Participation of older adults (aged ≥65 years) in SWOG cancer clinical trials.

1543 Background: Cancer disproportionately affects older adults. Approximately 60% of cancer diagnoses occur in adults aged 65 and older in the United States. However, disparities persist in participation of older adults in cancer clinical trials. Methods: Using 38 years of data from phase III trials of the SWOG Cancer Research Network between 1985 to 2022, this study examined clinical, socio-demographic, and trial factors associated with participation of older adults (≥65 Years) in cancer clinical trials. Summary statistics were used to describe patient and trial characteristics. To examine factors associated with enrollment of older adults, mixed-effects multivariate logistic regression was performed with the odds of being an older adult (≥65 years) as the dependent variable. Results: A total of 45,670 patients accrued to 64 SWOG phase III trials were included in the analysis. Across all trials, 30.6% participants were aged 65 and older, and 57.8% were female. Participants were predominantly non-Hispanic (96.2%) White (87.4%) and most resided in urban areas (82.4%). Regression analysis results showed that adjusted odds of enrollment as an older adult did not differ statistically significantly by cancer stage or intervention type (targeted therapy, immunotherapy, hormonal therapy, chemotherapy, radiation, or surgery). Compared with breast cancer trials (reference group with the lowest proportion of older adult enrollment), the odds of enrolled participants being older adults were higher in gastrointestinal cancer trials (OR=3.39), lung/thoracic cancer trials (OR=3.24), and genitourinary/prostate cancer trials (OR=6.77). Compared with White participants, Black participants (OR=0.64) and Asian/Pacific Islander (OR=0.64) had lower adjusted odds of being older adults. The odds of being aged ≥65 years were nearly twice as high among non-Hispanic participants compared with Hispanic participants (OR=1.85). Participants from rural areas had higher adjusted odds of being aged ≥65 years than those from urban areas (OR=1.10). No statistically significant differences were observed across Area Deprivation Index (ADI) quartiles. Conclusions: Although some progress has been made in the participation of older adults in cancer clinical trials in the past decades, more work needs to be done to enhance their participation (especially those belonging to underrepresented groups) in cancer clinical trials. Tailored and targeted recruitment efforts are needed to improve participation of diverse older adults in cancer clinical trials.