Abstract P1-09-19: Demographic trends in clinical trial withdrawal rate within the bubble study
Authors: EC Riley, D Jain, B Kantardzic, X Wu, SN Rai
Journal: Cancer Research (2013)

Abstract Introduction: There are well described barriers to clinical trial enrollment and participation among varied racial, ethnic and demographic groups. Little is known about clinical trial drop-out rate among these groups. The purpose of this study is to analyze the demographic and clinical characteristics of patients who originally signed consent and enrolled in the Bubble Study but then withdrew at a later date. The Bubble Study is a non- blinded, prospective observational cohort study designed to assess the adherence rate of adjuvant endocrine therapy among women with early stage breast cancer. Materials and Methods: From August 2012 to May of 2013, 75 women were enrolled into the Bubble Study. Demographic data (age, race and insurance status) and treatment factors (stage, surgery type, and therapy duration) were collected. Descriptive statistics (such as mean, median, standard deviation, minimum and maximum for continuous measures and frequency and percentage for discrete measures) were produced for the entire cohort and the subjects of cohort. Frequencies were compared using a Chi-square test (Fisher's exact test when expected cell frequencies are small). Continuous measures were compared using a two-sample t test or Wilcoxon rank sum test for normally or non-normally outcome measures, respectively (Matthews and Farewell, 2007). In addition, linear and logistic regression analyses were used to explore association with different factors. Results were declared significant at significance level of 5% and all analyses are performed using SAS (2003, 2005). Results: At the time of analysis, 75 patients enrolled into the Bubble Study. Table 1 summarizes the demographic, social economic, therapeutic factors such as race, age, stage, surgery type, insurance and therapy durations and their relevant frequency and percentage are presented. The p-values are shown based on the chi square test. Blacks represented 28% of the total enrollment. Private insurance represented the majority (61.3%) of those enrolled and Medicare, Medicaid and Uninsured followed in that order (24.3%, 13% and 1.3% respectively.) In regards to race and insurance status, there was no significant difference between the enrolled group and the withdrawal group although there was a trend toward Blacks and Medicare with higher rate of withdrawal. Stage, surgery type or age did not predict for withdrawal. The most common reasons reported for withdrawal were financial and/or insurance reasons (22%), inconvenience of pharmacy pick up (13%) and preference for the prior system (9%). Table 1 Patient CharacteristicsVariableTotalEnrolled GroupWithdrawal Groupp valueRace 0.11Black21129 White544113 Stage 0.5301082 I352510 II19154 III1156 Surgery Type 0.58BCS392910 mastectomy353411 Insurance 0.16Private463511 Medicare1899 Medicaid1082 Uninsured110 Therapy Duration 0.57less than 1 year312011 1-3 years34268 3-5 years1073 Conclusions: Demographic characteristics that traditionally predict for underrepresentation in clinical trial enrollment did not predict for withdrawal from the Bubble Study. Although small, this data set suggests disparities in clinical trial participation are largely due to enrollment rather than withdrawal. Larger analysis is needed to confirm these findings. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-09-19.