Time to metabolic atrophy after permanent prostate seed implantation based on magnetic resonance spectroscopic imaging

Metabolic Vulnerabilities of Prostate Cancer: Diagnostic and Therapeutic Opportunities

Cancer cells hijack metabolic pathways to support bioenergetics and biosynthetic requirements for their uncontrolled growth. Thus, cancer can be considered as a metabolic disease. In this review, we discuss the main metabolic features of prostate cancer with a particular focus on the link between oncogene-directed cancer metabolic regulation, metabolism rewiring, and epigenetic regulation. The potential of using metabolic profiling as a means to predict disease behavior and to identify novel therapeutic targets and new diagnostic markers will be addressed as well as the current challenges in metabolomics analyses. Finally, diagnostic and prognostic metabolic imaging approaches, including positron emission tomography, mass spectrometry, nuclear magnetic resonance, and their translational applications, will be discussed. Here, we emphasize how targeting metabolic vulnerabilities in prostate cancer may pave the way for novel personalized diagnostic and therapeutic interventions.

Metabolic Imaging in Humans

Metabolic imaging enhances understanding of disease metabolisms and holds great potential as a measurement tool for evaluating disease prognosis and treatment effectiveness. Advancement of techniques, such as magnetic resonance spectroscopy, positron emission tomography, and mass spectrometry, allows for improved accuracy for quantification of metabolites and present unique possibilities for use in clinic. This article reviews and discusses literature reports of metabolic imaging in humans published since 2010 according to disease type, including cancer, degenerative disorders, psychiatric disorders, and others, as well as the current application of the various related techniques.

Low-dose rate brachytherapy for patients with low- or intermediate-risk prostate cancer: A systematic review

INTRODUCTION

We review the current evidence for the role of low-dose rate brachytherapy (PB) in patients with low- or intermediate-risk prostate cancer using a systematic review of the literature.

METHODS

We searched MEDLINE and EMBASE (from January 1996 to October 2011), the Cochrane Library, relevant guideline web-sites, and websites for meetings specific for genitourinary diseases.

RESULTS

Ten systematic reviews and 55 single-study papers met the pre-planned study selection criteria. In the end, 36 articles were abstracted and analyzed for this systematic review. There is no evidence for a difference in efficacy between PB and external beam radiation therapy (EBRT), or between PB and radical prostatectomy (RP). During the 6 months to 3 years after treatment, PB was associated with less urinary incontinence and sexual impotency than RP, and RP was associated with less urinary irritation and rectal morbidity than PB. However, these differences diminished over time. PB conferred less risk of impotency and rectal morbidity in the three years after treatment than EBRT. Iodine-125 and alladium-103 did not differ with respect to biochemical relapse-free survival and patient-reported outcomes.

CONCLUSIONS

PB alone is a treatment option with equal efficacy to EBRT or RP alone in patients with newly diagnosed low- or intermediate-risk prostate cancer who require or choose active treatment.

The role of metabolic imaging in radiation therapy of prostate cancer

The goal of this study was to correlate prostatic metabolite concentrations from snap-frozen patient biopsies of recurrent cancer after failed radiation therapy with histopathological findings, including Ki-67 immunohistochemistry and pathologic grade, in order to identify quantitative metabolic biomarkers that predict for residual aggressive versus indolent cancer. A total of 124 snap-frozen transrectal ultrasound (TRUS)-guided biopsies were acquired from 47 men with untreated prostate cancer and from 39 men with a rising prostate-specific antigen and recurrent prostate cancer following radiation therapy. Biopsy tissues with Ki-67 labeling index ≤ 5% were classified as indolent cancer, while biopsy tissues with Ki-67 labeling index > 5% were classified as aggressive cancer. The majority (15 out of 17) of cancers classified as aggressive had a primary Gleason 4 pattern (Gleason score ≥ 4 + 3). The concentrations of choline-containing phospholipid metabolites (PC, GPC, and free Cho) and lactate were significantly elevated in recurrent cancer relative to surrounding benign tissues. There was also a significant increase in [PC] and reduction in [GPC] between untreated and irradiated prostate cancer biopsies. The concentration of the choline-containing phospholipid metabolites was significantly higher in recurrent aggressive (≈ twofold) than in recurrent indolent cancer biopsies, and the receiver operating characteristic (ROC) curve analysis of total choline to creatine ratio (tCho/Cr) demonstrated an accuracy of 95% (confidence interval = 0.88-1.00) for predicting aggressive recurrent disease. The tCho/Cr was significantly higher for identifying recurrent aggressive versus indolent cancer (tCho/Cr = 2.4 ± 0.4 versus 1.5 ± 0.2), suggesting that use of a higher threshold tCho/Cr ratio in future in vivo (1)H MRSI studies could improve the selection and therapeutic planning for patients who would benefit most from salvage focal therapy after failed radiation therapy.

