McDonald AM, et al. – This study quantifies subcutaneous adipose tissue characteristics by computed tomography (CT) as potential imaging biomarkers predictive of biochemical recurrence in men with high–risk prostate cancer receiving radiotherapy (RT). The results of this study displayed that lower subcutaneous adipose tissue density was correlated with a lower rate of BF following RT with androgen deprivation therapy (ADT) for men with high–risk prostate cancer. Future study is required to elucidate the biological underpinnings of this clinical finding and the role adipose tissue plays in modulating oncologic behavior and outcomes.

Methods

• Researchers performed a retrospective study including men with high-risk prostate cancer (PSA>20 ng/ml, Gleason score ≥8, or clinical extraprostatic extension) treated between 2001 and 2012.
• In this study, all patients received definitive, dose-escalated external beam RT along with a course of neoadjuvant, concurrent, and adjuvant androgen deprivation therapy (ADT).
• Each patient also had a treatment planning CT that included the L4-L5 vertebral interface and prostate specific antigen (PSA) measurements for at least 2 years following RT.
• The subcutaneous adipose tissue was contoured on a single axial CT slice at the level of L4-L5.
• They characterized and estimated the average CT attenuation, in Hounsfield units (HU), of the structure as SATHU. SATAREA was defined as the cross-sectional area of the structure (in cm2) that was then normalized by the square of patient height.
• They characterized biochemical failure (BF) as a PSA rise of 2 ng/ml from the nadir.
• Thereafter, freedom from BF (FFBF) was computed from start time of ADT using the Kaplan-Meier method.
• They stratified estimates of FFBF by SATHU and SATAREA quartiles.

Results

• The data showed that HU (±standard deviation) was -99.2 HU (±6.1 HU), and the mean SATAREA was 93.2 cm2/m2 (±39.4 cm2/m2).
• It was noted that the 5- and 8-year rates of FFBF across all patients were 81.5% and 73.5%, respectively.
• The results indicated that patients in the lowest quartile of SATHU experienced significantly higher FFBF compared to the other quartiles (Q4 vs. Q1, P = 0.017; Q4 vs. Q2, P = 0.045; Q4 vs. Q3, P = 0.044).
• There were no other differences in FFBF between quartiles of SATAREA or other quartiles of SATHU.