- Pictorial Review
- Open Access
Post-treatment MRI aspects of photodynamic therapy for prostate cancer
© The Author(s) 2014
- Received: 14 April 2014
- Accepted: 8 September 2014
- Published: 7 October 2014
Photodynamic therapy is a new focal therapy for prostate cancer.
In this technique, a photosensitising agent is introduced intravenously, then activated by local laser illumination to induce tumour necrosis. Treatment efficacy is assessed by magnetic resonance imaging (MRI).
Results and Conclusions
We illustrate specific post-treatment MRI aspects at early and late follow-up with pathological correlations.
• Dynamic phototherapy is a new and promising focal therapy for prostate cancer.
• One-week MRI shows increased volume of the treated lobe and large, homogeneous necrosis area.
• Six-month MRI shows significant changes of the prostate shape and signal.
• Six-month MRI becomes “base line” appearance for further follow-up or monitoring.
- Photodynamic therapy
- Prostate cancer
In 2012, with 417,000 new cases and 92,200 deaths, prostate cancer was the third most common cancer in Europe overall after female breast cancer and colorectal cancer . In men only it was the most common cancer, followed by lung and colorectal cancers. The incidence of prostate cancer, especially for localised disease, has been growing since the 1990s, a dynamic that may be attributable to the widespread use of prostate-specific antigen (PSA) tests  and increasing life expectancies.
The management of prostate cancer is still under debate in the urological community. Radical prostatectomy, external beam radiotherapy or brachytherapy are still considered gold-standard treatments, but carry with them well-known side effects (urinary incontinence, erectile dysfunction, intestinal toxicity). Active surveillance and watchful waiting are attractive options for localised tumours . Various focal treatments, such as phototherapy, cryotherapy, interstitial thermotherapy and dynamic high-frequency ultrasound (HIFU), are being evaluated [4, 5].
However, the changes induced by photodynamic therapy are poorly reported in the literature. Thus in the present pictorial review, we illustrate various MRI features in the follow-up of patients who underwent photodynamic therapy for localised prostate cancer. We studied early and late normal aspects, local complications and aspects of recurrence, with histopathological correlation.
The iconography presented in this paper comes from a group of 77 patients enrolled by our institution in a prospective international multicentric study (phase II/III), and who received photodynamic therapy with WST11 (Tookad soluble) for localised prostate cancer.
Inclusion criteria are: men over 18 years old; diagnosed prostate cancer histologically proved on biopsies (systematic biopsies most of the time, rarely targeted biopsies); eligible for active surveillance; no prior treatment for prostate cancer; TNM stage up to cT2b- N0/Nx- M0/Mx; Gleason score ≤ 3 + 3, 3 + 4 accepted in certain conditions; PSA <10 ng/ml. The prostate cancer diagnosis was histological. All patients had a pre-treatment MRI then post-treatment MRIs at 1 week (early post-treatment) and 6 months (late post-treatment). Some of the patients also had a post-treatment MRI at 3 months. Systematic biopsies with TRUS (trans-rectal ultrasound) guidance were performed at 6 months to explore correlations to MRI features. In case of positive biopsy at 6 months, function of the Gleason score, different options were proposed to the patients: treatment of the other lobe, retreatment on the same lobe, active surveillance or surgery.
All MRIs were performed with a 1.5-T MRI system (GE Excite, General Electrics, Milwaukee, IL). An external body surface coil (eight channels) was used, with a field of view (FOV) equal to 24 cm, except for the dynamic contrast-enhanced sequences for which FOV was 42 cm.
The imaging protocol included the following sequences: axial and coronal FRFSE T2 with fat saturation (4-mm slice thickness), axial FSE T1 (4-mm slice thickness), axial diffusion-weighted (b = 600 s/mm2); a three-dimensional (3D) dynamic contrast-enhanced T1 sequence (LAVA) with fat saturation after intravenous injection of 20 ml gadoterate meglumine (Dotarem, Guerbet, France), followed by axial and sagittal fat saturation contrast-enhanced FSE T1-weighted images. These last sequences were systematically realised, to better define boundaries of necrosis, especially in case of extra prostatic necrosis.
Pre- and post-treatment MRI exams were analysed on an imaging work station (Fujifilm Synapse 3D). We analysed MRI modifications for the areas treated with photodynamic therapy (optical fibre disposition map) and the histopathological results of systematic 6-month biopsies. Some patients underwent prostatectomy after the phototherapy treatment, permitting a more accurate radiological-pathological correlation.
PIRADS classification was not used for treatment planning. Pre-treatment MRI served only to plan the anatomic distribution of the optic fibres into the lobe to be treated, targeting the zones of positive biopsy. The PIRADS criteria were used for the follow-up MRI analyses.
Pre-treatment MRI was performed as a planning procedure to determine the position and the number of optical fibres and to exclude any loco-regional extension that would have contraindicated the treatment.
Early post-treatment MRI features
Finally, it is important to note that on the 1-week post-therapy images the surroundings of the gland may also show enhancement due to local inflammation.
Late post-treatment MRI features
Treatment-emergent adverse events (TEAEs) of photodynamic therapy. Data from Azzouzi et al. study 
UTI (urinary tractus infection)
Ischaemic optic neuropathy
Inflammatory prostatic cyst
The main post-photodynamic therapy complication is extraprostatic necrosis, defined as a lack of enhancement on T1-weighted contrast-enhanced MR images  involving the different structures surrounding the prostate.
Recurrence in the treated area
MRI detection of tumour recurrence in the treated area is made difficult by the loss of the normal hyperintensity of the peripheral prostate in T2-weighted images and the signal of the scar.
Thus, after photodynamic therapy, the diagnosis of recurrence is mainly based on PSA levels and systematic biopsy.
Photodynamic therapy is a new and promising focal treatment for localised prostate cancer. Early and late post-treatment MRI aspects are specific. Necrosis is obtained at 1 week and the final post treatment aspect at 6 months. Knowledge of these features permits the appreciation of treatment efficacy and the accurate diagnosis of complications or recurrence.
Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
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