146 Background: In patients treated with neoadjuvant lutenising hormone-releasing hormone agonist (LHRHa) therapy prior to radical prostate radiotherapy the PSA nadir in the first week of radiotherapy has been correlated with subsequent biochemical failure free survival (BFFS). Bicalutamide monotherapy (BC) is increasingly being used as a neoadjuvant therapy in place of LHRHa. We wished to compare the initial PSA response to neoadjuvant BC or LHRHa in this setting as well as examining subsequent biochemical failure rates. METHODS We retrospectively reviewed the case notes of consecutive men with prostate cancer treated with BC monotherapy prior to radical prostate radiotherapy from April 2004 to December 2008 and case-matched them to men treated with neoadjuvant LHRHa. PSA levels and kinetics prior to radiotherapy and subsequent BFFS were analysed. RESULTS Eighty nine men treated with BC with a median follow-up of 42 months were case matched to 89 men treated with LHRHa. There were no significant differences in age, initial PSA, Gleason, or T stage. The median nadir PSA on day 1 of radiotherapy was 2.2ng/mL (0.1-11.2) for BC patients and 0.9ng/mL (0.1-11.2) for LHRHa patients (p=0.0007). There were no significant differences in PSA velocity or doubling time during the neoadjuvant period. A PSA of <1.0ng/mL on day 1 of radiotherapy was seen in 29 (32%) and 47 (52%) of BC and LHRHa patients respectively. Biochemical failure was seen in 10 (11.2%) and 2 (2.2%) of BC and LHRHa patients respectively. PSA kinetics did not predict for subsequent BFFS at this duration of FU for men receiving neoadjuvant BC. CONCLUSIONS In this case-matched study, neoadjuvant BC therapy does not provide the same level of pre-radiotherapy PSA suppression when compared to neoadjuvant LHRHa. Higher biochemical failure rates are seen in patients treated with BC than LHRHa however this may be a result of prolonged castration. No significant financial relationships to disclose.