External control arms in oncology: current use and future directions.

Although randomized control trials allow for a comparison of treatment arms with minimal concern for confounding by known and unknown factors, a randomized study is not feasible in certain disease settings. When a randomized design is not possible, incorporating external control data into the study design can be an effective way to expand the interpretability of the results of an experimental arm by introducing the ability to carry out a formal or an informal comparative analysis. This paper provides an introduction to the concepts of external controls in oncology trials, followed by a review of relevant and current research on this topic. The paper also focuses on general considerations for designing a trial that may incorporate external control data, followed by case studies of the marketing applications submitted to the Food and Drug Administration that included external control data.

A Food and Drug Administration analysis of survival outcomes comparing the Adjuvant Paclitaxel and Trastuzumab trial with an external control from historical clinical trials.

BACKGROUND: Although the Adjuvant Paclitaxel and Trastuzumab (APT) trial has been adopted clinically, single-arm trials have limitations, and interest remains whether these patients with small node-negative human epidermal growth factor receptor 2 (HER2)-positive early breast cancer (EBC) would benefit from more intensive chemotherapy. This analysis explored whether external controls can contextualize single-arm studies to add to clinical decision making in the use of de-escalated therapy in patients with low-risk HER2-positive EBC. PATIENTS AND METHODS: Patient-level data from five randomized trials supporting drug approval in adjuvant HER2-positive EBC were pooled, and patients with low-risk EBC were selected (n = 1770). Patients treated concurrently with trastuzumab and either anthracycline/cyclophosphamide/taxane/trastuzumab (ACTH) or taxane/carboplatin/trastuzumab (TCH; n = 1366) were matched (1:1) to patients treated with paclitaxel and trastuzumab (TH) in the APT trial (n = 406) using propensity scores. Patients treated with anthracycline/cyclophosphamide/taxane (ACT; n = 374) were also matched (1:1) to those treated with TH. Propensity scores were estimated using covariates of age, tumor stage, estrogen receptor status, progesterone receptor status, and histological grade. RESULTS: After matching, the estimated probabilities of invasive disease-free survival (iDFS) at 3 and 5 years were 98.6% and 96.5% in the TH arm, and 96.6% and 92.9% in the ACTH/TCH arm, respectively. The estimated probabilities of overall survival (OS) at 3 and 5 years were 99.7% and 99.3% in the TH arm, and 99.0% and 97.4% in the ACTH/TCH arm, respectively. Comparing the TH arm with the ACT arm in the matched sample, the estimated difference in iDFS was 7.5% (TH 98.8% and ACT 91.3%) at 3 years and 12.6% (TH 96.1% and ACT 83.5%) at 5 years. The estimated difference in OS was 2.6% (TH 100% and ACT 97.4%) at 3 years, and 5.3% (TH 99.3% and ACT 94.0%) at 5 years. CONCLUSIONS: Our analyses suggest that patients' outcomes in both arms were in general similar, thus providing additional reassurance regarding de-escalation of therapy.

Analysis of time-to-treatment discontinuation of targeted therapy, immunotherapy, and chemotherapy in clinical trials of patients with non-small-cell lung cancer.

BACKGROUND: Pragmatic end points, such as time-to-treatment discontinuation (TTD), defined as the date of starting a medication to the date of treatment discontinuation or death has been proposed as a potential efficacy end point for real-world evidence (RWE) trials, where imaging evaluation is less structured and standardized. PATIENTS AND METHODS: We studied 18 randomized clinical trials of patients with metastatic non-small-cell lung cancer (mNSCLC), initiated after 2007 and submitted to U.S. Food and Drug Administration. TTD was calculated as date of randomization to date of discontinuation or death and compared to progression-free survival (PFS) and overall survival (OS) across all patients, as well as in treatment-defined subgroups [EGFR mutation-positive treated with tyrosine kinase inhibitor (TKI), EGFR wild-type treated with TKI, ALK-positive treated with TKI, immune checkpoint inhibitor (ICI), chemotherapy doublet with maintenance, chemotherapy monotherapy]. RESULTS: Overall across 8947 patients, TTD was more closely associated with PFS (r = 0.87, 95% CI 0.86-0.87) than with OS (0.68, 95% CI 0.67-0.69). Early TTD (PFS-TTD ≥ 3 months) occurred in 7.7% of patients overall, and was more common with chemo monotherapy (15.0%) while late TTD (TTD-PFS ≥ 3 months) occurred in 6.0% of patients overall, and was more common in EGFR-positive and ALK-positive patients (12.4% and 22.9%). In oncogene-targeted subgroups (EGFR positive and ALK positive), median TTDs (13.4 and 14.1 months) exceeded median PFS (11.4 and 11.3 months). CONCLUSIONS: At the patient level, TTD is associated with PFS across therapeutic classes. Median TTD exceeds median PFS for biomarker-selected patients receiving oncogene-targeted therapies. TTD should be prospectively studied further as an end point for pragmatic randomized RWE trials only for continuously administered therapies.

