title: Investigation of 90Y-avidin for prostate cancer brachytherapy: a dosimetric model for a phase I-II clinical study.
abstract: OBJECTIVE
  A novel method for prostate irradiation is investigated. Similarly to (125)I or (103)Pd seed brachytherapy, (90)Y-avidin could be injected via the perineum under ultrasound image guidance. This study inspects the theoretical feasibility with a dosimetric model based on Monte Carlo simulation.
  
  
  METHODS
  A geometrical model of the prostate, urethra and rectum was designed. The linear-quadratic model was applied to convert (125)I absorbed dose prescription/constraints into (90)Y dose through biological effective dose (BED) calculation. The optimal (90)Y-avidin injection strategy for the present model was obtained. Dose distribution was calculated by Monte Carlo simulation (PENELOPE,GEANT4). Dose volume histograms (DVH) for the prostate, urethra and rectum were compared to typical DVHs of (125)I seed brachytherapy, used routinely in our institute.
  
  
  RESULTS
  With (90)Y-avidin, at least 95% of the prostate must receive more than 70 Gy. The absorbed dose to 10% of the urethra (D(10%_urethra)) and the maximum absorbed dose to the rectum (D(max_rectum)) must be lower than 122 Gy. For the present model, the optimum strategy consists in multiple injections of (90)Y-avidin 50 μl drops, for a total volume of 3.1 ml. The minimum activity to deliver the prescribed absorbed dose is 0.7 GBq, which also fully respects urethral and rectal constraints. The resulting dose map has a maximum in the central region with a sharp decrease towards the urethra and the prostate edge. Notably, D(10%_urethra) is 95 Gy and D(max_rectum) is below 2 Gy. Prostate absorbed dose is higher with (90)Y-avidin than (125)I seeds, although the total volume receiving the prescribed absorbed dose is 1-2% lower. Urethral DVH strictly depends on the (90)Y distribution, to be optimized according to prostate shape; in our model, BED(30%_urethra) is 90 Gy with (90)Y-avidin, whereas for patients receiving (125)I seeds it ranges between 150 and 230 Gy. The rectal DVH is always more favourable with (90)Y.
  
  
  CONCLUSIONS
  The methodology is theoretically feasible and can deliver an effective treatment in T1-T2 prostate cancer. Pharmacokinetic and biodistribution studies in prostate cancer patients are needed for validation.
authors: Medical Physics Unit, European Institute of Oncology, Milan, Italy.
authors: Francesca
authors: F
authors: Botta
authors: Marta
authors: M
authors: Cremonesi
authors: Mahila E
authors: ME
authors: Ferrari
authors: Ernesto
authors: E
authors: Amato
authors: Francesco
authors: F
authors: Guerriero
authors: Andrea
authors: A
authors: Vavassori
authors: Anna
authors: A
authors: Sarnelli
authors: Stefano
authors: S
authors: Severi
authors: Guido
authors: G
authors: Pedroli
authors: Giovanni
authors: G
authors: Paganelli
mesh_terms: D001360:Avidin / Q000627:therapeutic use*; D001918:Brachytherapy / Q000379:methods*; D017321:Clinical Trials, Phase I as Topic; D017322:Clinical Trials, Phase II as Topic; D005240:Feasibility Studies; D006801:Humans; D008297:Male; D008954:Models, Biological; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011874:Radiometry; D015021:Yttrium Radioisotopes / Q000627:therapeutic use
chemical_list: D015021:Yttrium Radioisotopes; D001360:Avidin
references: Eur J Nucl Med Mol Imaging. 2007 Jan;34(1):68-77
references: 16755333
references: Phys Med Biol. 2008 Sep 21;53(18):5045-59
references: 18723926
references: Med Phys. 2007 Feb;34(2):471-80
references: 17388163
references: Eur J Nucl Med Mol Imaging. 2012 Nov;39(11):1702-11
references: 22890802
references: Clin Cancer Res. 2007 Sep 15;13(18 Pt 2):5646s-5651s
references: 17875802
references: Urology. 2002 May;59(5):692-7
references: 11992842
references: Semin Radiat Oncol. 2002 Jan;12(1):81-94
references: 11813153
references: J Natl Cancer Inst. 1998 Jan 7;90(1):25-9
references: 9428779
references: Int J Radiat Oncol Biol Phys. 2003 Jan 1;55(1):194-203
references: 12504054
references: Eur Urol. 2003 Nov;44(5):556-9
references: 14572754
references: Eur J Nucl Med Mol Imaging. 2010 Feb;37(2):203-11
references: 19760414
references: Int J Radiat Oncol Biol Phys. 1998 Mar 1;40(4):835-44
references: 9531368
references: Acta Oncol. 2005;44(3):265-76
references: 16076699
references: Int J Radiat Oncol Biol Phys. 2011 Apr 1;79(5):1336-42
references: 20605342
references: Am J Surg Pathol. 2008 Feb;32(2):229-35
references: 18223325
references: Med Phys. 2004 Mar;31(3):484-92
references: 15070244
references: Int J Radiat Oncol Biol Phys. 2003 Feb 1;55(2):378-85
references: 12527051
references: Med Phys. 2010 Aug;37(8):4249-56
references: 20879585
references: J Surg Oncol. 1997 Sep;66(1):65-75
references: 9290696
references: Q J Nucl Med Mol Imaging. 2011 Oct;55(5):560-6
references: 21242948
references: Eur J Nucl Med Mol Imaging. 2009 Oct;36(10):1696
references: 19618182
references: Int J Radiat Oncol Biol Phys. 2003 Oct 1;57(2):593-5; author reply 595-6
references: 12957275
references: Brachytherapy. 2004;3(1):10-9
references: 15110308
references: Urology. 2005 Jul;66(1):119-23
references: 15992909
references: Brachytherapy. 2009 Jul-Sep;8(3):309-12
references: 19213609
references: Eur Urol. 2011 Dec;60(6):1133-9
references: 21889832
references: Phys Med Biol. 2009 Jul 7;54(13):4171-80
references: 19521004
references: Phys Med Biol. 2011 Jan 21;56(2):357-65
references: 21160113
references: Int J Radiat Oncol Biol Phys. 2001 Jul 15;50(4):1021-31
references: 11429230
references: Radiother Oncol. 2000 Dec;57(3):315-21
references: 11104892
references: Brachytherapy. 2006 Apr-Jun;5(2):127-30
references: 16644468
references: Phys Med Biol. 2009 Oct 21;54(20):N479-87
references: 19779222
references: Med Phys. 2011 Jul;38(7):3944-54
references: 21858991
references: Prostate Cancer Prostatic Dis. 2008;11(3):237-40
references: 18364676