SUMMARY: Prostate cancer is the most common cancer in American men with the exclusion of skin cancer, and 1 in 8 men will be diagnosed with prostate cancer during their lifetime. It is estimated that in the United States, about 299,010 new cases of prostate cancer will be diagnosed in 2024 and 35,250 men will die of the disease.
The development and progression of prostate cancer is driven by androgens. Androgen Deprivation Therapy (ADT) or testosterone suppression has therefore been the cornerstone of treatment of advanced prostate cancer, and is the first treatment intervention. Treatment options for patients with intermediate and high risk prostate cancer include Radical Prostatectomy and External Beam Radiation Therapy. Three Phase III randomized studies have previously assessed the addition of Androgen Deprivation Therapy (ADT) to postoperative radiotherapy after Radical Prostatectomy, but none of these studies compared different durations of ADT and the optimal duration of Androgen Deprivation Therapy has remained unclear.
RADICALS was a multicenter, international, open-label, randomized, controlled, Phase III trial in prostate cancer.
This study addressed two important questions:
1) Which is the best way to use radiotherapy after surgery?
2) Which is the best way to use hormone treatment with any radiotherapy given after surgery?
The full background and other details related to the RADICALS trial is published elsewhere.
RADICALS-HD is a component of the RADICALS trial and the researchers hypothesized that long-course ADT would be more effective than short-course ADT in patients receiving postoperative radiotherapy. They therefore designed a prospective, international, randomized controlled trial to compare long-course versus short-course use of ADT in this setting. In the RADICALS-HD trial, 1523 patients were randomly assigned 1:1 to receive short-course ADT (N=761) or long-course ADT (N=762) in addition to postoperative radiotherapy at 138 centers in Canada, Denmark, Ireland, and the UK. Radiotherapy was started approximately 2 months after the start of hormone treatment, and patients received either 52.5 Gy in 20 fractions over 4 weeks or 66.0 Gy in 33 fractions over 6.5 weeks. Radiotherapy was given in the adjuvant setting for 43% of patients, and in the early salvage setting for 57% patients. Androgen Deprivation Therapy (ADT) consisted of Gonadotropin Releasing-Hormone analog given subcutaneously monthly for 6 months in the short-course ADT group and every 3 months for 24 months in the long-course ADT group. Outside Canada, Bicalutamide monotherapy 150 mg daily or monthly subcutaneous Degarelix were acceptable alternatives. Randomization was stratified by Gleason score, positive margins, radiotherapy timing, planned radiotherapy schedule, and planned type of ADT. The two treatment groups were well balanced. The median age was 65 years, 93% of patients had Gleason score of 7 or higher and 30% had Stage T3b disease or higher. The Primary outcome measure was Metastasis-Free Survival, defined as metastasis arising from prostate cancer or death from any cause.
With a median follow-up of 8.9 years, the long-course ADT for 24 months resulted in a superior Metastasis-Free Survival compared to short-course ADT for 6 months. The 10-year Metastasis-Free Survival was 78.1% in the long-course ADT group compared to 71.9% in the short-course ADT group (HR=0.77; P=0.029). This finding was consistent across all prespecified subgroups, including baseline PSA. Grade 3 or higher toxicity was reported in 19% of patients in the long-course ADT group, and in 14% of patients receiving short-course ADT (P=0.025).
It was concluded that compared to adding 6 months of ADT, adding 24 months of ADT to patients receiving postoperative radiotherapy after radical prostatectomy for prostate cancer, significantly improved Metastasis-Free Survival. Long-course ADT should therefore be offered in addition to postoperative radiotherapy to individuals who are willing to accept the additional duration of adverse effects. The researchers added that this is the first trial to compare different durations of ADT with postoperative radiotherapy after Radical Prostatectomy in prostate cancer.
Duration of androgen deprivation therapy with postoperative radiotherapy for prostate cancer: a comparison of long-course versus short-course androgen deprivation therapy in the RADICALS-HD randomised trial. Parker CC, Kynaston H, Cook AD, et al. The Lancet. 2024;403:2416-2425
