by standard methods of normalization, so that measures such as log ratios on the same slide are reliable measures of comparative expression. However, even after the normalization, there are still probe specific dye and slide variation among the data. We define a method to quantify the amount of the dye-by-probe and slide-by-probe interaction. This serves as a diagnostic, both visual and numeric, of the existence of probe-specific dye bias. We show how this improved the performance of two-color array analysis for arrays for genomic analysis of biological samples ranging from rice to human tissue. RESULTS: We develop a procedure for quantifying the extent of probe-specific dye and slide bias in two-color microarrays. The primary output is a graphical diagnostic of the extent of the bias which called ECDF (Empirical Cumulative Distribution Function), though numerical results are also obtained. CONCLUSION: We show that the dye and slide biases were high for human and rice genomic arrays in two gene expression facilities, even after the standard intensity-based normalization, and describe how this diagnostic allowed the problems causing the probe-specific bias to be addressed, and resulted in important improvements in performance. The R package LMGene which contains the method described in this paper has been available to download from Bioconductor.

Transient genome-wide transcriptional response to low-dose ionizing radiation in vivo in humans.

PURPOSE: The in vivo effects of low-dose low linear energy transfer ionizing radiation on healthy human skin are largely unknown. Using a patient-based tissue acquisition protocol, we have performed a series of genomic analyses on the temporal dynamics over a 24-hour period to determine the radiation response after a single exposure of 10 cGy. METHODS AND MATERIALS: RNA from each patient tissue sample was hybridized to an Affymetrix Human Genome U133 Plus 2.0 array. Data analysis was performed on selected gene groups and pathways. RESULTS: Nineteen gene groups and seven gene pathways that had been shown to be radiation responsive were analyzed. Of these, nine gene groups showed significant transient transcriptional changes in the human tissue samples, which returned to baseline by 24 hours postexposure. CONCLUSIONS: Low doses of ionizing radiation on full-thickness human skin produce a definable temporal response out to 24 hours postexposure. Genes involved in DNA and tissue remodeling, cell cycle transition, and inflammation show statistically significant changes in expression, despite variability between patients. These data serve as a reference for the temporal dynamics of ionizing radiation response following low-dose exposure in healthy full-thickness human skin.

Human in vivo dose-response to controlled, low-dose low linear energy transfer ionizing radiation exposure.

PURPOSE: The effect of low doses of low-linear energy transfer (photon) ionizing radiation (LDIR, <10 cGy) on human tissue when exposure is under normal physiologic conditions is of significant interest to the medical and scientific community in therapeutic and other contexts. Although, to date, there has been no direct assessment of the response of human tissue to LDIR when exposure is under normal physiologic conditions of intact three-dimensional architecture, vasculature, and cell-cell contacts (between epithelial cells and between epithelial and stromal cells). EXPERIMENTAL DESIGN: In this article, we present the first data on the response of human tissue exposed in vivo to LDIR with precisely controlled and calibrated doses. We evaluated transcriptomic responses to a single exposure of LDIR in the normal skin of men undergoing therapeutic radiation for prostate cancer (research protocol, Health Insurance Portability and Accountability Act-compliant, Institutional Review Board-approved). Using newly developed biostatistical tools that account for individual splice variants and the expected variability of temporal response between humans even when the outcome is measured at a single time, we show a dose-response pattern in gene expression in a number of pathways and gene groups that are biologically plausible responses to LDIR. RESULTS: Examining genes and pathways identified as radiation-responsive in cell culture models, we found seven gene groups and five pathways that were altered in men in this experiment. These included the Akt/phosphoinositide-3-kinase pathway, the growth factor pathway, the stress/apoptosis pathway, and the pathway initiated by transforming growth factor-beta signaling, whereas gene groups with altered expression included the keratins, the zinc finger proteins and signaling molecules in the mitogen-activated protein kinase gene group. We show that there is considerable individual variability in radiation response that makes the detection of effects difficult, but still feasible when analyzed according to gene group and pathway. CONCLUSIONS: These results show for the first time that low doses of radiation have an identifiable biosignature in human tissue, irradiated in vivo with normal intact three-dimensional architecture, vascular supply, and innervation. The genes and pathways show that the tissue (a) does detect the injury, (b) initiates a stress/inflammatory response, (c) undergoes DNA remodeling, as suggested by the significant increase in zinc finger protein gene expression, and (d) initiates a "pro-survival" response. The ability to detect a distinct radiation response pattern following LDIR exposure has important implications for risk assessment in both therapeutic and national defense contexts.

