Correlation of High BMI and Prostate Cancer
Correlation of High BMI and Prostate Cancer
The study cohort included all consecutive patients who underwent robotic RP at Henry Ford Hospital (Detroit, MI) between April 2005 and February 2014. We have excluded patients who had received neoadjuvant hormonal or radiation therapy. PSA level from a blood sample routinely collected before all RPs was measured and used with PSAD calculation. Patient weight and height were measured preoperatively. All RP specimens were weighted unfixed, inked, and entirely submitted for fixation and histologic evaluation in whole-mount sections along with bilateral seminal vesicles and all submitted lymph nodes. Pathologists reported histologic findings using the Gleason grading recommendations of the International Society of Urological Pathology (ISUP) 2005 consensus conference. Tumor volume was reported in a percentage of carcinoma occupying the prostate gland. A dedicated prostatectomy database of the Vattikuti Urology Institute at Henry Ford Hospital prospectively collected clinical, demographic, and pathologic information from all cases.
BMI was calculated as the preoperative patient weight in kilograms divided by the square of the height in meters (kg/m). The World Health Organization (WHO) BMI classification divides BMIs into four groups: underweight (BMI <18.5 kg/m), normal weight (BMI 18.5–24.99 kg/m), overweight (BMI 25–29.99 kg/m), and obese (BMI ≥30 kg/m). We applied this grouping to our patient population. PSA mass (an absolute amount of PSA in the patient's circulation) was calculated by multiplying plasma volume (mL) by PSA (ng/mL). Plasma volume was calculated by multiplying estimated body surface by a 1.67 adjustment factor. The following formula was used to calculate estimated body surface: (weight, kg) × (height, cm) × 0.007184. PSAD was calculated by dividing preoperative PSA level by the resected prostate weight. The volume of prostate cancer was calculated in cubic centimeters by multiplying prostate weight times percentage of the gland the pathologist estimated to be involved with cancer.
We analyzed the following variables: (1) preoperative serum PSA levels, (2) PSAD, (3) PSA mass, (4) tumor volume at RP, (5) RP Gleason score, and (6) pathologic stage at RP by BMI group. Statistical significance was assessed with analysis of variance and χ tests for continuous and categorical variables, respectively. Linear regression was used for the multivariable model to find consequential associations between continuous variables. All calculations were performed using SAS for Windows, version 9.2 (SAS Institute, Cary, NC). Analytical results were considered significant when the P value was .05 or less.
Materials and Methods
The study cohort included all consecutive patients who underwent robotic RP at Henry Ford Hospital (Detroit, MI) between April 2005 and February 2014. We have excluded patients who had received neoadjuvant hormonal or radiation therapy. PSA level from a blood sample routinely collected before all RPs was measured and used with PSAD calculation. Patient weight and height were measured preoperatively. All RP specimens were weighted unfixed, inked, and entirely submitted for fixation and histologic evaluation in whole-mount sections along with bilateral seminal vesicles and all submitted lymph nodes. Pathologists reported histologic findings using the Gleason grading recommendations of the International Society of Urological Pathology (ISUP) 2005 consensus conference. Tumor volume was reported in a percentage of carcinoma occupying the prostate gland. A dedicated prostatectomy database of the Vattikuti Urology Institute at Henry Ford Hospital prospectively collected clinical, demographic, and pathologic information from all cases.
BMI was calculated as the preoperative patient weight in kilograms divided by the square of the height in meters (kg/m). The World Health Organization (WHO) BMI classification divides BMIs into four groups: underweight (BMI <18.5 kg/m), normal weight (BMI 18.5–24.99 kg/m), overweight (BMI 25–29.99 kg/m), and obese (BMI ≥30 kg/m). We applied this grouping to our patient population. PSA mass (an absolute amount of PSA in the patient's circulation) was calculated by multiplying plasma volume (mL) by PSA (ng/mL). Plasma volume was calculated by multiplying estimated body surface by a 1.67 adjustment factor. The following formula was used to calculate estimated body surface: (weight, kg) × (height, cm) × 0.007184. PSAD was calculated by dividing preoperative PSA level by the resected prostate weight. The volume of prostate cancer was calculated in cubic centimeters by multiplying prostate weight times percentage of the gland the pathologist estimated to be involved with cancer.
We analyzed the following variables: (1) preoperative serum PSA levels, (2) PSAD, (3) PSA mass, (4) tumor volume at RP, (5) RP Gleason score, and (6) pathologic stage at RP by BMI group. Statistical significance was assessed with analysis of variance and χ tests for continuous and categorical variables, respectively. Linear regression was used for the multivariable model to find consequential associations between continuous variables. All calculations were performed using SAS for Windows, version 9.2 (SAS Institute, Cary, NC). Analytical results were considered significant when the P value was .05 or less.
