Drug Use Evaluation of Letrozole in Breast Cancer Patients at Regional Cancer Hospitals in Thailand

Background: Medication policy development in Thailand is continually promoting rational drug use. Letrozole,an endocrine therapy drug, is usually prescribed for post-menopausal status early and advanced stage breastcancer. After Ministry of Public Health announced Letrozole as compulsory licensed drug in 2009, more breastcancer patients can access to this drug at low cost especially those within universal coverage schemes. To ensurethat Letrozole is rationally prescribed, the drug utilization study was conducted.
Objectives: The aim of thisstudy was to describe the appropriate use of Letrozole in breast cancer and the relationship between appropriateuse and health benefit schemes. Materials and
Methods: A retrospective study to evaluate use of Letrozole inbreast cancer patients was performed for six months between January - June 2010 in seven regional cancerhospitals, Thailand. All prescriptions of Letrozole were identified from pharmacy dispensing databases andprescription papers. A medical record review was also performed to evaluate appropriate use referring to thedrug use evaluation criteria. The approved criterion of this study was referred from the guideline of Thai NationalFormulary version 2010.
Results: There were 681 prescriptions of Letrozole for 254 breast cancer patients withan average age of 58.6 ± 10.0 years. The patients in universal coverage scheme (UCS), civil servant medicationbenefit scheme (CSMBS) and social security scheme (SSS) were 77.7%, 18.5% and 8.7% respectively. 10.6% wereprescribed Letrozole for the first time. Letrozole were prescribed by oncologists (82.8%). The average numberof tablets per prescription was 58 ± 10. Calcium supplements were prescribed concomitant with Letrozole for19.4%. To assess drug use evaluation criteria, 45 prescriptions were excluded because of uncompleted clinical data,636 prescriptions were evaluated. The study showed 86 prescriptions (13.5%) with inappropriate use including6 (0.9%) not prescribed for estrogen receptor (ER) and/or progesterone receptor (PR) positive, 31 (4.9%) notprescribed for post-menopausal and 49 (7.7%) not prescribed for an appropriate duration. Appropriate usepercentages in different health benefit schemes were similar, 85.7% of CSMBS, 86.4% of SSS and 86.7% ofUCS. The relationship between health benefit scheme and appropriate use of Letrozole was not significantlydifferent, χ2 (2, N = 636) = 0.081, p > 0.05.
Conclusions: The study showed inappropriate use in breast cancerpatients because of non-compliance with duration, menopausal status and hormone receptor requirements. Toprescribe appropriate indication did not referred to the appropriate practice along the treatment. Drug useevaluation proved very useful for detecting the sign of inappropriate use and allows immediate feedback to thestakeholder for developing medication policy in the future. Importantly, there was no significantly difference inappropriate use of Letrozole across health benefit schemes.