A Systematic Review of the Role of Imaging before Salvage Radiotherapy for Post-prostatectomy Biochemical Recurrence

The clinical role of multimodality imaging in the detection of prostate cancer recurrence after radical prostatectomy and radiation therapy: past, present, and future

Detection of the recurrence sites in prostate cancer (PCa) patients affected by biochemical recurrence after radical prostatectomy (RP) and radiation therapy (RT) is still a challenge for clinicians, nuclear medicine physicians, and radiologists. In the era of personalised and precision care, this task requires the integration, amalgamation, and combined analysis of clinical and imaging data from multiple sources. At present, multiparametric Magnetic Resonance Imaging (mpMRI) and choline–positron emission tomography (PET) are giving encouraging results; their combination allows the effective detection of local, lymph nodal, and skeletal recurrences at low PSA levels. Future diagnostic perspectives include the clinical implementation of PET/MRI scanners, multimodal fusion imaging platforms for retrospective co-registration of PET and MR images, real-time transrectal ultrasound/mpMRI fusion imaging, and novel organ-specific PET radiotracers.

Economic evaluation of diagnostic localization following biochemical prostate cancer recurrence

OBJECTIVES

The aim of this study was to assess potential cost-effectiveness of using a prostate cancer specific functional imaging technology capable of identifying residual localized disease versus small volume metastatic disease for asymptomatic men with low but detectable prostate specific antigen (PSA) elevation following radical prostatectomy.

METHODS

Markov modeling was used to estimate the incremental impact on healthcare system costs (2012 USD) and quality-adjusted life-years (QALYs) of two alternative strategies: (i) using the new diagnostic to guide therapy versus (ii) current usual care-using a combination of computed tomography, magnetic resonance imaging, and bone scan to guide therapy. Costs were based on estimates from literature and Medicare reimbursement. Prostate cancer progression, survival, utilities, and background risk of all-cause mortality were obtained from literature. Base-case diagnostic sensitivity (75 percent), specificity (90 percent), and cost (USD 2,500) were provided by our industry partner GE Healthcare.

RESULTS

The new diagnostic strategy provided an average gain of 1.83 (95 percent uncertainty interval [UI]: 1.24-2.64) QALYs with added costs of USD 15,595 (95 percent UI: USD -6,330-44,402) over 35 years. The resulting incremental cost-effectiveness ratio was USD 8,516/QALY (95 percent UI: USD -2,947-22,372). RESULTS were most influenced by the utility discounting rate and test performance characteristics; however, the new diagnostic provided clinical benefits over a wide range of sensitivity and specificity.

CONCLUSION

This analysis suggests a diagnostic technology capable of identifying whether men with biochemical recurrence after radical prostatectomy have localized versus metastatic disease would be a cost-effective alternative to current standard work-up. The results support additional investment in development and validation of such a diagnostic.

Multiparametric MRI for recurrent prostate cancer post radical prostatectomy and postradiation therapy

The clinical suspicion of local recurrence of prostate cancer (PCa) after radical prostatectomy (RP) and after radiation therapy (RT) is based on the onset of biochemical failure. The aim of this paper was to review the current role of multiparametric-MRI (mp-MRI) in the detection of locoregional recurrence. A systematic literature search using the Medline and Cochrane Library databases was performed from January 1995 up to November 2013. Bibliographies of retrieved and review articles were also examined. Only those articles reporting complete data with clinical relevance for the present review were selected. This review article is divided into two major parts: the first one considers the role of mp-MRI in the detection of PCa local recurrence after RP; the second part provides an insight about the impact of mp-MRI in the depiction of locoregional recurrence after RT (interstitial or external beam). Published data indicate an emerging role for mp-MRI in the detection and localization of locally recurrent PCa both after RP and RT which represents an information of paramount importance to perform focal salvage treatments.

