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Resume Objectifs Evaluer la frequence du phenomene de « rebond » (elevation secondaire transitoire de la concentration serique du PSA) du PSA apres curietherapie de prostate et rechercher une correlation entre le rebond et les parametres cliniques et dosimetriques. Evaluer comment ce rebond du PSA peut mimer les criteres de rechute biochimique. Patients et methodes De mai 1998 a mai 2005, 1000 patients ont eu une curietherapie pour un cancer localise de la prostate de bas risque a l'institut Curie. Apres l'implantation, un dosage serique de PSA a ete realise tous les six mois. Nous avons defini le « rebond » comme toute augmentation du PSA d'au moins 0,1 ng/ml, suivie d'une diminution spontanee de celui-ci. Nous avons utilise les criteres de rechute biochimique definis par le consensus de l'ASTRO (trois elevations successives de la concentration serique de PSA), et analyse les correlations entre les rebonds de PSA, les parametres cliniques et dosimetriques, en analyse multifactorielle. Pour evaluer le phenomene de rebond avec un recul suffisant, cette serie a donc porte sur les patients traites par la technique en temps reel, avec grains libres d'125I (Isoseed, Bebig), jusqu'a decembre 2001. Dans ce groupe de 295 patients, la duree moyenne de suivi a ete de 40,3 mois (9–66 mois). Resultats Dans notre serie, 161 patients (55 %) ont eu une elevation transitoire de la concentration serique de PSA (« rebond ») d'au moins 0,1 ng/ml ; 145 patients (49 %) un rebond d'au moins 0,2 ng/ml, 93 patients (32 %) un rebond d'au moins 0,4 ng/ml, 43 patients (15 %) un rebond d'au moins 1 ng/ml. Le delai moyen d'apparition de cette elevation a ete de 19 mois (6–58), et la duree moyenne de six mois. L'amplitude moyenne de l'elevation a ete de 0,8 ng/ml (0,1–4,1 ng/ml). Trente-deux patients, soit 11 % du nombre total des patients, ont eu trois elevations successives du PSA avec un intervalle significatif entre les dosages (trois mois) et etaient donc en situation de rechute biochimique selon les criteres de l'ASTRO. Parmi ces 32 patients, 18 (56 %) ont vu leur PSA se normaliser completement et spontanement. Au total, seuls dix patients ont vu leur concentration serique de PSA continuer a augmenter et ont donc eu une authentique recidive biochimique. Pour les quatre derniers patients, la situation restait encore ambigue compte tenu des fluctuations persistantes du PSA et du recul insuffisant. En analyse multifactorielle, l'âge inferieur a 70 ans (p Conclusions Dans notre serie, 32 % des patients ont eu un rebond de la concentration serique de PSA d'au moins 0,4 ng/ml, en accord avec les donnees de la litterature. Ce rebond a ete observe jusqu'a cinq ans apres l'implantation, a atteint jusqu'a 4 ng/ml, et a dure six mois en moyenne. Parmi les 32 patients avec les criteres de rechute biochimique de l'ASTRO, 18 (56 %) avaient en fait un simple rebond. Les criteres de l'ASTRO ne sont donc pas adaptes au suivi biolochimique precoce apres curietherapie de prostate, et les resultats de la curietherapie doivent etre evalues avec un recul suffisant pour tenir compte du phenomene de rebond. Cela a des consequences cliniques pratiques evidentes, sur le diagnostic de recidive et la decision d'un eventuel traitement complementaire.

