Suneil Jain

DNA-Repair Defects and Olaparib in Metastatic Prostate Cancer

BACKGROUND Prostate cancer is a heterogeneous disease, but current treatments are not based on molecular stratification. We hypothesized that metastatic, castration-resistant prostate cancers with DNA-repair defects would respond to poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibition with olaparib. METHODS We conducted a phase 2 trial in which patients with metastatic, castration-resistant prostate cancer were treated with olaparib tablets at a dose of 400 mg twice a day. The primary end point was the response rate, defined either as an objective response according to Response Evaluation Criteria in Solid Tumors, version 1.1, or as a reduction of at least 50% in the prostate-specific antigen level or a confirmed reduction in the circulating tumor-cell count from 5 or more cells per 7.5 ml of blood to less than 5 cells per 7.5 ml. Targeted next-generation sequencing, exome and transcriptome analysis, and digital polymerase-chain-reaction testing were performed on samples from mandated tumor biopsies. RESULTS Overall, 50 patients were enrolled; all had received prior treatment with docetaxel, 49 (98%) had received abiraterone or enzalutamide, and 29 (58%) had received cabazitaxel. Sixteen of 49 patients who could be evaluated had a response (33%; 95% confidence interval, 20 to 48), with 12 patients receiving the study treatment for more than 6 months. Next-generation sequencing identified homozygous deletions, deleterious mutations, or both in DNA-repair genes--including BRCA1/2, ATM, Fanconis anemia genes, and CHEK2--in 16 of 49 patients who could be evaluated (33%). Of these 16 patients, 14 (88%) had a response to olaparib, including all 7 patients with BRCA2 loss (4 with biallelic somatic loss, and 3 with germline mutations) and 4 of 5 with ATM aberrations. The specificity of the biomarker suite was 94%. Anemia (in 10 of the 50 patients [20%]) and fatigue (in 6 [12%]) were the most common grade 3 or 4 adverse events, findings that are consistent with previous studies of olaparib. CONCLUSIONS Treatment with the PARP inhibitor olaparib in patients whose prostate cancers were no longer responding to standard treatments and who had defects in DNA-repair genes led to a high response rate. (Funded by Cancer Research UK and others; ClinicalTrials.gov number, NCT01682772; Cancer Research UK number, CRUK/11/029.).

Long-Term Follow-Up of a Large Active Surveillance Cohort of Patients With Prostate Cancer

PURPOSE Active surveillance is increasingly accepted as a treatment option for favorable-risk prostate cancer. Long-term follow-up has been lacking. In this study, we report the long-term outcome of a large active surveillance protocol in men with favorable-risk prostate cancer. PATIENTS AND METHODS In a prospective single-arm cohort study carried out at a single academic health sciences center, 993 men with favorable- or intermediate-risk prostate cancer were managed with an initial expectant approach. Intervention was offered for a prostate-specific antigen (PSA) doubling time of less than 3 years, Gleason score progression, or unequivocal clinical progression. Main outcome measures were overall and disease-specific survival, rate of treatment, and PSA failure rate in the treated patients. RESULTS Among the 819 survivors, the median follow-up time from the first biopsy is 6.4 years (range, 0.2 to 19.8 years). One hundred forty-nine (15%) of 993 patients died, and 844 patients are alive (censored rate, 85.0%). There were 15 deaths (1.5%) from prostate cancer. The 10- and 15-year actuarial cause-specific survival rates were 98.1% and 94.3%, respectively. An additional 13 patients (1.3%) developed metastatic disease and are alive with confirmed metastases (n = 9) or have died of other causes (n = 4). At 5, 10, and 15 years, 75.7%, 63.5%, and 55.0% of patients remained untreated and on surveillance. The cumulative hazard ratio for nonprostate-to-prostate cancer mortality was 9.2:1. CONCLUSION Active surveillance for favorable-risk prostate cancer is feasible and seems safe in the 15-year time frame. In our cohort, 2.8% of patients have developed metastatic disease, and 1.5% have died of prostate cancer. This mortality rate is consistent with expected mortality in favorable-risk patients managed with initial definitive intervention.

Gold nanoparticles as novel agents for cancer therapy

Gold nanoparticles are emerging as promising agents for cancer therapy and are being investigated as drug carriers, photothermal agents, contrast agents and radiosensitisers. This review introduces the field of nanotechnology with a focus on recent gold nanoparticle research which has led to early-phase clinical trials. In particular, the pre-clinical evidence for gold nanoparticles as sensitisers with ionising radiation in vitro and in vivo at kilovoltage and megavoltage energies is discussed.

