Lalitha K. Shankar

Progress and promise of FDG-PET imaging for cancer patient management and oncologic drug development

2-[18F]Fluoro-2-deoxyglucose positron emission tomography (FDG-PET) assesses a fundamental property of neoplasia, the Warburg effect. This molecular imaging technique offers a complementary approach to anatomic imaging that is more sensitive and specific in certain cancers. FDG-PET has been widely applied in oncology primarily as a staging and restaging tool that can guide patient care. However, because it accurately detects recurrent or residual disease, FDG-PET also has significant potential for assessing therapy response. In this regard, it can improve patient management by identifying responders early, before tumor size is reduced; nonresponders could discontinue futile therapy. Moreover, a reduction in the FDG-PET signal within days or weeks of initiating therapy (e.g., in lymphoma, non–small cell lung, and esophageal cancer) significantly correlates with prolonged survival and other clinical end points now used in drug approvals. These findings suggest that FDG-PET could facilitate drug development as an early surrogate of clinical benefit. This article reviews the scientific basis of FDG-PET and its development and application as a valuable oncology imaging tool. Its potential to facilitate drug development in seven oncologic settings (lung, lymphoma, breast, prostate, sarcoma, colorectal, and ovary) is addressed. Recommendations include initial validation against approved therapies, retrospective analyses to define the magnitude of change indicative of response, further prospective validation as a surrogate of clinical benefit, and application as a phase II/III trial end point to accelerate evaluation and approval of novel regimens and therapies.

Guidelines for the Development and Incorporation of Biomarker Studies in Early Clinical Trials of Novel Agents

The National Cancer Institute (NCI) Investigational Drug Steering Committee (IDSC) charged the Biomarker Task Force to develop recommendations to improve the decisions about incorporation of biomarker studies in early investigational drug trials. The Task Force members reviewed biomarker trials, the peer-reviewed literature, NCI and U.S. Food and Drug Administration (FDA) guidance documents, and conducted a survey of investigators to determine practices and challenges to executing biomarker studies in clinical trials of new drugs in early development. This document provides standard definitions and categories of biomarkers, and lists recommendations to sponsors and investigators for biomarker incorporation into such trials. Our recommendations for sponsors focus on the identification and prioritization of biomarkers and assays, the coordination of activities for the development and use of assays, and for operational activities. We also provide recommendations for investigators developing clinical trials with biomarker studies for scientific rationale, assay criteria, trial design, and analysis. The incorporation of biomarker studies into early drug trials is complex. Thus the decision to proceed with studies of biomarkers should be based on balancing the strength of science, assay robustness, feasibility, and resources with the burden of proper sample collection on the patient and potential impact of the results on drug development. The Task Force provides these guidelines in the hopes that improvements in biomarker studies will enhance the efficiency of investigational drug development. Clin Cancer Res; 16(6); 1745–55

Evaluation of lymph nodes with RECIST 1.1

Lymph nodes are common sites of metastatic disease in many solid tumours. Unlike most metastases, lymph nodes are normal anatomic structures and as such, normal lymph nodes will have a measurable size. Additionally, the imaging literature recommends that lymph nodes be measured in the short axis, since the short axis measurement is a more reproducible measurement and predictive of malignancy. Therefore, the RECIST committee recommends that lymph nodes be measured in their short axis and proposes measurement values and rules for categorising lymph nodes as normal or pathologic; either target or non-target lesions. Data for the RECIST warehouse are presented to demonstrate the potential change in response assessment following these rules. These standardised lymph node guidelines are designed to be easy to implement, focus target lesion measurements on lesions that are likely to be metastatic and prevent false progressions due to minimal change in size.

iRECIST: guidelines for response criteria for use in trials testing immunotherapeutics

Tumours respond differently to immunotherapies compared with chemotherapeutic drugs, raising questions about the assessment of changes in tumour burden-a mainstay of evaluation of cancer therapeutics that provides key information about objective response and disease progression. A consensus guideline-iRECIST-was developed by the RECIST working group for the use of modified Response Evaluation Criteria in Solid Tumours (RECIST version 1.1) in cancer immunotherapy trials, to ensure consistent design and data collection, facilitate the ongoing collection of trial data, and ultimate validation of the guideline. This guideline describes a standard approach to solid tumour measurements and definitions for objective change in tumour size for use in trials in which an immunotherapy is used. Additionally, it defines the minimum datapoints required from future trials and those currently in development to facilitate the compilation of a data warehouse to use to later validate iRECIST. An unprecedented number of trials have been done, initiated, or are planned to test new immune modulators for cancer therapy using a variety of modified response criteria. This guideline will allow consistent conduct, interpretation, and analysis of trials of immunotherapies.

