Cold spot mapping inferred from MRI at time of failure predicts biopsy-proven local failure after permanent seed brachytherapy in prostate cancer patients: Implications for focal salvage brachytherapy

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• 作者：Gilles Crehange ; Devan Krishnamurthy ; J. Adam Cunha ; Barby Pickett ; John Kurhanewicz ; I-Chow Hsu ; Alex ; er R. Gottschalk ; Katsuto Shinohara ; Mack Roach III ; Jean Pouliot
• 关键词：Prostate cancer ; Prostate permanent implant ; Seeds ; Local failure ; MR-based dosimetry
• 刊名：Radiotherapy and Oncology
• 出版年：November, 2013
• 年：2013
• 卷：109
• 期：2
• 页码：246-250
• 全文大小：770 K

文摘

Background and purpose

(1) To establish a method to evaluate dosimetry at the time of primary prostate permanent implant (pPPI) using MRI of the shrunken prostate at the time of failure (t_f).

(2) To compare cold spot mapping with sextant-biopsy mapping at t_f.

Material and methods

Twenty-four patients were referred for biopsy-proven local failure (LF) after pPPI. Multiparametric MRI and combined-sextant biopsy with a central review of the pathology at t_f were systematically performed.

A model of the shrinking pattern was defined as a Volumetric Change Factor (VCF) as a function of time from time of pPPI (t₀). An isotropic expansion to both prostate volume (PV) and seed position (SP) coordinates determined at t_f was performed using a validated algorithm using the VCF.

Results

pPPI CT-based evaluation (at 4 weeks) vs. MR-based evaluation: Mean D90% was 145.23 卤 19.16 Gy [100.0-167.5] vs. 85.28 卤 27.36 Gy [39-139] (p = 0.001), respectively. Mean V100% was 91.6 卤 7.9% [70-100%] vs. 73.1 卤 13.8% [55-98%] (p = 0.0006), respectively. Seventy-seven per cent of the pathologically positive sextants were classified as cold.

Conclusions

Patients with biopsy-proven LF had poorer implantation quality when evaluated by MRI several years after implantation. There is a strong relationship between microscopic involvement at t_f and cold spots.