Multi-Parametric MRI-Directed Focal Salvage Permanent Interstitial Brachytherapy for Locally Recurrent Adenocarcinoma of the Prostate: A Novel Approach

Even with the technological advances of dose-escalated IMRT with the addition of the latest image guidance technologies, local failures still occur. The combination of MRI-based imaging techniques can yield quantitative information that reflects on the biological properties of prostatic tissues. These techniques provide unique information that can be used for tumor detection in the treated gland. With the advent of these improved imaging modalities, it has become possible to more effectively image local recurrences within the prostate gland. With better imaging, these focal recurrences can be differentially targeted with salvage brachytherapy minimizing rectal and bladder toxicity. Here we report a novel use of MRI-directed focal brachytherapy after local recurrence. This technique offers a unique opportunity to safely and successfully treat recurrent prostate cancer, previously treated with definitive radiation therapy. The use of multi-parametric MRI-directed focal salvage permanent interstitial brachytherapy for locally recurrent adenocarcinoma of the prostate is a promising strategy to avoid more aggressive and expensive treatments that are associated with increased morbidity, potentially improving survival at potentially lower costs.

[Multiparametric prostate MRI for follow-up monitoring after radiation therapy]

CLINICAL/METHODICAL ISSUE

Radiation therapy is a therapeutic option with curative intent for patients with prostate cancer. Monitoring of prostate-specific antigen (PSA) values is the current standard of care in the follow-up. Imaging is recommended only for symptomatic patients and/or for further therapeutic options.

STANDARD RADIOLOGICAL METHODS

For detection of local recurrence magnetic resonance imaging (MRI) of the prostate is acknowledged as the method of choice.

PERFORMANCE

Good results for primary diagnosis were found especially in combination with functional techniques, whereas in recurrent prostate cancer only few studies with heterogeneous study design are available for prostate MRI. Furthermore, changes in different MRI modalities due to radiation therapy have been insufficiently investigated to date.

PRACTICAL RECOMMENDATIONS

As the initial results were promising prostate MRI and available therapeutic options for detection of local recurrence should be considered in patients with increased PSA.

Multiparametric 3T endorectal mri after external beam radiation therapy for prostate cancer

PURPOSE

To determine the best combination of magnetic resonance imaging (MRI) parameters for the detection of locally recurrent prostate cancer after external beam radiation therapy.

MATERIALS AND METHODS

Our Institutional Review Board approved this study with a waiver of informed consent. Twenty-six patients with suspected recurrence due to biochemical failure were part of this research. The MR protocol included T2-weighted, MR spectroscopy, and diffusion-weighted MRI. Transrectal ultrasound-guided biopsy was the standard of reference. We used logistic regression to model the probability of a positive outcome and generalized estimating equations to account for clustering. The diagnostic performance of imaging was described using receiver operating characteristic (ROC) curves.

RESULTS

The area under the ROC curve of MR spectroscopic imaging (MRSI) was 83.0% (95% confidence interval [CI] = 75.5-89.1). The combination of all MR techniques did not significantly improve the performance of imaging beyond the accuracy of MRSI alone, but a trend toward improved discrimination was noted (86.9%; 95% CI = 77.6-93.4; P = 0.09).

CONCLUSION

Incorporation of MRSI to T2-weighted and/or diffusion-weighted MRI significantly improves the assessment of patients with suspected recurrence after radiotherapy and a combined approach with all three modalities may have the best diagnostic performance.

Feasibility of MR imaging/MR spectroscopy-planned focal partial salvage permanent prostate implant (PPI) for localized recurrence after initial PPI for prostate cancer

PURPOSE

To assess the feasibility of magnetic resonance imaging (MRI)-planned partial salvage permanent prostate implant (psPPI) among patients with biopsy-proven local recurrence after initial PPI without evidence of distant disease.

METHODS AND MATERIALS

From 2003-2009, 15 patients underwent MRI/magnetic resonance spectroscopy (MRS) planning for salvage brachytherapy (psPPI, I-125 [n=14; 144 Gy]; Pd-103 [n=1; 125 Gy]) without hormone therapy. Full dose was prescribed to areas of recurrence and underdosage, without entire prostate implantation. Limiting urethral and rectal toxicity was prioritized. Follow-up was from salvage date to prostate-specific antigen (PSA) concentration failure (Phoenix criteria = nadir + 2.0; ASTRO = 3 consecutive rises), recurrence, distant metastases, or last follow-up PSA level. Progression-free survival (PFS) was defined as no PSA failure or biopsy-proven recurrence without all-cause mortality. Toxicity was scored using Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