Development of a 124I-labeled version of the anti-PSMA monoclonal antibody capromab for immunoPET staging of prostate cancer: Aspects of labeling chemistry and biodistribution

Correct staging of prostate cancer is an unmet clinical need. Radionuclide targeting of prostate-specific membrane antigen (PSMA) with 111In-labeled capromab pendetide (ProstaScint) is a clinical option for prostate cancer staging. We propose the use of 124I-labeled capromab to decrease the retention of radioactivity in healthy organs (due to the non-residualizing properties of the radiolabel). The use of 124I as a label should increase imaging sensitivity due to the advantages of PET as an imaging modality. Capromab targets the intracellular domain of PSMA; accumulation of radioactivity in the tumor should not depend on internalization of the antigen/antibody complex. Capromab was iodinated, and its targeting properties were compared with indium labeled counterpart in LNCaP xenografts in dual isotope mode. PSMA-negative xenografts (PC3) were used as a negative control. Radioiodinated capromab bound to PSMA specifically. Biodistribution of 125I/111In-capromab showed a more rapid clearance of iodine radioactivity from liver, spleen, kidneys, bones, colon tissue, as well as tumors. Maximum tumor uptake (13±8% ID/g for iodine and 29±9% ID/g for indium) and tumor-to-non-tumor ratios for both agents were measured 5 days post-injection (pi). High tumor accumulation and low uptake of radioactivity in normal organs were confirmed using microPET/CT 5 days pi of 124I-capromab.

A paradigm shift from anatomic to functional and molecular imaging in the detection of recurrent prostate cancer

Approximately a third of men with localized prostate cancer who are treated with external beam radiation therapy (EBRT) or radical prostatectomy (RP) develop biochemical failure (BF). Presumably, BF will progress to distant metastasis and prostate cancer-specific mortality in some patients over subsequent years. Accurate detection of recurrent disease is important because it allows for appropriate treatment selection (e.g., local vs systemic therapy) and early delivery of therapy (e.g., salvage EBRT), which affect patient outcome. In this article, we discuss the paradigm shift in imaging technology in the detection of recurrent prostate cancer. First, we discuss the commonly used morphological and anatomical imaging modalities and their role in the post-RP and post-EBRT settings of BF. Second, we discuss the accuracy of functional and molecular imaging techniques, many of which are under investigation. Further studies are needed to establish the role of imaging techniques for detection of cancer recurrence and clinical decision-making.

Anti-3-[(18)F]FACBC positron emission tomography-computerized tomography and (111)In-capromab pendetide single photon emission computerized tomography-computerized tomography for recurrent prostate carcinoma: results of a prospective clinical trial

PURPOSE

We prospectively evaluated the amino acid analogue positron emission tomography radiotracer anti-3-[(18)F]FACBC compared to ProstaScint® ((111)In-capromab pendetide) single photon emission computerized tomography-computerized tomography to detect recurrent prostate carcinoma.

MATERIALS AND METHODS

A total of 93 patients met study inclusion criteria who underwent anti-3-[(18)F]FACBC positron emission tomography-computerized tomography plus (111)In-capromab pendetide single photon emission computerized tomography-computerized tomography for suspected recurrent prostate carcinoma within 90 days. Reference standards were applied by a multidisciplinary board. We calculated diagnostic performance for detecting disease.

RESULTS

In the 91 of 93 patients with sufficient data for a consensus on the presence or absence of prostate/bed disease anti-3-[(18)F]FACBC had 90.2% sensitivity, 40.0% specificity, 73.6% accuracy, 75.3% positive predictive value and 66.7% negative predictive value compared to (111)In-capromab pendetide with 67.2%, 56.7%, 63.7%, 75.9% and 45.9%, respectively. In the 70 of 93 patients with a consensus on the presence or absence of extraprostatic disease anti-3-[(18)F]FACBC had 55.0% sensitivity, 96.7% specificity, 72.9% accuracy, 95.7% positive predictive value and 61.7% negative predictive value compared to (111)In-capromab pendetide with 10.0%, 86.7%, 42.9%, 50.0% and 41.9%, respectively. Of 77 index lesions used to prove positivity histological proof was obtained in 74 (96.1%). Anti-3-[(18)F]FACBC identified 14 more positive prostate bed recurrences (55 vs 41) and 18 more patients with extraprostatic involvement (22 vs 4). Anti-3-[(18)F]FACBC positron emission tomography-computerized tomography correctly up-staged 18 of 70 cases (25.7%) in which there was a consensus on the presence or absence of extraprostatic involvement.

