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Cure models are a popular topic within statistical literature but are not as widely known in the clinical literature. Many patients with cancer can be long-term survivors of their disease, and cure models can be a useful tool to analyze and describe cancer survival data. The goal of this article is to review what a cure model is, explain when cure models can be used, and use cure models to describe multiple myeloma survival trends. Multiple myeloma is generally considered an incurable disease, and this article shows that by using cure models, rather than the standard Cox proportional hazards model, we can evaluate whether there is evidence that therapies at the University of Arkansas for Medical Sciences induce a proportion of patients to be long-term survivors. Clin Cancer Res; 18(14); 3731–6. ©2012 AACR.

PDF file - 43K, Details of cure model parametrizations and summaries of regression results on the coefficient scale

The hazard ratio (HR) is widely used to quantify treatment effects. However, it may be difficult to interpret for patients and practitioners, especially when the hazard ratio is not constant over time. Alternative measures of the treatment effects have been proposed such as the difference of the restricted mean survival times (RMST), the difference in survival proportions at some fixed follow-up time, or the net chance of a longer survival. In this paper, we propose the restricted survival benefit (RSB), a quantity that can incorporate multiple useful measurements of treatment effects. Hence, it provides a framework for a comprehensive assessment of the treatment effects. We provide estimation and inference procedures for the RSB that accommodate censored survival outcomes, using methods of the inverse-probability-censoring-weighted (IPCW) U-statistic and the jackknife empirical likelihood. We conduct extensive simulation studies to examine the numerical performance of the proposed method, and we analyze data from a randomized Phase III clinical trial (SWOG S0777) using the proposed method.

Variable survival outcomes are seen following treatment for aggressive non-Hodgkin lymphoma (NHL). This study examined whether outcomes for aggressive B-cell NHL are associated with single nucleotide polymorphisms (SNPs) in oxidative stress-related genes, which can alter drug metabolism and immune responses. Genotypes for 53 SNPs in 29 genes were determined for 337 patients given anthracycline-based therapies. Their associations with progression-free survival (PFS) and overall survival (OS) were estimated by Cox proportional hazard regression; associations with hematologic toxicity were estimated by logistic regression. To validate the findings, the top three SNPs were tested in an independent cohort of 572 DLBCL patients. The top SNPs associated with PFS in the discovery cohort were the rare homozygotes for MPO rs2243828 (hazard ratio [HR] = 1.87, 95% confidence interval [CI] = 1.14-3.06, P = 0.013), AKR1C3 rs10508293 (HR = 2.09, 95% CI = 1.28-3.41, P = 0.0032) and NCF4 rs1883112 (HR = 0.66, 95% CI = 0.43-1.02, P = 0.06). The association of the NCF4 SNP with PFS was replicated in the validation dataset (HR = 0.66, 95% CI = 0.44-1.01, P = 0.05) and the meta-analysis was significant (HR = 0.66, 95% CI = 0.49-0.89, P0.01). The association of the MPO SNP was attenuated in the validation dataset, while the meta-analysis remained significant (HR = 1.64, 95% CI = 1.12-2.41). These two SNPs showed similar trends with OS in the meta-analysis (for NCF4, HR = 0.72, 95% CI = 0.51-1.02, P = 0.07 and for MPO, HR = 2.06, 95% CI = 1.36-3.12, P0.01). In addition, patients with the rare homozygote of the NCF4 SNP had an increased risk of hematologic toxicity. We concluded that genetic variations in NCF4 may contribute to treatment outcomes for patients with aggressive NHL.

Gossypol, a cottonseed extract, has been shown to have antiproliferative activity in a variety of cancer cell lines. The objective of this study was to determine the inhibitory effects of gossypol on cell proliferation. Five human carcinoma cell lines were evaluated including endometrial (RL95-2), ovarian (SKOV-3), medullary thyroid (TT), and adrenocortical (NCI-H295R and SW-13). Gossypol and the metabolite, apogossypol hexaacetate, were examined at concentrations up to 500 microg ml(-1) and the IC(50) was determined using the MTT assay. Gossypol and apogossypol hexaacetate produced a dose-dependent growth inhibition in all cellular lines examined. The IC(50) for gossypol ranged from 1.3 to 18.9 microM while the IC(50) for apogossypol hexaacetate ranged from 5.2 to 9.0 microM. The results indicate that gossypol possesses antiproliferative action toward human carcinoma cells in vitro. These investigations suggest that gossypol may have therapeutic potential for the treatment of cancer.

Purpose: To determine the effect of post-transplant immunotherapy with Interleukin-2 (IL-2) on the progression-free and overall survival of patients with non-Hodgkin’s lymphoma (NHL) after autologous stem cell transplantation and to assess the toxicity of post-transplant IL-2 therapy. Patients and Methods: Patients with previously treated low, intermediate, or high grade NHL (except Working Formulation Groups A and I) were treated with high-dose cyclophosphamide, etoposide, and total body irradiation (TBI) and an autologous peripheral blood stem cell transplant (PBSCT). Twenty-eight to 80 days after PBSCT, patients were randomized to treatment with IL-2 versus observation. Results: Between January 1995 and July 2004, three hundred ninety-four patients with low-grade (n=61) or intermediate-high grade NHL (n=315) were registered at one of 39 SWOG transplant centers. One hundred ninety patients did not proceed to randomization, because of patient refusal (44), grade V toxicity (30), disease progression (28), toxicity (28), or other reasons. Two hundred four patients were randomized to treatment with continuous infusion intravenous IL-2 (9 ×106 units/m2/day for four days followed five days later by 1.6 ×106 units/m2/day for 10 days) versus observation. The 4-year progression-free survival estimate for all eligible patients is 34%, and the 4-year overall survival estimate is 52%. There was no difference in progression-free survival (hazard ratio (HR) of IL-2 to observation = 0.90; p = 0.56) nor in overall survival (HR of IL-2 to observation = 0.88; p = 0.55). There were no deaths related to IL-2 treatment. Grade IV IL-2-related toxicities included hematologic (n=10), cardiovascular (4), renal/bladder (2), flu-like symptoms (1), lung (1), metabolic (1), and neurologic (1) and were reversible in all cases. Conclusions: These results confirm earlier SWOG findings that a regimen of cylophosphamide, etoposide and TBI followed by PBSCT can be administered to patients with relapsed or refractory NHL with acceptable toxicity and with encouraging progression-free and overall survival. Post-transplant therapy with IL-2 given at this dose and schedule of administration had no significant effect on post-transplant relapse, progression-free survival or overall survival.