Radioimmunoguided imaging of prostate cancer foci with histopathological correlation

Focal Prostate Stereotactic Body Radiation Therapy With Correlative Pathological and Radiographic-Based Treatment Planning

Introduction

Advances in multiparametric MRI (mpMRI) combining anatomic and functional imaging can accurately identify foci of adenocarcinoma within the prostate, offering the possibility of partial gland therapy. We performed tandem prospective pilot trials to investigate the feasibility of focal prostate SBRT (f-SBRT) based on correlating diagnostic mpMRI and biopsies with confirmatory pathology in treatment planning.

Materials and Methods

Patients with pathologic focal Gleason 6–7 disease and a corresponding PIRADS 4–5 lesion on mpMRI underwent targeted and comprehensive biopsies using MRI/ultrasound fusion under electromagnetic sensor navigation. After rigorous analysis for imaging biopsy concordance, five of 18 patients were eligible to proceed to f-SBRT. Chi-squared test was used for differences from expected outcomes, and concordance was estimated with binomial distribution theory and Wilson’s method.

Results

Six patients had Gleason 6 and 12 had Gleason 3 + 4 disease (mean PSA: 5.8 ng/ml, range: 2.2–8.4). Absolute concordance was 43.8% (95% CI: 0.20, 0.64). Patterns of discordance included additional sites of ipsilateral disease, bilateral disease, and negative target. Five were upstaged to a new NCCN risk category necessitating treatment escalation. The five patients with concordant pathology completed three-fraction f-SBRT with sparing of the surrounding normal structures (including contralateral neurovascular bundle), with no reported grade 2+ toxicities and favorable PSA responses (mean: 41% decrease).

Conclusions

On our pilot trials of f-SBRT planning using rigorous imaging and pathology concordance, image-guided confirmatory biopsies frequently revealed additional disease, suggesting the need for caution in partial-gland therapy. For truly focal disease, f-SBRT provided excellent dosimetry, minimal toxicity, and encouraging biochemical response. Clinical Trial Registration: www.clinicaltrials.gov, NCT02681614; NCT02163317.

Characterization of a novel liquid fiducial marker for multimodal image guidance in stereotactic body radiotherapy of prostate cancer

PURPOSE

Liquid fiducial markers have shown to be a promising alternative to solid gold markers in terms of imaging artifact reduction, patient comfort, and compatibility with different imaging modalities. This study aims to investigate the performance of the novel BioXmark^® liquid marker for state-of-the-art multimodal imaging used in prostate cancer (PCa) radiotherapy, encompassing kV CT/CBCT, multiparametric MRI, and kV x-ray imaging. In addition, automatic detection of the liquid markers in x-ray imaging for prostate motion monitoring during treatment was investigated.

METHODS

A total of eight BioXmark^® liquid markers with varying volumes (range 5-300 μL) were casted on a square grid into a gelatin phantom insert. A cylindrical gold marker (QLRAD, length = 7 mm, Ø = 1 mm) was inserted for reference. Liquid marker visibility and streaking artifacts in CT/CBCT imaging were evaluated by placing the gelatin phantom into a CIRS anthropomorphic phantom. Relevant MRI characteristics such as the T2 and T1 relaxation times, the ADC value, and the relative proton density (ρH) were quantified by placing the gelatin phantom insert next to a T1MES mapping phantom and a water-filled syringe for reference. Ex vivo multiparametric MRI images were acquired by placing the gelatin phantom next to a resected prostate specimen. Anterior-posterior x-ray projection images were obtained by placing the gelatin phantom insert on top of an anthropomorphic pelvic phantom with internal pelvic bony structures and were acquired for five positions relative to the bony anatomy and 24 clinically relevant x-ray exposure settings. To quantify individual automatic marker detection, single markers were artificially isolated in the x-ray images using postprocessing.

RESULTS

Markers of all sizes were clearly visible on CT and CBCT images with only the largest marker volumes (100-300 μL) displaying artifacts similar in size to the gold fiducial marker. Artifact size increased with increasing liquid marker volume. Liquid markers displayed good contrast in ex vivo T1-weighted and ρH-weighted images. The markers were not visible in the ex vivo T2-weighted image. The liquid markers induced a chemical shift artifact in the obtained ADC-map. Automated detection in x-ray imaging was feasible with high detection success (four of five positions) for marker volumes in the range of 25-200 μL. None of the liquid markers were detected successfully when superimposed on a bony edge, independent of their size.

CONCLUSIONS

This study is the first to show the compatibility of BioXmark^® liquid markers with multimodal image-guided radiotherapy for PCa. Compared to a solid gold marker, they had favorable results in both visibility and induced imaging artifacts. Liquid marker visibility in MRI imaging of the prostate does not solely depend on the low ρH value (not visible on T2-weighted image) but is also influenced by its relaxation times. Automated marker detection in x-ray images was feasible but better adapted marker detection algorithms are necessary for marker localization in the presence of bony edges. Hence, the liquid marker provides a minimally invasive (fine needles) and highly applicable alternative to current solid gold markers for multimodal image-guided prostate radiotherapy treatments.

The delineation of intraprostatic boost regions for radiotherapy using multimodality imaging

Dose escalation to the prostate improves tumor control but at the expense of increased rectal toxicity. Modern imaging can be used to detect the most common site of recurrence, the intraprostatic lesion (IPL), which has led to the concept of focusing dose escalation to the IPL in order to improve the therapeutic ratio. Imaging must be able to detect lesions with adequate sensitivity and specificity to accurately delineate the IPL. This information must be carefully integrated into the radiotherapy planning process to ensure the dose is targeted to the IPL. This review will consider the role and challenges of multiparametric MRI and PET computed tomography in delineating a tumor boost to be delivered by external beam radiotherapy.

