Ted Wun

Prospective Evaluation of Cancer Clinical Trial Accrual Patterns: Identifying Potential Barriers to Enrollment

PURPOSE Well-conducted cancer clinical trials are essential for improving patient outcomes. Unfortunately, only 3% of new cancer patients participate in clinical trials. Barriers to patient accrual in cancer clinical trials must be identified and overcome to increase patient participation. MATERIALS AND METHODS We prospectively tracked factors that potentially affected patient accrual into cancer clinical trials at the University of California Davis Cancer Center. Oncologists seeing new outpatients were asked to complete questionnaires regarding patient characteristics and the physicians decision-making on patient eligibility, protocol availability, and patient opinions on participation. Statistical analysis was performed to correlate these parameters with subsequent protocol accrual. RESULTS There were 276 assessable patients. At the initial visits, physicians did not consider clinical trials in 38% (105/276) of patients principally because of a perception of protocol unavailability and poor performance status. Physicians considered 62% (171/276) of patients for participation in clinical trials. Of these, only 53% (91/171) had an appropriate protocol available for site and stage of disease. Seventy-six of 90 patients (84%) with available protocols met eligibility criteria for a particular study. Only 39 of 76 patients (51%) agreed to participate in cancer clinical trials, for an overall accrual rate of 14% (39/276). The remainder (37/76, 49%) declined trial participation despite meeting eligibility criteria. The most common reasons were a desire for other treatment (34%), distance from the cancer center (13%), patient refusal to disclose reason (11%), and insurance denial (8%). Patients with private insurance were less likely to enroll in clinical trials compared to those with government-funded insurance (OR, 0.34; P =.03; 95% CI, 0.13 to 0.9). CONCLUSION Barriers to cancer clinical trial accrual can be prospectively identified and addressed in the development and conduct of future studies, which may potentially lead to more robust clinical trials enrollment. Investigation of patient perceptions regarding the clinical trials process and the role of third party-payers is warranted.

Venous Thromboembolism in Patients With Colorectal Cancer: Incidence and Effect on Survival

PURPOSE To describe the incidence and outcomes associated with venous thromboembolism (VTE) among patients with colorectal cancer. METHODS This was a retrospective analysis of all colorectal cancer patients diagnosed in California between 1993 and 1995 and 1997 to 1999. Principal outcomes were incident symptomatic VTE events and death. Associations between specific risk factors and principal outcomes were analyzed using Cox proportional hazards models. RESULTS Among 68,142 colorectal cancer patients, 50% were women, mean age was 70 +/- 15 years, and approximately 70% underwent a major operation. The 2-year cumulative incidence of VTE was 2,100 patients (3.1%), with an incidence rate that decreased significantly over time from 5.0% (events/100 patient-years) in months 0 to 6 to 1.4% during months 7 to 12 to 0.6% during the second year. Significant predictors of VTE included metastatic stage (hazard ratio [HR] = 3.2; 95% CI, 2.8 to 3.8) and three or more comorbid conditions (HR = 2.0; 95% CI, 1.7 to 2.3). The risk of VTE was significantly reduced among Asians/Pacific Islanders (HR = 0.4; 95% CI, 0.3 to 0.5.) and patients who underwent an abdominal operation (HR = 0.4; 95% CI, 0.3 to 0.4). In risk-adjusted models, VTE was a significant predictor of death within 1 year of cancer diagnosis among patients with local- (HR = 1.8; 95% CI, 1.4 to 2.3) or regional-stage disease (HR = 1.5; 95% CI, 1.3 to 1.8) but not among patients with metastatic disease (HR = 1.1; 95% CI, 1.0 to 1.2). CONCLUSION The incidence of VTE among colorectal cancer patients was highest in the first 6 months after diagnosis and decreased rapidly thereafter. Metastatic disease and the number of medical comorbidities were the strongest predictors of VTE. Incident VTE reduced survival among patients with local or regional disease, suggesting that, in these patients, VTE may reflect the presence of a biologically more aggressive cancer.

The effects of flavanol-rich cocoa and aspirin on ex vivo platelet function

BACKGROUND Flavanols modulate platelet function in vitro, but less is known of their in vivo effects and how they compare to pharmacological platelet inhibitors. We investigated the effect of a flavanol-rich cocoa beverage (897 mg/ml) in combination with and in comparison to aspirin on platelet function and activation in healthy subjects. METHODS AND RESULTS On separate test days in a crossover design, 16 healthy adults consumed aspirin (81 mg), cocoa (as a beverage), or aspirin plus cocoa. Platelet activation was measured by surface expression of P-selectin and PAC-1 binding to the activated conformation of the GPIIb/IIIa receptor (GPIIb/IIIa-act). Platelet function was measured on an analyzer (the PFA-100) that measures shear stress-induced platelet plug formation in response to collagen-epinephrine or collagen-ADP. Plasma epicatechin concentrations peaked approximately 2 h after subjects were given either the cocoa or aspirin plus cocoa. After 6 h, cocoa inhibited epinephrine-induced platelet function. Epinephrine-induced platelet function was inhibited 2 and 6 h after aspirin, and after aspirin plus cocoa. Epinephrine-stimulated P-selectin expression was inhibited by aspirin at 6 h, and after 2 and 6 h by aspirin plus cocoa. ADP-stimulated P-selectin expression was not affected by the treatments. Cocoa and aspirin, given separately, reduced epinephrine-stimulated GPIIb/IIIa-act expression at 2 and 6 h, respectively, and at 2 and 6 h when given together, suggesting an additive effective. ASA plus cocoa inhibited ADP-stimulated GPIIb/IIIa-act expression at 6 h. CONCLUSIONS Flavanol-rich cocoa inhibited epinephrine-stimulated platelet activation and function. These effects were qualitatively similar to aspirin, but less profound. These results emphasize the need to further examine the effects of food flavonoids for platelet modulating effects.

