Value of prostate specific antigen in predicting the existence of bone metastasis in scintigraphy

Diagnostic accuracy of bone scan at different PSA levels in biochemical recurrence of prostate cancer

OBJECTIVE

To determine the diagnostic accuracy of Bone Scan at different PSA levels for detecting skeletal metastases in men with biochemical recurrence of prostate cancer.

METHODS

We conducted a retrospective review of the statewide RIS-PACS to identify 251 men with biochemical recurrence who underwent both a Bone Scan and Ga68 PSMA PET/CT (within 2 months of each other) between September 2019 and December 2022 at a single institution. The Ga68 PSMA PET/CT report was considered to be the reference standard.

RESULTS

The median age was 72 years (IQR 67-76) with a median PSA level of 1 ng/ml (IQR 0.25-2.8). Using Ga68 PSMA PET/CT as the reference standard, 68/251 patients (25%) were positive for osseus metastases. Overall sensitivity and specificity of Bone Scan was 51% (95% CI 40-64%) and 99% (95% CI 98-100%) respectively. Using PSA banding, a PSA threshold of 20 ng/ml provided the greatest discriminatory benefit with sensitivity of the Bone Scan below the threshold being 46% (95% CI 33-59%) and above the threshold being 89% (95% CI 68-100%). Specificity remained consistently high both below and above this threshold.

CONCLUSION

Bone Scan provides greater diagnostic accuracy for detecting skeletal metastases in biochemical recurrence when the PSA level is above 20 ng/ml. This knowledge is valuable in optimising imaging algorithms in biochemical recurrence, particularly in regions where PSMA PET/CT is less readily available or affordable.

Determination of the optimal cut-off value of serum prostate-specific antigen in the prediction of skeletal metastases on technetium-99m whole-body bone scan by receiver operating characteristic curve analysis

Radionuclide whole-body bone scan is a useful investigation of choice to detect the skeletal metastases in prostate cancer. It is indicated in patients having elevated serum prostate-specific antigen (Sr. PSA) or patients with bone pain. Elevated Sr. PSA levels have high predictive value for skeletal metastases; however, there is no consensus regarding cut-off value of Sr. PSA above which bone scan is indicated. This study was performed to find out the accuracy of Sr. PSA test and to know the optimal cut-off value of Sr. PSA with high sensitivity and specificity in the prediction of skeletal metastases on bone scan in prostate cancer patients. A retrospective analysis of medical records of 307 prostate cancer patients referred to the department of nuclear medicine for bone scan between June 2009 and June 2014 was done. Of 307 patients, 15 cases were excluded due to nonavailability of Sr. PSA. Bone scan was performed 3 h after administration of 20 mCi Tc-99m methylene diphosphonate intravenously. Whole-body sweep imaging was performed and spot views were taken wherever required. Of 292 cases, 174 (59.58%) patients had positive bone scan for metastases and 118 (40.41%) patients had negative bone scan for metastases. Maximum and minimum Sr. PSA levels in positive and negative bone scan patients were 1260 and 0.02 ng/ml and 198.34 ng/ml and 0.01 ng/ml, respectively. On comparison of the mean Sr. PSA levels between positive and negative groups, we found significant Sr. PSA levels (P < 0.05). We used receiver operating characteristic (ROC) curve analyses to find out the accuracy of Sr. PSA test and to know the optimal cut-off value of Sr. PSA with maximum sensitivity and specificity in the prediction of skeletal metastases on bone scan. Area under ROC curve was 0.878 (87%). This indicates that the accuracy of Sr. PSA test in the prediction of skeletal metastases on bone scan was good. The optimal cut-off value of Sr. PSA in the prediction of positive bone scan for skeletal metastases in the management of prostate cancer was 29.16 ng/ml, with sensitivity and specificity of 89.0% and 74.6%, respectively. In this study, we conclude that the accuracy of Sr. PSA test in the prediction of skeletal metastases is good. ROC-derived optimal cut-off value of Sr. PSA for positive skeletal metastases on bone scan is >29.16 ng/ml; thus, the chances of getting positive bone scan for skeletal metastasis are less in prostate cancer patients with Sr. PSA <29.16 ng/ml. ROC-derived sensitivity and specificity of different possible cut-off points of Sr. PSA help reduce the false positive results and increase the diagnostic accuracy of bone scan in the detection of skeletal metastases in prostate cancer patients.

