Term Paper on "Prostascint Imaging"

Term Paper 12 pages (3324 words) Sources: 15 Style: APA

[EXCERPT] . . . .

PROSTASCINT IMAGING in DETECTION of BONE METASTASES in PROSTRATE CANCER: EXAMINATION of FALSE POSITIVE and FALSE NEGATIVE RESULTS and the ACCURACIES & INACCURACIES in DETECTION & DIAGNOSIS

The objective of this work is to make an extensive review of literature in the area of ProstaScint imaging effectiveness and accuracy in detecting distant metastases, and specifically bone metastases. This study specifically seeks findings concerning false positive and false negative results and the inaccuracies or accuracies in diagnosis of metastatic bone lesions due to prostrate cancer.

As the knowledge and experience in the clinical use of ProstaScint Imaging in detection of bone metastases in prostrate cancer grows the capacity to use this imaging in detection of prostrate bone metastases grows as well as does the accuracy of the use of ProstaScint imagine in this area of cancer detection, diagnoses and treatment.

LITERATURE REVIEW

The work of Samir Taneja (2004) entitled: "Imaging in the Diagnosis and management of Prostrate Cancer" published in the Urology Review relates a study of 160 men with high-risk disease defined by Gleason score, PSA, and clinical stage, 152 were studied with ProstaScint prior to surgical staging. www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1472828" of 64 patients with positive lymph nodes, 40 were read as positive by ProstaScint scan (PPV = 62%). Of 88 patients without lymph node metastases, 63 were read as negative by ProstaScint (specificity = 72%). Overall, the sensitivity for detection of lymph node metastases was 62%." Taneja states that in the reported study that CT and MRI "...demonstrated PPV of only 4% and 15%, respectively. Given the poor sensitivity and predictive value of CT/MRI in predicting extraprostatic disease, many clinicians rely upon algorithms or monograms to predict the risk of lymph node metastases." (Taneja, 2004) Taneja relates that Polascik and colleagues conducted a comparison of www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1472828" the ability of several clinical algorithms and ProstaScint scans in their prediction of lymphatic metastases. The participants in the study were 198 men with clinical T2-3 disease undergoing radical prostatectomy. The study states findings that "...of 39% of patients in this high-risk cohort were found to have lymph node metastases at surgery. From 40.5% to 45.4% of lymph node positive patients were predicted by clinical algorithm compared to 66.7% by ProstaScint alone. When integrating ProstaScint with clinical algorithms based upon Gleason score, disease volume, and pre-operative PSA, a PPV of 72.1% could be achieved." (Taneja, 2004) Included in the study's findings is that in the evaluation of patients "...prior to treatment, the use of ProstaScint scan may be particularly useful in staging individuals in the intermediate- to high-risk category. Although limited by its risk for false positive readings in inexperienced hands, the ProstaScint scan offers a useful tool for detection of lymph node metastases in newly diagnosed prostate cancer. Its use in high-risk disease allows the appropriate selection of candidates for potentially curative therapies. Current efforts to further improve specificity include fusion of the SPECT acquired images with 3D reconstructed MRI or CT." (Taneja, 2004) it is particularly important to note the statement of Taneja as follows: "The staging ability of the ProstaScint scan has been evaluated by a number of investigators. A fundamental necessity of the scan is experience in the interpreter. As the findings of the study are often subtle, with a high risk of false positive due to bowel or blood vessels overlying the lymph nodes, there may be an improvement in interpretive accuracy as the reader becomes more experienced. In the hands of experienced readers, the scan does appear to offer a valuable tool for staging of prostate cancer. The importance of reader experience in interpretation of ProstaScint scans is made evident by the reported data regarding staging. The PPV of the study varies in published reports from 11% to 66.7% in patients selected for radical prostatectomy (RP). In those series evaluating high-risk patients, the PPV was improved, probably due, in part, to the increased prevalence of metastatic nodal disease. In most studies to date, the predictive ability of ProstaScint is superior to that of CT/MRI in detecting lymph node metastases prior to therapy." (2004) Taneja (2004) claims that ProtaScint is capable of identifying the pelvis and retroperitoneal region nodes and when tested "against the pathologic outcome of lymph node sampling, the test displayed 89% sensitivity and 76% specificity." (Tenaja, 2004) ProstaScint is stated of Tenaja (2004) to have identified 42% of extraprostatic recurrence of patients evaluated. The study of Kahn (2007) reports 42% extraprostatic recurrence in 42% of evaluated patients evaluated. In a separate and larger study, Sodee and Faulhaber (2000) followed a cohort of patients for primary or recurrent disease and relates that "ProstaScint outcomes correlated significantly with the likelihood of isolated fossa recurrence."