Boosting imaging defined dominant prostatic tumors: a systematic review

INTRODUCTION

Dominant cancer foci within the prostate are associated with sites of local recurrence post radiotherapy. In this systematic review we sought to address the question: "what is the clinical evidence to support differential boosting to an imaging defined GTV volume within the prostate when delivered by external beam or brachytherapy".

MATERIALS AND METHODS

A systematic review was conducted to identify clinical series reporting the use of radiation boosts to imaging defined GTVs.

RESULTS

Thirteen papers describing 11 unique patient series and 833 patients in total were identified. Methods and details of GTV definition and treatment varied substantially between series. GTV boosts were on average 8 Gy (range 3-35 Gy) for external beam, or 150% for brachytherapy (range 130-155%) and GTV volumes were small (<10 ml). Reported toxicity rates were low and may reflect the modest boost doses, small volumes and conservative DVH constraints employed in most studies. Variability in patient populations, study methodologies and outcomes reporting precluded conclusions regarding efficacy.

CONCLUSIONS

Despite a large cohort of patients treated differential boosts to imaging defined intra-prostatic targets, conclusions regarding optimal techniques and/or efficacy of this approach are elusive, and this approach cannot be considered standard of care. There is a need to build consensus and evidence. Ongoing prospective randomized trials are underway and will help to better define the role of differential prostate boosts based on imaging defined GTVs.

Prostate-specific membrane antigen-based imaging

Prostate cancer (CaP) is the most common noncutaneous malignancy affecting men in North America. Despite significant efforts, conventional imaging of CaP does not contribute to patient management as much as imaging performed for other common cancers. Given the lack of specificity in conventional imaging techniques, one possible solution is to screen for CaP-specific antigenic targets and generate agents able to specifically bind. Prostate-specific membrane antigen (PSMA) is overexpressed in CaP tissue, with low levels of expression in the small intestine, renal tubular cells, and salivary gland. The first clinical agent for targeting PSMA was (111)In-capromab, involving an antibody recognizing the internal domain of PSMA. The second- and third-generation humanized PSMA binding antibodies have the potential to overcome some of the limitations inherent to capromab penditide (i.e., inability to bind to live CaP cells). One example is the humanized monoclonal antibody J591 (Hu mAb J591) that was developed primarily for therapeutic purposes but also has interesting imaging characteristics, including the identification of bone metastases in CaP. The major disadvantage of use of mAb for imaging is slow target recognition and background clearance in an appropriate time frame for diagnostic imaging. Urea-based compounds, such as small molecule inhibitors may also present promising agents for CaP imaging with single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Two such small-molecule inhibitors targeting PSMA, MIP-1072, and MIP-1095 have exhibited high affinity for PSMA. The uptake of (123)I-MIP-1072 and (123)I-MIP-1095 in CaP xenografts have imaged successfully with favorable properties amenable to human trials. While advances in conventional imaging will continue, Ab and small molecule imaging exemplified by PSMA targeting have the greatest potential to improve diagnostic sensitivity and specificity.

Review of salvage therapy for biochemically recurrent prostate cancer: the role of imaging and rationale for systemic salvage targeted anti-prostate-specific membrane antigen radioimmunotherapy

Despite local therapy with curative intent, approximately 30% of men suffer from biochemical relapse. Though some of these PSA relapses are not life threatening, many men eventually progress to metastatic disease and die of prostate cancer. Local therapy is an option for some men, but many have progression of disease following local salvage attempts. One significant issue in this setting is the lack of reliable imaging biomarkers to guide the use of local salvage therapy, as the likely reason for a low cure rate is the presence of undetected micrometastatic disease outside of the prostate/prostate bed. Androgen deprivation therapy is a cornerstone of therapy in the salvage setting. While subsets may benefit in terms of delay in time to metastatic disease and/or death, research is ongoing to improve salvage systemic therapy. Prostate-specific membrane antigen (PSMA) is highly overexpressed by the majority of prostate cancers. While initial methods of exploiting PSMA's high and selective expression were suboptimal, additional work in both imaging and therapeutics is progressing. Salvage therapy and imaging modalities in this setting are briefly reviewed, and the rationale for PSMA-based systemic salvage radioimmunotherapy is described.

State-of-the-art uroradiologic imaging in the diagnosis of prostate cancer

In the diagnostic process of prostate cancer, several radiologic imaging modalities significantly contribute to the detection and localization of the disease. These range from transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) to positron emission tomography (PET). Within this review, after evaluation of the literature, we will discuss the advantages and disadvantages of these imaging modalities in clarifying the patient's clinical status as to whether he has prostate cancer or not and if so, where it is located, so that therapy appropriate to the patient's disease may be administered. TRUS, specifically with the usage of intravenous contrast agents, provides an excellent way of directing biopsy towards suspicious areas within the prostate in the general (screening) population. MRI using functional imaging techniques allows for highly accurate detection and localization, particularly in patients with prior negative ultrasound guided biopsies. A promising new development is the performance of biopsy within the magnetic resonance scanner. Subsequently, a proposal for optimal use of radiologic imaging is presented and compared with the European and American urological guidelines on prostate cancer.

Image-guided radiotherapy for prostate cancer: a prospective trial of concomitant boost using indium-111-capromab pendetide (ProstaScint) imaging

PURPOSE

To evaluate, in a prospective study, the use of (111)In-capromab pendetide (ProstaScint) scan to guide the delivery of a concomitant boost to intraprostatic region showing increased uptake while treating the entire gland with intensity-modulated radiotherapy for localized prostate cancer.

