Robert Kwiecien

Sample Size Calculation in Clinical Trials: Part 13 of a Series on Evaluation of Scientific Publications

BACKGROUND In this article, we discuss the purpose of sample size calculation in clinical trials, the need for it, and the methods by which it is accomplished. Study samples that are either too small or too large are unacceptable, for clinical, methodological, and ethical reasons. The physicians participating in clinical trials should be directly involved in sample size planning, because their expertise and knowledge of the literature are indispensable. METHODS We explain the process of sample size calculation on the basis of articles retrieved by a selective search of the international literature, as well as our own experience. RESULTS We present a fictitious clinical trial in which two antihypertensive agents are to be compared to each other with a t-test and then show how the appropriate size of the study sample should be calculated. Next, we describe the general principles of sample size calculation that apply when any kind of statistical test is to be used. We give further illustrative examples and explain what types of expert medical knowledge and assumptions are needed to calculate the appropriate sample size for each. These generally depend on the particular statistical test that is to be performed. CONCLUSION In any clinical trial, the sample size has to be planned on a justifiable, rational basis. The purpose of sample size calculation is to determine the optimal number of participants (patients) to be included in the trial. Sample size calculation requires the collaboration of experienced biostatisticians and physician-researchers: expert medical knowledge is an essential part of it.

Concordance Analysis: Part 16 of a Series on Evaluation of Scientific Publications

BACKGROUND In this article, we describe qualitative and quantitative methods for assessing the degree of agreement (concordance) between two measuring or rating techniques. An assessment of concordance is particularly important when a new measuring technique is introduced. METHODS We give an example to illustrate a number of simple methods of comparing different measuring or rating techniques, and we explain the underlying principle of each method. We also give further illustrative examples from medical research papers that were retrieved by a selective literature search. RESULTS Methods of comparing different measuring or rating techniques are of two kinds: those with a nominal rating scale and those with a continuous rating scale. We only discuss methods for comparing one measuring or rating technique with another one. Moreover, we point out some common erroneous approaches to concordance analysis. CONCLUSION Concordance analysis is needed to establish the validity of a new diagnostic measuring or rating technique or to demonstrate the near-equivalence of multiple measuring or rating techniques. Erroneous approaches to concordance analysis can lead to false conclusions.

Treatment of young children with CNS-primitive neuroectodermal tumors/ pineoblastomas in the prospective multicenter trial HIT 2000 using different chemotherapy regimens and radiotherapy

BACKGROUND Especially in young children, primitive neuroectodermal tumors of the central nervous system (CNS-PNET) and pineoblastomas are associated with an unfavorable outcome, and only a few prospective trials have been conducted thus far. METHODS From January 2001 through January 2005, 17 eligible children aged <4 years with CNS-PNET not otherwise specified (n = 8), ependymoblastoma (n = 1), or pineoblastoma (n = 8) confirmed by central review were prospectively treated in the trial HIT 2000. In nonmetastatic disease (n = 11), up to 5 postoperative cycles of HIT-SKK systemic multiagent chemotherapy (8 months duration), followed by craniospinal radiotherapy (CSI), were given. In metastatic disease (M1-M3, n = 6), treatment consisted of a shorter induction chemotherapy (2-3 months) with carboplatin and etoposide, followed by tandem high-dose chemotherapy (HDCT) in case of good response to induction. During induction and HDCT, patients received intraventricular methotrexate. CSI was applied to all patients with poor response to induction or residual disease after HDCT and was optional for patients with residual disease before HDCT. RESULTS Five-year event-free survival and overall survival rates ± standard error for all eligible patients were 24% ± 10% and 40% ± 12%, respectively (median follow-up of survivors: 8.3 years). Only one patient with nonmetastatic disease remained free of relapse/progressive disease during induction. Three of 6 patients with metastatic disease responded to induction and received tandem-HDCT, followed by preventive CSI, and remain in continuous complete remission. CONCLUSIONS Short intensive induction chemotherapy followed by tandem-HDCT in young children with CNS-PNET/pineoblastomas seems to be superior to the prolonged and less intensive induction regimen.

