Treatment thresholds for osteoporosis in men on androgen deprivation therapy: T-score versus FRAX

Men treated by androgen deprivation therapy (ADT) for localized prostate cancer are at risk for fracture, but it is not known which men require pharmacologic treatment. We found that 33% of men on ADT had osteoporosis of spine, hip, or forearm by dual-energy X-ray absorptiometry (DXA), thus requiring treatment. Using the new fracture prediction algorithm (FRAX) tool with corrected femoral neck T-score identified only 17% requiring treatment, and, if calculated without femoral neck, 54% were identified to need treatment.

Men treated with androgen deprivation therapy (ADT) for prostate carcinoma live long enough to fracture. A new fracture prediction method, FRAX, is based on femoral neck DXA plus risk factors. Thus, DXA or FRAX could determine which men should receive osteoporosis therapy.

Of 115 men undergoing ADT referred for DXA testing, those with bone mineral density (BMD) in spine, hip, or forearm of >or=2.5 standard deviations below a normal male ethnicity-adjusted mean were considered treatment candidates. Using FRAX with and without femoral neck BMD, men were treatment candidates if the 10-year hip fracture risk was >or=3% or the major osteoporotic fracture risk was >or=20%.

The men averaged 77 years old; 58% were African-American, and 14.8% were current smokers. Mean femoral neck T-score was -1.4. Using DXA, 38 (33%) men would need treatment. When FRAX was calculated including the femoral neck T-score, only 20 men met criteria for treatment. However, when FRAX was calculated without the T-score, 62 men met criteria for treatment. Overlap among the groups was surprisingly modest.

DXA and FRAX identify different ADT men for treatment.