Phase I-II clinical trial design: a state-of-the-art paradigm for dose finding.

Background: Conventional phase I algorithms for finding a phase-2 recommended dose (P2RD) based on toxicity alone is problematic because the maximum tolerated dose (MTD) is not necessarily the optimal dose with the most desirable risk-benefit trade-off. Moreover, the increasingly common practice of treating an expansion cohort at a chosen MTD has undesirable consequences that may not be obvious. Patients and methods: We review the phase I-II paradigm and the EffTox design, which utilizes both efficacy and toxicity to choose optimal doses for successive patient cohorts and find the optimal P2RD. We conduct a computer simulation study to compare the performance of the EffTox design with the traditional 3 + 3 design and the continuous reassessment method. Results: By accounting for the risk-benefit trade-off, the EffTox phase I-II design overcomes the limitations of conventional toxicity-based phase I designs. Numerical simulations show that the EffTox design has higher probabilities of identifying the optimal dose and treats more patients at the optimal dose. Conclusions: Phase I-II designs, such as the EffTox design, provide a coherent and efficient approach to finding the optimal P2RD by explicitly accounting for risk-benefit trade-offs underlying medical decisions.

A phase II randomized trial of induction chemotherapy versus no induction chemotherapy followed by preoperative chemoradiation in patients with esophageal cancer.

BACKGROUND: The contribution of induction chemotherapy (IC) before preoperative chemoradiation for esophageal cancer (EC) is not known. We hypothesized that IC would increase the rate of pathologic complete response (pathCR). METHODS: Trimodality-eligibile patients were randomized to receive no IC (Arm A) or IC (oxaliplatin/FU; Arm B) before oxaliplatin/FU/radiation. Surgery was attempted ∼5-6 weeks after chemoradiation. The pathCR rate, post-surgery 30-day mortality, overall survival (OS), and toxic effects were assessed. Bayesian methods and Fisher's exact test were used. RESULTS: One hundred twenty-six patients were randomized dynamically to balance the two arms for histology, baseline stage, gender, race, and age. Fifty-five patients in Arm A and 54 in Arm B underwent surgery. The median actuarial OS for all patients (54 deaths) was 45.62 months [95% confidence interval (CI), 27.63-NA], with median OS 45.62 months (95% CI 25.56-NA) in Arm A and 43.68 months (95% CI 27.63-NA) in Arm B (P = 0.69). The pathCR rate in Arm A was 13% (7 of 55) and 26% (14 of 54) in Arm B (two-sided Fisher's exact test, P = 0.094). Safety was similar in both arms. CONCLUSIONS: These data suggest that IC produces non-significant increase in the pathCR rate and does not prolong OS. Further development of IC before chemoradiation may not be beneficial. Clinical trial no.: NCT 00525915 (www.clinicaltrials.gov).

Dynamic change in phosphorylated platelet-derived growth factor receptor in peripheral blood leukocytes following docetaxel therapy predicts progression-free and overall survival in prostate cancer.

In a placebo-controlled randomised study of the platelet-derived growth factor receptor (PDGFR) inhibitor imatinib mesylate and docetaxel in metastatic prostate cancer with bone metastases (n=116), no significant differences in progression-free and overall survival were observed. To evaluate pharmacodynamic correlates of outcomes, we assessed the association of plasma platelet-derived growth factor (PDGF) isoform kinetics and PDGFR inhibition with progression-free and overall survival by individual treatment arm. We found that in the docetaxel-placebo arm alone, the probability of decrease in PDGFR phosphorylation (Pr-Decr-pPDGFR) above 0.5 (vs 30 months (HR 3.1; P=0.04 in log-rank test). By contrast, in the docetaxel plus imatinib arm, the association of Pr-Decr-pPDGFR >0.5 with a rise in plasma PDGF isoform concentrations and inferior survival was not observed. The data suggest that dynamic changes in PDGFR phosphorylation in peripheral blood leukocytes predict docetaxel efficacy. Rising plasma PDGF concentrations may explain and/or mark docetaxel resistance. Validation and mechanistic studies addressing these unexpected findings should anticipate a confounding influence of concurrent PDGFR inhibitor therapy.

PR1 peptide vaccine induces specific immunity with clinical responses in myeloid malignancies.