METHODS AND MATERIALS

From September 2002 to November 2005, 71 patients were enrolled. Planning pelvic CT and (111)In-capromab pendetide scan images were coregistered. The entire prostate gland received 75.6 Gy/42 fractions, whereas areas of increased uptake in (111)In-capromab pendetide scan received 82 Gy. For patients with T3/T4 disease, or Gleason score ≥8, or prostate-specific antigen level >20 ng/mL, 12 months of adjuvant androgen deprivation therapy was given. In January 2005 the protocol was modified to give 6 months of androgen deprivation therapy to patients with a prostate-specific antigen level of 10-20 ng/mL or Gleason 7 disease.

RESULTS

Thirty-one patients had low-risk, 30 had intermediate-risk, and 10 had high-risk disease. With a median follow-up of 66 months, the 5-year biochemical control rates were 94% for the entire cohort and 97%, 93%, and 90% for low-, intermediate-, and high-risk groups, respectively. Maximum acute and late urinary toxicities were Grade 2 for 38 patients (54%) and 28 patients (39%) and Grade 3 for 1 and 3 patients (4%), respectively. One patient had Grade 4 hematuria. Maximum acute and late gastrointestinal toxicities were Grade 2 for 32 patients (45%) and 15 patients (21%), respectively. Most of the side effects improved with longer follow-up.

CONCLUSION

Concomitant boost to areas showing increased uptake in (111)In-capromab pendetide scan to 82 Gy using intensity-modulated radiotherapy while the entire prostate received 75.6 Gy was feasible and tolerable, with 94% biochemical control rate at 5 years.

111-In-capromab pendetide imaging using hybrid-γ camera-computer tomography technology is not reliable in detecting seminal vesicle invasion in patients with prostate cancer

OBJECTIVES

In this study, we evaluate the diagnostic utility of a hybrid γ-camera-computer tomography (SPECT-CT) indium-111 (111-In)-capromab pendetide scan in detecting seminal vesicle invasion (SVI) in select patients evaluated for primary surgical treatment of prostate cancer (CaP).

METHODS AND MATERIALS

We retrospectively analyzed a prospective database of patients who underwent preoperative SPECT-CT imaging with 111-In-capromab-pendetide as part of a staging evaluation who were subsequently treated with radical surgery in our center. Only patients with clinically localized disease were included. We calculated diagnostic properties of the hybrid scan in detecting SVI compared with final pathology. Regression analyses were performed, including scan and preoperative variables to predict SVI.

RESULTS

We retrieved 50 medical records matching our criteria. Median patient age was 61 years (range 45-74). Most patients had a clinical T1c CaP and biopsy Gleason score of 7 or higher. On final pathology, SVI was found in 12 (24%) specimens and radiotracer signal in the seminal vesicle region was reported in 15 (30%) imaging studies. Hybrid SPECT-CT imaging had a sensitivity of 25%, specificity of 61.9%, positive and negative predictive values of 20% and 74.3%, respectively, for detecting SVI. SPECT-CT results did not contribute significantly to SVI prediction on univariate (P = 0.627) or multivariate (P = 0.754) analyses.

CONCLUSIONS

SPECT-CT imaging with 111-In-capromab-pendetide is not reliable in detecting or excluding SVI in this select cohort. High rates of positive radiotracer signals from healthy seminal vesicles raise concerns regarding pharmacologic properties of this radiotracer molecule.

Advanced image-guided external beam radiotherapy

The goal of radiation therapy is to eradicate tumor stem cells while sparing healthy tissue. Therefore, the first aim must be to delineate tumor from healthy tissue. Advanced imaging techniques will enable one to reduce the uncertainty of microscopic extension of disease. Ultimately, advanced functional imaging systems correlated with image-registered pathological specimens will allow one to delineate disease extent from normal tissue at the tumor periphery. When it is not possible to determine the CTV margin with reasonable certainty, the margins must remain generous and conformal avoidance methodology could and should be deployed to spare critical normal structures. Of equal importance to defining the CTV is the need to guarantee that this target is indeed treated. For this purpose, image guidance using a variety of systems including portal images, ultrasound devices, and CT scanners at the time of treatment has been implemented. Some image-guided methods, portal images for instance, are more amenable for use with rigid structures such as encountered in the sinus whereas others like ultrasound or CT scanners are able to account for nonrigid setup variations. Several strategies for preventing organ motion from degrading the precision that radiotherapy offers have been described. In particular, a CT scan at the time of treatment delivery can also be used as the basis to reconstruct the dose received by the patient. Dose reconstruction will allow the dose just delivered to be superimposed on the pretreatment CT scan and will allow one to compare the reconstructed delivered dose distribution with the planned dose distribution to assess discrepancies between these. Furthermore, reconstruction of the delivered dose distributions holds the promise of allowing one to accumulate dose delivered to the tumor and normal structures on a fraction per fraction basis. This will ultimately allow for the determination of treatment-specific tumor control probabilities and normal tissue complication probabilities.

Central abdominal uptake of indium-111 capromab pendetide (ProstaScint) predicts for poor prognosis in patients with prostate cancer

OBJECTIVES

Central abdominal uptake (CAU) on immunoscintigraphy with capromab pendetide (CP) (ProstaScint) suggests the presence of metastases from prostate cancer, but tissue confirmation is difficult and invasive. We report the outcomes data from a cohort of patients with CAU on CP images obtained for staging.

METHODS

The records of 341 men with prostate cancer who underwent CP imaging at two institutions from 1994 to 1999 were reviewed. The patients were divided according to the presence or absence of CAU. Metastases were confirmed in 36 patients (52%) with CAU. The median follow-up was 4.1 years. Statistical analyses compared the differences in baseline characteristics, subsequent radiotherapy, intervention with androgen ablation, and survival.