At salvage, median age was 68 years, and PSA concentration was 3.5 ng/mL (range, 0.9-5.6 ng/mL). Abnormal MRI/MRS findings were evident in 40% of patients. Biopsy-proven recurrences consisted of a single focus (80%) or 2 foci (20%). At recurrence, Gleason score was 6 (67%) or ≥7 (27%). Median interval between initial and salvage implantation was 69 months (range, 28-132 months). psPPI planning characteristics limited doses to the rectum (mean V100 = 0.5% [0.07 cc]) and urethra (V100 = 12% [0.3 cc]). At median follow-up (23.3 months; range, 8-88 months), treatment failure (n=2) resulted only in localized recurrence; both patients underwent second psPPI with follow-up PSA tests at 12 and 26 months, resulting in 0.6 and 0.7 ng/mL, respectively. American Society for Radiation Oncology PFS rates at 1, 2, and 3 years were 86.7%, 78.4%, and 62.7%, respectively, with 5 patients for whom treatment failed (n=3 with negative transrectal ultrasound-guided biopsy results). Phoenix PFS rates at 1, 2, and 3 years were 100%, 100%, and 71.4%. 73%, respectively; achieved PSA nadir of <0.5 ng/mL; and 47% of patients had a nadir of <0.1 ng/mL. Treatment-related toxicity was minimal, with no operative interventions, fistulas, or other grade ≥3 gastrointestinal (GI)/genitourinary (GU) toxicity. Thirteen percent had grade 1 GI and 33% had grade 2 GU toxicities. Postsalvage, 20% of patients had no erectile dysfunction, 67% of patients had medication-responsive erectile dysfunction, and 13% of patients had erectile dysfunction refractory to medication.

CONCLUSIONS

Focal psPPI with MR-planning in highly selected patients is feasible with short-term control comparable to conventional salvage, with less toxicity. Longer follow-up is needed to confirm its impact on quality of life and treatment.

Imaging techniques for local recurrence of prostate cancer: for whom, why and how?

Since there are salvage solutions, it is important to detect local recurrence of prostate cancer as early as possible. The first sign is "biochemical failure" in that the prostate specific antigen (PSA) concentration rises again. The definition of biochemical failure varies depending on the initial treatment: PSA greater than 0.2ng/mL after prostatectomy, nadir+2ng/mL after radiotherapy. There is no standardised definition of biochemical failure after cryotherapy, focused ultrasound, or brachytherapy. Magnetic resonance imaging (MRI) (particularly dynamic MRI) can detect local recurrence with good sensitivity. The role of spectroscopy is still under discussion. For the moment, ultrasound techniques are less effective than MRI.

Locally advanced prostate cancer: three-dimensional magnetic resonance spectroscopy to monitor prostate response to therapy

PURPOSE

To correlate results of three-dimensional magnetic resonance spectroscopic imaging (MRSI) with prostate-specific antigen (PSA) levels and time since external beam irradiation (EBRT) in patients treated with long-term hormone therapy (HT) and EBRT for locally advanced disease to verify successful treatment by documenting the achievement of metabolic atrophy (MA).

METHODS AND MATERIALS

Between 2006 and 2008, 109 patients were consecutively enrolled. MA was assessed by choline and citrate peak area-to-noise-ratio <5:1. Cancerous metabolism (CM) was defined by choline-to-creatine ratio >1.5:1 or choline signal-to-noise-ratio >5:1. To test the strength of association between MRSI results and the time elapsed since EBRT (TEFRT), PSA levels, Gleason score (GS), and stage, logistic regression (LR) was performed. p value <0.05 was statistically significant. The patients' outcomes were verified in 2011.

RESULTS

MRSI documented MA in 84 of 109 and CM in 25 of 109 cases. LR showed that age, GS, stage, and initial and recent PSA had no significant impact on MRSI results which were significantly related to PSA values at the time of MRSI and to TEFRT. Patients were divided into three groups according to TEFRT: <1 year, 1-2 years, and >2 years. MA was detected in 54.1% of patients of group 1, 88.9% of group 2, and in 94.5% of group 3 (100% when PSA nadir was reached). CM was detected in 50% of patients with reached PSA nadir in group 1. Local relapse was found in 3 patients previously showing CM at long TEFRT.

CONCLUSION

MA detection, indicative of successful treatment because growth of normal or abnormal cells cannot occur without metabolism, increases with decreasing PSA levels and increasing time on HT after EBRT. This supports long-term HT in advanced prostate cancer. Larger study series are needed to assess whether MRSI could predict local relapse by detecting CM at long TEFRT.

A pilot study of endorectal magnetic resonance imaging and magnetic resonance spectroscopic imaging changes with dutasteride in patients with low risk prostate cancer

OBJECTIVE

•To evaluate the effects of dutasteride on treatment-naïve prostate cancer in men using serial magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) in this pilot study.

PATIENTS AND METHODS

•This investigator-initiated prospective single-arm study was approved by the institutional committee on human research ethics board. •The target accrual was 10 patients. Newly diagnosed prostate cancer patients with low risk disease either with symptomatic benign prostatic hypertrophy or deemed to require pre-brachytherapy androgen suppression therapy were eligible. In the latter group, dutasteride was used to achieve cytoreduction. •All patients received 6 months of dutasteride 3.5 mg daily and underwent baseline blood work, health-related quality of life indices and MRI/MRSI, which were repeated at 1, 3 and 6 months. •MRSI spectra were examined and scored as healthy or cancerous. The change in cancerous volumes over time was evaluated.