PR1, an HLA-A2-restricted peptide derived from both proteinase 3 and neutrophil elastase, is recognized on myeloid leukemia cells by cytotoxic T lymphocytes (CTLs) that preferentially kill leukemia and contribute to cytogenetic remission. To evaluate safety, immunogenicity and clinical activity of PR1 vaccination, a phase I/II trial was conducted. Sixty-six HLA-A2+ patients with acute myeloid leukemia (AML: 42), chronic myeloid leukemia (CML: 13) or myelodysplastic syndrome (MDS: 11) received three to six PR1 peptide vaccinations, administered subcutaneously every 3 weeks at dose levels of 0.25, 0.5 or 1.0 mg. Patients were randomized to the three dose levels after establishing the safety of the highest dose level. Primary end points were safety and immune response, assessed by doubling of PR1/HLA-A2 tetramer-specific CTL, and the secondary end point was clinical response. Immune responses were noted in 35 of 66 (53%) patients. Of the 53 evaluable patients with active disease, 12 (24%) had objective clinical responses (complete: 8; partial: 1 and hematological improvement: 3). PR1-specific immune response was seen in 9 of 25 clinical responders versus 3 of 28 clinical non-responders (P=0.03). In conclusion, PR1 peptide vaccine induces specific immunity that correlates with clinical responses, including molecular remission, in AML, CML and MDS patients.

Fludarabine with pharmacokinetically guided IV busulfan is superior to fixed-dose delivery in pretransplant conditioning of AML/MDS patients.

We hypothesized that IV busulfan (Bu) dosing could be safely intensified through pharmacokinetic (PK-) dose guidance to minimize the inter-patient variability in systemic exposure (SE) associated with body-sized dosing, and that this should improve outcome of AML/MDS patients undergoing allogeneic stem cell transplantation. To test this hypothesis, we treated 218 patients (median age 50.7 years, male/female 50/50%) with fludarabine 40 mg/m2 once daily x4, each dose followed by IV Bu, randomized to 130 mg/m2 (N=107) or PK-guided to average daily SE, AUC of 6000 µM min (N=111), stratified for remission status and allo-grafting from HLA-matched donors. Toxicity and GvHD rates in the groups were similar; the risk of relapse or treatment-related mortality remained higher in the fixed-dose group throughout the 80-month observation period. Further, PK-guidance yielded safer disease control, leading to improved overall and PFS, most prominently in MDS patients and in AML patients not in remission at allogeneic stem cell transplantation. We conclude that AML/MDS patients receiving pretransplant conditioning treatment with our 4-day regimen may benefit significantly from PK-guided Bu dosing. This could be considered an alternative to fixed-dose delivery since it provides the benefit of precise dose delivery to a predetermined SE without increasing risk(s) of serious toxicity and/or GvHD.

Treatment of newly diagnosed acute promyelocytic leukemia without cytarabine.

PURPOSE: To determine the effect of omission of cytarabine (ara-C) from treatment of newly diagnosed acute promyelocytic leukemia (APL), which allows administration of more anthracycline. PATIENTS AND METHODS: Induction consisted of all-trans retinoic acid (ATRA) 45 mg/m2 daily until complete remission (CR) and idarubicin 12 mg/m2 daily for 4 days beginning on day 5 of ATRA. Patients in CR received two courses of idarubicin 12 mg/m2 daily for 3 days and then, until 2 years post-CR date, alternated three cycles of mercaptopurine, vincristine, methotrexate, and prednisone (POMP) with one cycle of idarubicin 12 mg/m2 daily for 2 days. Results in the 43 patients treated (41 with t(15;17) on standard or Southern analysis) were compared with those in 57 historic newly diagnosed APL patients given ara-C with either doxorubicin, amsacrine (AMSA), or daunorubicin without ATRA, using logistic and Cox regression to assess effects of non-treatment-related covariates on patient outcomes. RESULTS: The CR rate in the current group was 77% (95% confidence interval [CI], 62% to 88%) and was not significantly different from the historic rate. In contrast, disease-free survival (DFS) in CR is superior in the current group (probability at 1 year 0.87; 95% CI, 0.73 to 1.0). This has translated into superior overall DFS for the current group (P = .03 adjusting for the predictive covariates initial WBC and platelet count; 1-year DFS probability 0.67; 95% CI, 0.52 to 0.82; median follow-up 102 weeks). The current treatment appears better both in patients with and without t(15; 17) on standard cytogenetic analysis. CONCLUSION: Given the difficulties inherent in comparing sequential studies and recognizing the multiple differences in treatment between current and historic groups, our results suggest that a large randomized trial incorporating use of ATRA should assess the utility of omitting ara-C from treatment of newly diagnosed APL, thus allowing delivery of more anthracycline.