CONCLUSIONS

Better diagnostic performance was noted for anti-3-[(18)F]FACBC positron emission tomography-computerized tomography than for (111)In-capromab pendetide single photon emission computerized tomography-computerized tomography for prostate carcinoma recurrence. The former method detected significantly more prostatic and extraprostatic disease.

Application of C-11-acetate positron-emission tomography (PET) imaging in prostate cancer: systematic review and meta-analysis of the literature

To review the literature on the application of (11) C-acetate positron-emission tomography (PET) imaging in prostate cancer. We systematically reviewed the available literature and presented the results in meta-analysis format. PubMed, SCOPUS, ISI web of knowledge, Science Direct, Springer, and Google Scholar were searched with 'Acetate AND PET AND Prostate' as keywords. All studies that evaluated accuracy of (11) C-acetate imaging in primary or recurrent prostate cancer were included, if enough data could be extracted for calculation of sensitivity and/or specificity. In all, 23 studies were included in the study. For evaluation of primary tumour, pooled sensitivity was 75.1 (69.8-79.8)% and specificity was 75.8 (72.4-78.9)%. For detection of recurrence, sensitivity was 64 (59-69)% and specificity was 93 (83-98)%. Sensitivity for recurrence detection was higher in post-surgical vs post-radiotherapy patients and in patients with PSA at relapse of >1 ng/mL. Studies using PET/computed tomography vs PET also showed higher sensitivity for detection of recurrence. Imaging with (11) C-acetate PET can be useful in patients with prostate cancer. This is especially true for evaluation of patients at PSA relapse, although the sensitivity is overall low. For primary tumour evaluation (localisation of tumour in the prostate and differentiation of malignant from benign lesions), (11) C-acetate is of limited value due to low sensitivity and specificity. Due to the poor quality of the included studies, the results should be interpreted with caution and further high-quality studies are needed.

The PROCAINA (PROstate CAncer INdication Attitudes) Project (Part I): a survey among Italian radiation oncologists on postoperative radiotherapy in prostate cancer

PURPOSE

Radiotherapy (RT) has an established role in the postoperative treatment of prostate cancer patients with extracapsular extension, positive surgical margins or a detectable post-operative prostate-specific antigen (PSA). Despite the large number of patients treated with postoperative RT, some issues about optimal technique, doses, volumes, timing and association with androgen deprivation are still subject of debate. The aim of this survey was to determine the patterns of choice of Italian radiation oncologists in two different clinical cases of postoperative prostate cancer patients.

STUDY DESIGN

During the 2010 National Congress of the Italian Association of Radiation Oncology (AIRO), four clinical cases were presented to the attending radiation oncologists. Two of them were cases of postoperative prostate cancer, differing in T stage of the primary tumour according to the TNM classification, preoperative staging procedures, preoperative PSA (iPSA), Gleason score of biopsies and definitive pathological specimen after surgery and postoperative PSA. For each clinical case, the radiation oncologists were asked to: (a) give indication to new pre-treatment procedures for staging; b) give indication to postoperative treatment; (c) to define specifically, where indicated, the total dose, type of fractionation, treatment volumes, type of technique, type of image-guided setup control; (d) indicate whether adjuvant hormonal therapy should be prescribed; (e) define criteria that mostly influenced the prescription. A descriptive statistical analysis was then performed.

RESULTS

A total of 300 questionnaires were distributed amongst radiation oncologists attending the congress; 128 were completed and considered for this analysis (41%). Some important differences were shown in prescribing and performing postoperative radiotherapy, and some significant differences with international guidelines and data available from the literature were also reviewed and discussed.

CONCLUSIONS

Despite the results of clinical trials, significant differences still exist among Italian radiation oncologists in deciding postoperative treatment in prostate cancer patients. These patients probably deserve a more uniform approach based on updated, detailed and evidence-based recommendations.

