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. 2018 Apr 12;13(1):65.
doi: 10.1186/s13014-018-1014-1.

The dose distribution in dominant intraprostatic tumour lesions defined by multiparametric MRI and PSMA PET/CT correlates with the outcome in patients treated with primary radiation therapy for prostate cancer

Constantinos Zamboglou  1   2   3 , Christina Marie Klein  4 , Benedikt Thomann  5   6 , Thomas Franz Fassbender  7   6 , Hans C Rischke  4   6 , Simon Kirste  4   6 , Karl Henne  4   6 , Natalja Volegova-Neher  4   6 , Michael Bock  8   6 , Mathias Langer  8   6 , Philipp T Meyer  7   6 , Dimos Baltas  5   6 , Anca L Grosu  4   6
Affiliations

The dose distribution in dominant intraprostatic tumour lesions defined by multiparametric MRI and PSMA PET/CT correlates with the outcome in patients treated with primary radiation therapy for prostate cancer

Constantinos Zamboglou et al. Radiat Oncol. .

Abstract

Background: We hypothesized that dominant intraprostatic lesions (DILs) could be depictured by multimodal imaging techniques (MRI and/or PSMA PET/CT) in patients with primary prostate cancer (PCa) and investigated possible effects of radiotherapy (RT) dose distribution within the DILs on the patients’ outcome.

Methods: One hundred thirty-eight patients with localized prostate cancer (PCa) and visible DIL underwent primary external beam RT between 2008 and 2016 with an aimed prescription dose of 76 Gy to the whole prostate. Seventy-five patients (54%) additionally received androgen deprivation therapy. Three volumes were retrospectively generated: DIL using pretreatment MRI and/or PSMA PET/CT, prostatic gland (PG) and the subtraction between PG and DIL (SPG). The minimum dose (Dmin), maximum dose (Dmax) and mean dose (Dmean) in the three respective volumes were calculated. Biochemical recurrence free survival (BRFS) was considered in uni- and multivariate Cox regression analyses. An explorative analysis was performed to determine cut-off values for the three dose parameters in the three respective volumes.

Results: With a median follow-up of 45 months (14–116 months) 15.9% of patients experienced BR. Dmin (cut-off: 70.6 Gy, HR = 0.39, p = 0.036) applied to the DIL had an impact on BRFS in multivariate analysis, in contrast to the Dmin delivered to PG and SPG which had no significant impact (p > 0.05). Dmin was significantly (p < 0.004) lower in patients with BR than in patients without BR. Dmax within DIL-imaging (cut-off: 75.8 Gy, HR = 0.31, p = 0.009) and in both PG und SPG (cut-off: 76 Gy, HR = 0.32, p = 0.009) had a significant impact on the BRFS. 95% of patients with a Dmax ≥76 Gy in SPG had a Dmin ≥70.6 Gy in DIL-imaging. Dmean in all of the three volumes had no significant impact on BRFS (p > 0.05).

Conclusions: The dose distribution within DILs defined by PSMA PET/CT and/or MRI is an independent risk factor for BR after primary RT in patients with PCa. These findings support the implementation of imaging based DIL interpretation for RT treatment planning, although further validation in larger patient cohorts with longer follow-up is needed.

Keywords: Dominant lesion; MRI; PSMA PET/CT; Prostate cancer; Radiation dose.

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Conflict of interest statement

Ethics approval and consent to participate

All patients gave written consent to undergo pretreatment imaging (MRI and/or PSMA PET/CT) and radiotherapy. This retrospective analysis is in compliance with the principles of the Declaration of Helsinki and its subsequent amendments [28]. It was approved by the local Ethics Committee.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Correlation between tumor volume depicted in multimodal imaging and dose distribution. A 82 year old patient with biopsy confirmed PCa (Gleason score 9) and an initial PSA of 8 ng/ml underwent mpMRI (a:T2w, b:ADC), PSMA PET/CT (c) and a planning CT (d) before EBRT. MpMRI depicted one lesion in the left lobe and PSMA PET depicted one lesion in the left lobe and one lesion in the right lobe. In picture D the IMRT dose-distribution with contours of the prostatic gland (red), PSMA PET (blue) and MRI (orange) are shown. Dmax (red dot) was located outside the DIL-imaging volume
Fig. 2
Fig. 2
Comparison of Dmin values in patients with and without BR. Dmin was significant (p < 0.004) lower in patients with BR (72.4 Gy, range: 53.7–75.9 Gy) than in patients without BR (73.4 Gy, range: 63.3–78.3 Gy). Mann-Whitney test was used for comparison
Fig. 3
Fig. 3
Kaplan-Meier curves for BRFS. Statistical comparison with Log-rank test revealed p < 0.017 and p < 0.009 when tested on Dmin (cut-off value 70.6 Gy) and Dmax (cut-off value 75.8 Gy), respectively
See this image and copyright information in PMC

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