RESULTS

CAU was detected in 69 patients (20%). A total of 262 patients underwent pelvic radiotherapy after the scan, 57 (83%) with CAU and 205 (75%) without (P = 0.2). Of the 69 patients with positive CAU findings and the 272 patients with negative CAU findings, 10 (14.5%) and 14 (5.1%) had died during the follow-up period (P = 0.007). Prostate cancer-specific death occurred in 5 (7.2%) of 69 patients with CAU-positive findings versus 2 of 272 with CAU-negative findings, for a rate 10 times greater in the CAU-positive group (P = 0.02). The results were independent of either the use or timing of androgen blockade.

CONCLUSIONS

The results of our study have shown that CAU on CP immunoscintigraphy is clinically important and correlates with a significantly greater risk of prostate cancer-specific death. These findings suggest that patients with CAU should be considered for earlier intervention with systemic therapy.

Imaging in Oncology from The University of Texas M. D. Anderson Cancer Center: Diagnosis, Staging, and Surveillance of Prostate Cancer

OBJECTIVE

The purpose of this article is to discuss the epidemiology, risk factors, and presentation of prostate cancer. After reviewing the prostate anatomy, the article will show how imaging plays an important role in establishing the diagnosis, staging, and monitoring the therapeutic response in prostate cancer, with a focus on adenocarcinomas.

CONCLUSION

Imaging studies, in the appropriate laboratory and clinical context, contribute essential information that enhances the capacity to provide individualized risk stratification, a suitable treatment strategy, and monitoring for the patient with prostate cancer.

The role of indium-111 radioimmunoscintigraphy in post-radical retropubic prostatectomy management of prostate cancer patients

Indium-111 radioimmunoscintigraphy (RIS) has an increasing role in the treatment of prostate cancer and is most commonly performed at this disease site using labeled monoclonal antibody against prostate-specific membrane antigen. There are many limitations of RIS, including low spatial resolution, low diagnostic yield and limited availability. Despite these limitations, the efficacy of RIS has been demonstrated in many clinical studies, including multi-institutional investigations. The highest sensitivity and specificity of RIS appears to be in the post-radical retropubic prostatectomy (post-RRP) setting. RIS has recently been explored for its role in clinical radiotherapy decision-making, and was found to have a significant impact in selecting patients for radiotherapy and for the general radiotherapy treatment volume definition. RIS has also recently been explored for its role in radiotherapy planning and was found to impact clinical target volume design. However, manual editing of the RIS volume is still necessary when projected into the radiotherapy-planning scan, as there is often overlap in the RIS-defined uptake regions with normal structures (rectum, bladder and symphysis bone marrow). The impact of RIS on biochemical control has been explored, with studies in this area yielding conflicting results. It appears that the maximum impact of RIS is possible when areas of labeled antibody uptake regions are co-registered with the radiotherapy-planning computed tomography scan. The larger RIS-guided target volumes do not appear to be prohibitive in increasing radiotherapy-related toxicity. Future directions of the use of RIS for post-RRP prostate cancer are discussed.

Biochemical disease-free survival rates following definitive low-dose-rate prostate brachytherapy with dose escalation to biologic target volumes identified with SPECT/CT capromab pendetide

PURPOSE

To report biochemical disease-free survival (bDFS) after conformal brachytherapy with dose escalation to biological target volumes (BTVs) identified by Capromab Pendetide with single photon emission computed tomography and computed tomography image fusion (SPECT/CT).

METHODS AND MATERIALS

Two hundred thirty-nine (T1c-T3b NxM0) consecutive patients were evaluated by SPECT/CT before treatment. Intraprostatic SPECT/CT BTVs were identified and targeted for 150% dose escalation during brachytherapy seed implant (SI). Patients received either SI alone (n = 150) or external beam radiation therapy (EBRT) plus SI boost (EBRT+SI) (n = 89), with (n = 50) and without (n = 189) neoadjuvant hormone ablation therapy. Risk factors (RF) (prostate-specific antigen [PSA] >10 ng/mL, Stage > or = T2b, and Gleason grade > or = 7) defined risk group (RG) categories [none, 1, and > or = 2 RF define low, intermediate, and high RG] for bDFS calculations using four failure criteria: American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definition, PSA >1.0 ng/mL (PSA >1), PSA >0.5 ng/mL after nadir (PSA >0.5), and PSA nadir+2 ng/mL rise in PSA clinical nadir (CN+2). Median followup was 47.2 months (range, 24.8-96.1).

RESULTS

Seven-year actuarial bDFS rates were 88.0%, 82.1%, 80.4%, and 79.9% using the ASTRO, PSA >1, PSA >0.5, and CN+2 failure criteria, respectively. ASTRO-defined bDFS rates were 96.0%, 87.0%, and 72.5% for low, intermediate, and high RG's.

CONCLUSION

The data presented here demonstrate the feasibility of performing SPECT/CT BTV dose escalation in a mature series.

Rectal morbidity after permanent prostate brachytherapy with dose escalation to biologic target volumes identified by SPECT/CT fusion

PURPOSE

To evaluate rectal morbidity after dose escalation to biologic target volumes identified by capromab pendetide (ProstaScint) single-photon emission tomography images coregistered with computed tomography (SPECT/CT).

METHODS AND MATERIALS

Two hundred thirty-nine consecutive patients diagnosed with T1c-T3b NxM0 adenocarcinoma of the prostate were treated with brachytherapy seed implant (SI) dose escalation to SPECT/CT-identified biologic target volumes, from February 1997 through December 2002. Patients received SI (n=150) or external beam radiation therapy plus SI (n=89). Rectal morbidity was evaluated by clinician scoring using the modified Radiation Therapy Oncology Group criteria. The median followup was 47.2 (range 24.8-96.1) months.