RESULTS

•Of the 10 patients enrolled, nine patients completed the entire study. One patient withdrew after 3 months because of drug-related toxicity. •Because a significant decrease in citrate and polyamines on MRSI spectra was noted at 1 month compared with baseline, healthy tissue appeared to be more like cancer and thus created a false impression that the cancer had grown after 1 month. To reduce this bias, comparisons were made between the 1-month and 6-month scans. •The median MR cancer volumes at 6 months and 3 months were 100% and 101% of the 1-month value, respectively. Three of the nine patients had a 30-45% decrease in cancer volume at 6 months relative to 1-month measures. Of the others, two had no change in cancer volume and four had an increase (range 65-167% of the 1-month value). •The median cancer volume (range) at baseline was only 0.5 (0.1-5.6) mL.

CONCLUSIONS

•The inclusion of only men with low volume disease may have limited our ability to accurately assess response rates after dutasteride due to the background effects on normal prostate metabolism. Despite this, one-third of patients had a 30-45% reduction in cancer volume at 6 months. •Future studies including men with larger volume disease may enable estimates of response rates to be made more accurately.

MRS-guided HDR brachytherapy boost to the dominant intraprostatic lesion in high risk localised prostate cancer

Background

It is known that the vast majority of prostate cancers are multifocal. However radical radiotherapy historically treats the whole gland rather than individual cancer foci.

Magnetic resonance spectroscopy (MRS) can be used to non-invasively locate individual cancerous tumours in prostate. Thus an intentionally non-uniform dose distribution treating the dominant intraprostatic lesion to different dose levels than the remaining prostate can be delivered ensuring the maximum achievable tumour control probability.

The aim of this study is to evaluate, using radiobiological means, the feasibility of a MRS-guided high dose rate (HDR) brachytherapy boost to the dominant lesion.

Methods

Computed tomography and MR/MRS were performed for treatment planning of a high risk localised prostate cancer. Both were done without endorectal coil, which distorts shape of prostate during the exams.

Three treatment plans were compared:

- external beam radiation therapy (EBRT) only

- combination of EBRT and HDR brachytherapy

- combination of EBRT and HDR brachytherapy with a synchronous integrated boost to the dominant lesion

The criteria of plan comparison were: the minimum, maximum and average doses to the targets and organs at risk; dose volume histograms; biologically effective doses for organs at risk and tumour control probability for the target volumes consisting of the dominant lesion as detected by MR/MRS and the remaining prostate volume.

Results

Inclusion of MRS information on the location of dominant lesion allows a safe increase of the dose to the dominant lesion while dose to the remaining target can be even substantially decreased keeping the same, high tumour control probability. At the same time an improved urethra sparing was achieved comparing to the treatment plan using a combination of EBRT and uniform HDR brachytherapy.

Conclusions

MRS-guided HDR brachytherapy boost to dominant lesion has the potential to spare the normal tissue, especially urethra, while keeping the tumour control probability high.

Locally recurrent prostate cancer after external beam radiation therapy: diagnostic performance of 1.5-T endorectal MR imaging and MR spectroscopic imaging for detection

PURPOSE

To determine if performing magnetic resonance (MR) spectroscopic imaging, compared with performing T2-weighted MR imaging alone, improves the detection of locally recurrent prostate cancer after definitive external beam radiation therapy.

MATERIALS AND METHODS

This retrospective single-institution study was approved by the committee on human research, with a waiver of informed consent, and was compliant with HIPAA requirements. Sixty-four men who underwent endorectal MR imaging, MR spectroscopic imaging, and transrectal ultrasonographically guided biopsy for suspected local recurrence of prostate cancer after definitive external beam radiation therapy were retrospectively identified. Thirty-three patients had also received androgen therapy. Recurrent cancer was determined to be present or absent in the left and right sides of the prostate at T2-weighted MR imaging and MR spectroscopic imaging by a radiologist and a spectroscopist, respectively. Area under the receiver operating characteristic curve (A(Z)) was calculated for T2-weighted MR imaging alone and combined T2-weighted MR imaging and MR spectroscopic imaging by using generalized estimating equations and by using biopsy results as the reference standard.

RESULTS

Recurrent prostate cancer was identified at biopsy in 37 (58%) of the 64 men. Recurrence was unilateral in 28 patients and bilateral in nine (total of 46 affected prostate sides). A(Z) analysis revealed that use of combined T2-weighted MR imaging and MR spectroscopic imaging (A(Z) = 0.79), as compared with T2-weighted MR imaging alone (A(Z) = 0.67), significantly improved the detection of local recurrence (P = .001).

CONCLUSION

The addition of MR spectroscopic imaging to T2-weighted MR imaging significantly improves the diagnostic accuracy of endorectal MR imaging in the detection of locally recurrent prostate cancer after definitive external beam radiation therapy.

