Role of choline PET/CT in guiding lymph nodal radiation treatment and in predicting outcome in recurrent prostate cancer patients

Objectives To assess the role of 11C-Choline PET/CT in guiding helical tomotherapy (HTT) and in predicting outcome for lymphnode (LN) recurrent prostate cancer (PCa).

Methods 83 pts with PCa recurrence (median PSA: 2.64 ng/mL) treated with HTT on LN relapse as detected by PET/CT were recruited. Three pts were treated 3 times, 5 pts twice (total number of therapies = 94: 52% pelvic and 48% extrapelvic+/-pelvic LNs). PET/CT positive (+) LNs received a median dose of 65.5Gy/28 fractions and LN chains of the PET/CT+ LN received 51.8Gy/28 fractions. Actuarial overall (OS), loco-regional free (LRFS) and clinical relapse free (CRFS) survivals were calculated. Predictors of OS were assessed with Cox univariate and multivariate analyses. Acute toxicity for all treatments and late events in 49 pts with 2-y follow-up were assessed. Median follow-up was 22 months (range: 3-99).

Results Median PSA after HTT was 0.44 ng/mL. The 2-y OS, LRFS and CRFS were 87%, 90% and 50%, respectively. A nadir <0.1 ng/mL and PSA reduction of more than 80% at 3 and 9 months together with PET/CT+ LN location (extra vs intra-pelvic) and 2Gy equivalent dose to PET/CT+ LN (EQD2) were found to have a significant impact on OS. In a multivariable model (p=0.0004, AUC=0.81, 95%CI:0.71-0.89), a nadir <0.1 ng/ml (HR:0.28), extra-pelvic PET/CT+ LN (HR:7.9) and EQD2>69Gy (HR:0.39) were independently predictive of the risk of death. Grade 2-3, rectal and genital-urinary (GU) acute toxicity rates were 3% and 5%, respectively; grade 2-3, rectal and GU late toxicity rates were 3% and 8%, respectively.

Conclusions Choline PET/CT is valuable in guiding HTT, which was found to be effective and safe. Choline positive LN location has a role in predicting patient outcome.