RESULTS

The rate of acute Grades I and II toxicity was 29.9% and 3.7%, respectively, and chronic Grade I toxicity was 15.4%, 12.4%, 2.3%, and 1.8% at 1, 2, 3, and 4 years postimplant, respectively. Chronic Grade II toxicities were 1.8%, 1.9%, 1.5%, and 0.9% at 1, 2, 3, and 4 years, respectively. No Grade III rectal toxicity was reported. Chronic Grade IV rectal toxicity was 0.5% and 0.6% at 1.5 and 2.5 years, respectively. Ninety-six percent of patients reported freedom from all rectal toxicity after 3 years.

CONCLUSIONS

Dose intensification to occult tumor targets without increasing rectal toxicity may be achieved using SPECT/CT ProstaScint. Additional research to define the role of molecular imaging in prostate cancer is warranted.

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.

Molecular imaging and radioimmunoguided surgery

Molecular imaging comprises a series of diagnostic modalities that provide information on the physiology and molecular composition of cells and tissues. One of these modalities, radioimmunodetection, uses radiolabeled monoclonal antibodies (mAbs) to image tissues. Two radioimmunodetection modalities are described in this article: immunoscintigraphy and radioimmunoguided surgery (RIGS). In immunoscintigraphy, the radioactivity is measured with the use of an external gamma camera and used to create images. In RIGS, the radioactivity is detected intraoperatively with the use of a handheld gamma probe to help the surgeon detect foci of otherwise occult disease. Both techniques have the potential to improve the preoperative and intraoperative localization of cancer. Multiple studies have been performed on the efficacy of RIGS on different malignancies, especially colorectal cancer. Despite the good sensitivity of the technique, some concerns revolve around the high rate of false positives and the real significance of leaving RIGS-positive tissue behind in terms of long-term outcomes and survival. More studies are warranted to further develop the technique and determine the specific role it will play on the diagnosis and management of surgical disease. Surgeons should actively participate in these studies and in expanding the applications of this promising technology.

Enhancing the utility of prostascint SPECT scans for patient management

This project investigated reducing the artifact content of In-ill ProstaScint SPECT scans for use in treatment planning and management. Forty-one patients who had undergone CT or MRI scans and simultaneous Tc-99m RBC/In-111 ProstaScint SPECT scans were included. SPECT volume sets, reconstructed using Ordered Set-Expectation Maximum (OS-EM) were compared against those reconstructed with standard Filtered Back projection (FBP). Bladder activity in Tc-99m scans was suppressed within an ellipsoidal volume. Tc-99m voxel values were subtracted from the corresponding In-111 after scaling based on peak activity within the descending aorta. The SPECT volume data sets were merged with the CT or MRI scans before and after processing. Volume merging, based both on visual assessment and statistical evaluation, was not affected. Thus iterative reconstruction together with bladder suppression and blood pool subtraction may improve the interpretation and utility of ProstaScint SPECT scans for patient management.

The evolution of imaging in advanced prostate cancer

Medical advances will be driven by the enhancement of imaging for diagnosis, refinement of treatment, and evaluation of treatment efficacy. The convergence of technology in materials science, biology, and the computer industry has greatly advanced diagnostic imaging. Precision in control of the spatial and temporal properties of light and its heterogeneous scattering properties have extended our capability for imaging. Refinements in radioimmunoscintigraphy for image acquisition, fusion of images, and outcome data now suggest use for image-guided therapy. Novel MRI agents appear to provide significant imaging capabilities to detect malignant lymph nodes. Future applications of optical coherence tomography, electron paramagnetic resonance imaging, nanotechnology, molecular imaging, and hyperspectral spectroscopy promise further refinements to image tissues for diagnosis.

The Impact of a Negative 111 Indium-Capromab Pendetide Scan Before Salvage Radiotherapy

PURPOSE

We determined the prognostic role, if any, of the ProstaScint (111)indium-capromab pendetide scan before salvage radiotherapy for biochemical recurrence after RP for localized prostate cancer.

MATERIALS AND METHODS

We reviewed the records of 649 patients who underwent a ProstaScint scan from 1998 to 2004. A total of 44 patients were identified who had biochemical recurrence after RP and underwent a ProstaScint scan immediately before salvage radiotherapy. All patients received salvage radiotherapy to the prostatic bed unless pelvic lymph node uptake was identified on the scan, resulting in initial whole pelvic radiotherapy with 45 Gy, followed by a conformal boost to the prostate bed in 6. The median salvage radiotherapy dose to the prostate bed was 72 Gy. Patient demographics, pathological information, PSA values and ProstaScint results were collected retrospectively. The majority of ProstaScint scans were digitally fused with noncontrast pelvic computerized tomography images for interpretation. PSA progression after radiotherapy was defined using American Society for Therapeutic Radiation and Oncology criteria.

RESULTS

At a mean followup of 22 months 43 of 44 patients (97%) experienced a PSA decrease after salvage radiotherapy with a mean PSA nadir of 0.16 ng/ml compared to a mean pre-radiotherapy PSA of 1.7 ng/ml. Of the 44 patients 15 (34%) showed post-radiotherapy PSA progression. When the entire cohort was analyzed, patients with negative ProstaScint scans had statistically lower post-radiotherapy PSA progression rates than patients with positive scans (1 of 10 or 10% vs 14 of 34 or 41%, p = 0.026). Patients with negative ProstaScint results were also statistically more likely to have a pre-radiotherapy PSA of less than 1.0 ng/ml (p = 0.005), no seminal vesicle involvement (p = 0.006), a greater mean PSA doubling time (p = 0.008) and received no hormone therapy (p = 0.003). When patients with pre-radiotherapy PSA less than 1.0 ng/ml were analyzed, a negative ProstaScint scan suggested but did not provide a statistically significant advantage over pre-radiotherapy PSA alone for predicting post-radiotherapy PSA progression (1 of 9 or 11% for negative vs 5 of 15 or 33% for positive scans, p = 0.20).