Dosimetry for quantitative analysis of the effects of low-dose ionizing radiation in radiation therapy patients.

We have developed and validated a practical approach to identifying the location on the skin surface that will receive a prespecified biopsy dose (ranging down to 1 cGy) in support of in vivo biological dosimetry in humans. This represents a significant technical challenge since the sites lie on the patient's surface outside the radiation fields. The PEREGRINE Monte Carlo simulation system was used to model radiation dose delivery, and TLDs were used for validation on phantoms and for confirmation during patient treatment. In the developmental studies, the Monte Carlo simulations consistently underestimated the dose at the biopsy site by approximately 15% (of the local dose) for a realistic treatment configuration, most likely due to lack of detail in the simulation of the linear accelerator outside the main beam line. Using a single, thickness-independent correction factor for the clinical calculations, the average of 36 measurements for the predicted 1-cGy point was 0.985 cGy (standard deviation: 0.110 cGy) despite patient breathing motion and other real-world challenges. Since the 10-cGy point is situated in the region of high-dose gradient at the edge of the field, patient motion had a greater effect, and the six measured points averaged 5.90 cGy (standard deviation: 1.01 cGy), a difference that is equivalent to approximately a 6-mm shift on the patient's surface.

Integration of novel therapeutics into combined modality therapy of locally advanced non-small cell lung cancer.

Novel therapeutic agents (NTA) directed against a wide array of newly described molecular targets are now entering clinical investigation, many in the treatment of non-small cell lung cancer (NSCLC). The great majority of these clinical trials have been directed toward patients with advanced stage (metastatic) disease. More recently, study of NTAs has turned toward earlier-stage disease. Locally advanced, or stage III, NSCLC represents a large and heterogeneous group of patients and several clinically distinct substages. During the last 15 years, randomized clinical trials have shown improved survival with sequential chemoradiation compared with radiation alone and, more recently, the superiority of concurrent versus sequential chemoradiation. As NTAs have increasingly shown clinical activity against NSCLC, questions of how to incorporate them into clinical trials in stage III disease, whether they should be given together with radiotherapy, substituting for chemotherapy, or whether they should be added to current chemoradiation strategies, all remain as issues. Here, we describe conceptual issues, preclinical rationale, and ongoing or planned clinical trials incorporating NTAs into current treatment paradigms for unresectable stage III NSCLC.

Effect of food or proton pump inhibitor treatment on the bioavailability of dacomitinib in healthy volunteers.

This phase 1, open-label crossover study evaluated the relative bioavailability of dacomitinib in healthy volunteers under fed and fasted conditions and following coadministration with rabeprazole, a potent acid-reducing proton pump inhibitor (PPI). Twenty-four male subjects received a single dacomitinib 45-mg dose under 3 different conditions separated by washout periods of ≥ 16 days: coadministered with rabeprazole 40 mg under fasting conditions; alone under fasting conditions; and alone after a high-fat, high-calorie meal. Increased peak exposure of 23.7% (90% confidence interval [CI], 5.3%-45.2%) was detected with dacomitinib taken after food versus fasting. The adjusted geometric mean ratio (fed/fasted) for area under the plasma concentration-time curve from time zero to infinity (AUCinf ) was 114.2% (90%CI, 104.7%-124.5%) and not considered clinically meaningful. In the fasted state, a decrease in dacomitinib AUCinf was observed following rabeprazole versus dacomitinib alone (PPI+fasted/fasted alone): 71.1% (90%CI, 61.7%-81.8%). Dacomitinib was generally well tolerated. Dacomitinib may be taken with or without food. Use of long-acting acid-reducing agents, such as PPIs with dacomitinib should be avoided if possible. Shorter-acting agents such as antacids and H2-receptor antagonists may have lesser impact on dacomitinib exposure and may be preferable to PPIs if acid reduction is clinically required.

Combined Pan-HER and ALK/ROS1/MET Inhibition with Dacomitinib and Crizotinib in Advanced Non-Small Cell Lung Cancer: Results of a Phase I Study.

