Cohort Study of Somatostatin-Based Radiopeptide Therapy With [90Y-DOTA]-TOC Versus [90Y-DOTA]-TOC Plus [177Lu-DOTA]-TOC in Neuroendocrine Cancers

Purpose Radiopeptide therapy is commonly performed with a single radioisotope. We aimed to compare the effectiveness Patients and Methods In a cohort study, patients with metastasized neuroendocrine cancer were treated with repeated cycles of (90)yttrium-labeled tetraazacyclododecane-tetraacetic acid modified Tyr-octreotide ([Y-90-DOTA]-TOC) or with cycles alternating between [Y-90- DOTA]-TOC and (177)lutetium-labeled DOTATOC ([Lu-177- DOTA]-TOC) until tumor progression or permanent toxicity. Multivariable Cox regression and competing risk regression were used to study predictors of survival and renal toxicity in patients completing three or more treatment cycles. Results A total of 486 patients completed three or more treatment cycles; 237 patients received [Y-90-DOTA]-TOC and 249 patients received [Y-90-DOTA]-TOC + [Lu-177-DOTA]-TOC. Patients receiving [Y-90-DOTA]-TOC + [Lu-177-DOTA]-TOC had a significantly longer survival than patients receiving [Y-90-DOTA]-TOC alone (5.51 v 3.96 years; hazard ratio, 0.64; 95% CI, 0.47 to 0.88; P = .006). The rates of severe hematologic toxicities (6.3% v 4.4%; P = .25) and severe renal toxicity (8.9% v 11.2%; P = .47) were comparable in both groups. Conclusion [Y-90-DOTA]-TOC + [Lu-177-DOTA]-TOC was associated with improved overall survival compared with [Y-90-DOTA]-TOC alone in patients completing three or more cycles of treatment. Contrary to the current practice in radiopeptide therapy, our results suggest an advantage of using a combination of radioisotopes.