Role of MRI in follow-up after focal therapy for prostate carcinoma

OBJECTIVE

In patients with clinically suspected local recurrence of prostate cancer, a lobulated hyperintense mass in the radical prostatectomy fossa can be readily visualized with T2-weighted MRI, but this imaging technique is less successful after treatments such as radiation therapy, high-intensity focused ultrasound, and cryosurgery. We describe the additional value of functional techniques in the assessment of local recurrence.

CONCLUSION

The use of functional MRI techniques such as MR spectroscopy, diffusion-weighted imaging, and dynamic contrast-enhanced MRI has shown promise in increasing overall imaging performance in the detection of local recurrence.

3D MR-spectroscopic imaging assessment of metabolic activity in the prostate during the PSA "bounce" following 125iodine brachytherapy

PURPOSE

A temporary increase in prostate-specific antigen (PSA) values is observed in 30%-40% of men following (125)I brachytherapy (BT) for prostate cancer. We present the results of a study to characterize prostate metabolic activity during the PSA "bounce" and to correlate metabolic changes with PSA levels using three-dimensional magnetic resonance spectroscopic imaging (3D-MRSI).

METHODS AND MATERIALS

3D-MRSI was performed in 24 patients during the PSA bounce. Eight of these had also had a baseline 3D-MRSI scan before BT for the purpose of tumor mapping. The 3D-MRSI was repeated at 6- and 12-month intervals, and PSA levels were monitored every 3 months. Twenty-one of the patients had favorable-risk prostate cancer, and 3 had intermediate risk.

RESULTS

The choline+creatine signal intensity, although markedly reduced, was observable following BT. Diffuse activity not corresponding to original biopsy-positive sites was observed in 22 cases, and 2 cases were documented to have local recurrence. No statistically significant correlation between metabolic activity and PSA levels at each interval was found.

CONCLUSION

Post-BT prostate 3D-MRSI shows evidence of diffuse metabolic activity unrelated to residual malignancy. This supports the benign nature of the PSA bounce and suggests an inflammatory etiology. In the situation of a rising PSA, observation of focal activity on MRI/3D-MRSI could be a useful adjunct to suggest local recurrence at an earlier interval after brachytherapy when prostate biopsies would still be unhelpful. Longer follow-up is necessary to confirm the complex relationship between metabolic activity and PSA levels.

Prognostic factors in patients with acute liver failure undergoing live donor liver transplantation

Mortality from acute liver failure (ALF) is high. Live donor liver transplantation (LDLT) is the treatment of choice for ALF in Asia, because cadaveric donors are rare. We sought to review our results in ALF patients with undergoing LDLT at our center. One hundred two LDLTs were performed at our center from April 2002 to November 2007, 15 (14%) because of ALF. Mean (SEM; median, range) follow-up was 1,065 (189; 1400; 3-2046) days. Nine patients (60%) had acute exacerbation of chronic hepatitis B; and 6 (40%) had drug-induced liver injury. Age was 47 (3; 50; 27-65) years. Ten patients (67%) were men. At transplantation, laboratory values were included bilirubin, 449 (35) micromol/L; creatinine concentration, 182 (32) mmol/L. The international normalized ratio was 2.4 (0.2). The Model for End-Stage Liver Disease (MELD) score was 34 (2). Both inpatient and long-term mortality was 20% 3 of 15 patients died. The 5-year survival was 80%. Compared with survivors, patients who died had a significantly higher creatinine concentration 289 vs 155 micromol/L, international normalized ratio (3.4 vs 2.1), MELD score (47 vs 32). We conclude that despite being sick with median and mean MELD scores of 32 and 34, 80% of patients with ALF can achieve good long-term survival after LDLT.

Changes in prostate shape and volume and their implications for radiotherapy after introduction of endorectal balloon as determined by MRI at 3T

PURPOSE

To determine the changes in prostate shape and volume after the introduction of an endorectal coil (ERC) by means of magnetic resonance imaging (MRI) at 3T.

METHODS AND MATERIALS

A total of 44 consecutive patients with biopsy-proven prostate cancer underwent separate MRI examinations at 3T with a body array coil and subsequently with an ERC inflated with 50 mL of fluid. Prospectively, two experienced readers independently evaluated all data sets in random order. The maximal anteroposterior, right-to-left, and craniocaudal prostate diameters, as well as the total prostate and peripheral zone and central gland volumes were measured before and after ERC introduction. The changes in prostate shape and volume were analyzed using Wilcoxon's test for paired samples.

RESULTS

The introduction of the ERC significantly changed the prostate shape in all three directions, with mean changes in the anteroposterior, right-to-left, and craniocaudal diameters of 15.7% (5.5 mm), 7.7% (3.5 mm), and 6.3% (2.2 mm), respectively. The mean total prostate, peripheral zone, and central gland volume decreased significantly after ERC introduction by 17.9% (8.3 cm(3)), 21.6% (4.8 cm(3)), and 14.2% (3.4 cm(3)), respectively.

CONCLUSION

ERC introduction as observed by 3T MRI changed the prostate shape and volume significantly. The mean anteroposterior diameter was reduced by nearly one-sixth of its original diameter, and the mean total prostate volume was decreased by approximately 18%. This could cause difficulties and should be considered when using ERC-based MRI for MRI-computed tomography fusion and radiotherapy planning.