Exploratory analysis of the association of depth of response and survival in patients with metastatic non-small-cell lung cancer treated with a targeted therapy or immunotherapy.

BACKGROUND: Response Evaluation Criteria in Solid Tumors (RECIST) permits rapid evaluation of new therapeutic strategies in cancer. However, RECIST does not capture the heterogeneity of response in highly active therapies. Depth of tumor response may provide a more granular view of response. We explored the association between, depth of response (DepOR), with overall survival (OS) and progression-free survival (PFS) for patients with NSCLC being treated with an ALK inhibitor (ALKi) or an anti-PD-1 antibody (Ab). METHODS: Experimental arms from two randomized controlled trials (RCTs) of an ALKi and two RCTs of an anti-PD-1 Ab were separately pooled. Patient responses were grouped into DepOR 'quartiles' by percentage of maximal tumor shrinkage (Q1 = 1%-25%, Q2 = 26%-50%, Q3 = 51%-75%, and Q4 = 76%-100%), Q0 had no shrinkage. We carried out a retrospective exploratory responder analysis to evaluate the association between DepOR and OS or PFS using hazard ratios (HR) generated by the Cox proportional hazards model. RESULTS: In the pooled ALK analysis there were 12, 39, 70, 144, and 40 patients in quartiles 0-4, respectively. The DepOR versus PFS/OS analyses HR were: 0.19/0.94 for Q1 0.11/0.56 for Q2, 0.05/0.28 for Q3, and 0.03/0.05 for Q4. In the PD-1 trials within quartiles 0-4 there were 168, 70, 44, 45, and 28 patients, respectively. The DepOR versus PFS/OS analyses HR were 0.3/0.52 for Q1, 0.22/0.47 for Q2, 0.09/0.07 for Q3, and 0.07/0.14 for Q4. CONCLUSIONS: Our analysis suggests a greater DepOR is associated with longer PFS and OS for patients receiving ALKi or anti-PD1 Ab. Overall, this suggests that DepOR may provide an additional outcome measure for clinical trials, and may allow better comparisons of treatment activity.

Drug Development, Trial Design, and Endpoints in Oncology: Adapting to Rapidly Changing Science.

As a result of enhanced understanding of genetic and immunologic underpinnings of cancer, there has been progress in development of targeted and immunotherapies in oncology. The traditional linear sequential model of drug development has evolved. Early clinical trials of breakthrough therapies often include expansion cohorts, termed "seamless drug development." The US Food and Drug Administration (FDA) uses expedited programs, such as breakthrough designation and accelerated approval ensuring that transformative therapies are available to patients earlier in the cycle of evidence generation.

A Benefit-Risk Analysis Approach to Capture Regulatory Decision-Making: Non-Small Cell Lung Cancer.

Drug regulators around the world make decisions about drug approvability based on qualitative benefit-risk analyses. There is much interest in quantifying regulatory approaches to benefit and risk. In this work the use of a quantitative benefit-risk analysis was applied to regulatory decision-making about new drugs to treat advanced non-small cell lung cancer (NSCLC). Benefits and risks associated with 20 US Food and Drug Administration (FDA) decisions associated with a set of candidate treatments submitted between 2003 and 2015 were analyzed. For benefit analysis, the median overall survival (OS) was used where available. When not available, OS was estimated based on overall response rate (ORR) or progression-free survival (PFS). Risks were analyzed based on magnitude (or severity) of harm and likelihood of occurrence. Additionally, a sensitivity analysis was explored to demonstrate analysis of systematic uncertainty. FDA approval decision outcomes considered were found to be consistent with the benefit-risk logic.

