Clinical Impact of Intensified 5-Fluorouracil-Based Chemotherapy Using a Prospective Pharmacokinetically-Guided Dosing Approach: Comparative Study in Elderly and Non-Elderly Patients with Metastatic Colorectal Cancer

We compared clinical outcome and pharmacokinetic (PK) parameters of a new pharmacokinetically-guided dosing strategy in two groups of patients (age < or >= 65 years) with metastatic colorectal cancer (mCRC). We retrospectively analyzed all the patients with mCRC, receiving standard LV5FU2 regimen during cycle-1, intensified from cycle-2 onwards according to an adaptation schedule based on the area under the concentration-time curve (AUC) value (mg.h/l.m(2)) of 5-FU measured during cycle-1. Among the 103 eligible patients, the 48 elderly (median age 70 range 65-80) did not differ significantly from the 55 non-elderly patients (median age 59 range 33-64) in PK parameters (including AUC at cycle-1 and cycle-2), efficacy (objective response rate of 27% [16.1-40.9] in younger and 35% [22.2-50.5] in older patients, p = 0.4) and tolerability (33.3% of overall grade 3-4 toxicities in older patients and 34.5% in younger, p = 0.9). Our data indicated high dose-intensity values, not significantly different between elderly and non-elderly patients. It was feasible to increase the 5-FU continuous infusion dose in 43/55 (78%) younger and 40/48 (83%) older patients (p=0.509) and even to double it in half of the patients of both groups. Aging did not seem to limit intensified chemotherapy or to affect the PK behavior of the 5-FU.