New statistical strategy for monitoring safety and efficacy in single-arm clinical trials.

PURPOSE: Efficacy and toxicity are both important outcomes in cancer clinical trials. Nonetheless, most statistical designs for phase II trials only provide rules for evaluating treatment efficacy, and moreover only allow early stopping after fixed cohorts of patients have been treated. We illustrate a new statistical design strategy for monitoring both adverse and efficacy outcomes on a patient-by-patient basis in phase II and other single-arm clinical trials. DESIGN: The new strategy is used to design a phase II trial of the experimental regimen idarubicin plus cytarabine (ara-C) plus cyclosporine for treatment of patients with intermediate-prognosis acute myelogenous leukemia (AML). The design requires a maximum of 56 patients and provides continuous monitoring boundaries to terminate the trial if the toxicity rate is unacceptably high or the complete remission (CR) rate is unacceptably low compared with the rates of these events with the standard regimen of anthracycline plus ara-C. RESULTS: The design has an 88% to 91% probability of stopping the trial early with a median of 15 to 18 patients if the toxicity rate of the experimental regimen is .05 to .10 above that of the standard and there is no improvement in the CR rate. If there is a .15 improvement in the CR rate and the toxicity rate is no more than .05 above that of the standard, then there is at least an 83% probability that the trial will run to completion. CONCLUSION: The proposed monitoring strategy provides a flexible, practical means to continuously monitor both safety and efficacy in single-arm cancer clinical trials. The design strategy can be implemented easily using a freely available menu-driven computer program, and provides a scientifically sound alternative to the use of ad hoc safety monitoring rules.

Treatment of newly diagnosed AML, RAEB-t or RAEB with lisofylline or placebo in addition to chemotherapy.

To determine whether the addition of lisofylline (LSF) to idarubicin (12 mg/m2 daily x 3) + ara-C (1.5 g/m2 daily x 4) affects the rates of infection, serious infection, CR or mortality during remission induction of newly diagnosed AML, RAEB-t or RAEB, we randomized 70 patients to 3 mg/kg lisofylline or placebo every 6 h i.v., to begin 6 h before the first dose of idarubicin and to continue until recovery of neutrophil and platelet counts or for 28 days, whichever came first. Eligibility required that patients be below age 71 years, have no history of abnormal counts, or chemotherapy for a prior malignancy, and have a creatinine <1.6 mg/dl and bilirubin <3.0 mg/dl. The study was double-blinded and infections were tabulated separately and independently at MD Anderson and by a three-member outside panel of experts. Logistic regression was used to assess the relative effects of treatment arm (LSF or placebo), age, performance status, treatment site (laminar air flow room or not), and cytogenetics on rates of infection and serious infection following the first course of chemotherapy, and on CR rate. There were 84% and 87% concordance between the expert panel and MD Anderson enumerations of infection and serious infections, respectively. Both analyses found no significant (P < 0.05) differences between the rates of infection, or serious infection, in the placebo and LSF groups. CR, 60-day, and overall mortality rates were similar in the two groups, as were time to neutrophil and blood count recovery and outcome once in CR. Logistic regression analyses supported the above conclusions. Severe nausea/vomiting and mucositis were more frequent in the LSF group. Our results suggest that larger studies of LSF in newly diagnosed AML, RAEB-t, or RAEB are not warranted.

Caspase 2 and caspase 3 as predictors of complete remission and survival in adults with acute lymphoblastic leukemia.

Dysregulation of apoptosis is an important mechanism in leukemogenesis. Caspases are cysteine proteases that play a major role in the activation of apoptotic pathways and chemotherapy-induced cell death. High levels of inactive, uncleaved caspase 2 and caspase 3 have recently been associated with poor survival in patients with acute myelogenous leukemia. We hypothesized a similarly significant role for caspase 2 and caspase 3 in patients with acute lymphoblastic leukemia. We determined levels of uncleaved caspase 2 and caspase 3 by quantitative Western blot analysis in peripheral blood samples of 45 adults with newly diagnosed ALL. We evaluated patient prognostic variables and caspase levels using multivariate logistic and Cox regression models to determine their impact on complete remission rate and overall survival probability. Levels of caspase 2 and, to a lesser degree, caspase 3 were highly associated with cytogenetic abnormalities, with lower levels in the diploid group (P = 0.016 and P = 0.10, respectively). No association between either caspase level and the percentage of bone marrow blasts was found. A high level of caspase 3 (>0.37 as determined graphically) was significantly associated with achieving complete remission (CR; P = 0.006). A multivariate logistic regression analysis including age, WBC count, percentage of peripheral and marrow blasts, hemoglobin, albumin, lactate dehydrogenase, bilirubin, and creatinine determined that a high level of caspase 3 was the most significant predictor of CR (P = 0.025, adjusted), with albumin the only other significant variable (P = 0.031). Caspase 2 levels were not associated with probability of CR. In a multivariate Cox model for survival, however, levels of caspase 2 above 0.37 were associated with a lower survival probability than were levels below that threshold (P = 0.064). High levels of caspase 3 may have a significant effect on achieving CR. Because of the limited power (n = 45) of our study, the significance of caspase 2 and caspase 3 on overall survival remains to be validated by further investigations.