CONCLUSIONS

Our early experience supports an improved prognosis in patients receiving salvage pelvic radiotherapy for biochemical recurrence after RP who have a negative pre-radiotherapy ProstaScint scan. However, this finding is not necessarily independent of pre-radiotherapy PSA.

Technology Insight: monoclonal antibody imaging of prostate cancer

Imaging is a critical component of diagnosis, staging and monitoring, all of which factor heavily in treatment decision-making for cancer patients. Agents, such as antibodies, can target molecules that are relatively unique to cancer cells. Prostate-specific membrane antigen (PSMA) is the most well-established, highly restricted prostate-cancer-related cell membrane antigen known. Ten years ago, the FDA approved (111)In-capromab pendetide for use in imaging soft-tissue, but not bone, sites of metastatic prostate cancer for presurgical staging or the evaluation of PSA relapse after local therapy. For presurgical patients with high-risk disease but negative bone, CT and MRI scans, capromab demonstrated the ability to identify some patients with positive nodes, thereby sparing them an unnecessary surgical procedure. But there have been no follow-up studies to indicate that high-risk patients with a negative capromab scan have a lower failure rate after surgery. In the setting of PSA relapse, capromab is compromised by its inability to sensitively image bone metastases; bone is the first site of metastatic prostate cancer in 72% of patients. The problem with imaging bone metastases is that capromab detects an antigenic site on the intracellular portion of PSMA-a site not accessible to circulating antibodies. Early results indicate that second-generation antibodies that target the extracellular domain of PSMA might provide significant benefits in the imaging of prostate cancer.

Update on fused capromab pendetide imaging of prostate cancer

The primary objective of this overview is to apprise clinical urologists and oncologists of the current state of fused multimodality imaging of prostate cancer, which can be applied to optimize treatment by ensuring that a patient's disease is characterized as well as current imaging technology permits. The focus of this study is the monoclonal antibody capromab pendetide, which targets prostate specific membrane antigen (PSMA), a type II membrane glycoprotein strongly associated with prostate cancer. Identifying where capromab pendetide uptake occurs can be done accurately if this functional imaging modality is combined with a modality that provides anatomic detail, such as computed tomography (CT) or magnetic resonance imaging (MRI). Image fusion, or coregistration, which is overlaying the functional images of capromab pendetide uptake on the anatomic CT or MRI images, provides a detailed map of cancer localization inside and outside the prostate gland. This same principle of fusing functional images on anatomic images is the basis for enormous growth of positron emission tomography with CT during the past 2 years. Positron emission tomography imaging has a different functionality base than does capromab pendetide, and thus the 2 modalities should be complementary. However, the key to both functional imaging modalities is accurate fusion with anatomic images, which is illustrated in our case reports. The cases cited demonstrate the need to optimize every phase of imaging from patient preparation to reading and reporting increased PSMA concentration seen on the fused images. Reference is also made to applying capromab pendetide/CT fused imaging to radiation therapy planning.

Procedure for unmasking localization information from ProstaScint scans for prostate radiation therapy treatment planning

PURPOSE

To demonstrate a method to extract the meaningful biologic information from (111)In-radiolabeled capromab pendetide (ProstaScint) SPECT scans for use in radiation therapy treatment planning by removing that component of the (111)In SPECT images associated with normal structures.

METHODS AND MATERIALS

We examined 20 of more than 80 patients who underwent simultaneous (99m)Tc/(111)In SPECT scans, which were subsequently registered to the corresponding CT/MRI scans.A thresholding algorithm was used to identify (99m)Tc uptake associated with blood vessels and CT electron density associated with bone marrow. Corresponding voxels were removed from the (111)In image set.

RESULTS

No single threshold value was found to be associated with the (99m)Tc uptake that corresponded to the blood vessels. Intensity values were normalized to a global maximum and, as such, were dependent upon the quantity of (99m)Tc pooled in the bladder. The reduced ProstaScint volume sets were segmented by use of a thresholding feature of the planning system and superimposed on the CT/MRI scans.

CONCLUSIONS

ProstaScint images are now closer to becoming a biologically and therapeutically useful and accurate image set. After known sources of normal intensity are stripped away, the remaining areas that demonstrate uptake may be segmented and superimposed on the treatment-planning CT/MRI volume.

Impact of Fusion of Indium-111 Capromab Pendetide Volume Data Sets with Those from MRI or CT in Patients with Recurrent Prostate Cancer

OBJECTIVE

Our goal was to evaluate the impact of image fusion on the interpretation of indium-111 Prosta-Scint SPECT scans.

MATERIALS AND METHODS

Sixty-seven consecutive patients referred for rising prostate-specific antigen (PSA) levels after initial therapy for primary prostate cancer underwent SPECT 96 hr after infusion of (111)In Prosta-Scint, with simultaneous technetium-99m blood pool imaging. Volume data sets from the SPECT scans were then fused with those from CT and MR images of the pelvis using a 3D landmark-based warping program. The SPECT scans were initially interpreted without benefit of MRI or CT fusion. The fused Prosta-Scint MRI-CT volumes were reevaluated by a nuclear radiologist and an MRI radiologist. Independent reviews before and after fusion were available in these patients. Validation of results after fusion was performed through correlation with PSA changes after radiation therapy.

