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98 Background: A uniform fractionation schedule is used to deliver external beam RT for localised prostate tumours Individualising fractionation according to tumour biology may improve outcomes. In addition recurrence rates after RT vary considerably and better prognostic markers are needed to guide treatment choices. This study aims to identify if the cell proliferation marker Ki67 predicts response to RT fractionation in CHHiP, a randomised trial of 3 RT fractionation schedules. It also aims to identify if Ki67 predicts prognosis. Methods: A matched case:control study design was used, patients with biochemical or clinical failure > 2 years after RT (BCR) were matched to patients without recurrence according to established prognostic factors (Gleason score, PSA, Tumour-stage) and fractionation schedule. Immunohistochemical (IHC) staining of diagnostic biopsy sections was carried out using the MIB1 Ki67 antibody. Two independent investigators scored Ki67 using the unweighted global method (1) to derive a mean and maximum percentage of cells staining positive (mean Ki67 and maximum Ki67 respectively). Conditional logistic regression models were fitted with interaction terms between the biomarker and the fractionation schedules to determine whether Ki67 predicted BCR according to fractionation. Secondly models were fitted using the entire case:control study sample to estimate the prognostic value of Ki67 on risk of BCR. Results: Ki67 results were available for 173 matched pairs. The interaction terms between Ki67 and the fractionation schedules were not significant. However mean and maximum Ki67 were significant prognostic markers for BCR in a model adjusted for established prognostic factors. Conditioning on matching variables and age, the odds of BCR is estimated to increase by 9% per 1 point increase in mean Ki67 (OR = 1.09, 95%CI:1.04–1.15, p = 0.001). Conclusions: Ki67 did not predict BCR according to fractionation schedule in CHHiP, however it did predict prognosis independently of established prognostic factors. Additional IHC biomarkers are under evaluation.

4640 Background: Dynamic sentinel node biopsy (DSNB) in combination with ultrasound scan (USS) has been the technique of choice at our centre since 2004 for the assessment of non palpable inguinal lymph nodes in patients with squamous cell carcinoma of the penis (SCCp). Sensitivity/false-negative rates may vary depending on whether results are reported per patient or per node basin and with and without USS. The purpose of this study was to determine the long-term outcome of DSNB and ultrasound-guided fine needle aspiration cytology (FNAC) in our cohort of newly diagnosed patients and to analyse any variation in sensitivity of the procedure. Methods: A prospective cohort study over 6 years (2004 to 2010). Inclusion criteria: New diagnosis SCCp, T1G2 or greater definitive histology, non-palpable nodes in inguinal basin. Exclusion: patient with persistent/untreated local disease. Sensitivity of the procedure was calculated, per node basin, per patient, DSNB alone, USS/DSNB combined. Minimum follow up 12 months. Results: 500 inguinal basins in 264 patients underwent USS+/-FNAC and DSNB. 70 (14%) positive inguinal basins in 57(22%) patients were identified. 9 (2%) inguinal basins had no tracer uptake. 2 inguinal basins were confirmed false negative at 8 and 12 months. 2 inguinal basins had positive USS+FNAC and negative DSNB. Overall sensitivity of the technique is reported in the table. Conclusions: DSNB in combination with USS has excellent performance characteristics to stage patients with clinically node-negative penile cancer with a 3% false negative rate. USS improves performance by 4% over DSNB alone. There is no difference in performance of the combined technique if it is reported per node basin or per patient. [Table: see text]