Advances in MR spectroscopy of the prostate

Commercial MR imaging/magnetic resonance spectroscopic imaging (MRSI) packages for staging prostate cancer on 1.5-T MR scanners are now available. The technology is becoming mature enough to begin assessing its clinical utility in selecting, planning, and following prostate cancer therapy. Before therapy, 1.5-T MR imaging/MRSI has the potential to improve the local evaluation of prostate cancer presence and volume and has a significant incremental benefit in the prediction of pathologic stage when added to clinical nomograms. After therapy, two metabolic biomarkers of effective and ineffective therapy have been identified and are being validated with 10-year outcomes. Accuracy can be improved by performing MR imaging/MRSI at higher magnetic field strengths, using more sensitive hyperpolarized (13)C MRSI techniques and through the addition of other functional MR techniques.

Permanent prostate seed brachytherapy: a current perspective on the evolution of the technique and its application

This Review highlights current areas of controversy and development in the field of transperineal permanent prostate seed implantation brachytherapy (PPI), in particular the technological evolution of PPI treatment planning that has led to intra-operative treatment planning and execution, the use of MRI spectroscopy and ultrasonography to target intraprostatic tumor foci, and the introduction of (131)Cs as a new PPI isotope. Here we present a comprehensive review of mature data for PPI monotherapy and PPI combined with supplemental external beam radiation therapy, and a critical discussion of issues pertinent to supplemental EBRT. We also present our current policies in the treatment of prostate cancer at the University of California, San Francisco.

Current role and future perspectives of magnetic resonance spectroscopy in radiation oncology for prostate cancer

Prostatic neoplasms are not uniformly distributed within the prostate volume. With recent developments in three-dimensional intensity-modulated and image-guided radiation therapy, it is possible to treat different volumes within the prostate to different thresholds of doses. This approach has the potential to adapt the dose to the biologic aggressiveness of various clusters of tumor cells within the gland. The definition of tumor burden volume in prostate cancer can be facilitated by the use of magnetic resonance spectroscopy (MRS). The increasing sensitivity and specificity of MRS to the prostate is causing new interest in its potential role in the definition of target subvolumes at higher risk of failure following radical radiotherapy. Prostate MRS might also play a role as a noninvasive predictive factor for tumor response and treatment outcome. We review the use of MRS in radiation therapy for prostate cancer by evaluating its accuracy in the classification of aggressive cancer regions and target definition; its current role in the radiotherapy planning process, with special interest in technical issues behind the successful inclusion of MRS in clinical use; and available early experiences as a prognostic tool.

Prostate and lymph node proton magnetic resonance (MR) spectroscopic imaging with external array coils at 3 T to detect recurrent prostate cancer after radiation therapy

In a patient suspected of having recurrent prostate cancer after radiation therapy, we demonstrate the feasibility of noninvasive proton magnetic resonance spectroscopic (1H-MRS) imaging of the prostate and a lymph node at 3 T using a matrix of external surface coils. Written informed consent was obtained from the patient. With 1H-MRS imaging, high choline with low citrate signal was observed in the prostate, and in the lymph node a signal of choline-containing compounds was identified. The tissue level of the compounds in the enlarged lymph node was estimated to be 8.1 mmol/kg water. Subsequent histopathological analysis of systematic transrectal ultrasound-guided prostate biopsy and computed tomography-guided biopsy of the lymph node confirmed the presence of prostate cancer in both.

Advances in the Treatment of Localized Prostate Cancer: The Role of Anatomic and Functional Imaging in Men Managed With Radiotherapy

Radiation therapy is an active modality in the management of local and regional prostate cancer, but can be curative only if all existing disease is encompassed within the treatment portal. In addition to the ability to deliver sufficient radiation dose, accurate targeting is critical to achieve better treatment outcomes. Failure to accommodate daily variations in setup and organ motion potentially limits the efficacy of sophisticated conformal techniques (three-dimensional conformal radiotherapy and intensity-modulated radiotherapy). Increased use of various online and real-time imaging techniques is an important step toward enhancing treatment accuracy. The incorporation of functional imaging techniques into treatment planning is another important step. The addition of biologic and metabolic information regarding the location and extent of disease combined with real-time online imaging will allow us to better determine where, how, and with what to treat appropriate targets and improve cure rates.