The prognostic impact of BCL2 protein expression in acute myelogenous leukemia varies with cytogenetics.

BCL2 protein exerts an antiapoptotic effect on cells and decreases chemosensitivity. To determine whether BCL2 expression is prognostic of patient outcome in acute myelogenous leukemia (AML), we measured its level in 198 newly diagnosed, untreated AML patients by Western blotting using whole-cell lysates from low-density peripheral blood cells. BCL2 expression was not associated with the percentage of blasts (R2 = 0.10), French-American-British classification type, or cytogenetic abnormality. Smoothed martingale residual plots indicated that high BCL2 protein level was an adverse prognostic factor for patients with either favorable or intermediate prognosis cytogenetics [FIPC; inv(16), t(8:21), t(15:17), or diploid or insufficient metaphases] but was a favorable prognostic factor for patients with unfavorable prognosis cytogenetics (UC; -5, -7, +8, 11q23, Ph1, or miscellaneous changes). Patients with FIPC and high BCL2 (highest quartile) had a significantly shorter median survival (78 weeks versus not reached; P = 0.009) than did those with lower (lower three quartiles) levels of BCL2. Among those with UC, as BCL2 level decreased from the fourth quartile to the third or the combined first and second quartiles, the median survival decreased (from 94 to 45 or 17 weeks, respectively; P = 0.003). Lower expression of BCL2 in UC was associated with shorter remission duration (P = 0.05). In multivariate analyses performed using either overall or event-free survival as the end point, for either all patients or within either cytogenetic subgroup, BCL2 level was an independent prognostic factor. Similar analysis revealed that BCL2 level was an independent predictor of remission duration for UC patients as well. These data suggest that BCL2 is involved differently in different types (favorable versus unfavorable) of AML and that therapeutic strategies aimed at modulating BCL2 function may be more likely to work in patients with favorable cytogenetic abnormalities.

Phase II study of accelerated fractionation radiation therapy with carboplatin followed by vincristine chemotherapy for the treatment of glioblastoma multiforme.

PURPOSE: To conduct a Phase II one-arm study to evaluate the long-term efficacy and safety of accelerated fractionated radiotherapy combined with intravenous carboplatin for patients with previously untreated glioblastoma multiforme tumors. METHODS AND MATERIALS: Between 1988 and 1992, 83 patients received 1.9-2.0 Gy radiation three times a day with 2-h infusions of 33 mg/m2 carboplatin for two 5-day cycles separated by 2 weeks; following radiotherapy, patients received procarbazine, lomustine (CCNU), and vincristine (PCV) for 1 year or until tumor progressed. RESULTS: Eighty-three patients were evaluable for analysis. Seventy-four of the 83 patients (89%) received one or more courses of PCV; their median survival was 55 weeks. Total resection was performed in 20% (15 of 74), subtotal resection in 69% (51 of 74), and biopsy in 11% (8 of 74); reoperation (total or subtotal resection) was performed in 28 patients (37%). Survival was worst for those > or = 61 year old (median 35 weeks). Fits of the Cox proportional hazards regression model showed covariates individually predictive of improved survival were younger age (p < 0.01), smaller log of radiation volume (p = 0.008), total or subtotal resection vs. biopsy (p = 0.056), and higher Karnofsky performance status (p = 0.055). A multivariate analysis showed that age (p = 0.013) and extent of initial surgery (p = 0.003) together were predictive of a better survival with no other variables providing additional significance. Only 8.4% (7 of 83) of patients had clinically documented therapy-associated neurotoxicity ("radiation necrosis"). CONCLUSION: When comparable selection criteria were applied, the survival in this study is similar to the results currently attainable with other chemoradiation approaches. The relative safety of accelerated fractionated radiotherapy, as used in this study with carboplatin, enables concomitant full-dose administration of chemotherapy or radiosensitizing agents in glioblastoma multiforme patients.

