ESTRO 38 Abstract book

S77 ESTRO 38

OC-0160 When PI-RADS and ISUP meet each other: identification of candidates for pelvic lymph node dissection C. Draulans 1,2 , W. Everaerts 3,4 , S. Isebaert 1,2 , T. Gevaert 4 , R. Oyen 5,6 , S. Joniau 3,4 , E. Lerut 6,7 , L. De Wever 5 , A. Laenen 8 , B. Weynand 6,7 , E. Vanhoutte 5 , G. De Meerleer 1,2 , K. Haustermans 1,2 1 University Hospitals Leuven, Department of Radiation Oncology, Leuven, Belgium ; 2 KU Leuven, Department of Oncology, Leuven, Belgium ; 3 University Hospitals Leuven, Department of Urology, Leuven, Belgium ; 4 KU Leuven, Department of Development and Regeneration, Leuven, Belgium; 5 University Hospitals Leuven, Department of Radiology, Leuven, Belgium ; 6 KU Leuven, Department of Imaging and Pathology, Leuven, Belgium; 7 University Hospitals Leuven, Department of Histopathology, Leuven, Belgium ; 8 KU Leuven, Leuven Biostatistics and Statistical Bioinformatics Center, Leuven, Belgium Purpose or Objective The aim of this study is to update the current nomograms predicting lymph node invasion (LNI) in prostate cancer (PCa) patients with today’s state-of-the-art available tumor information. This tumor information includes magnetic resonance imaging (MRI) based tumor staging and detailed biopsy information according to the International Society of Urological Pathology (ISUP). Material and Methods Between 2008 and 2017, 420 clinical N0 staged PCa patients underwent a radical prostatectomy with pelvic lymph node dissection (PLND). The initial PSA value (iPSA), preoperative tumor stage by MRI (iT-stage), tumor multifocality on MRI, zonal tumor location on MRI, ISUP grade group on biopsy for each positive core, percentage of tumor involvement and exact tumor length in each core and percentage of positive biopsy cores were registered. Using this information, we developed a multivariable model predicting LNI to create a coefficient-based nomogram. A concordance index (C-index) was estimated to quantify the discriminative performance of the model. Results On MRI, 180 (42.9 %) patients had iT1 or iT2 disease, 224 (53.3 %) iT3 and 16 (3.8 %) iT4 PCa based on features described in the literature, similar to the current PI-RADS v2 criteria. A median of 21 (IQR, 16 – 27) lymph nodes was removed per patient. Overall, 71 (16.9 %) patients were finally diagnosed with LNI. A multivariable model detected the iPSA value, MRI based iT-stage, maximum tumor length in one core (mm) and ISUP grade group corresponding to the maximum tumor involvement in one core as independent predictors of LNI (p < 0.05). After 5-fold internal cross validation, the predictive accuracy of our updated MRI and ISUP based nomogram for LNI (table 1) was 79.7 %.

California Davis, Radiation Oncology, Sacramento, USA ; 5 Washington University, Radiation Oncology, St. Louis, USA ; 6 MD Anderson, Radiation Oncology, Houston, USA ; 7 UCSF, Radiation Oncology, San Francisco, USA; 8 Hotel- Dieu de Quebec, Radiation Oncology, Quebec, Canada; 9 Thomas Jefferson University, Radiation Oncology, Philadelphia, USA; 10 Roswell Park Cancer Insitute, Radiation Oncology, Buffalo, USA ; 11 Centre Hospitalier de l'Université de Montreal-Notre Dame, Radiation Oncology, Montreal, Canada; 12 William Beaumont Hospital, Radiation Oncology, Royal Oak, USA; 13 Christiana Care Health Services, Radiation Oncology, Newark, USA; 14 Cedars-Sinai Medical Center, Radiation Oncology, Los Angeles, USA Purpose or Objective This is a report of long-term patient outcome following treatment with external beam radiation therapy (EBRT) and prostate high dose rate (HDR) brachytherapy from a prospective phase II, multi-institutional collaborative trial Patients with clinically localized (T1c-T3b) prostate cancer without prior history of TURP or hip prosthesis were eligible for this study. All patients were treated with a combination of 45 Gy in 25 fractions from EBRT and one HDR implant delivering 19 Gy in 2 fractions. Adverse events (AE) were collected using CTCAE v3. Biochemical failure was assessed using the ASTRO definition and the Phoenix definition. Local failure was determined by clinical exam and distant failure required documentation of regional nodal recurrence or distant disease relapse. Disease-specific deaths included those due to prostate cancer, other causes with active malignancy, and complications of treatment. Cumulative incidence was used to estimate time to severe late GI/GU toxicity, biochemical failure, disease-specific mortality, local failure, and distant failure. Competing risks were death without an event. Overall survival was estimated using the Kaplan Meier method. Results One hundred twenty-nine patients were enrolled from 7/04 to 5/06. One hundred and twenty-five patients were eligible and AE data was available for 115 patients. The pretreatment characteristics (NCCN intermediate to high risk) of the patients were as follows: median age was 68 (range: 48-80), T1c-T2c 91%, T3a-T3b 9%,PSA ≤ 10 70%, PSA >10-≤20 30%, GS 2-6 10%, GS 7 72%, and GS 8-10 18%. Forty-three percent of patients received adjuvant hormonal therapy. There were 6 (5.2%) patients with grade 3 GI/GU AEs, and no late grade 4-5 GI/GU AEs. The single Grade 3 GI AE was proctitis. The grade 3 GU AEs were:cystitis (n=1), pollakiuria (n=1), renal/genitourinary, other (n=1), urethral stricture (n=1), urinary incontinence (n=1), and urinary retention (n=2). At 5 and 10 years, the rate of late grade 3-5 GI/GU AEs was 17.0% and 19.2%. Five- and 10-years overall survival rates were 95.0% and 75.7%. The biochemical failure rates using the ASTRO definition: 5-year and 10-year rates of 9.8% and 14.7%; using Phoenix definition: 5-and 10-years rates of 14.0% and 22.6%. The 10-year rate of prostate specific mortality was 6.4%. At 5 and 10 years, the rates of distant failure were 4.2% and 7.7%. The rates of local failure at 5 and 10 years were 1.7% at both time points. Conclusion This prospective trial demonstrates the feasibility to use HDR in a multi-institutional setting with excellent long- term outcomes and very modest toxicity. This project was supported by grants U10CA180868 (NRG Oncology Operations), U10CA180822 (NRG Oncology SDMC) from the National Cancer Institute (NCI). conducted by RTOG. Material and Methods

Conclusion We report an updated MRI and ISUP based nomogram predicting the presence of LNI in PCa patients. This nomogram will overcome stage migration and will prevent overtreatment, which is a potential risk when MRI