ISTANBUL, Turkey—Patients with locally advanced prostate cancer treated with radiotherapy and adjuvant hormonal therapy gain as much as 12% longer progression-free survival (PFS), compared with those given radiotherapy alone, according to a large study of pooled data reported at the 31st Congress of the European Society for Medical Oncology (ESMO) (abstract 2 O).
Paolo Carlini, MD, of the Regina Elena Cancer Institute, Rome, Italy, presented the results of a pooled analysis of 4,373 patients enrolled in seven randomized phase III clinical trials of patients with locally advanced disease designed to determine if hormonal treatment plus radiotherapy decreases recurrence rate over radiotherapy alone. The researchers also gathered data on overall survival and cancer- specific overall survival.
Two Statistical Models
To measure the impact of adding hormonal therapy, the investigators used two different statistical models—the fixedeffect and random-effect models (FEM and REM). FEM assumes that the trials all have a similar true effect, while REM assumes that the true effect varies among trials around an unknown mean.
The study showed an absolute benefit in progression-free survival, overall survival, and cancer-specific overall survival of 10.5%, 6.2%, and 3.3%, respectively, with the addition of hormonal therapy. The number of patients needed to treat for one to benefit was 9, 16, and 30, respectively. The researchers also found that long-term hormonal therapy had a greater impact on progression-free survival than short-term treatment, with an overall benefit of 12% for long-term therapy vs 9.3% for short-term therapy.
The combination treatment significantly decreased recurrence rates under both the statistical models. The relative risk (RR) under FEM was 0.74 (P < .0001) and under REM, 0.69 (P < .0001). Similarly, overall survival was longer under both models, with a relative risk of 0.84 under FEM (P < .001) and 0.81 under REM (P = .003). Cancer-specific overall survival was also significantly better for hormonal therapy using FEM (RR 0.74, P = .001) and REM (RR 0.64, P = .023).
At a press briefing, study author Emilio Bria, MD, of the Regina Elena Cancer Institute, speculated that several factors may have contributed to the benefits seen with hormonal therapy. “The increased efficacy of radiotherapy in the presence of hormone therapy may be due to radiosensitization, to the reduction of local tumor burden, or perhaps to the killing of occult disseminated cells outside the irradiated volume,” he said.