The incremental value of contrast-enhanced MRI in the detection of biopsy-proven local recurrence of prostate cancer after radical prostatectomy: effect of reader experience

OBJECTIVE

The purpose of this study is to retrospectively assess the incremental value of contrast-enhanced MRI (CE-MRI) to T2-weighted MRI in the detection of postsurgical local recurrence of prostate cancer by readers of different experience levels, using biopsy as the reference standard.

MATERIALS AND METHODS

Fifty-two men with biochemical recurrence after prostatectomy underwent 1.5-T endorectal MRI with multiphase contrast-enhanced imaging and had biopsy within 3 months of MRI. Two radiologists (reader 1 had 1 year and reader 2 had 6 years of experience) independently reviewed each MRI study and classified the likelihood of recurrent cancer on a 5-point scale. Areas under receiver operating characteristic curves (A(z)) were calculated to assess readers' diagnostic performance with T2-weighted MRI alone and combined with CE-MRI. Interobserver agreement was assessed using Cohen kappa statistics.

RESULTS

Thirty-three patients (63%) had biopsy-proven local recurrence of prostate cancer. With the addition of CE-MRI to T2-weighted imaging, the A(z) for cancer detection increased significantly for reader 1 (0.77 vs 0.85; p = 0.0435) but not for reader 2 (0.86 vs 0.88; p = 0.7294). The use of CE-MRI improved interobserver agreement from fair (κ = 0.39) to moderate (κ = 0.58).

CONCLUSION

CE-MRI increased interobserver agreement and offered incremental value to T2-weighted MRI in the detection of locally recurrent prostate cancer for the relatively inexperienced reader.

Diffusion-weighted MRI for locally recurrent prostate cancer after external beam radiotherapy

OBJECTIVE

The objectives of our study were to establish the apparent diffusion coefficients (ADCs) of tumor and nontumor irradiated tissues in patients with suspected postradiation recurrence of prostate cancer and to determine the sensitivity and specificity of a combination of T2-weighted and diffusion-weighted imaging (DWI) for detecting local recurrence.

MATERIALS AND METHODS

Twenty-four patients with rising prostate-specific antigen levels after having completed radiation therapy 30-130 months earlier (median, 62 months) underwent endorectal T2-weighted imaging and DWI (b = 0, 100, 300, 500, and 800 s/mm(2)) followed by transrectal ultrasound (TRUS)-guided biopsy. Images were scored prospectively as positive for tumor if a region of low signal intensity on T2-weighted imaging within the prostate corresponded with a focally restricted area on the ADC map. A region of interest (ROI) was drawn around the suspicious lesion on a single slice of the ADC map and a corresponding ROI was drawn around presumed nontumor irradiated peripheral zone and central gland tissues on the opposite side of the prostate. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were determined against TRUS-guided biopsy reference standard (octant, n = 17; sextant, n = 5; two samples, n = 1; 12 samples, n = 1).

RESULTS

Sixteen of 24 patients (66.7%) had positive histology findings. The median tumor ROI area was 0.37 cm(2) (quartiles, 0.30 and 0.82 cm(2)). The sensitivity, specificity, PPV, and NPV for detecting tumor were 93.8%, 75%, 88.2%, and 85.7%, respectively. A cutoff ADC of 1216 × 10(-6) mm(2)/s could predict tumor with 100% sensitivity and 96% specificity (area under the receiver operating characteristic curve = 0.992).

CONCLUSION

An ADC derived from DWI is a useful adjunct to T2-weighted MRI for detecting local tumor recurrence larger than 0.4 cm(2) within the prostate.

Postoperative radiotherapy in prostate cancer: the case of the missing target

PURPOSE

Postoperative radiotherapy (XRT) increases survival in high-risk prostate cancer patients. Approximately 50% of patients on long-term follow-up relapse despite adjuvant XRT and the predominant site of failure remains local. Four consensus guidelines define postoperative clinical target volume (CTV) in prostate cancer. We explore the possibility that inadequate CTV coverage is an important cause of local failure. This study evaluates the utility of preoperative magnetic resonance imaging (MRI) in defining prostate bed CTV.

