The 6-MP versus placebo clinical trial in acute leukemia.

BACKGROUND: This article gives the status of clinical cancer research in the 1950's-1960's and tells the story of the development and conduct of the 6-mercaptopurine (6-MP) versus placebo clinical trial in acute leukemia through the initiation, design, conduct and analysis stages, with emphasis on the ethical aspects of randomizing patients to 6-MP or placebo when in remission. PURPOSE: The specific objective was to compare the lengths of remission for patients receiving 6-MP or placebo after achieving complete or partial remission from steroid treatment. METHODS: A randomized, double-blind, placebo controlled sequential study was conducted in which patients were paired by remission status at each of the eleven institutions participating in the study, and randomized to 6-MP or placebo within each pair of patients. A preference for 6-MP or placebo was recorded depending on which patient in the pair had the longer remission. The preferences were plotted according to a restricted sequential procedure devised by Peter Armitage and, depending on which boundary of the design was crossed, a statistically significant difference could be declared favoring 6-MP, placebo or no preference. CONCLUSIONS: The trial established the efficacy of 6-MP for maintaining longer remissions in acute leukemia and led to the concept of 'adjuvant chemotherapy', namely that patients with minimal disease have a substantially better response to chemotherapy than patients with advanced disease, a concept that has been followed in many other forms of cancer. Statistically, the fact that many patients were still in remission when the study was stopped (i.e. the length of remission data for these patients was 'right censored') led to the development of a generalized Wilcoxon test and was an important influence on Cox's development of the proportional hazards model. The trial had an innovative design in the early 1960's and has been an important influence on subsequent clinical research in cancer and statistical research in survival analysis.

Treatment-subgroup interaction: an example from a published, phase II clinical trial.

Phase II trial designs that ignore between-patient heterogeneity and do not allow for treatment-subgroup interactions may produce very large false positive and false negative error rates if efficacy varies by subgroup. Recent discussions of this problem were illustrated with scenarios and computer simulations. In this short communication, we reanalyzed a published phase II trial to highlight the need to consider between-patient heterogeneity and the possibility of treatment-subgroup interaction when designing and analyzing phase II studies. The single-arm trial evaluated amsacrine plus cytosine arabinoside, vincristine, and prednisone (a combination abbreviated as OAP) for adult acute leukemia, when standard treatment was adriamycin plus OAP. We carried out an analysis of covariance (ANCOVA) incorporating data from historical control patients who met eligibility criteria for the trial and received standard treatment at the study center in the years immediately preceding the trial. Patients administered experimental treatment and control patients were classified as having favorable or unfavorable prognosis according to their predicted probability of response to standard treatment. When the prognostic subgroup of patients was ignored, the response rates for experimental and standard treatment appeared similar. However, fitting an ANCOVA model determined that the effects of subgroup, treatment, and their interaction were statistically significant: experimental treatment was superior to standard treatment in patients with unfavorable prognosis and inferior to standard treatment in patients with favorable prognosis. This real-world example of treatment-subgroup interaction highlights the need to employ phase II designs that consider between-patient heterogeneity and the possibility that efficacy differs by subgroup.

The properties of high-dimensional data spaces: implications for exploring gene and protein expression data.

High-throughput genomic and proteomic technologies are widely used in cancer research to build better predictive models of diagnosis, prognosis and therapy, to identify and characterize key signalling networks and to find new targets for drug development. These technologies present investigators with the task of extracting meaningful statistical and biological information from high-dimensional data spaces, wherein each sample is defined by hundreds or thousands of measurements, usually concurrently obtained. The properties of high dimensionality are often poorly understood or overlooked in data modelling and analysis. From the perspective of translational science, this Review discusses the properties of high-dimensional data spaces that arise in genomic and proteomic studies and the challenges they can pose for data analysis and interpretation.

Cyberknife radiosurgery for breast cancer spine metastases: a matched-pair analysis.

BACKGROUND: There are few options for breast cancer patients with spinal metastases recurrent within a previous radiation treatment field. CyberKnife radiosurgery has been used in our institution to treat such patients. To evaluate their outcomes, as there are no comparable radiation treatment options, the outcomes were compared between 18 patients with spinal metastases from breast cancer treated with CyberKnife stereotactic radiosurgery, 17 of which had prior radiotherapy to the involved spinal region and were progressing, and 18 matched patients who received conventional external beam radiotherapy (CRT) up-front for spinal metastases. METHODS: Radiosurgery was delivered in 3 to 5 fractions to doses ranging from 2100 to 2800 cGy. Women were matched to patients in a CRT group with respect to time from original diagnosis to diagnosis of metastases, estrogen receptor / progesterone receptor (ER/PR) status, presence or absence of visceral metastases, prior radiotherapy, and prior chemotherapy. Survival and complications were compared between treatment groups. Surviving patients were followed out to 24 months. RESULTS: The CyberKnife and CRT groups were comparable along all matching dimensions and in performance status before treatment. Outcomes of treatment were similar for patients in both groups; ambulation, performance status, and pain worsened similarly across groups posttreatment. Survival and the number of complications appeared to favor the CyberKnife group, but the differences did not reach statistical significance. CONCLUSIONS: The statistical comparability of the CyberKnife and CRT groups reflects the small sample size and stringent requirements for significance of the matched-pair analysis. Nevertheless, comparability in these difficult cases shows that salvage CyberKnife treatment is as efficacious as initial CRT without added toxicity.

