12010 Background: Geriatric assessment (GA) can predict chemotherapy (chemo) toxicity in older adults (age ≥65) with cancer. However, evidence regarding the effect of GA-driven intervention (GAIN) on the incidence of chemo toxicity has been limited. Therefore, we conducted a randomized controlled trial evaluating the impact of GAIN vs. standard of care (SOC) on chemo toxicity in older adults with cancer. Methods: Patients (pts) age ≥65, diagnosed with a solid malignancy, and starting a new chemo regimen at City of Hope were eligible (NCT02517034). In a 2:1 ratio, 600 pts were randomly assigned to either GAIN (n = 398) or SOC (n = 202) arms. All pts completed a baseline GA prior to chemo. In the GAIN arm, a multidisciplinary team led by a geriatric oncologist, nurse practitioner, social worker, physical/occupation therapist, nutritionist, and pharmacist, reviewed GA results and implemented interventions based on predefined triggers built into the GA’s various domains. In the SOC arm, GA results were sent to treating oncologists to use at their discretion. Pts were followed until either end of chemo or 6 months after start of chemo, whichever occurred first. The primary endpoint was incidence of grade 3-5 chemo-related toxicity (NCI CTCAE v.4.0). Secondary endpoints included advance directive (AD) completion, emergency room (ER) visits, hospitalizations, and average length of stay (ALOS). Chi-square and Fisher’s exact tests were used to compare the categorical outcomes, and Kruskal-Wallis test was used to compare the ALOS between arms. Results: Pt characteristics were balanced between arms. Median age was 71 (range 65-91). Cancer types included: 33% gastrointestinal, 23% breast, 16% lung, 15% genitourinary, and 13% other. Most (71%) had stage IV disease. The incidence of grade 3-5 chemo-related toxicity was 50.5% (95% CI: 45.6-55.4%) in the GAIN arm and 60.4% (95% CI: 53.7-67.1%) in the SOC arm (p = 0.02). Compared to SOC, the GAIN arm had a reduction of 9.9% (95% CI: 1.6-18.2%) in chemo-related toxicity. At the end of study, AD completion increased 24.1% in the GAIN arm vs. 10.4% in the SOC arm (p < 0.001). No significant differences in ER visits (27.4% vs. 30.7%), hospitalizations (22.1% vs. 19.3%), or ALOS (median 4.8 vs. 5.0 days) were observed between the GAIN and SOC arms, respectively. Conclusions: Integration of multidisciplinary GA-driven interventions reduced grade 3-5 chemo-related toxicity and improved AD completion in older adults with cancer. GA-driven interventions should be included as a part of cancer care for all older adults. Clinical trial information: NCT02517034 .