Fewer Injections and Lower Drug Costs With Long-Acting GnRH Depot Formulations: A Nationwide Analysis of 2.3 Million Patient-Years in Japan.

BACKGROUND

Androgen deprivation therapy (ADT) is the base of treatment for prostate cancer, and gonadotropin-releasing hormone (GnRH) drugs are given as depot injections. Long-acting formulations may reduce the number of injections and the drug cost, but this impact has not been quantified in real practice.

METHODS

We used the National Database Open Data of Japan from fiscal year (FY) 2017 to FY2024, and studied leuprorelin, goserelin, and degarelix in men aged 40 years or older. Patient-years were estimated by weighting the dispensed quantity by the period that each formulation covers. Descriptive statistics (patient numbers, drug, and formulation shares) were based on all products, whereas the analyses of the number of administrations and drug cost were restricted to originator products. Shapley value decomposition was used to divide the change in injections and in drug cost into factors.

RESULTS

In total, 2 276 025 patient-years were analyzed. The share of each drug did not change greatly, but a clear shift to long-acting formulations was seen. The 6-month formulation of leuprorelin exceeded the 3-month formulation in FY2021 and was used more often in older patients. The number of patients increased by 12.9% (from 269 328 to 304 181 patient-years; +10.0% for originator products, used for the administration and cost analyses), but injections decreased by 21.5%, from 1 275 081 to 1 000 324. Injections per patient per year decreased from 4.97 to 3.55. The shift to long-acting formulations was the main factor for this decrease (-383 932 injections), and it also reduced the drug cost by 7.7 billion JPY per year.

CONCLUSIONS

The shift to long-acting GnRH formulations was associated with a reduction in injections of about one in five, even though the number of patients increased and was estimated to account for part of the reduction in drug cost. Because the oncological effect is similar among GnRH drugs, a further shift to long-acting formulations may lower the burden on patients and on health care.