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95 Background: Abiraterone acetate (AA) improves OS and rPFS in first line mCRPC patients (pts). After AA progression D is commonly used as standard second line therapy. However, the value of maintaining AA in combination with D despite progression has not been tested beyond small exploratory studies (Tagawa ST, Eur Urol 2016) ABIDO is a randomized-phase II trial that evaluates efficacy and safety of D + AA vs D after first-line AA progression in mCRPC. Methods: Asymptomatic or minimally symptomatic mCRPC pts with no visceral metastases, ECOG PS 0-1, and adequate organ functions were included. The study has two stages: In stage I pts receive AA (1000 mg/d + prednisone (P) 10 mg qd) until radiological or unequivocal clinical progression. In stage II pts were randomized to D 75 mg/m2 q3wk in combination with AA 1000 mg/d (arm A) or without AA (arm B) The primary endpoint was rPFS and the secondary endpoints radiological response (RR), OS, PSA-response, PSA-PFS and safety. Results: 88 pts were randomized, (46 arm A, 42 Arm B). Median age was 69 y/o, 43% had ECOG 0 and 91%/11%/5% had bone, liver and lung metastases. Median rPFS was 11.4 months (m) in arm A vs 10.5 m in ARM B; 12-m rPFS was 43% vs 45%; Median PSA PFS was 6.2 vs 5.5 m and median OS was 17.3 vs 16.9 m. Twenty four pts (52%) in arm A and 19 (46%) in arm B achieve ≥50% PSA response. RR was achieved in 15% vs 7% of pts and disease control rate in 74% in both arms. No statistically significant differences were found in efficacy parameters. Half of pts received 10 cycles of D (median 7 and 8). D median dose intensity was 86% and 90% for each arm and 91% for AA. Eleven pts discontinued treatment due to non-hematological toxicity, 5 in arm A and 6 in arm B. Most frequent G3-4 toxicities per arm (A/B) were: neutropenia (57%/29%; P=0.027), febrile neutropenia (17%/10%), diarrhea (9%/7%), and asthenia (11%/10%). Conclusions: ABIDO trial was unable to demonstrate the significant clinical benefit of maintenance AA approach + D after AA first-line therapy. No differences were observed in RR, PSA PFS, rPFS and OS. In AA + D cohort, more frequent and severe hematological toxicity (neutropenia and febrile neutropenia) were reported. Clinical trial information: NCT02036060.

176 Background: Cabazitaxel (CBZ) improves overall survival in mCRPC that progresses during or after docetaxel treatment. CABASEM is a phase II study to evaluate the efficacy and safety of a weekly schedule of CBZ for 'unfit' (ECOG2, previous neutropenic fever with docetaxel, or radiotherapy to

198 Background: Different treatments efficacy for mCRPC when progression after docetaxel x 6 cycles + ADT (as CHAARTED scheme) are unknown as all pivotal trials where performed in patients who progressed to mCPRC after ADT. Methods: A retrospective analysis of 175 mCRPC patients of 10 spanish hospitals who were treated with docetaxel + ADT as first line treatment was performed. Patients characteristics at diagnosis (age, gleason) and at progression to mCRPC were analyzed (PSA, presence of visceral mets, type of progression). As efficacy endpoints, clinical and objective response, and survival from progression to mCRPC were analyzed. Results: Median age at diagnosis 65.2 years old (range 44-84). Metastatic at diagnosis 173. Bone metastasis 155 (88,5%), visceral 31 (17.7%), gleason >7 130 (74,3%), number docetaxel cycles: 6 (80%), 5 (5,7%)