The development of novel agents for the treatment of colorectal cancer: a critical review of current practice and some suggestions for the future.

The pathways to approval of new therapeutic agents in the United States and globally rely on the performance of well-designed clinical trials demonstrating both safety and efficacy. We recognize that the last decade has seen some great successes in improving outcomes for patients with cancer and, specifically, for patients with colorectal cancer. The development of novel agents active in colon cancer has led to improved survival and cure rates. However, because of the number of agents now available and the established practice patterns, it is becoming increasingly difficult to test new agents in cancer, particularly in colorectal cancer. The focus of this article is to review the current clinical trial designs with a critical eye and propose novel approaches to bringing new agents into the armamentarium of agents effective against colorectal cancer. Our current standards for drug development are increasingly problematic, and it is imperative that we develop new expectations and supporting standards in cancer drug development.

Gene selection for microarray data analysis using principal component analysis.

Principal component analysis (PCA) has been widely used in multivariate data analysis to reduce the dimensionality of the data in order to simplify subsequent analysis and allow for summarization of the data in a parsimonious manner. It has become a useful tool in microarray data analysis. For a typical microarray data set, it is often difficult to compare the overall gene expression difference between observations from different groups or conduct the classification based on a very large number of genes. In this paper, we propose a gene selection method based on the strategy proposed by Krzanowski. We demonstrate the effectiveness of this procedure using a cancer gene expression data set and compare it with several other gene selection strategies. It turns out that the proposed method selects the best gene subset for preserving the original data structure.

SCC-112, a novel cell cycle-regulated molecule, exhibits reduced expression in human renal carcinomas.

We report here the identification and an initial characterization of a novel cell cycle-regulated molecule, SCC-112. SCC-112 cDNA (6744 bp) encodes a longest open reading frame (ORF) comprised of 1297 amino acids, representing a approximately 150-kDa nuclear protein. SCC-112 mRNA and protein levels were relatively high during the G2/M phase of the cell cycle in MDA-MB 435 breast cancer cells. Transient expression of SCC-112 cDNA in COS-1 cells led to an increase in the number of cells in sub-G1 phase and enhanced activity of caspase-3, a downstream effector of apoptosis. Stable transfection of SCC-112 cDNA in MDA-MB 231 breast cancer cells also led to an increase in the number of cells in sub-G1 phase ( approximately 2-3-fold), indicative of apoptosis. The examination of the paired sets of human normal and tumor tissues revealed that the SCC-112 mRNA level was significantly high in normal breast and kidney tissues as compared to the corresponding primary tumor tissues (P<0.0001; breast, n=50, and kidney, n=20). Consistent with these observations, SCC-112 protein expression (150 kDa) was high in a majority of the normal renal tissues examined as compared to the matched renal tumor tissues (67%, 1.2-fold to>10-fold, n=18). Taken together, these findings suggest that the SCC-112 gene expression is likely to be associated with normal cell growth and proliferation.

Treatment of children and adolescents with localized parameningeal sarcoma: experience of the Intergroup Rhabdomyosarcoma Study Group protocols IRS-II through -IV, 1978-1997.

BACKGROUND: We reviewed 611 patients with parameningeal sarcoma entered on Intergroup Rhabdomyosarcoma Study Group (IRSG) Protocols-II through IV (1978-1997), to delineate treatment results and evaluate prognostic factors. PROCEDURE: Primary sites were the middle ear/mastoid (N = 138), nasopharynx/nasal cavity (N = 235), paranasal sinuses (N = 132), parapharyngeal region (N = 29), and the pterygopalatine/infratemporal fossa (N = 77). Treatment was initial biopsy or surgery followed by multiagent chemotherapy and radiation therapy (XRT). Beginning in 1977, patients with cranial nerve palsy, cranial base bony erosion, and/or intracranial extension at diagnosis were considered as having meningeal involvement. They received triple intrathecal medications, whole brain XRT, and then spinal XRT. These treatments were successively eliminated from 1980 to 1991. RESULTS: The 611 patients' overall survival rate at 5 years was 73% (95% confidence interval, 70-77%). Favorable prognostic factors were: age 1-9 years at diagnosis; primary tumor in the nasopharynx/nasal cavity, middle ear/mastoid, or parapharyngeal areas; no meningeal involvement; and non-invasive tumors (T1). Thirty-five of 526 patients (6.7%) with information about presence/absence of meningeal involvement at diagnosis developed central nervous system (CNS) extension at 5-164 weeks (median, 46 weeks) after starting therapy. The estimated 5-year cumulative incidence rate of CNS extension during the study period was 5-7% (P = 0.88). CONCLUSIONS: Biopsy, XRT to the target volume, and systemic chemotherapy are successful treatments for the large majority of patients with localized parameningeal sarcoma. Carefully defining and irradiating the initial volume should reduce the risk of CNS failure. Aggressive initial surgical management of these patients is unnecessary.