Comparison of 100-day mortality rates associated with i.v. busulfan and cyclophosphamide vs other preparative regimens in allogeneic bone marrow transplantation for chronic myelogenous leukemia: Bayesian sensitivity analyses of confounded treatment and center effects.

We evaluated the 100-day mortality rates associated with busulfan-based myeloablative conditioning regimens based on data from 1812 chronic myelogenous leukemia patients who underwent allogeneic blood or marrow transplantation (allotx). In all, 47 patients received intravenous (i.v.) busulfan and cyclophosphamide (i.v.BuCy2) with allotx at MD Anderson Cancer Center (MDACC) during 1995-1999. The remaining 1765 patients, whose data were supplied by the International Bone Marrow Transplant Registry (IBMTR), received alternative preparative regimens, primarily Cy-total body irradiation ( approximately 45%) or oral BuCy ( approximately 35%) during 1997-1998. As patients were not randomized between conditioning regimens, the i.v.BuCy2-versus-alternative treatment effect is confounded with a possible center effect due to nontreatment differences associated with factors differing between MDACC and the IBMTR centers. Additional complications are that the i.v.BuCy2-MDACC patients all survived 100 days, and three prognostic subgroups were included. Bayesian sensitivity analyses were performed to assess treatment effect on the probability of 100-day mortality, over a range of possible MDACC-versus-IBMTR center effects. For these patients, the posterior probability that i.v.BuCy2 was superior to alternative conditioning regimens ranges from 0.54 to 0.99, depending on prognosis and the magnitude of the assumed center effect.

Serum cytokine levels in infectious mononucleosis at diagnosis and convalescence.

Infection with the Epstein-Barr virus (EBV) is common worldwide. A significant number of infected individuals develop infectious mononucleosis (IM). IM is manifested in most patients as a benign disease with mild symptoms. However, serious complications may develop in a subset of patients. Because EBV-infected B lymphocytes produce various cytokines that may provide the cells with a proliferative advantage, cytokine concentrations in serum samples taken from IM patients were measured in order to identify the cytokines responsible for the clinical manifestations of the disease. The concentrations of interleukin-1beta (IL-1beta), IL-2, IL-6, IL-8, IL-10, tumor necrosis factor-alpha (TNF-alpha), and lymphotoxin (LT) were measured using an enzyme-linked immunosorbent assay (ELISA) in serum obtained from 14 IM patients during the acute phase of the disease and during convalescence, 5 patients with identical clinical manifestations who did not have IM (sick controls), and 11 healthy volunteers. It was found that the serum levels of TNF-alpha and IL-6 were significantly high in patients with acute IM compared with the serum levels in healthy individuals (P = 0.008 and P < 0.001, respectively) but returned to normal at convalescence (P = 0.009 and P = 0.005 respectively). However, whereas TNF-alpha concentrations were significantly higher (P = 0.04) in patients with acute IM than in the sick controls, no significant difference in IL-6 concentrations was found between the two groups of patients. Changes in IL-10 concentration were not statistically significant, and IL-1beta, IL-2, IL-8, and LT were detected only sporadically. The data in this study suggest that TNF-alpha may have a specific role in causing the clinical manifestations of IM. Further studies should determine the clinical significance of TNF-alpha inhibition in IM.

Adenoviral infections in adult allogeneic hematopoietic SCT recipients: a single center experience.

Disseminated adenoviral infection (AI) is associated with profound immunosuppression and poor outcome after allogeneic hematopoietic SCT (allo-HSCT). A better understanding of AI in allo-HSCT recipients can serve as a basis to develop more effective management strategies. We evaluated all adult patients who received allo-HSCT at MD Anderson Cancer Center between 1999 and 2008. Among the 2879 allo-HSCT patients, 73 (2.5%) were diagnosed with AI. Enteritis (26%) and pneumonia (24%) were the most common clinical manifestations; pneumonia was the most common cause of adenovirus-associated death. A multivariable Bayesian logistic regression showed that when the joint effects of all covariates were accounted for, cord blood transplant, absolute lymphocyte count (ALC) ≤ 200/mm(3) and male gender were associated with a higher probability of disseminated AI. The OS was significantly worse for patients with AI that was disseminated rather than localized (median of 5 months vs median of 28 months, P<0.001) and for patients with ALC ≤ 200/mm(3) (P<0.001). Disseminated AI, in patients who received allo-HSCT, is a significant cause of morbidity and mortality. Strategies for early diagnosis and intervention are essential, especially for high-risk patients.