The role of nonrandomized trials in the evaluation of oncology drugs.

Although randomized trials provide the most reliable evidence of a drug's safety and efficacy, there are situations where randomized trials are not possible or ethical. In this article we discuss when and how single-arm trials can be used to support full approval of oncology drugs. These include situations in which an unprecedented effect on tumor response is observed in a setting of high unmet medical need, clinical trial patients have been well characterized, enabling a target population to be clearly defined, experience exists in a sufficient number of patients to allow adequate assessment of the risk:benefit relationship, and a proper historical context can be provided for analysis. We also discuss how response rates might be considered predictive of long-term outcomes or clinically meaningful in and of themselves in certain contexts.

Optimizing dosing of oncology drugs.

The purpose of this article is to acknowledge the challenges in optimizing the dosing of oncology drugs and to propose potential approaches to address these challenges in order to optimize effectiveness, minimize toxicity, and promote adherence in patients. These approaches could provide better opportunities to understand the sources of variability in drug exposure and clinical outcomes during the development and premarketing evaluation of investigational new drugs.

The advisory process for anticancer drug regulation: a global perspective.

PURPOSE: This paper summarizes the role of external advisors in oncology drug development and regulation from a global perspective. DESIGN: Recently, representatives from the United States Food and Drug Administration, European Medicines Agency, the Japanese Pharmaceuticals and Medical Devices Agency, the Australian Therapeutic Goods Administration and Health Canada held a meeting in conjunction with the American Society of Clinical Oncology meeting. The role of external advisors in oncology drug development and regulation in each of these jurisdictions was presented and discussed. RESULTS: All regulatory bodies described have experience with two forms of outside expertise: advice from individual experts and advice from a group of experts assembled as an advisory group. Regulatory jurisdictions use individual experts variably. In some regions, individual experts provide advice based on knowledge and experience during the drug development phase or in the planning phase for the submission of a drug registration package. In other regions, these individuals serve as external evaluators with the primary responsibility for the review of a clinical trials package submitted for drug registration. Advisory boards have been formalized in all jurisdictions discussed. Advisory boards have a role in discussing specific applications as well as broad policy issues. A common theme is a composition of a core panel of experts with augmentation by additional expertise as needed for consideration of specific scientific questions. In all jurisdictions, advisory board recommendations are not binding on the regulatory body. CONCLUSIONS: Global oncology drug development and registration involves the use of experts by regulatory authorities. The types of experts needed, the expert's role and the transparency of the advisory process reflect the individual needs in different regions.

Anticancer drug discovery and development throughout the world.

This year's American Society of Clinical Oncology International Symposium devoted 2 hours to a lively discussion of various aspects of anticancer drug discovery and development throughout the world. The scientific program started with an overview of efforts directed toward promoting international collaboration in natural product-derived anticancer drug discovery. This was followed by a discussion on the importance of interethnic differences and pharmacogenetics in anticancer drug development. Thereafter, this part of the program was completed by a description of the activities of the newly created Singapore-Hong Kong-Australia Drug Development Consortium and an overview of the contribution of Japan to anticancer drug development. The logistics and regulatory aspects of clinical trials with new anticancer agents in different parts of the world were then presented, with an emphasis on Europe, North America, and Japan. The program was completed with a panel discussion of the efforts to harmonize the exchange of clinical data originating from one region of the globe with other territories, with input from official representatives of the United States Food and Drug Administration and the Medical Devices Evaluation Center of Japan.

Phase I trial of i.v. administered tirapazamine plus cyclophosphamide.

Our objective was to determine the maximum tolerated doses of tirapazamine and cyclophosphamide given i.v. in combination. Eligible patients had advanced solid tumors refractory to conventional treatment. Tirapazamine (escalated from 80 to 390 mg/m(2)) was given i.v. over 2 h and followed by cyclophosphamide over 1 h. The cyclophosphamide dose was fixed at 1000 mg/m(2) until the tirapazamine dose of 390 mg/m(2) was reached. Once that dose of tirapazamine was reached, the cyclophosphamide dose was escalated to 1250 and 1500 mg/m(2). Twenty-eight patients were enrolled. The dose-limiting toxicity was granulocytopenia. One patient had transient deafness for 2 days. Four other patients had grade 1 ototoxicity. Grade 1 and 2 muscle cramps were observed at all dose levels. Other toxic effects observed included fatigue, nausea, vomiting, headache, diarrhea, drug fever, elevated transaminases and elevated creatine phosphokinase. Three patients had stable disease and the longest time to progression was 5 months. The combination of tirapazamine and cyclophosphamide is feasible, and the dose-limiting toxicity is granulocytopenia. The use of growth factors could possibly allow escalation of tirapazamine doses in future phase II trials. Without growth factor support, the recommended doses of tirapazamine and cyclophosphamide when administered in this schedule are 260 and 1000 mg/m(2), respectively.