METHODS AND MATERIALS

Twenty prostate cancer patients treated with postoperative XRT who also had preoperative staging MRI were included. The four guidelines were applied and the CTVs were expanded to create planning target volumes (PTVs). Preoperative MRIs were fused with postoperative planning CT scans. MRI-based prostate and gross visible tumors were contoured. Three-dimensional (3D) conformal four- and six-field XRT plans were developed and dose-volume histograms analyzed. Subtraction analysis was conducted to assess the adequacy of prostate/gross tumor coverage.

RESULTS

Gross tumor was visible in 18 cases. In all 20 cases, the consensus CTVs did not fully cover the MRI-defined prostate. On average, 35% of the prostate volume and 32% of the gross tumor volume were missed using six-field 3D treatment plans. The entire MRI-defined gross tumor volume was completely covered in only two cases (six-field plans). The expanded PTVs did not cover the entire prostate bed in 50% of cases. Prostate base and mid-zones were the predominant site of inadequate coverage.

CONCLUSIONS

Current postoperative CTV guidelines do not adequately cover the prostate bed and/or gross tumor based on preoperative MRI imaging. Additionally, expanded PTVs do not fully cover the prostate bed in 50% of cases. Inadequate CTV definition is likely a major contributing factor for the high risk of relapse despite adjuvant XRT. Preoperative imaging may lead to more accurate CTV definition, which should result in further improvements in survival for patients with high-risk prostate cancer.

Influence of (11)C-choline PET/CT on the treatment planning for salvage radiation therapy in patients with biochemical recurrence of prostate cancer

BACKGROUND AND PURPOSE

The present study evaluates the incidence of (11)C-choline PET/CT positive findings in patients with recurrent prostate cancer referred for salvage radiotherapy (SRT) and the influence on the definition of the planning target volume (PTV).

MATERIAL AND METHODS

Thirty-seven patients treated with radical prostatectomy and referred to SRT to the prostatic fossa because of biochemical relapse, were analysed retrospectively. All patients underwent (11)C-choline PET/CT before radiotherapy. The influence of PET/CT on the extent of the PTV was analysed. The median total follow up after SRT was 51.2 months.

RESULTS

11/37 (30%) patients had a positive finding in the (11)C-choline PET/CT, 5 (13%) outside of the prostatic fossa (iliac lymph nodes), implicating an extension of the PTV. Patients with positive (11)C-choline PET/CT had a significant higher PSA value than patients with no pathologic uptake (p=0.03). Overall, at the end of follow up 56% of the patients had a PSA ≤ 0.2ng/ml and 44% had a biochemical relapse of prostate cancer.

CONCLUSIONS

(11)C-choline PET/CT detects abnormalities outside of the prostatic fossa in 13% of patients referred for SRT because of biochemical relapse after radical prostatectomy, affecting the extent of the PTV. Prospective studies need to be implemented to evaluate the benefit of SRT with a PTV based on (11)C-choline PET/CT.

Detection of recurrent prostate carcinoma with anti-1-amino-3-18F-fluorocyclobutane-1-carboxylic acid PET/CT and 111In-capromab pendetide SPECT/CT

PURPOSE

To compare the diagnostic performance of the synthetic amino acid analog radiotracer anti-1-amino-3-fluorine 18-fluorocyclobutane-1-carboxylic acid (anti-3-(18)F-FACBC) with that of indium 111 ((111)In)-capromab pendetide in the detection of recurrent prostate carcinoma.

MATERIALS AND METHODS

This prospective study was approved by the institutional review board and complied with HIPAA guidelines. Written informed consent was obtained. Fifty patients (mean age, 68.3 years ± 8.1 [standard deviation]; age range, 50-90 years) were included in the study on the basis of the following criteria: (a) Recurrence of prostate carcinoma was suspected after definitive therapy for localized disease, (b) bone scans were negative, and (c) anti-3-(18)F-FACBC positron emission tomography (PET)/computed tomography (CT) and (111)In-capromab pendetide single photon emission computed tomography (SPECT)/CT were performed within 6 weeks of each other. Studies were evaluated by two experienced interpreters for abnormal uptake suspicious for recurrent disease in the prostate bed and extraprostatic locations. The reference standard was a combination of tissue correlation, imaging, laboratory, and clinical data. Diagnostic performance measures were calculated and tests of the statistical significance of differences determined by using the McNemar χ(2) test as well as approximate tests based on the difference between two proportions.