Treatment of adult nonmetastatic medulloblastoma patients according to the paediatric HIT 2000 protocol: A prospective observational multicentre study

BACKGROUND Medulloblastoma in adulthood is rare. Knowledge is limited, and the efficacy and toxicity of chemotherapy--especially in nonmetastatic disease--is still elusive. METHODS Seventy adults aged ≥21 years (median age: 28.5 years) with nonmetastatic medulloblastoma were followed as observational patients within the prospective paediatric multicentre trial HIT 2000. Treatment consisted of radiotherapy (35.2 Gy to the craniospinal axis and a boost to 55.2 Gy to the posterior fossa) followed in most patients by maintenance chemotherapy (lomustine (CCNU), vincristine and cisplatin, n=49). RESULTS The implementation of maintenance chemotherapy was feasible. Peripheral neuropathy (74%) and haematotoxicity (55%) during maintenance chemotherapy appear to be more common in adults than in children. At a median follow-up of 3.7 years, the 4-year event-free survival (EFS) and overall survival (OS) rates±standard error (SE) were 68%±7% and 89%±5%. Patients with desmoplastic medulloblastoma and lateral tumour location (n=19) had a lower EFS compared to patients with centrally located desmoplastic tumours (n=10) (p=0.011). Absence of residual postoperative tumour (n=40) was associated to a lower rate of progression/relapse compared to present (n=11) or unknown (n=12) residual tumour status (p=0.006). Lateral tumour location and unknown residual tumour status were independent negative prognostic factors. CONCLUSIONS Maintenance chemotherapy is applicable in adults with nonmetastatic medulloblastoma. Histological subtype and tumour location were newly identified risk factors in this age-group, and should be further analysed in prospective trials.

Intraventricular methotrexate as part of primary therapy for children with infant and/or metastatic medulloblastoma: Feasibility, acute toxicity and evidence for efficacy

BACKGROUND To assess feasibility, acute toxicity, and efficacy of intraventricular methotrexate administered as part of the primary therapy in medulloblastoma. METHODS From 2001 to 2007, 240 patients < 22 years from 61 treatment centres were registered. Patients received 2-3 cycles of intraventricular methotrexate with systemic chemotherapy in three different treatment arms of the prospective multicentre trial HIT2000 (150 children > 4 years with metastatic, 59 < 4 years with non-metastatic, 31 < 4 years with metastatic medulloblastoma). RESULTS 211 patients received an intraventricular access device with a subcutaneous reservoir for the application of chemotherapy. Reservoir-associated complications were documented in 57 (27%) patients, mostly due to infection (n = 32) and reservoir malfunction (n = 19), requiring removal in 39 (18%) patients. Acute neurotoxicity likely associated with intraventricular MTX was observed in 9/202 documented patients. Toxicity was usually mild, apart from one therapy-associated death due to toxic oedema followed by seizures. Of 519 treatment cycles including intraventricular methotrexate, 226 (43%) were reduced or omitted, most frequently due to the absence of an intraventricular device. Survival rates were higher in patients receiving ⩾ 75% of the scheduled intraventricular methotrexate dose compared to those receiving < 75% in both univariate and multivariate models (event-free survival (EFS), 61.5 versus 46.2%, p = 0.004; OS, 75.5% versus 60.4%, p = 0.015; hazard ratio: EFS 1.723, p = 0.016; OS 1.648, p = 0.051). CONCLUSION Intraventricular methotrexate therapy was feasible and mostly well tolerated. Infections were the most frequent complication. A higher cumulative dose of intraventricular methotrexate was associated with better survival. Further evaluation of efficacy and late effects is warranted.

Treatment of children with central nervous system primitive neuroectodermal tumors/pinealoblastomas in the prospective multicentric trial HIT 2000 using hyperfractionated radiation therapy followed by maintenance chemotherapy.

PURPOSE The prognosis for children with central nervous system primitive neuroectodermal tumor (CNS-PNET) or pinealoblastoma is still unsatisfactory. Here we report the results of patients between 4 and 21 years of age with nonmetastatic CNS-PNET or pinealoblastoma diagnosed from January 2001 to December 2005 and treated in the prospective GPOH-trial P-HIT 2000-AB4. METHODS AND MATERIALS After surgery, children received hyperfractionated radiation therapy (36 Gy to the craniospinal axis, 68 Gy to the tumor region, and 72 Gy to any residual tumor, fractionated at 2 × 1 Gy per day 5 days per week) accompanied by weekly intravenous administration of vincristine and followed by 8 cycles of maintenance chemotherapy (lomustine, cisplatin, and vincristine). RESULTS Twenty-six patients (15 with CNS-PNET; 11 with pinealoblastoma) were included. Median age at diagnosis was 11.5 years old (range, 4.0-20.7 years). Gross total tumor resection was achieved in 6 and partial resection in 16 patients (indistinct, 4 patients). Median follow-up of the 15 surviving patients was 7.0 years (range, 5.2-10.0 years). The combined response rate to postoperative therapy was 17 of 20 (85%). Eleven of 26 patients (42%; 7 of 15 with CNS-PNET; 4 of 11 with pinealoblastoma) showed tumor progression or relapse at a median time of 1.3 years (range, 0.5-1.9 years). Five-year progression-free and overall survival rates (± standard error [SE]) were each 58% (± 10%) for the entire cohort: CNS-PNET was 53% (± 13); pinealoblastoma was 64% (± 15%; P=.524 and P=.627, respectively). CONCLUSIONS Postoperative hyperfractionated radiation therapy with local dose escalation followed by maintenance chemotherapy was feasible without major acute toxicity. Survival rates are comparable to those of a few other recent studies but superior to those of most other series, including the previous trial, HIT 1991.

