The shift to long-acting GnRH depot formulations in Japan was associated with a reduction in injections of about one in five and an estimated reduction in drug cost of 7.7 billion JPY per year, even as the number of patients increased.
Key Findings
Methods
A total of 2,276,025 patient-years of GnRH therapy for prostate cancer were analyzed from Japan's National Database Open Data from FY2017 to FY2024.
The study covered fiscal years 2017 through 2024.
Men aged 40 years or older were included.
Drugs analyzed were leuprorelin, goserelin, and degarelix.
Patient-years were estimated by weighting dispensed quantity by the period each formulation covers.
Descriptive statistics were based on all products; administration and cost analyses were restricted to originator products.
Results
The number of patients receiving GnRH therapy increased by 12.9% over the study period, rising from 269,328 to 304,181 patient-years.
For originator products specifically, the increase was 10.0% in patient-years.
This patient growth occurred alongside a decrease in total injections.
The increase in patient numbers was identified as a factor counteracting injection reductions from formulation shifts.
Results
Despite the increase in patient numbers, total injections decreased by 21.5%, from 1,275,081 to 1,000,324.
Injections per patient per year fell from 4.97 to 3.55.
This represents a reduction of approximately one in five injections overall.
The analysis of injections was restricted to originator products.
Results
The shift to long-acting formulations was identified as the main factor driving the decrease in total injections, accounting for −383,932 injections.
Shapley value decomposition was used to attribute changes in injection counts and drug costs to specific factors.
The formulation shift factor (−383,932 injections) was the dominant contributor to the overall reduction.
The increase in patient numbers partially offset the injection reduction achieved by the formulation shift.
Results
A clear shift toward long-acting GnRH formulations occurred over the study period, with the 6-month leuprorelin formulation surpassing the 3-month formulation in FY2021.
The 6-month leuprorelin formulation exceeded the 3-month formulation in usage by FY2021.
The 6-month formulation was used more often in older patients.
The overall share of each drug (leuprorelin, goserelin, degarelix) did not change greatly, but a clear shift to long-acting formulations within drugs was observed.
Results
The shift to long-acting GnRH formulations was estimated to reduce drug costs by 7.7 billion JPY per year.
Shapley value decomposition was used to attribute cost changes to the formulation shift factor.
The drug cost reduction attributable to the formulation shift was 7.7 billion JPY per year.
Long-acting formulations thus contributed to both fewer injections and lower drug expenditure simultaneously.
Conclusions
Because the oncological effect is considered similar among GnRH drugs, the authors conclude that a further shift to long-acting formulations may lower the burden on patients and on health care.
The paper notes that oncological equivalence among GnRH drugs supports preferring formulations with practical advantages.
Patient burden reduction is framed in terms of fewer clinic visits and injections.
Health care system savings are framed in terms of reduced drug costs and resource use.
What This Means
This research suggests that a major shift toward longer-lasting injectable forms of hormone therapy for prostate cancer in Japan led to significantly fewer injections for patients and lower drug costs for the health care system. Using a nationwide database covering over 2.3 million patient-years between 2017 and 2024, researchers tracked how often men received gonadotropin-releasing hormone (GnRH) drugs — the standard hormone treatment for prostate cancer — and which formulations they received. Over this period, longer-acting versions (particularly the 6-month leuprorelin injection, which overtook the 3-month version by 2021) became increasingly common, especially among older patients.
Even though the total number of patients on these therapies grew by about 13%, the total number of injections given actually fell by more than 21% — dropping from roughly 1.28 million to 1 million injections per year. The average number of injections per patient per year fell from about 5 to about 3.5. Statistical analysis attributed the bulk of this reduction directly to the switch to longer-acting formulations. Additionally, this formulation shift was estimated to save approximately 7.7 billion Japanese yen per year in drug costs, even as more patients were being treated.
This research suggests that transitioning patients to longer-acting depot formulations of GnRH therapy — which work similarly in terms of cancer control — can meaningfully reduce how often patients need to visit a clinic for injections and can generate substantial savings for health care systems. The findings highlight that policy or clinical decisions favoring longer-acting equivalents, where medically appropriate, could benefit both patients (through reduced treatment burden) and health systems (through cost savings), without apparent trade-offs in oncological outcomes.
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T. Kawahara, Akihito Hashizume, Masanobu Yamazaki, D. Takamoto, T. Takeshima, H. Uemura, et al.. (2026). Fewer Injections and Lower Drug Costs With Long‐Acting GnRH Depot Formulations: A Nationwide Analysis of 2.3 Million Patient‐Years in Japan. Cancer Reports. https://doi.org/10.1002/cnr2.70688