RESULTS

Six patients with sites that could not be evaluated and three without their original Prosta-Scint scanning reports were excluded; thus, 58 patients were studied clinically. Seventy-four of 161 prefusion-positive sites were found to be negative after fusion. These 74 sites subsequently were identified primarily as showing bowel, vessel, or marrow uptake after fusion. In two patients, nodal disease was identified although the review before perfusion indicated none. Twenty-five patients previously thought to have nodal disease appeared to have only local disease after fusion. After local radiation therapy, PSA levels decreased in 12 of 25 patients, increased in five, and were unavailable in eight.

CONCLUSION

Although Prosta-Scint SPECT alone can help in the proper management of recurrent prostate cancer, fusion with MRI-CT of the pelvis can improve the specificity of the examination.

Results of permanent prostate brachytherapy, 13 years of experience at a single institution

BACKGROUND AND PURPOSE

To understand the influence of treatment techniques on the final outcome, as well as the relation of risk groups and of PSA nadir on the outcome, we reviewed our experience over more than 10 years.

PATIENTS AND METHODS

Patients were treated in the period 1989 through 2000. Available for this evaluation are 351 patients. The distribution of cases by T stage was T1a, b (9%), T1c (49%), T2 (42%), and by grading G1 (58%), G2 (38%), G3 (1%) and Gx (3%). The technique of plantation of seeds varied over the years, starting with single seeds using a Mick applicator (104 patients), followed by Rapid strands without (70) and with pre-planning (177). Risk groups are categorised as low (iPSA <10 ng/ml, T1-2, grade 1), 116 patients; intermediate (iPSA 10-20 ng/ml, or grade 2-3), 114 patients; and high risk (both factors, or iPSA >20 ng/ml), 121 patients. The mean follow-up time was 50 months, median 48 and range 24-123 months.

RESULTS

Overall actuarial survival at 5 and 7 years was 85 and 76%, respectively. Forty patients died, eight (2%) because of or with prostate cancer. Alive are 310 patients (88%), with 223 patients bNED (71%), 51 (16%) with PSA failure, 21 (7%) with local and 15 (5%) with distant recurrence. Total bNED was 72%. Although results are better since the introduction of Rapid strands, 79% bNED versus 54% bNED for single seeds (P = 0.14) also the increase in activity per cm(3) prostate volume accounts for this improvement. With pre-planning a significant better result (P < 0.03) is obtained as compared to single seeds or strands without planning. Categorisation into risk groups results in a significant difference (P < 0.007) of bNED with risk factors, respectively, 57% for the high, 75% for the intermediate and 89% for the low risk group. Also PSA nadir had a significant effect on outcome; patients who reach a nadir of < or =0.5 ng/ml have a 91% chance of cure.

CONCLUSIONS

Results of permanent seed implantation improved with the introduction of strands, however, better staging and the increase in activity per cm(3) prostate volume also contributed to this improvement. A significant better result was obtained with pre-planning. Categorisation in risk groups corresponds very well with treatment outcome. Finally, a strong relation is found with PSA nadir.

Four-year biochemical outcome after radioimmunoguided transperineal brachytherapy for patients with prostate adenocarcinoma

PURPOSE

To evaluate 4-year biochemical outcomes for patients with prostate adenocarcinoma who underwent radioimmunoguided (Prostascint) permanent prostate brachytherapy.

METHODS AND MATERIALS

Eighty patients with clinical T1C-T3A NxM0 prostate cancer underwent ProstaScint-guided prostate brachytherapy using either (103)Pd or (125)I between February 1997 and December 2000. Sixty-seven patients underwent prostate brachytherapy alone, whereas 13 patients received neoadjuvant hormonal manipulation before implantation. Risk factors (RF) included PSA >10, Stage >or=T2b, and Gleason grade >or=7. Sixty patients had low-risk disease (0 RF), 17 were intermediate risk (1 RF), and 3 were high risk (2 RF). Biochemical disease-free survival (bDFS) was calculated using the American Society for Therapeutic Radiology and Oncology (ASTRO) consensus criteria, a PSA cutoff of 1.0 ng/mL, and a PSA cutoff of 0.5 ng/mL.

RESULTS

Four-year bDFS for the entire cohort was 97.4% using the ASTRO consensus criteria. Low-risk patients (60) had a 4-year bDFS of 100%; intermediate- and high-risk patients (20 patients) were 89.2%. The hormonally naïve group (67 patients) had a 4-year bDFS of 96.9% and a median PSA nadir of 0.2 ng/mL. Median time to nadir was 19.8 months (range: 1.9-53.2 months). For the neoadjuvant hormonal therapy group (13 patients), ASTRO-defined bDFS was 100%. Overall, 85.2% of patients had a posttreatment PSA <or=1.0 ng/mL, and 75.9% had a PSA <or=0.5 ng/mL at a median follow-up of 36 months.

CONCLUSIONS

At a median follow-up of 36 months, ProstaScint-guided transperineal brachytherapy results in a high probability of actuarial 4-year biochemical disease-free survival for patients with localized prostate cancer.

Intensity-Modulated Radiation Therapy for Prostate Cancer

Prostate cancer is among the most common solid malignancies. A number of treatment alternatives exist for localized prostate cancer, including observation, prostatectomy, brachytherapy, and external-beam radiation therapy (EBRT). External-beam radiation therapy has changed dramatically during the past several years. Older techniques paved the way for 3-dimensional conformal radiation therapy (CRT), which in turn facilitated the introduction of intensity-modulated radiation therapy (IMRT). The prostate has served as a model disease site for the implementation of IMRT. As indicated by a growing body of experience, IMRT for prostate cancer represents a major technologic and clinical advance for radiation therapy. In this article, a review is provided of the evolution of EBRT leading to IMRT, the unique features making the prostate an ideal disease site for employing IMRT, the details of the clinical implementation of prostate IMRT and supporting technologic advancements, and the currently reported clinical outcomes of IMRT in prostate cancer. In addition, future directions of prostate IMRT, both technologic and clinical, are discussed.