Consensus recommendations for a standardized Brain Tumor Imaging Protocol in clinical trials

A recent joint meeting was held on January 30, 2014, with the US Food and Drug Administration (FDA), National Cancer Institute (NCI), clinical scientists, imaging experts, pharmaceutical and biotech companies, clinical trials cooperative groups, and patient advocate groups to discuss imaging endpoints for clinical trials in glioblastoma. This workshop developed a set of priorities and action items including the creation of a standardized MRI protocol for multicenter studies. The current document outlines consensus recommendations for a standardized Brain Tumor Imaging Protocol (BTIP), along with the scientific and practical justifications for these recommendations, resulting from a series of discussions between various experts involved in aspects of neuro-oncology neuroimaging for clinical trials. The minimum recommended sequences include: (i) parameter-matched precontrast and postcontrast inversion recovery-prepared, isotropic 3D T1-weighted gradient-recalled echo; (ii) axial 2D T2-weighted turbo spin-echo acquired after contrast injection and before postcontrast 3D T1-weighted images to control timing of images after contrast administration; (iii) precontrast, axial 2D T2-weighted fluid-attenuated inversion recovery; and (iv) precontrast, axial 2D, 3-directional diffusion-weighted images. Recommended ranges of sequence parameters are provided for both 1.5 T and 3 T MR systems.

Validation of novel imaging methodologies for use as cancer clinical trial end-points

The success or failure of a clinical trial, of any phase, depends critically on the choice of an appropriate primary end-point. In the setting of phases II and III cancer clinical trials, imaging end-points have historically, and continue presently to play a major role in determining therapeutic efficacy. The primary goal of this paper is to discuss the validation of imaging-based markers as end-points for phase II clinical trials of cancer therapy. Specifically, we outline the issues that must be considered, and the criteria that would need to be satisfied, for an imaging end-point to supplement or potentially replace RECIST- defined tumour status as a phase II clinical trial end-point. The key criteria proposed to judge the utility of a new end-point primarily relate to its ability to accurately and reproducibly predict the eventual phase III end-point for treatment effect, which is usually assessed by a difference between two arms on progression free or overall survival, both at the patient and more importantly at the trial level. As will be demonstrated, the level of evidence required to formally and fully validate a new imaging marker as an appropriate end-point for phase II trials is substantial. In many cases, this level of evidence will only become available by conducting a series of coordinated prospectively designed multicentre clinical trials culminating in a formal meta-analysis. We also include a discussion of situations where flexibility may be required, relative to the ideal rigorous evaluation, to accommodate inevitable real-world feasibility constraints.

Repeatability of 18F-FDG Uptake Measurements in Tumors: A Metaanalysis

PET with the glucose analog 18F-FDG is increasingly used to monitor tumor response to therapy. To use quantitative measurements of tumor 18F-FDG uptake for assessment of tumor response, the repeatability of this quantitative metabolic imaging method needs to be established. Therefore, we determined the repeatability of different standardized uptake value (SUV) measurements using the available data. Methods: A systematic literature search was performed to identify studies addressing 18F-FDG repeatability in malignant tumors. The level of agreement between test and retest values of 2 PET uptake measures, maximum SUV (SUVmax) and mean SUV (SUVmean), was assessed with the coefficient of repeatability using generalized linear mixed-effects models. In addition, the influence of tumor volume on repeatability was assessed. Principal component transformation was used to compare the reproducibility of the 2 different uptake measures. Results: Five cohorts were identified for this metaanalysis. For SUVmax and SUVmean, datasets of 86 and 102 patients, respectively, were available. Percentage repeatability is a function of the level of uptake. SUVmean had the best repeatability characteristics; for serial PET scans, a threshold of a combination of 20% as well as 1.2 SUVmean units was most appropriate. After adjusting for uptake rate, tumor volume had minimal influence on repeatability. Conclusion: SUVmean had better repeatability performance than SUVmax. Both measures showed poor repeatability for lesions with low 18F-FDG uptake. We recommend the evaluation of biologic effects in PET by reporting a combination of minimal relative and absolute changes to account for test–retest variability.

