Effects of immune-enhancing nutrition on radical cystectomy outcomes: Primary results from the randomized phase III double-blind clinical trial (S1600).

4501 Background: SWOG S1600 was a randomized, double-blind, phase III trial comparing the impact of consuming Specialized IMmunonutrition (SIM) to oral nutritional support (ONS) on postoperative complications following radical cystectomy (RC). SIM is fortified with nutrients: L-arginine; omega-3 fatty acids; and dietary nucleotides. Methods: Patients with bladder carcinoma planning to undergo RC were enrolled and randomized 1:1 to SIM vs. ONS. The primary endpoint was any (≥Grade I) postoperative complication assessed by the Clavien-Dindo (CD) scale at Day 30 after RC. Multivariable logistic regression was used, adjusted for the stratification factors: diversion type (neobladder vs. ileal conduit), prior neoadjuvant chemotherapy (any vs. none), and baseline nutrition status (well-nourished vs. moderate malnutrition). Additional outcomes included 90-day complications and high-grade (CD ≥Grade III) complications. Two-year progression-free survival (PFS) and overall survival (OS) were assessed; differences by arm were reported using Log-rank test statistics. Protocol-specified intention-to-treat (ITT) analyses based on all randomized patients and 1-sided alpha=.05 tests were performed. Results: Among N=203 enrolled patients (99 on SIM, 104 on ONS), median age was 68.8 years, 20% were female and 5% were Black. Five patients did not meet eligibility criteria (1 on SIM, 4 on ONS) but were included under the ITT design. Seventeen patients withdrew consent prior to their Day 30 assessment, and 8 patients were not assessed; thus, n=178 (90 on SIM, 88 on ONS) were evaluable at Day 30. The proportion of patients experiencing CD Grade ≥1 complications was 62.2% for SIM and 58.0% for ONS; in multivariable regression, there was no difference in Grade ≥1 complications by arm (OR=1.18, 95% CI, 0.64-2.18, 1-sided p=.71). There were no differences by arm in high-grade complications at Day 30, in any or high-grade complications at Day 90 or overall. To date, among all 203 patients, 17 on SIM and 26 on ONS have progressed or died, with 2-year PFS estimates of 77.2% and 68.3%, respectively (1-sided p=.16). Nine patients on SIM and 17 on ONS have died, with 2-year OS estimates of 87.4% and 78.2%, respectively (1-sided p=.07). Conclusions: There was no difference in any grade CD complications by type of nutritional supplement for patients with bladder cancer undergoing RC. Fewer patients on the SIM arm have progressed or died, although differences were not statistically significant; follow-up for survival will continue through 3-years after enrollment. Future work to understand the interaction of diet on cancers sensitive to immune modulation is needed. Clinical trial information: NCT03757949 .