5052 Background: Circulating tumor cells (CTCs) enumeration using CellSearch correlates with clinical outcome in prostate cancer, but is limited for gene expression analysis. AdnaTest ProstateCancer is a commercially available CTC immune-enrichment and PCR-related detection method that allows gene expression studies (Antonarakis E, NEJM 2014). It has demonstrated incremental detection of CTCs in patients with no CTCs identified by CellSearch (Samoila A, ASCO 2013) but needs to be clinically qualified. There is a strong need for studies to assess the association with the clinical outcome in CRPC. Methods: Between February and November 2015, 98 asymptomatic or oligo-symptomatic chemotherapy-naïve mCRPC pts were recruited in 16 institutions. Although initially designed to study the predictive value of TMPRSS2-ETS, data emerging after the trial was initiated led the group to prioritize alternative predefined exploratory biomarkers, including plasma AR (Grande E, ASC0 2017 #) and CTC characterization (Grande E, ESMO 2016). Outcome measures included PSA-PFS (sPFS), radiographic PFS (rPFS) and OS. Cox regression was used for survival analyses and Fisher’s exact test for PSA response. Results: Ninety-eight patients had CTC blood samples available. CTCs were detected at baseline, 12 weeks and progression in 36% (35/98), 27% (26/95) and 78% (32/41), respectively. The CTC conversion rate (positive to negative after 12 w) was 43% (15/35). All CTC conversions had ≥50% decline in PSA (15/15) whereas only 35% (7/20) of pts with persistent CTCs. At first interim analysis, with a median follow-up of 10.6 months, detection of CTCs at baseline was associated with worse sPFS (median, 7.59 m versus NR, HR, 3.67; 95% CI 1.90-7.10; P < 0.001), rPFS (median, 12.9 m versus NR; HR, 7.61; 95% CI, 2.80-20.64; P < 0.001) and OS (medians NR, HR, 9.51; 95% CI, 1.11-81.52; P = 0.0398). CTC positive pts were less likely to have a ≥90% decline in PSA (OR, 2.88; 95% CI, 1.13-7.72; P = 0.02). Conclusions: CTC detection using AdnaTest is associated with an adverse outcome in chemotherapy-naïve asymptomatic or oligo-symptomatic mCRPC pts. Clinical trial information: NCT02288936.

e16080Background: Normal and pathological angiogenesis is under the control of various developmental genetic programs, including Notch and Hedgehog pathways. More recently, miRNAs have emerged as k...

5058Background: Abiraterone acetate (AA) improves OS and rPFS in asymptomatic/minimally symptomatic mCRPC patients (pts) who are chemotherapy (CT) naive through CYP17 inhibition. Upon progression t...

e15597 Background: The IMRCC prognostic model for mRCC treated with VEGF-targeted agents (Heng, JCO '09) has been externally validated (Heng, Lancet Oncol '13), however, pt treated with Pz were not...

4525 Background: Treatment of mTCC progressing to cisplatin is an unmet need. Prognostic factors (PF) for worse overall survival (OS) are ECOG >0, Hb

1525 Background: Mammographic density (MD) is one of the strongest determinants of breast cancer (BC). In this case-control study, we compared MD in BRCA1/2 mutation carriers and non-carriers from ...

4578 Background: Deregulation of stem cell signaling pathways, such as Notch and Sonic Hedgehog (SHH) seems necessary for tumor initiation, maintenance and progression. Preclinical evidence support...

e16034 Background: Docetaxel (D) is standard first-line chemotherapy in patients (pts) with mCRPC. Cabazitaxel (C), a novel taxane developed to overcome D resistance, showed an overall survival imp...

e12513 Background: Family history (FH) of breast cancer (BC), ovarian cancer (OC), and individual features (IF), like early age of onset, bilateral BC, coexistence of BC and OC, and triple negative BC (TNBC) younger than 50 years, are suspicion criteria of hereditary BC. Although it is assumed in the literature that 15-30% of BC cases can be familial BC (FBC), only 5-10% of BC are hereditary, explained by a germline mutation in BRCA1 or 2. Moreover, there is no international consensus to define FBC (e.g. number of relatives affected, age of onset), in contrast with, e.g. Lynch syndrome and Amsterdam/Bethesda criteria, in order to offer genetic counseling. In Spain, there are not population-based studies analyzing the real percentage of BC with familial and/or individual high risk features. Methods: A retrospective study based on 10,641 Spanish BC patients diagnosed from 1998-2001, collected in the “El Álamo III project”, was conducted. Specific data regarding FBC were analyzed: IF (age of onset, bilateral breast cancer, ovarian cancer and TNBC; and FH features (first and second degree relatives with BC and /or OC). Results: The Table summarizes the results. Conclusions: 21% of BC patients in Spain diagnosed from 1998 to 2001 have at least one relative with BC and/or OC. In addition, 2.8 % of patients with no FH of BC/OC fulfill high risk criteria. However, several study characteristics, such as 18% patients with no FH recorded, and lack of data regarding age of affected relatives, limit the interpretation of these results, being necessary to improve the family data collection in further “El Álamo” project studies. [Table: see text]