Cocoa and Wine Polyphenols Modulate Platelet Activation and Function

There is speculation that dietary polyphenols can provide cardioprotective effects due to direct antioxidant or antithrombotic mechanisms. We report in vitro and postingestion ex vivo effects of cocoa procyanidins, a procyanidin-rich cocoa beverage and dealcoholized red wine (DRW) on human platelet activation. In a series of in vitro studies, cocoa procyanidin trimers, pentamers or DRW (3 and 10 micromol/L) were incubated with citrated peripheral whole blood in the presence and absence of platelet agonists. Platelet activation was detected using fluorescent-labeled monoclonal antibodies recognizing the fibrinogen binding conformation of GPIIb-IIIa (referred to herein as PAC-1 binding) and the activation-dependent platelet epitope CD62P (P-selectin). The percentage of CD42a-positive platelets coexpressing PAC-1 binding and/or CD62P was determined by multiparameter flow cytometry. Procyanidin trimers, pentamers and DRW added to whole blood in vitro increased PAC-1 binding and P-selectin expression. In contrast, procyanidin trimers, pentamers and DRW inhibited the platelet activation in response to epinephrine. The effects on platelet activation of cocoa beverage and DRW consumption were also studied in healthy subjects. Citrated blood was obtained before and 2 and 6 h after the ingestion of a cocoa beverage, a caffeine-containing beverage, DRW or water. Platelet activation was measured by flow cytometry. The consumption of DRW did not affect the expression of activation-dependent platelet antigens, either unstimulated or after ex vivo activation with epinephrine. However, the consumption of DRW increased PAC-1 binding in response to 100 micromol/L ADP ex vivo. Cocoa consumption reduced platelet response to agonists ex vivo. The ingestion of water had no effect on platelet activation, whereas a caffeine-containing beverage augmented the response of platelets to epinephrine. In summary, select cocoa procyanidins and DRW added to whole blood in vitro increased expression of platelet activation markers in unstimulated platelets but suppressed the platelet activation response to epinephrine. In contrast, cocoa consumption suppressed unstimulated and stimulated platelet activation in whole blood. This suppressive effect observed on platelet reactivity may explain in part the reported cardioprotective effects of dietary polyphenols.

Platelet activation and platelet-erythrocyte aggregates in patients with sickle cell anemia

Vascular occlusion and vasculopathy underlie much of the morbidity in patients with sickle cell anemia. Platelets may play a role in this vasculopathy. Samples from 12 adults patients with sickle cell anemia were examined for evidence of platelet activation and formation of platelet-erythrocyte aggregates (PEA) using fluorescent-labeled monoclonal antibodies and flow cytometry. We noted an increased expression of activation-dependent antigens on the platelets from patients with sickle cell anemia compared with those from both white and black control subjects. In addition, patients with sickle cell anemia had increased levels of platelet microparticles and PEA. Platelets are activated in patients with sickle cell anemia and they adhere to sickle erythrocytes. The significance of this activation and adherence are the subject of further investigation.

Platelet activation in patients with sickle cell disease

Vascular occlusion and vasculopathy underlie much of the morbidity in patients with sickle cell anaemia. Platelets may play a role in this vasculopathy. Samples from 43 patients with sickle cell disease (SCD) were examined for evidence of platelet activation using fluorescent‐labelled monoclonal antibodies and flow cytometry. There was increased expression of activation‐dependent antigens on the platelets from patients with SCD compared to those from both Caucasian and African‐American controls. In addition, SCD patients had increased levels of platelet microparticles. Platelets are activated in patients with sickle cell disease. The contribution of platelet activation to sickle cell pathophysiology is under active investigation in our laboratories.