Lessons learned from independent central review

Independent central review (ICR) is advocated by regulatory authorities as a means of independent verification of clinical trial end-points dependent on medical imaging, when the data from the trials may be submitted for licensing applications [Food and Drug Administration. United States food and drug administration guidance for industry: clinical trial endpoints for the approval of cancer drugs and biologics. Rockville, MD: US Department of Health and Human Services; 2007; Committee for Medicinal Products for Human Use. European Medicines Agency Committee for Medicinal Products for Human Use (CHMP) guideline on the evaluation of anticancer medicinal products in man. London, UK: European Medicines Agency; 2006; United States Food and Drug Administration Center for Drug Evaluation and Research. Approval package for application number NDA 21-492 (oxaliplatin). Rockville, MD: US Department of Health and Human Services; 2002; United States Food and Drug Administration Center for Drug Evaluation and Research. Approval package for application number NDA 21-923 (sorafenib tosylate). Rockville, MD: US Department of Health and Human Services; 2005; United States Food and Drug Administration Center for Drug Evaluation and Research. Approval package for application number NDA 22-065 (ixabepilone). Rockville, MD: US Department of Health and Human Services; 2007; United States Food and Drug Administration Center for Drug Evaluation and Research. Approval package for application number NDA 22-059 (lapatinib ditosylate). Rockville, MD: US Department of Health and Human Services; 2007; United States Food and Drug Administration Center for Biologics Evaluation and Research. Approval package for BLA numbers 97-0260 and BLA Number 97-0244 (rituximab). Rockville, MD: US Department of Health and Human Services; 1997; United States Food and Drug Administration. FDA clinical review of BLA 98-0369 (Herceptin((R)) trastuzumab (rhuMAb HER2)). FDA Center for Biologics Evaluation and Research; 1998; United States Food and Drug Administration. FDA Briefing Document Oncology Drugs Advisory Committee meeting NDA 21801 (satraplatin). Rockville, MD: US Department of Health and Human Services; 2007; Thomas ES, Gomez HL, Li RK, et al. Ixabepilone plus capecitabine for metastatic breast cancer progressing after anthracycline and taxane treatment. JCO 2007(November):5210-7]. In addition, clinical trial sponsors have used ICR in Phase I-II studies to assist in critical pathway decisions including in-licensing of compounds [Cannistra SA, Matulonis UA, Penson RT, et al. Phase II study of bevacizumab in patients with platinum-resistant ovarian cancer or peritoneal serous cancer. JCO 2007(November):5180-6; Perez EA, Lerzo G, Pivot X, et al. Efficacy and safety of ixabepilone (BMS-247550) in a phase II study of patients with advanced breast cancer resistant to an anthracycline, a taxane, and capecitabine. JCO 2007(August):3407-14; Vermorken JB, Trigo J, Hitt R, et al. Open-label, uncontrolled, multicenter phase II study to evaluate the efficacy and toxicity of cetuximab as a single agent in patients with recurrent and/or metastatic squamous cell carcinoma of the head and neck who failed to respond to platinum-based therapy. JCO 2007(June):2171-7; Ghassan KA, Schwartz L, Ricci S, et al. Phase II study of sorafenib in patients with advanced hepatocellular carcinoma. JCO 2006(September):4293-300; Boué F, Gabarre J, GaBarre J, et al. Phase II trial of CHOP plus rituximab in patients with HIV-associated non-Hodgkins lymphoma. JCO 2006(September):4123-8; Chen HX, Mooney M, Boron M, et al. Phase II multicenter trial of bevacizumab plus fluorouracil and leucovorin in patients with advanced refractory colorectal cancer: an NCI Treatment Referral Center Trial TRC-0301. JCO 2006(July):3354-60; Ratain MJ, Eisen T, Stadler WM, et al. Phase II placebo-controlled randomized discontinuation trial of sorafenib in patients with metastatic renal cell carcinoma. JCO 2006(June):2502-12; Jaffer AA, Lee FC, Singh DA, et al. Multicenter phase II trial of S-1 plus cisplatin in patients with untreated advanced gastric or gastroesophageal junction adenocarcinoma. JCO 2006(February):663-7; Bouché O, Raoul JL, Bonnetain F, et al. Randomized multicenter phase II trial of a biweekly regimen of fluorouracil and leucovorin (LV5FU2), LV5FU2 plus cisplatin, or LV5FU2 plus irinotecan in patients with previously untreated metastatic gastric cancer: a Fédération Francophone de Cancérologie Digestive Group Study-FFCD 9803. JCO 2004(November):4319-28]. This article will focus on the definition and purpose of ICR and the issues and lessons learned in the ICR setting primarily in Phase II and III oncology studies. This will include a discussion on discordance between local and central interpretations, consequences of ICR, reader discordance during the ICR, operational considerations and the need for specific imaging requirements as part of the study protocol.

Recommendations for the assessment of progression in randomised cancer treatment trials

Progression-free survival (PFS) is an increasingly important end-point in cancer drug development. However, several concerns exist regarding the use of PFS as a basis to compare treatments. Unlike survival, the exact time of progression is unknown, so progression times might be over-estimated (or under-estimated) and, consequently, bias may be introduced when comparing treatments. In addition, the assessment of progression is subject to measurement variability which may introduce error or bias. Ideally trials with PFS as the primary end-point should be randomised and, when feasible, double-blinded. All patients eligible for study should be evaluable for the primary end-point and thus, in general, have measurable disease at baseline. Appropriate definitions should be provided in the protocol and data collected on the case-report forms, if patients with only non-measurable disease are eligible and/or clinical, or symptomatic progression are to be considered progression events for analysis. Protocol defined assessments of disease burden should be obtained at intervals that are symmetrical between arms. Independent review of imaging may be of value in randomised phase II trials and phase III trials as an auditing tool to detect possible bias.

Considerations for the use of imaging tools for phase II treatment trials in oncology.

In the context of assessing tumor response, imaging tools have the potential to play a vital role in phase II and III treatment trials. If the imaging test is able to predict potential phase III success in a reliable fashion, it would be a useful tool in phase II trial design as it may provide for a more rapid and timely response assessment. The benefits and challenges of using anatomic imaging measures as well as the promising molecular imaging measures, primarily fluorodeoxyglucose-positron emission tomography, are discussed here. The general issues related to successful implementation of advanced imaging in the context of phase II treatment trials are discussed.