INTRODUCTION: This phase I study investigated the activity of the irreversible pan-human epidermal growth factor receptor inhibitor dacomitinib in combination with the mesenchymal-epithelial transition factor/anaplastic lymphoma kinase/ROS proto-oncogene 1, receptor tyrosine kinase inhibitor crizotinib in advanced non-small cell lung cancer. METHODS: Patients with progression after at least one line of chemotherapy or targeted therapy received dacomitinib once daily and crizotinib once daily or twice daily, with doses escalated until intolerable toxicity; the expansion cohorts received the maximum tolerated dose of the combination. The primary objective was to define the recommended phase II dose; secondary objectives included assessment of safety and activity of the combination in epidermal growth factor receptor inhibitor-resistant patients and correlation with tumor biomarkers. RESULTS: Seventy patients were treated in the dose-escalation (n = 33) and expansion phases (n = 37), with the maximum tolerated dose defined as dacomitinib, 30 mg once daily, plus crizotinib, 200 mg twice daily. Grade 3 or 4 treatment-related adverse events were reported in 43% of patients: the most common were diarrhea (16%), rash (7%), and fatigue (6%). There were 16 deaths; none were considered treatment related. One patient (1%) had a partial response; 46% had stable disease. Most of the tumor samples analyzed had activating epidermal growth factor receptor gene (EGFR) mutations (18 of 20 [90%]); 50% (10 of 20) had a concurrent resistance mutation. Only one sample showed MMNG HOS Transforming gene (MET) amplification (the patient had progressive disease), whereas 59% (13 of 22) and 47% (14 of 30) had high levels of expression of epidermal growth factor receptor and mesenchymal-epithelial transition factor on the basis of H-scores, respectively. There was no apparent association between biomarker expression and antitumor activity. CONCLUSION: The combination of dacomitinib and crizotinib showed limited antitumor activity in patients with advanced non-small cell lung cancer and was associated with substantial toxicity.

Clinical implications of radiation-induced genomic instability.

Radiation-induced genomic instability encompasses a range of measurable end points such as chromosome destabilization, sister chromatid exchanges, gene mutation and amplification, late cell death and aneuploidy, all of which may be causative factors in the development of clinical disease, including carcinoma. Clinical implications of genomic instability can be broadly grouped into two main areas: as a marker for increased cancer risk/early detection, and as a consequence of radiation therapy (IR) that may be causative of, or a strong marker for, the induction of a therapy-induced second malignancy. Research in human populations has been limited, but broadly encompasses three populations: those exposed to alpha-particle irradiation, those with a cancer diagnosis who were examined for lymphocyte sensitivity to IR as a biomarker for risk of cancer induction, and those who successfully completed radiation therapy for an index cancer and who were examined for the induction of a second malignancy. This review examines each of those populations in turn and offers some potential future research directions to better elucidate the role of radiation-induced genomic instability in clinical disease.

Current and future therapeutic approaches in locally advanced (stage III) non-small cell lung cancer.

In the treatment of locally advanced (stage III) non-small cell lung cancer, randomized clinical trials have shown that sequential administration of platinum-based chemotherapy followed by radiotherapy improves outcome compared with radiotherapy alone. More recently, concurrent chemoradiotherapy has been shown to be superior to sequential therapy. Incorporating full-dose chemotherapy into induction or consolidation phases is aimed at the eradication of distant micrometastases. These approaches are currently being examined in clinical trials. The role of neoadjuvant and adjuvant therapy in resectable stage IIIA patients remains controversial. Integration of newer cytotoxic agents (paclitaxel, docetaxel, gemcitabine, vinorelbine, and irinotecan) and molecularly targeted agents into the treatment of stage-III patients may result in improved long-term outcomes and is currently under study.

Tirapazamine: prototype for a novel class of therapeutic agents targeting tumor hypoxia.

Preclinical models in vitro and in vivo have shown that tumor hypoxia alters the malignant cell phenotype, selecting for p53 mutations, stimulating angiogenesis and metastasis, and markedly reducing the efficacy of both radiotherapy and chemotherapy. Similarly, clinical studies measuring pretreatment tumor oxygen status confirm that the presence of hypoxia confers a negative impact on local control, disease-free survival, and overall survival. Despite these data and extensive past research efforts, the promise of developing selective hypoxic-cell sensitizers has been largely unfulfilled. In contrast, tirapazamine is the rationally designed prototype for a new class of therapeutic agents targeting tumor hypoxia: hypoxic cytotoxins. Tirapazamine is bioreductively activated in hypoxic cells and has been shown to potentiate the cytotoxicity of radiation and a number of chemotherapeutic drug classes, in particular platinum compounds and taxanes. This article reviews the preclinical and clinical development of tirapazamine, as well as current trials in non-small cell lung cancer designed to provide proof of principle for this new category of cancer therapeutics.