Cell-Specific Radiosensitization by Gold Nanoparticles at Megavoltage Radiation Energies

PURPOSE Gold nanoparticles (GNPs) have been shown to cause sensitization with kilovoltage (kV) radiation. Differences in the absorption coefficient between gold and soft tissue, as a function of photon energy, predict that maximum enhancement should occur in the kilovoltage (kV) range, with almost no enhancement at megavoltage (MV) energies. Recent studies have shown that GNPs are not biologically inert, causing oxidative stress and even cell death, suggesting a possible biological mechanism for sensitization. The purpose of this study was to assess GNP radiosensitization at clinically relevant MV X-ray energies. METHODS AND MATERIALS Cellular uptake, intracellular localization, and cytotoxicity of GNPs were assessed in normal L132, prostate cancer DU145, and breast cancer MDA-MB-231 cells. Radiosensitization was measured by clonogenic survival at kV and MV photon energies and MV electron energies. Intracellular DNA double-strand break (DSB) induction and DNA repair were determined and GNP chemosensitization was assessed using the radiomimetic agent bleomycin. RESULTS GNP uptake occurred in all cell lines and was greatest in MDA-MB-231 cells with nanoparticles accumulating in cytoplasmic lysosomes. In MDA-MB-231 cells, radiation sensitizer enhancement ratios (SERs) of 1.41, 1.29, and 1.16 were achieved using 160 kVp, 6 MV, and 15 MV X-ray energies, respectively. No significant effect was observed in L132 or DU145 cells at kV or MV energies (SER 0.97-1.08). GNP exposure did not increase radiation-induced DSB formation or inhibit DNA repair; however, GNP chemosensitization was observed in MDA-MB-231 cells treated with bleomycin (SER 1.38). CONCLUSIONS We have demonstrated radiosensitization in MDA-MB-231 cells at MV X-ray energies. The sensitization was cell-specific with comparable effects at kV and MV energies, no increase in DSB formation, and GNP chemopotentiation with bleomycin, suggesting a possible biological mechanism of radiosensitization.

Biological consequences of nanoscale energy deposition near irradiated heavy atom nanoparticles

Gold nanoparticles (GNPs) are being proposed as contrast agents to enhance X-ray imaging and radiotherapy, seeking to take advantage of the increased X-ray absorption of gold compared to soft tissue. However, there is a great discrepancy between physically predicted increases in X-ray energy deposition and experimentally observed increases in cell killing. In this work, we present the first calculations which take into account the structure of energy deposition in the nanoscale vicinity of GNPs and relate this to biological outcomes, and show for the first time good agreement with experimentally observed cell killing by the combination of X-rays and GNPs. These results are not only relevant to radiotherapy, but also have implications for applications of heavy atom nanoparticles in biological settings or where human exposure is possible because the localised energy deposition high-lighted by these results may cause complex DNA damage, leading to mutation and carcinogenesis.

Evaluation of cytotoxicity and radiation enhancement using 1.9 nm gold particles: potential application for cancer therapy

High atomic number (Z) materials such as gold preferentially absorb kilovoltage x-rays compared to soft tissue and may be used to achieve local dose enhancement in tumours during treatment with ionizing radiation. Gold nanoparticles have been demonstrated as radiation dose enhancing agents in vivo and in vitro. In the present study, we used multiple endpoints to characterize the cellular cytotoxic response of a range of cell lines to 1.9 nm gold particles and measured dose modifying effects following transient exposure at low concentrations. Gold nanoparticles caused significant levels of cell type specific cytotoxicity, apoptosis and increased oxidative stress. When used as dose modifying agents, dose enhancement factors varied between the cell lines investigated with the highest enhancement being 1.9 in AGO-1522B cells at a nanoparticle concentration of 100 microg ml(-1). This study shows exposure to 1.9 nm gold particles to induce a range of cell line specific responses including decreased clonogenic survival, increased apoptosis and induction of DNA damage which may be mediated through the production of reactive oxygen species. This is the first study involving 1.9 nm nanometre sized particles to report multiple cellular responses which impact on the radiation dose modifying effect. The findings highlight the need for extensive characterization of responses to gold nanoparticles when assessing dose enhancing potential in cancer therapy.

Prostate stereotactic ablative body radiotherapy using a standard linear accelerator: Toxicity, biochemical, and pathological outcomes

BACKGROUND AND PURPOSE Biological dose escalation through stereotactic ablative radiotherapy (SABR) holds promise of improved patient convenience, system capacity and tumor control with decreased cost and side effects. The objectives are to report the toxicities, biochemical and pathologic outcomes of this prospective study. MATERIALS AND METHODS A phase I/II study was performed where low risk localized prostate cancer received SABR 35 Gy in 5 fractions, once weekly on standard linear accelerators. Common Terminology Criteria for Adverse Events v3.0 and Radiation Therapy Oncology Group late morbidity scores were used to assess acute and late toxicities, respectively. Biochemical control (BC) was defined by the Phoenix definition. RESULTS As of May 2012, 84 patients have completed treatment with a median follow-up of 55 months (range 13-68 months). Median age was 67 years and median PSA was 5.3 ng/ml. The following toxicities were observed: acute grade 3+: 0% gastrointestinal (GI), 1% genitourinary (GU), 0% fatigue; late grade 3+: 1% GI, 1% GU. Ninety-six percent were biopsy negative post-treatment. The 5-year BC was 98%. CONCLUSIONS This novel technique employing standard linear accelerators to deliver an extreme hypofractionated schedule of radiotherapy is feasible, well tolerated and shows excellent pathologic and biochemical control.