Intravenous BU plus Mel: an effective, chemotherapy-only transplant conditioning regimen in patients with ALL.

We investigated the administration of i.v. BU combined with melphalan (Mel) in patients with ALL undergoing allogeneic hematopoietic SCT. Forty-seven patients with a median age of 33 years (range 20-61) received a matched sibling (n=27) or matched unrelated donor transplant (n=20) for ALL in first CR (n=26), second CR (n=13), or with more advanced disease (n=8). BU was infused daily for 4 days, either at a fixed dose of 130 mg/m² (5 patients) or using pharmacokinetic (PK) dose adjustment (42 patients), to target an average daily area-under-the-curve (AUC) of 5000 µmol/min, determined by a test dose of i.v. BU at 32 mg/m². This was followed by a rest day, then two daily doses of Mel at 70 mg/m². Stem cells were infused on the following day. The 2-year OS, PFS and non-relapse mortality (NRM) rates were 35% (95% confidence interval (CI), 23-51%), 31% (95% CI, 21-48%) and 37% (95% CI, 23-50%), respectively. Acute NRM at 100 days was favorable at 12% (95% CI, 5-24%); however, the 2-year NRM was significantly higher for patients older than 40 years, 58% vs 20%, mainly due to GVHD.

Phase I/II study of gemtuzumab ozogamicin added to fludarabine, melphalan and allogeneic hematopoietic stem cell transplantation for high-risk CD33 positive myeloid leukemias and myelodysplastic syndrome.

We investigated the hypothesis that gemtuzumab ozogamicin (GO), an anti-CD33 immunotoxin would improve the efficacy of fludarabine/melphalan as a preparative regimen for allogeneic hematopoietic stem cell transplantation (HSCT) in a phase I/II trial. Toxicity was defined as grades III-IV organ damage, engraftment failure or death within 30 days. 'Response' was engraftment and remission (CR) on day +30. We sought to determine the GO dose (2, 4 or 6 mg m(-2)) giving the best trade-off between toxicity and response. All patients were not candidates for myeloablative regimens. Treatment plan: GO (day -12), fludarabine 30 mg m(-2) (days -5 to -2), melphalan 140 mg m(-2) (day -2) and HSCT (day 0). GVHD prophylaxis was tacrolimus and mini-methotrexate. Diagnoses were AML (n=47), MDS (n=4) or CML (n=1). Median age was 53 years (range, 13-72). All but three patients were not in CR. Donors were related (n=33) or unrelated (n=19). Toxicity and response rates at 4 mg m(-2) were 50% (n=4) and 50% (n=4). GO dose was de-escalated to 2 mg m(-2): 18% had toxicity (n=8) and 82% responded (n=36). 100-day TRM was 15%; one patient had reversible hepatic VOD. Median follow-up was 37 months. Median event-free and overall survival was 6 and 11 months. GO 2 mg m(-2) can be safely added to fludarabine/melphalan, and this regimen merits further evaluation.

Mixed Poisson likelihood regression models for longitudinal interval count data.

In many longitudinal studies it is desired to estimate and test the rate over time of a particular recurrent event. Often only the event counts corresponding to the elapsed time intervals between each subject's successive observation times, and baseline covariate data, are available. The intervals may vary substantially in length and number between subjects, so that the corresponding vectors of counts are not directly comparable. A family of Poisson likelihood regression models incorporating a mixed random multiplicative component in the rate function of each subject is proposed for this longitudinal data structure. A related empirical Bayes estimate of random-effect parameters is also described. These methods are illustrated by an analysis of dyspepsia data from the National Cooperative Gallstone Study.

Incorporating historical control data in planning phase II clinical trials.

Phase II studies of new medical treatments often use historical data on the standard treatment for comparative evaluation. Incorrectly disregarding inherent variability in the historical data may lead to erroneous conclusions regarding the efficacy of the experimental treatment. We propose an approach to phase II trial design which accounts for both inter-study and intra-study variation. Our results indicate that it is sometimes best to randomize a proportion of the patients to a control arm. We choose this proportion to maximize the precision of the estimated experimental treatment effect. We evaluate operating characteristics of the design numerically, and provide illustrations based on historical data from cancer chemotherapy trials.