Multiparametric MRI and post implant CT-based dosimetry after prostate brachytherapy with iodine seeds: The higher the dose to the dominant index lesion, the lower the PSA bounce.
OBJECTIVE
To determine whether post-implant MRI-based dosimetry of the Dominant Intra-prostatic Lesion (DIL) could best predict the occurrence of PSA bounce after prostate brachytherapy.


METHODS
We selected 66 patients with a low risk prostate cancer treated with (125)I prostate brachytherapy as monotherapy. Post-implant dosimetry based on day 30 CT-scan and multiparametric MRI co-registration was generated: planned D90, D95, V100, V150 values were calculated for each DIL. Bounce was defined as a PSA elevation ⩾ 0.2 ng/mL from the previous baseline value followed by a decrease to or below the prior nadir with no additional treatment.


RESULTS
After a median follow-up of 35.5 months (range 13.2-72.5), a PSA bounce occurred in 24 (36.4%) patients. The mean planned D90 of the DIL was significantly lower in bouncers: 196 ± 61 Gy vs. 234 ± 62 Gy, p = 0.018. The mean planned V150 of the DIL was 56 ± 32% for bouncers while it was 75 ± 30% for non-bouncers, p = 0.026.


CONCLUSIONS
A lower planned D90 or V150 in the DIL were predictive of PSA bounce after prostate brachytherapy. PSA bounce could be caused by delayed cell death related to sublethal damage accumulation in the tumor.
Department of Radiation Oncology, Georges François Leclerc Cancer Center, Dijon, France; Medical Imaging Group, Laboratory of Electronics, Computer Science and Imaging (Le2I), CNRS 6306, University of Burgundy, France.
Magali
M
Quivrin
Medical Imaging Group, Laboratory of Electronics, Computer Science and Imaging (Le2I), CNRS 6306, University of Burgundy, France; Department of Radiology, University Hospital Le Bocage, Dijon, France.
Romaric
R
Loffroy
Department of Urology, University Hospital Le Bocage, Dijon, France.
Luc
L
Cormier
Department of Medical Physics and Radiation Oncology, Georges François Leclerc Cancer Center, Dijon, France.
Frédéric
F
Mazoyer
Department of Biostatistics, Georges François Leclerc Cancer Center, Dijon, France.
Aurélie
A
Bertaut
Department of Surgery, Georges François Leclerc Cancer Center, Dijon, France.
Damien
D
Chambade
Department of Radiation Oncology, Georges François Leclerc Cancer Center, Dijon, France.
Etienne
E
Martin
Department of Radiation Oncology, Georges François Leclerc Cancer Center, Dijon, France.
Philippe
P
Maingon
Medical Imaging Group, Laboratory of Electronics, Computer Science and Imaging (Le2I), CNRS 6306, University of Burgundy, France; Department of MR Spectroscopy, University Hospital Le Bocage, Dijon, France.
Paul
P
Walker
Department of Radiation Oncology, Georges François Leclerc Cancer Center, Dijon, France; Medical Imaging Group, Laboratory of Electronics, Computer Science and Imaging (Le2I), CNRS 6306, University of Burgundy, France. Electronic address: gcrehange@cgfl.fr.
Gilles
G
Créhange
D000368:Aged; D001918:Brachytherapy; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011874:Radiometry; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
D007457:Iodine Radioisotopes; D017430:Prostate-Specific Antigen
Brachytherapy; Dosimetry; Iodine seeds; MRI; PSA bounce; Prostate