Approval summary: gemtuzumab ozogamicin in relapsed acute myeloid leukemia.

PURPOSE: Gemtuzumab ozogamicin (Mylotarg; Wyeth Laboratories, Philadelphia, PA) consists of a semisynthetic derivative of calicheamicin, a cytotoxic antibiotic linked to a recombinant monoclonal antibody directed against the CD33 antigen present on leukemic myeloblasts in most patients with acute myeloid leukemia (AML). In this study, we review the preclinical and clinical profiles of this immunoconjugate and the regulatory review that led to marketing approval by the United States Food and Drug Administration. EXPERIMENTAL DESIGN: From the literature and manufacturer's data, we review the activity, tolerability, and pharmacokinetics of gemtuzumab ozogamicin in preclinical and Phase I studies and its activity, efficacy, and side effects in three Phase 2 trials of 142 patients with relapsed AML. RESULTS: In Phase I studies, the major toxicity was myelosuppression, especially neutropenia and thrombocytopenia, resulting from the expression of CD33 on myeloid progenitor cells. The Phase 2 dose was 9 mg/m(2) infused i.v. over 4 h, repeated on day 14. A minority of patients experienced acute infusion-related symptoms, usually transient and occasionally requiring hospitalization. The complete response (CR) rate with full recovery of hematopoiesis was 16%. A subset of patients [CRs with incomplete platelet recovery (CRps)] was identified with blast clearance and neutrophil recovery but incomplete platelet recovery. The duration of responses of CRps appeared to be similar to those of the CRs, although the numbers were small. The question of the equivalence of these response groups was a central issue in the review of this new drug application (NDA). After considerable discussion, the Oncology Drugs Advisory Committee recommended allowing inclusion of CRps resulting in an overall response rate in the Phase 2 studies of 30%. In the subgroup of patients over 60 years of age, the overall response rate was 26%. Response duration was difficult to establish because of the high prevalence of postremission therapies. Tolerability and ease of administration may be improved compared with conventional chemotherapy, except for hepatotoxicity, with 31% of patients exhibiting abnormal liver enzymes. One patient died of liver failure in the Phase 2 trials. CONCLUSIONS: Marketing approval of gemtuzumab ozogamicin was granted on May 17, 2000 by the United States Food and Drug Administration under the Accelerated Approval regulations. Gemtuzumab ozogamicin is indicated for the treatment of patients with CD33 positive AML in first relapse who are 60 years of age or older and who are not considered candidates for cytotoxic chemotherapy. The approved dose was 9 mg/m(2) i.v. over 4 h and repeated in 14 days. Completion of the ongoing studies of gemtuzumab ozogamicin in relapsed AML and initiation of randomized clinical trials comparing the effects of gemtuzumab ozogamicin in combination with conventional induction chemotherapy to conventional chemotherapy alone on survival are mandated to confirm clinical benefit under the accelerated approval Subpart H regulations. Postmarketing reports of fatal anaphylaxis, adult respiratory distress syndrome (ARDS), and hepatotoxicity, especially venoocclusive disease (VOD) in patients treated with gemtuzumab ozogamicin, with and without associated hematopoietic stem cell transplantation (HSCT), have required labeling revisions and the initiation of a registration surveillance program. Tumor lysis and ARDS have been reported in patients with leukocytes above 30,000/ml treated with gemtuzumab ozogamicin; therefore, the reduction of leukocyte counts to below 30,000/ml is recommended prior to treatment. Patients should be carefully monitored for acute hypersensitivity, hypoxia, and delayed hepatotoxicity following treatment with gemtuzumab ozogamicin.

Improved overall survival among responders to preoperative chemoradiation for locally advanced rectal cancer.