ACR Appropriateness Criteria® Prostate Cancer-Pretreatment Detection, Surveillance, and Staging

Despite the frequent statement that "most men die with prostate cancer, not of it," the reality is that prostate cancer is second only to lung cancer as a cause of death from malignancy in American men. The primary goal during baseline evaluation of prostate cancer is disease characterization, that is, establishing disease presence, extent (local and distant), and aggressiveness. Prostate cancer is usually diagnosed after the finding of a suspicious serum prostate-specific antigen level or digital rectal examination. Tissue diagnosis may be obtained by transrectal ultrasound-guided biopsy or MRI-targeted biopsy. The latter requires a preliminary multiparametric MRI, which has emerged as a powerful and relatively accurate tool for the local evaluation of prostate cancer over the last few decades. Bone scintigraphy and CT are primarily used to detect bone and nodal metastases in patients found to have intermediate- or high-risk disease at biopsy. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Results of multiparametric transrectal ultrasound-based focal high-dose-rate dose escalation combined with supplementary external beam irradiation in intermediate- and high-risk localized prostate cancer patients

PURPOSE

Clinical results of a biologic information-based focused dose escalation combined with dose de-escalation for the whole organ in external beam radiotherapy + high-dose-rate brachytherapy (HDR-BT) boost application for localized prostate cancer in a consecutively treated patient cohort.

METHODS AND MATERIALS

One hundred thirty patients were treated with external beam radiotherapy (50 Gy) complementary to two multiparametric transrectal ultrasound-guided 15 Gy HDR-BT fractions. Real-time multiparametric transrectal ultrasound-based biologic planning for high-dose-rate boost dose planning used the summation of gray scale and Doppler sonography imaging + biopsy information. Target subvolumes received HDR-BT dose escalation up to 60 Gy/fraction. Dose-volume histogram parameters, organ at risks doses, and toxicity results were investigated.

RESULTS

The median followup was 4.3 years, the median age was 68.62 years, and the mean initial prostate-specific antigen was 18.69 ng/mL. Low-, intermediate-, and high-risk constituted 69%, 21%, and 10% of the patients, respectively. The mean peripheral dose was 3.9 Gy per fraction. Prostate-specific antigen nadir was in 93% of the patients ≤1 ng/mL. Quality parameters were as follows: D₉₀: 6.58 Gy, V₁₀₀: 30.36%, V₁₅₀: 9.96%, V₂₀₀: 3.16%, uD_0.1: 7.34 Gy, uD₂: 9.34 Gy, rD₀₁: 10.56 Gy, and rD₂: 8.32 Gy, respectively. We observed G1, G2, G3 urinary toxicity in 17/130, 11/130, and 2/130 patients, respectively. Rectal toxicity: G1 and G2 occurred in 19/130 and 2/130 patients with mean dose values G1: 8.2 Gy and G2: 8.76 Gy. Analysis of variance test resulted in no correlation between toxicities and any other investigated factors.

CONCLUSIONS

Focused extreme dose escalation with low prostate mean peripheral dose results in excellent long-term outcome data and very high focal boost doses and is causing no enhancement in late treatment toxicity.

Are Bone Scans Necessary in Men With Low Prostate Specific Antigen Levels Following Localized Therapy?

PURPOSE

The prostate specific antigen level at which to recommend a bone scan after treatment of early prostate cancer is controversial. We identified the incidence of bone metastases at varying prostate specific antigen levels in asymptomatic men following radical prostatectomy, radiation therapy and watchful waiting.

MATERIALS AND METHODS

Data were obtained from the Early Prostate Cancer trial comparing placebo with bicalutamide in addition to standard care for localized prostate cancer. As part of the trial patients were required to have routine bone scans regardless of prostate specific antigen levels. The prostate specific antigen levels were divided into subgroups and the incidence of positive bone scans was calculated for each group.

RESULTS

The incidence of positive bone scans in patients treated with watchful waiting and given bicalutamide or placebo was low (0.7% to 3.2%) at prostate specific antigen levels less than 20 ng/ml. At greater than this level the sample sizes were smaller but there was a significant increase in the incidence of positive bone scans. In the groups treated with radiation therapy or radical prostatectomy, regardless of the addition of bicalutamide, the incidence of positive bone scans was low (0.2% to 1.4%) at prostate specific antigen levels less than 5 ng/ml. The sample sizes were smaller at prostate specific antigen levels greater than 5 ng/ml so the results are harder to interpret.

CONCLUSIONS

Bone scans can be confidently eliminated in the followup of patients with early prostate cancer after standard care of those with prostate specific antigen levels less than 5 ng/ml. This level can be increased to 20 ng/ml with caution in those patients treated with watchful waiting.