Results of Long-Term Follow-Up of Patients with Prostate Adenocarcinoma After Radiotherapy with Short-Term Androgen Deprivation
Adding short-term androgen deprivation to radiotherapy improved overall survival, disease-specific mortality, and the incidence of distant metastases in men diagnosed with prostate adenocarcinoma. Subsequent analysis investigated whether the beneficial effect of androgen deprivation is long-lasting.
Analyzed Patient Population
Data from patients enrolled in the original RTOG-9408 study, conducted between 1994 and 2001, were used for the analysis. Patients had a confirmed diagnosis of prostate adenocarcinoma in stages T1b-T2b N0 and a prostate-specific antigen (PSA) value ≤ 20 µg/l. Stratification was based on PSA values, tumor differentiation (grade), and surgical vs. clinical lymph node staging for radiotherapy alone or in combination with androgen deprivation therapy (ADT). ADT consisted of flutamide and goserelin or leuprorelin for 4 months.
Findings
The median long-term follow-up for all patients was 10.4 years (range 0.11-21.98) and for surviving patients was 14.8 years (range 0.16-21.98).
In the radiotherapy group, 10-year and 18-year overall survival (OS) was 56% and 23%, respectively, compared to 63% and 23% in the combination therapy group (hazard ratio [HR] 0.94; 95% confidence interval [CI] 0.85-1.05; p = 0.94). However, since the risk was not proportionally distributed over the observation period (p = 0.003), the survival analysis estimated the so-called restricted mean survival time (RMST). The RMST after 18 years was 11.8 years (95% CI 11.41-12.10) for combined therapy and 11.3 years (95% CI 10.90-11.62) for radiotherapy (p = 0.052). Thus, the difference between treatment arms was 6 months in favor of combining short-term ADT with radiotherapy.
Disease-specific mortality after 10 and 18 years was 7% and 14% in the radiotherapy-only population, 3% and 8% in the combination therapy population (HR 0.56; 95% CI 0.41-0.75; p < 0.001). The cumulative incidence of distant metastases reached 8% and 13% after 10 and 18 years in the radiotherapy group, 5% and 9% in the combination therapy group (HR 0.67; 95% CI 0.49-0.92; p = 0.012).
The rate of occurrence of late grade ≥ 3 liver, gastrointestinal, and genitourinary toxicity was ≤ 1%, 3%, and 8% in the combination therapy group and ≤ 1%, 2%, and 5% in the radiotherapy-only group.
Conclusion
Long-term follow-up of patients showed that overall survival converges after approximately 15 years. However, the addition of 4 months of ADT to radiotherapy provided patients treated in this way with an additional 6 months of life.
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Source: Jones C. U., Pugh S. L., Sandler H. M. et al. Adding short-term androgen deprivation therapy to radiation therapy in men with localized prostate cancer: long-term update of the NRG/RTOG 9408 randomized clinical trial. Int J Radiat Oncol Biol Phys 2022; 112 (2): 294-303, doi: 10.1016/j.ijrobp.2021.08.031.
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