Effects of low-dose ionizing radiation on gene expression in human skin biopsies.

PURPOSE: Several investigations have demonstrated that significant biologic effects can occur in animals, animal cells, immortalized human cell lines, and primary human cells after exposure to doses of ionizing radiation in the low-dose, < or =1-10 cGy region (LDIR). However, little information is available as to how these and other observations pertain to human responses to LDIR, though such knowledge is required for reducing the uncertainty of assessing human risks due to these exposures. We therefore undertook these translational studies to begin the development of a unique data set of human cellular responses to LDIR as measured by gene expression changes when exposure occurs to a normal tissue with its complex cellular mixture and three-dimensional architecture. METHODS AND MATERIALS: Using full-thickness human skin resected during esthetic surgery, we obtained biopsy cores and exposed the tissue to LDIR ex vivo. Gene expression changes in five core regulatory genes were assessed by real-time RT-PCR. RESULTS: Results indicate that skin is a good biologic model for assessing LDIR in humans, though meticulous attention to sample processing is necessary. LDIR does produce changes in gene expression, though time- and dose-response relationships may be complex. CONCLUSION: These proof-of-principle studies have provided a crucial initial step toward validation of LDIR risk assessment models in humans. We have demonstrated the feasibility of this approach and provide initial evidence that ionizing radiation exposures as low as 1 cGy are biologically active in human skin.

Survival and cell cycle kinetics of human prostate cancer cell lines after single- and multifraction exposures to ionizing radiation.

PURPOSE: Fractionated radiation therapy is frequently used to treat prostate cancer with an underlying assumption that each daily dose of ionizing radiation (IR) results in equal cell killing. We used three human prostate cancer cell lines to evaluate how survival after a single 2-Gy dose may predict responses after daily repeated 2-Gy exposures. METHODS AND MATERIALS: LNCaP, CWR22R, and PC3 cells were used in these studies. Survival after IR exposures was assessed using clonogenic assays and cell cycle responses were determined by flow cytometry. RESULTS: The experimentally determined multifraction survival differed significantly from that predicted from their single-dose SF2. LNCaP and CWR22R cells showed lower than predicted survivals; PC3 cells exhibited greater than predicted survival. Daily IR exposures resulted in changes in the cell cycle distributions beyond those caused by a single exposure to IR. CONCLUSIONS: Our results show that in these prostate cancer cells: (1) survival after a clinically relevant dose of IR does not predict survival after multifraction IR, (2) cell cycle responses after a single 2 Gy dose can differ from those that occur when cells receive daily 2 Gy doses, and (3) some cell cycle changes that result from fractionated IR may predict their ultimate survival responses from such treatment.

Radiation-induced effects in unirradiated cells: a review and implications in cancer.

A long-held central dogma of radiation biology has been that the carcinogenic effects of ionizing radiation (IR) are induced by the direct and radiolytic actions of IR on nuclear DNA. Numerous investigations, however, have revealed that several cancer relevant effects of IR can occur in cells that have received only cytoplasmic or plasmalemmal membrane exposure to IR. Further, mounting evidence now indicates that many effects that have been attributed to IR-induced damage to nuclear DNA or that occur following irradiation of the cytoplasmic compartment of cells can also occur in cells that have received no direct exposure to IR per se. These so-called , i.e., radiation-induced effects in unirradiated cells, include cell killing, increases in intracellular reactive oxygen species, the induction of mutations, enhanced cell growth, the induction of apoptosis, the induction of genomic instability and neoplastic transformation. In this report, we summarize the evidence that demonstrates IR can cause this array of effects in non-irradiated cells, and we discuss recent findings concerning the potential mechanisms that may underlie IR-induced effects in unirradiated, or cells. Additionally, we discuss IR-induced bystander effects and their possible relationship to some in vivo observations, how bystander effects may pertain to carcinogenesis the treatment of tumors with radiotherapy, and how effects in bystander cells contribute to uncertainties in assessing cancer risks associated with exposure to IR.

