For antineoplastic agents, the estimation of the DDD was primarily based on standard dosing or recommended dosing expressed per body weight. Where relevant and clinically appropriate, dosing based on body surface area (BSA) of 1.73 m2 was also taken into account.
Determining a single main indication for DDD assignment can be challenging for antineoplastic agents, particularly for substances authorised for a wide range of indications and associated with multiple dosing regimens. This reflects their highly individualised use and wide dosage ranges, which may vary substantially according to the type and severity of the neoplastic disease, as well as the frequent use of concomitant or combination therapy. In such cases, the indication selected for DDD estimation was the one most closely aligned with the WHO Essential Medicines List (EML). For substances not included in the WHO EML, the selected indication was based on the most prevalent disease or, where available, on utilisation data reflecting predominant clinical use.
For antineoplastic agents, drug consumption is in some countries expressed in grams. This approach has historically been applied for these agents due to the substantial variability in dosing and the resulting limitations of DDD-based measures.