The work of Quintana and Blend (2000) entitled: "The Dual-Isotope ProstaScint Imaging Procedures: Clinical Experience and Staging Results in 145 Patients" published in the Journal of Clinical Nuclear Medicine reports a study evaluating the effectiveness of ProstaScint for staging 145 patients with prostrate cancer, 19 newly diagnosed and 126 with recurrence. Results of the study that: "With clinical follow-up in 13 of 19 (68%) patients with primary disease, 10 of 13 (78%) had organ-confined disease. With follow-up in 64 of 126 (51%) patients with possible recurrent disease, 49 of 64 (77%) were found to have prostatic fossa activity only. Disease stage was deemed more advanced in 3 of 13 (22%) patients with primary cancer and in 13 of 64 (20%) of those with recurrent disease based on ProstaScint findings when all other imaging tests were inconclusive. Six patients with recurrent disease had negative results of their scans. In the 16 patients with more advanced disease, 3 of 59 lesions (5%) were documented as false positive, and there were no reported cases of false-negative findings." (Quintana and Blend, 2000) in one of two open-label, multi-center, uncontrolled pivotal phase 3 trials, 160 patients with a tissue diagnosis of prostrate cancer and who were considered to be high risk for lymph node metastases underwent Prostascint staging. Of these 160, 152 had an interpretable scan and surgical staging with 40 scans being true positive, 25 being false positive, 63 true negative and 24 false negative. The following figure shows the results for immunoscintigraphy.

The report states that sixty-five patients, or 43% had positive Indium in 111 ProstaScint images for pelvic lymph node metastases. Of these 65 patients 25 patients (38%) did not have metastatic prostrate cancer at surgery. Eighty-seven patients (57%) had negative Indium in 111 ProstaScint imagines: Of these 24 patients (28%) did have metastatic prostrate cancer at surgery. The overall accuracy in 111 ProstaScint immunoscintigraphy was 68%. A second open label, multi-center, uncontrolled pivotal phase 3 trial involving 183 patients with a high clinical suspicion of residual or recurrent prostate cancer following radical prostatectomy underwent evaluation. Patients with a rising PSA, a negative bone scan and a negative or equivocal standard diagnostic techniques underwent ProstaScint immunoscintigraphy before biopsy of the prostatic fossa. Results shown that 158 patients had a scan that was interpretable and prostatic fossa biopsy. Of these 158, 29 scans were false positive, 70 were true negative and 30 were false negative. The following figure shows the results of this study.

The study states: "Fifty-eight patients (37%) had positive Indium in 111 ProstaScint images in the prostatic fossa: Of these 50% (29 patients) did not have recurrent prostate cancer on biopsy. One hundred patients (63%) had negative Indium in 111 ProstaScint images: Of these 30% (30 patients) had recurrent prostate cancer on biopsy. The overall accuracy of Indium in 111 ProstaScint® immunoscintigraphy, as measured against prostatic fossa biopsy, was 63% (99/158)." (Rieger, 2001; ProstaScint Kit, nd)

It is related that clinical trials have not studied specifically the ability of ProstaScint to image distant (extra-pelvic) metastases, and a limited number of patients with distant (primarily bone) metastases were enrolled. The study states that 13 of 16 patients, or 81% with CT evidence of distant soft tissue disease had positive extrafossa ProstaScint scans. Of the 61 patients, 35, or 57% with bone scan evidence of disease had positive Indium in the 111 ProstaScint skeletal uptake; however Indium in 111 ProstaScint imaging did not identify most sites of abnormal bone uptake on bone scan. The Indium in 111 ProstaScint scan did, however, demonstrate sites of bone marrow metastases that were not seen on bone scan in 2 of 43 patients in the phase 1 study. (Rieger, 2001; ProstaScint Kit, nd)

The work of Mark Scholz entitled: "Newly Diagnose Prostrate Cancer: Evaluating the Options" states that in a multi-center study that compared ProstaScint imaging to PLND in 51 prostrate carcinoma patients who were identified as high risk for lymph node metastases, "ProstaScint surpassed the combined diagnostic performance of CT, MRI and U.S. with an overall accuracy of 81%." (2004) Scholz additionally states that other data from this study "provided evidence of the potential beneficial impact of ProstaScint imaging on health outcomes. Two patients were found to have histologically proven 'skip metastases' near the level of the aortic bifurcation, which is outside the conventional location of standard pelvic exploration. Both… READ MORE

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