OBJECTIVES: COLLECT assesses comorbidities in patients with Chronic Lymphocytic Leukemia (CLL), the secondary objective of the MABERYC study was to validate it. The aim is to assess the clinical utility and the validity of the COLLECT to guide treatment regimen prescribed to CLL patients. METHODS: MABERYC study included patients with CLL, being or not previously treated, initiating treatment with Rituximab+chemotherapy. COLLECT scale was administered at baseline and 12 months following treatment finalization. Treatment response (TR) and safety was also assessed in the last visit. COLLECT categorizes comorbidity in low (0-3), moderate (4-6) and high (≥7). Changes in COLLECT were categorized in improvement (reduction≥2), without changes (variation<2), and worsening (increase≥2). RESULTS: MABERYC included 218 patients, 179 completed COLLECT at baseline. Patients had a mean age of 67.5 years, 73% were male, 53% were naïve, 37% had moderate and 27% high comorbidity. At baseline, 42% of patients initiated treatment with Rituximab-Fludarabine-Ciclofosfamide (RFC), 30% with Rituximab-Bendamustine (RB), 18% with Rituximab-Clorambucile (RC) and 10% other patterns. Mean COLLECT score was higher in older patient, higher ECOG, previously treated (5.2 vs 4.2) and those receiving less aggressive treatments (5.8 RC, 5.4 RB, 3.6 RFC). Changes in COLLECT were analysed in 134 patients. CR could be associated to improvement in comorbidity. Complete remission was reached by 53% of patients with COLLECT improvement, 47% without changes, and 32% with COLLECT worsening. Number of adverse events (AE) treatment related trend to be higher in patient with lower comorbidity (1.6 vs 0.9), using more aggressive treatments. Total number of AEs (related or not related to treatment) trend to be higher in patients with higher comorbidity (7.8 vs 5.8). CONCLUSIONS: COLLECT assess comorbidity which is related with patients’ profile, treatment regiment prescribed, CR and AEs. The COLLECT scale can assist decision-making on the intensity of the chemotherapy regimen to prescribe.