Children <1 Year Show an Inferior Outcome When Treated According to the Traditional LGG Treatment Strategy: A Report From the German Multicenter Trial HIT-LGG 1996 for Children With Low Grade Glioma (LGG)

Children diagnosed with LGG at an age <1 year are reported to have an impaired prognosis in comparison to older patients. Analysis of this subgroup could reveal the necessity to develop risk‐adapted treatment approaches.

Everolimus therapy is associated with reduced lipoprotein-associated phospholipase A2 (Lp-Pla2) activity and oxidative stress in heart transplant recipients

BACKGROUND Several studies demonstrated decreased severity and incidence of cardiac allograft vasculopathy (CAV) in heart transplant recipients receiving immunosuppressive therapy with everolimus. However, data regarding the influence of everolimus on risk factors predisposing to CAV are hitherto limited. We here systematically evaluated cardiovascular risk factors in heart transplanted patients, who underwent conversion to everolimus or were maintained on conventional therapy with calcineurin inhibitors (CNI). METHODS 50 Patients receiving everolimus and 91 patients receiving CNI in addition to mycophenolate mofetil and low-dosed steroids were included in the study. CAV risk factors were determined in plasma or urine using standard enzymatic or immunochemical methods. RESULTS No significant differences were observed between both groups with regard to lipid (total, LDL- and HDL-cholesterol), metabolic (glucose, insulin), inflammatory (C-reactive protein, IL-6, myeloperoxidase) and cardiac (troponin I, NT-proBNP) risk factors. However, significantly lower activity of lipoprotein-associated phospholipase A2 (Lp-PLA2) and a negative correlation between the Lp-PLA2 activity and the everolimus concentration were observed in plasmas from everolimus-treated patients. Conversion to everolimus significantly lowered Lp-PLA2 activity in heart transplant recipients. Studies in vitro revealed reduced Lp-PLA2 expression in hepatocytes and macrophages pre-exposed to everolimus. In addition, reduced plasma markers of oxidative stress including oxidized LDL, 8-iso-prostaglandin F2α and protein carbonyls were noted in heart transplant recipients receiving everolimus therapy. CONCLUSION Our results suggest that everolimus specifically lowers plasma activity and cellular production of Lp-PLA2 and thereby dampens oxidative stress. These effects may additionally contribute to the reduced CAV incidence observed in heart transplant recipients receiving everolimus therapy.

Prothrombin and factor X are elevated in multiple sclerosis patients

Animal models have implicated an integral role for coagulation factors in neuroinflammatory diseases such as multiple sclerosis (MS) beyond their role in hemostasis. However, their relevance in humans requires further elucidation. This study aimed to determine whether levels of coagulation factors differ between patients with neuroimmunological disorders and respective controls. Individuals suffering from relapsing–remitting and secondary progressive MS had significantly higher prothrombin and factor X levels than healthy donors, whereas levels were unchanged in primary progressive MS and neuromyelitis optica patients. Our study demonstrates that coagulation factors may be key mediators in neuroinflammation and may therefore provide future targets for therapeutic strategies. Ann Neurol 2016;80:946–951

Sample size calculation for the one-sample log-rank test.

An improved method of sample size calculation for the one-sample log-rank test is provided. The one-sample log-rank test may be the method of choice if the survival curve of a single treatment group is to be compared with that of a historic control. Such settings arise, for example, in clinical phase-II trials if the response to a new treatment is measured by a survival endpoint. Present sample size formulas for the one-sample log-rank test are based on the number of events to be observed, that is, in order to achieve approximately a desired power for allocated significance level and effect the trial is stopped as soon as a certain critical number of events are reached. We propose a new stopping criterion to be followed. Both approaches are shown to be asymptotically equivalent. For small sample size, though, a simulation study indicates that the new criterion might be preferred when planning a corresponding trial. In our simulations, the trial is usually underpowered, and the aspired significance level is not exploited if the traditional stopping criterion based on the number of events is used, whereas a trial based on the new stopping criterion maintains power with the type-I error rate still controlled.