Defining biochemical failure following radiotherapy with or without hormonal therapy in men with clinically localized prostate cancer: recommendations of the RTOG-ASTRO Phoenix Consensus Conference

In 1996 the American Society for Therapeutic Radiology and Oncology (ASTRO) sponsored a Consensus Conference to establish a definition of biochemical failure after external beam radiotherapy (EBRT). The ASTRO definition defined prostate specific antigen (PSA) failure as occurring after three consecutive PSA rises after a nadir with the date of failure as the point halfway between the nadir date and the first rise or any rise great enough to provoke initiation of therapy. This definition was not linked to clinical progression or survival; it performed poorly in patients undergoing hormonal therapy (HT), and backdating biased the Kaplan-Meier estimates of event-free survival. A second Consensus Conference was sponsored by ASTRO and the Radiation Therapy Oncology Group in Phoenix, Arizona, on January 21, 2005, to revise the ASTRO definition. The panel recommended: (1) a rise by 2 ng/mL or more above the nadir PSA be considered the standard definition for biochemical failure after EBRT with or without HT; (2) the date of failure be determined "at call" (not backdated). They recommended that investigators be allowed to use the ASTRO Consensus Definition after EBRT alone (no hormonal therapy) with strict adherence to guidelines as to "adequate follow-up." To avoid the artifacts resulting from short follow-up, the reported date of control should be listed as 2 years short of the median follow-up. For example, if the median follow-up is 5 years, control rates at 3 years should be cited. Retaining a strict version of the ASTRO definition would allow comparisons with a large existing body of literature.

192Ir low dose rate brachytherapy for boosting locally advanced prostate cancers after external beam radiotherapy: A phase II trial

BACKGROUND AND PURPOSE

To evaluate on 201 locally advanced prostatic cancers prospectively treated in a phase II trial, the efficacy of a combination of external beam radiotherapy (39.6 Gy) and (192)Ir low dose rate brachytherapy (Bt) (40-45 Gy).

PATIENTS AND METHODS

Sixty-four patients were included in the intermediate prognosis group with only one of the following adverse factors (PSA > 10 ng/ml, Gleason score > or = 7 or clinical stage > or =T2b) and 137 in the unfavourable group when at least two of these factors were present.

RESULTS

The actuarial 4 years biochemical no evidence of disease is 82.8% for the entire population. It is, respectively, 97 and 76% in the intermediate and unfavourable prognosis groups (P < 0.0001). Grade > or =3 late urinary complications occurred in 13 patients (6.5%). Eight patients (4%) presented late grade 2 rectal complications but no grades 3-5 was observed.

CONCLUSIONS

Even if an alpha/beta of 1.5-3 Gy theoretically favours the use of a high dose rate mode of irradiation, the early results presented here are as good as those reported for similar groups of patients with high dose rate treatments. Late toxicity is identical but our urinary toxicity is within the less favourable and rectal toxicity within the most favourable results. We can postulate that while inducing very high hyperdosage regions (V150) mainly focused on the peripheral zone, most of the Bt techniques consist of a more ablative treatment. Many of the radiobiological studies on Bt did not in fact take into account the heterogeneity of irradiation inside the CTV. This study highlights the need to explore pulsed dose rate therapies, permanent implant and new available radioisotopes such as (169)Ytterbium that will offer the safety of low and lower dose rates. The actual late toxicity of the different Bt techniques is not yet inexistent indeed.

Radiotherapy in the management of common genitourinary malignancies

A continued role for radiation therapy in the multidisciplinary management of genitourinary malignancies seems certain. Treatment outcomes continue to improve, accompanied by diminishing rates of toxicity. With continued technologic advances in the delivery of radiation, including the use of adaptive radiotherapy, the discovery and application of novel treatment agents, and the combined efforts of urologists, medical oncologists, and radiation oncologists, patients who have genitourinary malignancies have an excellent chance of cure.

Three-dimensional conformal external beam radiotherapy compared with permanent prostate implantation in low-risk prostate cancer based on endorectal magnetic resonance spectroscopy imaging and prostate-specific antigen level

PURPOSE

To evaluate the metabolic response by comparing the time to resolution of spectroscopic abnormalities (TRSA) and the time to prostate-specific antigen level in low-risk prostate cancer patients after treatment with three-dimensional conformal external beam radiotherapy (3D-CRT) compared with permanent prostate implantation (PPI). Recent studies have suggested that the treatment of low-risk prostate cancer yields similar results for patients treated with 3D-CRT or PPI.

METHODS AND MATERIALS

A total of 50 patients, 25 in each group, who had been treated with 3D-CRT or PPI, had undergone endorectal magnetic resonance spectroscopy imaging before and/or at varying times after therapy. The 3D-CRT patients had received radiation doses of > or =72 Gy compared with 144 Gy for the PPI patients. The spectra from all usable voxels were examined for detectable levels of metabolic signal, and the percentages of atrophic and cancerous voxels were tabulated.

RESULTS

The median time to resolution of the spectroscopic abnormalities was 32.2 and 24.8 months and the time to the nadir prostate-specific antigen level was 52.4 and 38.0 months for the 3D-CRT and PPI patients, respectively. Of the 3D-CRT patients, 92% achieved negative endorectal magnetic resonance spectroscopy imaging findings, with 40% having complete metabolic atrophy. All 25 PPI patients had negative endorectal magnetic resonance spectroscopy imaging findings, with 60% achieving complete metabolic atrophy.