Nanodosimetric effects of gold nanoparticles in megavoltage radiation therapy

BACKGROUND AND PURPOSE The addition of gold nanoparticles (GNPs) to tumours leads to an increase in dose due to their high density and energy absorption coefficient, making it a potential radiosensitiser. However, experiments have observed radiosensitisations significantly larger than the increase in dose alone, including at megavoltage energies where golds relative energy absorption is lowest. This work investigates whether GNPs create dose inhomogeneities on a sub-cellular scale which combine with non-linear dose dependence of cell survival to be the source of radiosensitisation at megavoltage energies. MATERIALS AND METHODS Monte Carlo simulations were carried out to calculate dose in the vicinity of a single GNP on the nanoscale. The effect of this nanoscale dose distribution was then modelled for MDA-MB-231 cells exposed to 2 nm GNPs, and compared to experimental results. RESULTS Dramatic dose inhomogeneities occur around GNPs exposed to megavoltage radiation. When analysed using the Local Effect Model, these inhomogeneities lead to significant radiosensitisation, in agreement with experimental results. CONCLUSIONS This work suggests that GNP radiosensitisation is driven by inhomogeneities in dose on the nanoscale, rather than changes in dose over the entire cell, which may contribute to the similar radiosensitisation observed in megavoltage and kilovoltage experiments. The short range of these inhomogeneities and the variation in enhancement in different cells suggests sub-cellular localisation is important in determining GNP radiosensitisation.

Active Surveillance for the Management of Localized Prostate Cancer (Cancer Care Ontario Guideline): American Society of Clinical Oncology Clinical Practice Guideline Endorsement

PURPOSE To endorse Cancer Care Ontarios guideline on Active Surveillance for the Management of Localized Prostate Cancer. The American Society of Clinical Oncology (ASCO) has a policy and set of procedures for endorsing clinical practice guidelines developed by other professional organizations. METHODS The Active Surveillance for the Management of Localized Prostate Cancer guideline was reviewed for developmental rigor by methodologists. The ASCO Endorsement Panel then reviewed the content and the recommendations. RESULTS The ASCO Endorsement Panel determined that the recommendations from the Active Surveillance for the Management of Localized Prostate Cancer guideline, published in May 2015, are clear, thorough, and based upon the most relevant scientific evidence. ASCO endorsed the Active Surveillance for the Management of Localized Prostate Cancer guideline with added qualifying statements. The Cancer Care Ontario recommendation regarding 5-alpha reductase inhibitors was not endorsed by the ASCO panel. RECOMMENDATIONS For most patients with low-risk (Gleason score ≤ 6) localized prostate cancer, active surveillance is the recommended disease management strategy. Factors including younger age, prostate cancer volume, patient preference, and ethnicity should be taken into account when making management decisions. Select patients with low-volume, intermediate-risk (Gleason 3 + 4 = 7) prostate cancer may be offered active surveillance. Active surveillance protocols should include prostate-specific antigen testing, digital rectal examinations, and serial prostate biopsies. Ancillary radiologic and genomic tests are investigational but may have a role in patients with discordant clinical and/or pathologic findings. Patients who are reclassified to a higher-risk category (Gleason score ≥ 7) or who have significant increases in tumor volume on subsequent biopsies should be offered active therapy.

Cell type-dependent uptake, localization, and cytotoxicity of 1.9 nm gold nanoparticles

Background This follow-up study aims to determine the physical parameters which govern the differential radiosensitization capacity of two tumor cell lines and one immortalized normal cell line to 1.9 nm gold nanoparticles. In addition to comparing the uptake potential, localization, and cytotoxicity of 1.9 nm gold nanoparticles, the current study also draws on comparisons between nanoparticle size and total nanoparticle uptake based on previously published data. Methods We quantified gold nanoparticle uptake using atomic emission spectroscopy and imaged intracellular localization by transmission electron microscopy. Cell growth delay and clonogenic assays were used to determine cytotoxicity and radiosensitization potential, respectively. Mechanistic data were obtained by Western blot, flow cytometry, and assays for reactive oxygen species. Results Gold nanoparticle uptake was preferentially observed in tumor cells, resulting in an increased expression of cleaved caspase proteins and an accumulation of cells in sub G1 phase. Despite this, gold nanoparticle cytotoxicity remained low, with immortalized normal cells exhibiting an LD50 concentration approximately 14 times higher than tumor cells. The surviving fraction for gold nanoparticle-treated cells at 3 Gy compared with that of untreated control cells indicated a strong dependence on cell type in respect to radiosensitization potential. Conclusion Gold nanoparticles were most avidly endocytosed and localized within cytoplasmic vesicles during the first 6 hours of exposure. The lack of significant cytotoxicity in the absence of radiation, and the generation of gold nanoparticle-induced reactive oxygen species provide a potential mechanism for previously reported radiosensitization at megavoltage energies.