Subcutaneous adipose tissue characteristics and the risk of biochemical recurrence in men with high-risk prostate cancer

To assess 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).

This retrospective study included men with high-risk prostate cancer (PSA>20ng/ml, Gleason score ≥8, or clinical extraprostatic extension) treated between 2001 and 2012. 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. The average CT attenuation, in Hounsfield units (HU), of the structure was calculated and defined as SATHU. SATAREA was defined as the cross-sectional area of the structure (in cm(2)) that was then normalized by the square of patient height. Biochemical failure (BF) was defined as a PSA rise of 2ng/ml from the nadir. Freedom from BF (FFBF) was calculated from start time of ADT using the Kaplan-Meier method. Estimates of FFBF were stratified by SATHU and SATAREA quartiles.

A total of 171 men met the inclusion criteria with a median follow-up of 5.6 years. The mean SATHU (±standard deviation) was -99.2HU (±6.1HU), and the mean SATAREA was 93.2cm(2)/m(2) (±39.4cm(2)/m(2)). The 5- and 8-year rates of FFBF across all patients were 81.5% and 73.5%, respectively. 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). No other differences in FFBF were observed between quartiles of SATAREA or other quartiles of SATHU.

Lower subcutaneous adipose tissue density was associated with a lower rate of BF following RT with ADT for men with high-risk prostate cancer. Further research is needed to elucidate the biological underpinnings of this clinical finding and the role adipose tissue plays in modulating oncologic behavior and outcomes.

Urologic oncology. 2017 Aug 07 [Epub ahead of print]

Andrew M McDonald, John B Fiveash, Robert S Kirkland, Rex A Cardan, Rojymon Jacob, Robert Y Kim, Michael C Dobelbower, Eddy S Yang

Department of Radiation Oncology, University of Alabama at Birmingham, Hazelrig-Salter Radiation Oncology Center, Birmingham, AL. Electronic address: ., Department of Radiation Oncology, University of Alabama at Birmingham, Hazelrig-Salter Radiation Oncology Center, Birmingham, AL.

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