The aim of this study was to determine if the response to preoperative radiation and chemotherapy with continuous infusion 5-fluorouracil (5-FU) was predictive for survival among patients with locally advanced rectal cancer. Preoperative chemoradiation (CTX/XRT) that delivered 45 Gy in 25 fractions over 5 weeks with continuous infusion 5-FU (300 mg/m2/day) was given to 117 patients. The pretreatment stage distribution, as determined by endorectal ultrasound (u), included uT2N0 in 2%, uT3N0 in 47%, uT3N1 in 49%, and uT4N0 in 2% of cases; endorectal ultrasound was not performed in 13% of cases (15 patients). Approximately 6 weeks after completion of CTX/XRT, surgery was performed. Adjuvant chemotherapy, consisting of 400 to 425 mg/m2 of 5-FU plus 20 mg/m2 leucovorin for 5 days, was administered every 28 days for 4 to 6 cycles after surgical resection. Among the 74 patients treated with adjuvant chemotherapy, the preoperative stage of disease was 31 with T3N0 and 43 T3N1. Median follow-up was 46 months (range 2 to 89 months). The pathologic tumor stages were Tis-2N0 in 26%, T2N1 in 5%, T3N0 in 21%, T3N1 in 15%, T4N0 in 5%, and T4N1 in 1%; a complete response (CR) to preoperative CTX/XRT was pathologically confirmed in 32 (27%) of patients. Tumor down-staging occurred in 72 (62%) cases. A sphincter-saving procedure (SP) was possible in 59% of patients. The median DFS and overall survival rates for responders were 46 months and 47 months, respectively; for non-responders these outcome measures were 38 months and 41 months, respectively. Log-rank analysis showed that the distant metastatic-free survival rates improved with any response to CTX/XRT (p < 0.00001), CR to CTX/XRT (p < 0.009) and SP (p < 0.012). Likewise, these parameters also significantly influenced DFS rates (CTX/XRT p < 0.00001; CR p < 0.006; and SP p < 0.008). Control of pelvic disease was influenced by clinical size (p < 0.002) and SP (p < 0.016) on univariate analysis. On multivariate analysis only clinical size (p < 0.002) continued to be a significant factor for local control. Factors on multivariate analysis that resulted in significant improvements in cancer-specific survival included any response to preoperative CTX/XRT (p < 0.017) and administration of adjuvant chemotherapy (p < 0.034). Any response to preoperative CTX/XRT improved distant metastatic-free and disease-free survival rates. Multivariate analysis confirmed that a response to preoperative CTX/XRT predicted for improvements in overall survival among patients with locally advanced rectal cancer. Patients who fail to respond to preoperative 5-FU based chemotherapy given concomitantly with radiation have higher rates of distant metastases with adjuvant 5-FU therapy.

Effect of food on the oral bioavailability of UFT and leucovorin in cancer patients.

UFT is composed of tegafur (FT), a prodrug of 5-fluorouracil (5-FU), and uracil in a fixed combination (1:4). In conjunction with leucovorin, UFT is being developed for the first-line oral treatment of metastatic colorectal cancer. The effect of food on the oral bioavailability of UFT (2 x 100 mg capsules; dose in terms of FT) and leucovorin (2 x 15 mg tablets) was evaluated in a single-dose, randomized, two-way crossover study. Patients (n = 25) were assigned to receive both drugs after an overnight fast or 5 min after completion of a high-fat meal (721 calories) with a 3-day washout period between treatments; then they were permitted to continue on oral UFT/leucovorin therapy for safety assessment. UFT (300 mg/m2/day as three divided doses) and leucovorin (90 mg/day as three divided doses) were given for 28 days. After a 7-day rest, the 28-day cycle was repeated. Pharmacokinetics (n = 22 patients) were determined for FT, 5-FU, uracil, leucovorin, and 5-methyltetrahydrofolate (an active metabolite of leucovorin). The absence of food-effect on peak plasma concentration (CMAX) and the area under the curve (AUC) was concluded if the 90% confidence interval for the ratio of the treatment means was entirely contained in 0.75-1.33. Administration of UFT with food resulted in a 34% decrease in CMAX of FT, whereas the AUC of FT remained unchanged. Food decreased the CMAX and AUC values of uracil and 5-FU by 37-76%. On the contrary, the CMAX and AUC values of leucovorin and 5-methyltetrahydrofolate were increased by 14-60% with food. Time to reach CMAX for all analytes was significantly (P < or = 0.001) delayed by food. Except for the AUCs of FT, the statistical criterion for concluding a lack of food-effect was not met. These data suggest that UFT/leucovorin should not be dosed simultaneously with food. It is recommended that food should not be consumed for 1 h before and after an oral dose of UFT and leucovorin in a manner similar to pivotal Phase III trials. The 28-day oral regimen of UFT and leucovorin was generally well tolerated in the population studied.