Evaluation of Factors Affecting Awareness of and Willingness to Participate in Cancer Clinical Trials

PURPOSE Annually, only 3% of patients participate in cancer clinical trials (CCTs). Barriers to accrual include lack of CCT awareness and uncertain third-party payer coverage. In January 2002, a California law (Senate Bill 37 [SB37]) required all third-party payers to reimburse patient care costs related to CCTs. We evaluated the level of awareness of patients and/or their family members/friends regarding CCTs and SB37. METHODS We used both a written survey for patients and/or their family members and friends seen in oncology clinics, and a verbal telephone version for Cancer Information Service callers. We tested for correlations between CCT awareness and SB37 knowledge, and willingness to participate in CCTs. RESULTS Of 1,188 respondents, 59% were aware of CCTs, 19% knew of SB37, and 36% were very likely to consider a CCT. There were significant positive correlations between CCT awareness and willingness to participate (P < .001, Spearman), and between SB37 knowledge and willingness to participate (P = .001, Pearson chi2). Reduced awareness was seen in respondents who were either black or African American (odds ratio [OR], 0.44; P = .004), Hispanic (OR, 0.56; P = .03), had an annual income less than 25,000 dollars (OR, 0.38; P < .001), or had less than a college degree (OR, 0.12 to 0.53; P < .001 to .013). Reduced willingness to participate in CCTs was seen in black or African American participants (OR, 0.38; P < .001), Asians (OR, 0.44; P < .006), or respondents aged 18 to 24 years (OR, 0.35; P = .002). CONCLUSION These results support the hypothesis that improving CCT awareness and SB37 knowledge especially among lower income, less educated, and minority patients, may potentially overcome barriers to participation and subsequently increase accrual in California.

Venous Thromboembolism (VTE) in Patients with Cancer: Epidemiology and Risk Factors

Although cancer is recognized as a major risk factor for venous thromboembolism, the exact magnitude of the problem and specific risk factors most strongly associated with the development of VTE is not well defined. Several recent studies have shown that the incidence of VTE is highest in patients who present with metastatic cancer, particularly cancers associated with a high one-year mortality rate, such as pancreatic cancer. The incidence rate of VTE is highest in the first few months after the diagnosis of cancer, and it decreases over time thereafter. For most cancers, it is not clear to what extent undergoing major surgery adds to the already high risk of VTE associated with the presence of the cancer. However, patients with glioma clearly have a very high incidence of VTE soon after they undergo any invasive neurosurgical procedure. Active chemotherapy, the use of erythropoetin agents, and the use of certain anti-cancer therapies such as thalidomide, high-dose steroids, and anti-angiogenic therapy also increase the risk of thrombosis. Similar to patients without cancer, the risk of VTE is higher in patients with coexisting chronic medical illnesses. Development of VTE is clearly associated with decreased survival and this effect is greater among patients initially diagnosed with local or regional stage cancer compared to patients with metastatic cancer.

Venous thromboembolism in patients with acute leukemia: incidence, risk factors, and effect on survival

A population-based cohort was used to determine the incidence and risk factors associated with development of venous thromboembolism (VTE) among Californians diagnosed with acute leukemia between 1993 to 1999. Principal outcomes were deep vein thrombosis in both the lower and upper extremities, pulmonary embolism, and mortality. Among 5394 cases with acute myelogenous leukemia (AML), the 2-year cumulative incidence of VTE was 281 (5.2%). Sixty-four percent of the VTE events occurred within 3 months of AML diagnosis. In AML patients, female sex, older age, number of chronic comorbidities, and presence of a catheter were significant predictors of development of VTE within 1 year. A diagnosis of VTE was not associated with reduced survival in AML patients. Among 2482 cases with acute lymphoblastic leukemia (ALL), the 2-year incidence of VTE in ALL was 4.5%. Risk factors for VTE were presence of a central venous catheter, older age, and number of chronic comorbidities. In the patients with ALL, development of VTE was associated with a 40% increase in the risk of dying within 1 year. The incidence of VTE in acute leukemia is appreciable, and is comparable with the incidence in many solid tumors.

Splenectomy and the incidence of venous thromboembolism and sepsis in patients with immune thrombocytopenia.

Patients with immune thrombocytopenia (ITP) who relapse after an initial trial of corticosteroid treatment present a therapeutic challenge. Current guidelines recommend consideration of splenectomy, despite the known risks associated with surgery and the postsplenectomy state. To better define these risks, we identified a cohort of 9976 patients with ITP, 1762 of whom underwent splenectomy. The cumulative incidence of abdominal venous thromboembolism (AbVTE) was 1.6% compared with 1% in patients who did not undergo splenectomy; venous thromboembolism (VTE) (deep venous thrombosis and pulmonary embolus) after splenectomy was 4.3% compared with 1.7% in patients who did not undergo splenectomy. There was increased risk of AbVTE early (<90 days; hazard ratio [HR] 5.4 [confidence interval (CI), 2.3-12.5]), but not late (≥90 days; HR 1.5 [CI, 0.9-2.6]) after splenectomy. There was increased risk of VTE both early (HR 5.2 [CI, 3.2-8.5]) and late (HR 2.7 [CI, 1.9-3.8]) after splenectomy. The cumulative incidence of sepsis was 11.1% among the ITP patients who underwent splenectomy and 10.1% among the patients who did not. Splenectomy was associated with a higher adjusted risk of sepsis, both early (HR 3.3 [CI, 2.4-4.6]) and late (HR 1.6 or 3.1, depending on comorbidities). We conclude that ITP patients post splenectomy are at increased risk for AbVTE, VTE, and sepsis.