RESULTS

For disease detection in the prostate bed, anti-3-(18)F-FACBC had a sensitivity of 89% (32 of 36 patients; 95% confidence interval [CI]: 74%, 97%), specificity of 67% (eight of 12 patients; 95% CI: 35%, 90%), and accuracy of 83% (40 of 48 patients; 95% CI: 70%, 93%). (111)In-capromab pendetide had a sensitivity of 69% (25 of 36 patients; 95% CI: 52%, 84%), specificity of 58% (seven of 12 patients; 95% CI: 28%, 85%), and accuracy of 67% (32 of 48 patients; 95% CI: 52%, 80%). In the detection of extraprostatic recurrence, anti-3-(18)F-FACBC had a sensitivity of 100% (10 of 10 patients; 95% CI: 69%, 100%), specificity of 100% (seven of seven patients; 95% CI: 59%, 100%), and accuracy of 100% (17 of 17 patients; 95% CI: 80%, 100%). (111)In-capromab pendetide had a sensitivity of 10% (one of 10 patients; 95% CI: 0%, 45%), specificity of 100% (seven of seven patients; 95% CI: 59%, 100%), and accuracy of 47% (eight of 17 patients; 95% CI: 23%, 72%).

CONCLUSION

anti-3-(18)F-FACBC PET/CT was more sensitive than (111)In-capromab pendetide SPECT/CT in the detection of recurrent prostate carcinoma and is highly accurate in the differentiation of prostatic from extraprostatic disease.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11102023/-/DC1.

Treatment of men with rising prostate-specific antigen levels following radical prostatectomy

Approximately one-third of patients who undergo radical prostatectomy for prostate cancer will develop a detectable prostate-specific antigen (PSA) level within 10 years. Biochemical recurrence of disease is defined as a rising PSA level in the absence of clinical or radiographic evidence of disease. Management of PSA recurrence is controversial, as prostate cancer may take an indolent course, or it may aggressively develop into metastatic disease. The only potentially curative treatment for biochemical failure after prostatectomy is salvage radiotherapy. Noncurative treatment options include hormone therapy or clinical trials of a novel systemic agent. This article will address management options for a rising PSA level after prostatectomy, as well as ongoing studies exploring molecular biomarkers as prognostic tumor markers and potential targets for prostate cancer therapy.

Is there a role for ¹¹C-choline PET/CT in the early detection of metastatic disease in surgically treated prostate cancer patients with a mild PSA increase <1.5 ng/ml?

PURPOSE

The aim of this study was to evaluate the potential usefulness of whole-body (11)C-choline PET/CT in the re-staging of prostate cancer (PC) patients previously treated with radical prostatectomy (RP), who presented a mild increase of prostate-specific antigen (PSA) <1.5 ng/ml (early biochemical relapse) during follow-up (FU).

METHODS

We evaluated 102 consecutive patients (mean age = 68 years, range = 54-82 years) previously treated with RP and who presented during FU a mild increase of trigger PSA serum levels <1.5 ng/ml: mean 0.86 ± 0.40 ng/ml (range 0.2-1.5) and median 0.93 ng/ml (range 0.67-1.10). In this patient series (11)C-choline PET/CT was used as the first imaging examination at the time of the detection of a mild serum PSA increase <1.5 ng/ml. (11)C-Choline PET/CT was performed following standard procedures in our centre. At the time of PET/CT, 86 patients were not receiving any pharmacologic treatment, while 16 were under anti-androgenic therapy. Positive PET findings were validated by: (a) transrectal ultrasound (TRUS)-guided biopsy in cases of local recurrence, (b) surgical lymphadenectomy, (c) other imaging procedures or (d) FU lasting for at least 12 months. Univariate and multivariate analyses were used to evaluate the following variables: age, TNM staging, Gleason score, time from RP to the biochemical relapse, anti-androgen therapy at the time of (11)C-choline PET/CT scan, trigger PSA value and PSA kinetics, i.e. PSA doubling time (PSAdt) and PSA velocity (PSAvel), in order to assess the significant predictive factors related to the findings of a positive (11)C-choline PET/CT scan.