To assess the frequency and features of the PSA bounce phenomenon in a series of patients treated with permanent implant brachytherapy for prostate cancer, and to evaluate the percentage of cases in which this bounce could have mimicked a biochemical relapse according to the American Society for Therapeutic Radiology and Oncology consensus criteria.From January 1999 to December 2001, 295 patients were treated with a permanent prostate implantation (real-time technique, with free (125)I seeds) by the Paris Institut Curie/Hospital Cochin/Hospital Necker Paris group. Duration of followup is 40.3 months (9-66 months). PSA level was reported at intervals not exceeding 6 months. Bounce was defined by temporary elevation in PSA level, followed by a spontaneous decrease.In our series, 161 patients (55%) showed a transitory PSA increase (bounce) of at least 0.1 ng/mL; 145 patients (49%) a bounce of 0.2 ng/mL; 93 patients (32%) a bounce of 0.4 ng/mL; and 43 patients (15%) a bounce of at least 1 ng/mL. Mean PSA bounce was 0.8 ng/mL (0.1-4.1), and mean time to bounce was 19 months. Thirty-two patients (11% of total) presented three successive PSA increases, and therefore were to be considered as experiencing a biochemical relapse according to the American Society for Therapeutic Radiology and Oncology (ASTRO) consensus criteria. Among those 32 patients, 18 (56%) subsequently showed, without any treatment, a complete normalization of their PSA. In multivariate analysis, age70 (p0.0001) and D90200Gy (p0.003) were identified as independent factors for a PSA bounce of at least 0.4 ng/mL.The observed rate of 32% of patients showing a PSA bounce of at least 0.4 ng/mL in our series is in good agreement with what has been previously reported in the literature. Among 32 patients fulfilling the classical ASTRO criteria for a biochemical relapse, 18 (56%) subsequently showed a spontaneous PSA decrease, questioning the ASTRO consensus for the biochemical followup of patients undergoing permanent implant prostate brachytherapy.

Resume Dans les dix dernieres annees, la curietherapie prostatique par implantation permanente s’est imposee comme une reelle alternative therapeutique dans le traitement des cancers localises de la prostate. La publication recente de resultats a 10-12 ans montre des resultats equivalents, pour une population selectionnee, a ceux de la chirurgie et de la radiotherapie conformationnelle, avec un faible taux de complications. Les criteres de selection ont bien ete definis par les societes savantes : tumeur classee T1 ou T2, concentration serique de PSA

Real-time ultrasound (US)-based dosimetry performed during (125)I loose seed implantation provides the radiation oncologist with an estimation of the dose distribution at seed insertion. However, for a number of reasons, this distribution may not reflect the real (reference) dosimetry as determined by subsequent CT, usually performed 1-2 months after implantation. The present study compared the two dosimetry data sets (US and CT) to evaluate how predictive extemporaneous US-based dosimetry can be of the real dose distribution.A total of 450 patients with prostate cancer were treated with loose (125)I seed implantation between June 1999 and October 2002 by the Institut Curie/Hospital Cochin (Paris) Group. The mean patient age was 65 years. Most patients (74%) had Stage T1c; the stage did not exceed T2b for the others. All patients had a prostate-specific antigen level of15 ng/mL and was10 ng/mL for 72%; 84% had a Gleason score ofor =6 and did not exceed 7 for the others; and 56% were treated with neoadjuvant hormonal therapy for a mean of 4.3 months. All patients were treated with loose seed implantation. Real-time US-based dosimetry was performed intraoperatively for all patients. CT-based dosimetry was performed 2 months after implantation, using the VariSeed software. The minimal dose to 90% of the outlined volume (D(90)) and percentage of volume receiving at least 100% of the prescribed dose (V(100)) were calculated with the two methods and compared for all patients.On CT-based dosimetry, the D(90) was found to beor =145 Gy (range, 115-240 Gy) in all patients except one. A large majority (86%) of patients showed a CT-based V(100) of95%, and 48% had a V(100) of98%. The mean CT-based D(90)/US-based D(90) ratio was 1.0 (range, 0.66-1.33). For 89% of the patients, the difference between the two values was20% and for 62% was10%. The mean CT-based V(100)/US-based V(100) ratio was 0.98 (range, 0-1.02), with 89% of patients showing a difference of5%.Our results indicate that the D(90) and V(100) values obtained intraoperatively with our real-time US-based dosimetry are in reasonable agreement with the subsequent values obtained with CT-based dosimetry performed 2 months after implantation. Recent innovations in our dose planning software allowed better control of the longitudinal seed position and could still improve the correlation between real-time US-based dosimetry and the subsequent CT-based dose distribution.