Brachytherapy: update and results

Prostate cancer is the most common noncutaneous malignancy and the second most common cause of cancer mortality in American men. Treatment options for these patients include radical prostatectomy, external beam radiation therapy, hormonal therapy, and prostate brachytherapy. Patients with clinically and radiographically localized disease, especially young patients with few comorbid illnesses, are good candidates for prostate brachytherapy. Prostate brachytherapy has gained widespread acceptance throughout the past two decades and data from several large series of patients are now available. This article describes current techniques, treatment issues, and clinical results of permanent seed implants.

Image guidance for precise conformal radiotherapy

PURPOSE

To review the state of the art in image-guided precision conformal radiotherapy and to describe how helical tomotherapy compares with the image-guided practices being developed for conventional radiotherapy.

MATERIALS AND METHODS

Image guidance is beginning to be the fundamental basis for radiotherapy planning, delivery, and verification. Radiotherapy planning requires more precision in the extension and localization of disease. When greater precision is not possible, conformal avoidance methodology may be indicated whereby the margin of disease extension is generous, except where sensitive normal tissues exist. Radiotherapy delivery requires better precision in the definition of treatment volume, on a daily basis if necessary. Helical tomotherapy has been designed to use CT imaging technology to plan, deliver, and verify that the delivery has been carried out as planned. The image-guided processes of helical tomotherapy that enable this goal are described.

RESULTS

Examples of the results of helical tomotherapy processes for image-guided intensity-modulated radiotherapy are presented. These processes include megavoltage CT acquisition, automated segmentation of CT images, dose reconstruction using the CT image set, deformable registration of CT images, and reoptimization.

CONCLUSIONS

Image-guided precision conformal radiotherapy can be used as a tool to treat the tumor yet spare critical structures. Helical tomotherapy has been designed from the ground up as an integrated image-guided intensity-modulated radiotherapy system and allows new verification processes based on megavoltage CT images to be implemented.

Evaluation of preoperative ProstaScint scans in the prediction of nodal disease

Diagnostic methods are limited for detecting microscopic soft tissue metastases in patients with prostate cancer. Previous studies using (111)Indium Capromab Pendetide (ProstaScint scan) analyzed patients with extensive localized tumor (prostate specific antigen (PSA) >20 ng/ml) not optimal for surgical therapy. We evaluated the role of the ProstaScint trade mark scan in a preoperative population to provide histological documentation and to assess its utility in a surgical population. A total of 22 preoperative patients, underwent a ProstaScint scan. The mean preoperative PSA was 16.0 ng/ml (range 3.9-33 ng/ml). The mean Gleason score at biopsy was 6.9 (range 6-9). Each patient underwent a radical retropubic prostatectomy and bilateral pelvic lymph node dissection, which included resection of both obturator and common iliac lymph nodes. Histologic analysis of the resected lymph nodes provided the standard of comparison with the ProstaScint scan. The results of the scan and pathology for all 22 patients were compared with the bilateral obturator and iliac nodes, creating 88 data points. Nine areas (10%) were positive on the scan. One of these (11%) was a true positive while the other eight (89%) were false positives. Seventy-nine areas (90%) were negative on scan results. Of these, five areas (6%) were false negatives and 74 areas (94%) were true negatives. The scan yielded a sensitivity of 17%, specificity of 90%, negative predictive value (NPV) of 94% and a positive predictive value (PPV) of 11%. The high false positive rate and low PPV of ProstaScint scans overestimates metastatic lymph nodes disease, and is not useful when used preoperatively.

Combination conformal radiotherapy and radioimmunoguided transperineal 103Pd implantation for patients with intermediate and unfavorable risk prostate adenocarcinoma

PURPOSE

To report outcomes for prostate cancer patients treated with external beam radiation therapy (EBRT) and permanent prostate brachytherapy utilizing radioimmunoguided targeting of biological tumor volumes (BTVs).

METHODS AND MATERIALS

Between February 1997 and October 2001, 66 patients with intermediate- to high-risk prostate cancer underwent EBRT and ProstaScint-guided transperineal brachytherapy. Thirty patients received neoadjuvant hormonal manipulation, while 36 patients did not. Median patient age was 66 years (range, 49-78 years). The median follow-up was 41 months (range, 24-78 months). No patients were lost to follow-up. Risk factors (RF) used for risk stratification included PSA >10 ng/ml (35 patients), Stage T2b or greater (22 patients), and Gleason score > or = 7 (55 patients). Results for biochemical disease free survival (bDFS) were reported using the ASTRO consensus definition for biochemical failure, PSA < or = 1.0 ng/mL or PSA< or = 0.5 ng/mL. Survival was estimated by the Kaplan-Meier method.

RESULTS

Five-year overall survival was 93.1% and 5-year bDFS by the ASTRO definition was 89.3% with a median follow up of 41 months. Patients with intermediate- (1 RF) and high-risk (2-3 RF) prostate cancer exhibited 5-year ASTRO-defined bDFS of 100% and 81.9%, respectively. There was no significant difference in bDFS between the patients treated with or without hormone therapy (HT). The 5-year ASTRO-defined bDFS was 89.8% for the 30 patients treated with HT and 88.9% for the 36 patients who did not receive HT (p = 0.843). For the patients without HT the median PSA nadir was 0.11 ng/mL. The median time to nadir was 23 months (range, 6-66 months).

CONCLUSIONS

With limited follow-up, the results of EBRT plus radioimmunoguided brachytherapy for intermediate- to high-risk prostate cancer appear favorable. The addition of HT did not appear to affect bDFS significantly, but interpretation is confounded by possible selection bias and the limited power of this study.