RESULTS

Overall, (11)C-choline PET/CT showed positive findings in 29 of 102 patients (28% of cases). In detail, (11)C-choline PET/CT detected: local relapse in 7 patients, bone metastases in 13 patients (4 single and 9 multiple) and lymph node metastases in 9 patients (6 single and 3 multiple). Positive PET findings were validated by: (a) TRUS-guided biopsy in 7 patients with local recurrence, (b) surgery and lymphadenectomy in 3 patients, (c) other targeted imaging procedures (MR or bone scan) in 5 patients and (d) clinical FU lasting a minimum of 12 months and including also a contrast-enhanced CT (CECT), an MR, a bone scan and a repeated (11)C-choline PET/CT in 14 patients. Age, time to biochemical relapse (TTR), initial T staging, Gleason score and trigger PSA were not statistically significant in predicting a positive (11)C-choline PET/CT scan both at univariate and multivariate analysis. Instead, PSA kinetics (PSAdt and PSAvel), N status and anti-androgenic therapy at the time of PET scan were statistically significant predictive factors at univariate analysis. Of note, only PSAdt and initial N status were found to be significant and independent predictive factors at multivariate analysis. The mean PSAdt in PET-positive patients was 4.34 months (SD 2.82) while in PET-negative patients it was 13.30 months (SD 9.75) (p = 0.0001). The optimal threshold for PSAdt established by receiver-operating characteristic (ROC) analysis was 7.25 months (AUC 0.85; 95% confidence interval 0.77-0.91) providing 93% sensitivity, 74% specificity, 60% positive predictive value and 96% negative predictive value.

CONCLUSION

In our study, (11)C-choline PET/CT was able to detect recurrent disease in 28% of the patients with mild biochemical relapse characterized by very low trigger PSA levels (PSA <1.5 ng/ml). Very interestingly (11)C-choline PET/CT detected distant unexpected metastases in 21% of the patients. At multivariate statistical analysis only PSAdt and node status were shown to be significant and independent predictive factors for positive (11)C-choline PET/CT. Therefore, (11)C-choline could be suggested to be performed early during initial biochemical relapse in patients presenting with fast PSA kinetics. The early detection of the site of recurrence could lead to a prompt instauration of the most appropriate treatment, i.e. local surgery or radiation treatment vs systemic treatment. In this view, one of the main advantages should be the avoidance of unnecessary local radiotherapy in those patients showing distant metastasis at (11)C-choline PET/CT.

Radionuclide and hybrid imaging of recurrent prostate cancer

Prostate cancer is one of the most common cancers in men, leading to substantial morbidity and mortality. After definitive therapy with surgery or radiation, many patients have biochemical relapse of disease--ie, an increase in their prostate-specific antigen level--which often precedes clinically apparent disease by months or even years. Therefore, imaging of the site and extent of tumour recurrence (local, regional, distant, or a combination) is of great interest. Conventional morphological imaging methods showed limited accuracy for assessment of recurrent prostate cancer; however, in recent years, functional and molecular imaging have offered the possibility of imaging molecular or cellular processes of individual tumours, often with more accuracy than morphological imaging. Hybrid imaging modalities (PET-CT, and single-photon emission CT [SPECT]-CT) have been introduced that combine functional and morphological data and allow whole-body imaging. Here, we review the contribution of radionuclide imaging and hybrid imaging for assessment of recurrent prostate cancer (local vs regional vs distant disease). We discuss available data on PET-CT and SPECT-CT, and provide an overview of experimental tracers and their preclinical and clinical development. Finally, we present a perspective on the potential of future hybrid magnetic resonance-PET imaging.