CONCLUSION

The results of this study suggest that metabolic and biochemical responses of the prostate are more pronounced after PPI. Our results have not proved PPI is more effective at curing prostate cancer, but they have demonstrated that it may be more effective at destroying prostate metabolism.

Radiotherapy in the Management of Clinically Localized Prostate Cancer: Evolving Standards, Consensus, Controversies and New Directions

Major advances have been made in the definitive use of various forms of radiotherapy (RT) in the management of clinically localized prostate cancer (PCa). Despite tremendous gains, the radiation oncology community continues to struggle with several key questions. In general, the areas of controversy pertain to how to improve the therapeutic ratio of RT. Specifically, key issues include dose escalation; the relative benefit of alternative forms of RT (ie, brachytherapy and protons); target localization; the use, timing, and duration of androgen deprivation; and the need for pelvic nodal irradiation. Multiple efforts have been made to address each of these issues; however, there is no consensus on how to resolve them. This review is an evidence-based critique of the available treatment approaches considered for the optimal use of radiotherapy as definitive management of clinically localized PCa.

Accuracy of finite element model-based multi-organ deformable image registration

As more pretreatment imaging becomes integrated into the treatment planning process and full three-dimensional image-guidance becomes part of the treatment delivery the need for a deformable image registration technique becomes more apparent. A novel finite element model-based multiorgan deformable image registration method, MORFEUS, has been developed. The basis of this method is twofold: first, individual organ deformation can be accurately modeled by deforming the surface of the organ at one instance into the surface of the organ at another instance and assigning the material properties that allow the internal structures to be accurately deformed into the secondary position and second, multi-organ deformable alignment can be achieved by explicitly defining the deformation of a subset of organs and assigning surface interfaces between organs. The feasibility and accuracy of the method was tested on MR thoracic and abdominal images of healthy volunteers at inhale and exhale. For the thoracic cases, the lungs and external surface were explicitly deformed and the breasts were implicitly deformed based on its relation to the lung and external surface. For the abdominal cases, the liver, spleen, and external surface were explicitly deformed and the stomach and kidneys were implicitly deformed. The average accuracy (average absolute error) of the lung and liver deformation, determined by tracking visible bifurcations, was 0.19 (s.d.: 0.09), 0.28 (s.d.: 0.12) and 0.17 (s.d.: 0.07) cm, in the LR, AP, and IS directions, respectively. The average accuracy of implicitly deformed organs was 0.11 (s.d.: 0.11), 0.13 (s.d.: 0.12), and 0.08 (s.d.: 0.09) cm, in the LR, AP, and IS directions, respectively. The average vector magnitude of the accuracy was 0.44 (s.d.: 0.20) cm for the lung and liver deformation and 0.24 (s.d.: 0.18) cm for the implicitly deformed organs. The two main processes, explicit deformation of the selected organs and finite element analysis calculations, require less than 120 and 495 s, respectively. This platform can facilitate the integration of deformable image registration into online image guidance procedures, dose calculations, and tissue response monitoring as well as performing multi-modality image registration for purposes of treatment planning.

Magnetic resonance imaging in prostate cancer

With the recently published National Institute of Clinical Excellence guidelines, it is now generally accepted that magnetic resonance imaging (MRI) is the imaging method of choice for staging prostate cancer in patients for whom radical treatment is being considered. MRI offers the single most accurate assessment of local disease and regional metastatic spread. As well as detecting extraprostatic extension, this technique can locate the site of intraprostatic disease, which may prove useful in planning disease-targeting therapies currently being developed. However, numerous studies have reported widely varying accuracies indicating that MRI is not the perfect imaging modality; microscopic and early macroscopic invasion cannot be reliably shown using current technology. The role of MRI including advantages, limitations and future developments will be discussed.

Use of MRI and spectroscopy in evaluation of external beam radiotherapy for prostate cancer

PURPOSE

To characterize the metabolic response in the prostate, the time to resolution of disease, and the correlation between magnetic resonance imaging (MRI) with spectroscopy (MRSI) results, biopsy findings, and serum prostate-specific antigen (PSA) level after external beam radiotherapy.

METHODS AND MATERIALS

A total of 55 patients underwent MRSI before and/or at varying times after external beam radiotherapy. The percentage of the cancerous, healthy, and atrophic voxels was calculated, and the time to resolution of disease was determined and compared with the PSA nadir.

RESULTS

Of the 55 patients, 70% had negative MRSI and 30% had positive MRSI findings. A strong correlation was found between negative MRSI and negative biopsy findings (n = 11) and between positive MRSI and positive biopsy findings (n = 7). A weak correlation was observed between the PSA level and the MRSI and biopsy findings. The mean time to disease resolution was 40.3 months and the mean time to PSA nadir was 50 months. With time, an increase in atrophy and a decline in cancerous metabolism was found.

CONCLUSION

When used in conjunction with PSA measurement and biopsy, the results of this study suggest that MRSI contributes to a greater level of confidence in determining the outcome and may be a useful adjunct for assessing local control before PSA failure when striving to distinguish the benign "blip" from local recurrence.