Phase I bioequivalency study of MitoExtra and mitomycin C in patients with solid tumors.

BACKGROUND: This study compares serum pharmacokinetics, urinary excretion patterns, and relative bioequivalencies of single doses of MitoExtra (ME; SuperGen, San Ramon, CA) and mitomycin C (MMC). METHODS: Thirty-five patients were entered into this open-label, single-institution, crossover study with 2 treatment arms. Each patient received alternating courses of ME and MMC as 15 mg/m(2) single intravenous doses via a short intravenous infusion. Patients were sequentially assigned to receive either ME or MMC as their first treatment course. The courses were given in 6-week intervals and could be repeated up to 4 times in patients with responding disease. Pharmacokinetic parameters were analyzed during the first two courses of therapy. RESULTS: The noncompartmental pharmacokinetic analysis conducted on serum and urine data obtained from patients who received both ME and MMC indicates that the kinetic disposition of these two formulations is similar. This is evident when the mean (+/- standard deviation) values of the various pharmacokinetic parameters are compared. There were no significant differences in any of the kinetic parameters obtained between treatments in all patients examined. The statistical evaluation conducted on the 25 patients that completed both arms of the 2-way pharmacokinetic crossover demonstrates that ME is bioequivalent to MMC. Hematologic and nonhematologic toxicities were similar between the two treatments. There were three clinically significant infusion-related complications associated with MMC administration and none associated with ME. CONCLUSIONS: The similar pharmacokinetics of MMC and ME suggest complete release of MMC from the hydroxypropyl-Beta-cyclodextrin carrier contained in the ME formulation. Further studies are needed to define the pharmacodynamics, toxicity, and efficacy of this drug-carrier complex.

Phase I and pharmacokinetic study of exatecan mesylate (DX-8951f): a novel camptothecin analog.

PURPOSE: To determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetic (PK) profile, and recommended phase II dose of Exatecan mesylate (DX-8951f) when administered as a 24-hour continuous infusion every 3 weeks to patients with solid tumors. PATIENTS AND METHODS: Twenty-two patients with advanced solid tumors, all previously treated, and with performance status < or = 2, were entered. The starting dose of DX-8951f was 0.15 mg/m(2); the dose was escalated according to the modified continual reassessment method. The drug was administered until disease progression or until unacceptable toxic effects occurred. RESULTS: Seven dose escalations were completed, and a total of 53 courses were delivered (median, two courses; range, one to eight courses) during the study. At doses 1.2 mg/m(2) and lower, toxicities were mostly grade 1, primarily hematologic. In the initial cohort of three patients treated at 2.4 mg/m(2), grade 2 hematologic toxicity was observed. Of the six additional patients entered at 2.4 mg/m(2), three had grade 3 or 4 granulocytopenia. At doses higher than 2.4 mg/m(2), DLT granulocytopenia was observed. Nonhematologic toxicities, including nausea, vomiting, diarrhea, fatigue, and alopecia, were mild to moderate. Neither complete nor partial responses were observed, but four patients had stable disease. The PK profile of DX-8951f seemed linear at the doses administered. The plasma clearance, total volume of distribution, and terminal elimination half-life were approximately 3 L/h, 40 L, and 14 hours, respectively. CONCLUSION: The DLT of this DX-8951f schedule was granulocytopenia for minimally pretreated patients, and both granulocytopenia and thrombocytopenia for heavily pretreated patients. The MTD for both minimally and heavily pretreated patients was 2.4 mg/m(2). DX-8951f seems to have a linear PK profile on the basis of single-dose administration. The recommended phase II dose with this schedule is 2.4 mg/m(2) for minimally pretreated patients. A lower dose should be used for heavily pretreated patients.