Combination therapy improves prostate cancer survival for patients with potentially lethal prostate cancer: The impact of Gleason pattern 5.

ABSTRACT

PURPOSE: To investigate the impact of Gleason pattern 5 (GP5) prostate cancer after either external beam radiotherapy (EBRT) or the combination of EBRT with low-dose rate brachytherapy boost (combo). METHODS AND MATERIALS Between 1998 and 2008, 467 patients with National Comprehensive Cancer Network high-risk prostate cancer were treated with EBRT (n = 326) or combo (low-dose rate to 90-108 Gy using I-125 followed by EBRT) (n = 141). Freedom from biochemical failure, freedom from metastasis (FFM), cancer-specific survival (CSS), and overall survival were evaluated. RESULTS: Combo patients were younger (66 vs. 72 years, p < 0.001) and had fewer comorbidities (Charlson comorbidity index 3.7 vs. 4.4, p < 0.001). EBRT patients had higher tumor stages (T3-4 30% vs. 21%, p = 0.03) and lower Gleason scores (8-10 61% vs. 75%, p = 0.01). Androgen deprivation therapy use was similar between cohorts (85% vs. 87%, p = 0.5), but EBRT patients had longer androgen deprivation therapy use (median 14 vs. 12 months, p = 0.05). GP5 predicted worse FFM (p < 0.001, hazard ratio [HR] 3.3, 95% confidence interval [CI]1.8-6.2]) and CSS (p < 0.001, HR 5.9, 95% CI 2.7-12.9) for the EBRT group, but not for the combo group (p = 0.86, HR 0.48, 95% CI 0.1-2.4 for metastasis and p = 0.5, HR 1.6, 95% CI 0.33-8.0 for CSS). In those with GP5 (n = 143), combo was associated with improved outcomes in all endpoints. On univariate analysis, 5-year outcomes for combo vs. EBRT were as follows freedom from biochemical failure 89% vs. 65%, FFM 89% vs. 67%, CSS 93% vs. 78%, and overall survival 88% vs. 67% (p < 0.05 for all). CONCLUSION: Combo was associated with improved outcomes for men with GP5 prostate cancer. This highlights the importance of local therapy, especially in patients with the highest pathologic grade disease.