Incidence and predictors of lower extremity lymphedema after postoperative radiotherapy for prostate cancer.

Background: To assess the rate and predictors of lower extremity lymphedema (LEL) after radiotherapy (RT) following radical prostatectomy (RP) ± pelvic lymph node dissection (PLND) for prostate cancer.

Methods: Patients (pts) treated with adjuvant or salvage RT after RP ± PLND and a minimum 2-year follow-up were included. LEL was defined as a volume difference ≥ 10% between limbs evaluated using circumferential measurements with a flexible non-stretch tape. The following predictors were investigated at logistic regression: age (continuous); body mass index (BMI, continuous); exercise level (low vs. medium/high); smoking (yes vs. no); cigarette pack/year (continuous); hypertension (yes ns no); vascular comorbidity (yes vs. no); diabetes (yes vs. no); PLND (yes vs. no); number of examined nodes (continuous); whole pelvis radiotherapy (WPRT) (yes vs. no); time between RP and RT (continuous); planning target volume (PTV) volume (continuous); PTV/BMI (continuous). Statistical significance was claimed for p < 0.05.

Results: 101 pts were examined. The median time from surgery to RT was 36.1 months (mths) (IQR: 15.0-68.3), the median time from RT to the date of study examination was 51.1 months (IQR: 36.8-65.3). 14 pts developed LEL (13.9%), 3 pts (2.9%) before RT, 11 pts (10.8%) after RT. The median time from RT to LEL was 4 mths (IQR: 0.5-17.3). At multivariable analysis (MVA) diabetes mellitus (DM) (OR = 32.8, p = 0.02), time between surgery and RT (OR = 0.966, p = 0.039) and exercise (OR = 0.03, p = 0.002) were independently correlated to LEL. The number of examined nodes was highly correlated to LEL at univariate analysis (OR = 1.066, p = 0.025) but was not confirmed at MVA (p = 0.719). Interestingly, the distribution of the examined nodes was statistically different between pts with low (median N = 12) vs. medium/high (N = 5) exercise (p = 0.034).

Conclusions: Clinically detectable LEL involves a minority of pts after RT. DM is a predisposing factor, while awaiting RT delivery has a protective effect favoring salvage over adjuvant RT.