Enhancement of radiation cytotoxicity by UCN-01 in non-small cell lung carcinoma cells.

Thoracic ionizing radiation is a standard component of combined-modality therapy for locally advanced non-small cell lung cancer. To improve low 5-year survival rates (5- 15%), new strategies for enhancing the effectiveness of ionizing radiation are needed. The kinase inhibitor UCN-01 has multiple cell cycle effects, including abrogation of DNA damage-induced S- and G(2)-phase arrest, which may limit DNA repair prior to mitosis. To test the hypothesis that therapy-induced cell cycle effects would have an impact on the efficacy of a combination of UCN-01 plus ionizing radiation, the cell cycle responses of the non-small cell lung cancer cell lines Calu1 (TP53-null) and A549 (wild-type TP53) to 2 Gy ionizing radiation were correlated with clonogenic survival after irradiation plus UCN-01. Irradiated cells were exposed to UCN-01 simultaneously and at 3-h increments after irradiation. In Calu1 cells but not A549 cells, sequence-dependent potentiation of radiation by UCN-01 was observed, with maximal interaction occurring when UCN-01 was administered 6 h after irradiation. This coincided with the postirradiation time with the greatest depletion of cells from G(1). Abrogation of G(2) arrest was observed regardless of TP53 status. The role of TP53 was investigated using siRNA to achieve gene silencing. These studies demonstrated that radiation plus UCN-01 was more effective in cells with diminished TP53 activity, associated with a reduced G(1) checkpoint arrest. These studies indicate that simultaneous elimination of multiple DNA damage-induced checkpoints in G(1), S and G(2) may enhance the effects of radiation and that drug scheduling may have an impact on clinical efficacy.

Film dosimetry in the peripheral region using multiple sensitometric curves.

We present a method for applying film dosimetry to the peripheral region utilizing multiple sensitometric curves. There are many instances when the dose to the peripheral region outside the field edges is of clinical and/or research interest. Published peripheral dose data may be insufficient if detailed dose modeling is required, and in those cases measurements must be performed. Film dosimetry is an attractive approach for dose measurement in the peripheral region because it integrates dose, overcoming the low-dose-rate problem, and is time efficient, as it acquires an entire plan of data in a single exposure. However, film response increases at energies below approximately 300 keV. As the scattered photon spectrum changes with distance from the field edge, this increased film sensitivity causes changes in the film response along profiles perpendicular to the field edge. A single sensitometric curve is therefore no longer sufficient for accurate conversion of the optical density to dose. Our new method uses multiple sensitometric curves defined at increasing distances from the field edge. To convert an optical density profile, the dose at each point in the profile is defined as a linear combination of the doses calculated using the two sensitometric curves that bracket the point of interest. A single set of sensitometric curves derived at one field size and source-to-surface distance (SSD) can be applied to density profiles for other field sizes and SSDs. We verified our new method by comparison to ion chamber measurements using three different types of film. Agreement with chamber measurements was within 7%, or less than 2 mm in regions of high gradient, over a wide range of field sizes and SSDs.

Concurrent chemoradiation strategies in the management of unresectable stage III non-small-cell lung cancer.

Locally advanced or unresectable stage III non-small-cell lung cancer (NSCLC) patients treated with combined-modality therapy with chemotherapy plus thoracic radiation have improved survival compared to those treated with radiotherapy alone. Furthermore, recent studies in good performance status, stage III patients have shown that concurrent chemoradiotherapy improves survival compared to sequential chemoradiotherapy. However, the optimal chemoradiation approach continues to evolve and is the subject of this review. Since the majority of patients completing chemoradiotherapy will succumb to distant metastatic disease, active systemic agents targeting this tumor compartment are required. Recent data suggest that full-dose chemotherapy designed to eradicate distant micrometastases given either as induction or consolidation has the potential to yield improved patient outcomes. Many of these chemotherapeutic agents are also potent radiosensitizers, hence providing enhanced local control. The integration of these chemotherapeutic agents into chemoradiotherapy programs in stage III NSCLC is the focus of current trials. Ongoing research with novel therapeutic agents with activity against distant micrometastases, refined radiation techniques, and enhanced imaging methodologies to aid in accurate staging are being pursued and should lead to improved survival and toxicity outcomes in this disease.