223Ra Therapy of Advanced Metastatic Castration-Resistant Prostate Cancer: Quantitative Assessment of Skeletal Tumor Burden for Prognostication of Clinical Outcome and Hematologic Toxicity

Predictive and Prognostic 18F-Fluorocholine PET/CT Radiomics Nomogram in Patients with Castration-Resistant Prostate Cancer with Bone Metastases Treated with 223Ra

PURPOSE

We aimed to develop a nomogram able to predict treatment failure, skeletal events, and overall survival (OS) in patients with castration-resistant prostate cancer with bone metastases (CRPC-BM) treated with Radium-223 dichloride (223Ra).

PATIENTS AND METHODS

Patients from the Castilla-La Mancha Spanish region were prospectively included in the ChoPET-Rad multicenter study from January 2015 to December 2022. Patients underwent baseline, interim, and end-of-treatment bone scintigraphy (BS) and 18F-Fluorocholine PET/CT (FCH PET/CT) scans, obtaining multiple imaging radiomics as well as clinical and biochemical variables during follow-up and studying their association with the previously defined end-points. Survival analysis was performed using the Kaplan-Meier method and Cox regression. Multivariate logistic and Cox regression models were calculated, and these models were depicted by means of nomograms.

RESULTS

Median progression-free survival (PFS) and OS were 4 and 14 months (mo), respectively. The variables that showed independent and significant association with therapeutic failure were baseline alkaline phosphatase (AP) levels (p = 0.022) and the characteristics of BM on the CT portion of PET/CT (p = 0.017). In the case of OS, the significant variables were therapeutic failure (p = 0.038), the number of lines received after 223Ra (p < 0.001), average SUVmax (p = 0.002), bone marrow infiltration in FCH PET/CT (p = 0.006), and interim FCH PET/CT response (p = 0.048). Final nomograms included these variables, showing good discrimination among the 100 patients included in our study. In the study of skeletal events, only OS showed a significant association in the multivariate analysis, resulting in an inconsistent nomogram design.

CONCLUSIONS

FCH PET/CT appears to be a good tool for evaluating patients eligible for treatment with 223Ra, as well as for their follow-up. Thus, findings derived from it, such as the morphological characteristics of BM in the CT, bone marrow infiltration, or the response to 223Ra in the interim study, have proven to be solid and useful variables in the creation of nomograms for predicting therapeutic failure and OS.

Prospective Assessment of Bone Metabolism Biomarkers and Survival in Metastatic Castration-resistant Prostate Cancer Patients Treated with Radium-223: The PRORADIUM Study

BACKGROUND

Radium-223 is an active therapy option for bone metastatic castration-resistant prostate cancer (mCRPC). The lack of adequate biomarkers for patient selection and response assessment are major drawbacks for its use.

OBJECTIVE

To assess the prognostic value of bone metabolism biomarkers (BMBs) in ra-223-treated mCRPC patients.

DESIGN, SETTING, AND PARTICIPANTS

A prospective cohort study of mCRPC patients treated with Ra-223 (PRORADIUM study: NCT02925702) was conducted.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The main objective of the study was to evaluate the association between high (≥median) baseline values in at least three bone formation (bone alkaline phosphatase [BAP] and C-terminal type-I collagen propeptide) and bone resorption (N-terminal telopeptide and pyridinoline) biomarkers, and survival. The independent prognostic value of each BMB was also assessed. The association with time to radiographic, clinical, and prostate-specific antigen (PSA) progression; time to skeletal-related events; and PSA response were secondary objectives. Multivariable (MV) Cox-regression models were evaluated.

RESULTS AND LIMITATIONS

A total of 169 patients were included. Of the patients, 70.4% received Ra-223 in second/third line; 144 (85.2%) were Eastern Cooperative Oncology Group 0-1, 126 (74.6%) were in pain, and 80 (47.5%) had more than ten bone metastases. Sixty-seven (39.6%) patients had elevation in at least three BMBs. The median overall survival was 12.1 mo (95% confidence interval [CI]: 10-14.7). No association was observed with other treatment-related secondary outcome parameters. Patients with high values in three or more BMBs had significantly worse survival (9.9 vs 15.2 mo; hazard ratio [HR]: 1.8 [95% CI: 1.3-2.5]; p < 0.001) in the univariate analysis, but not independent in the MV analysis (HR: 1.33; 95% CI: 0.89-2; p = 0.181). High baseline BAP was the only biomarker associated with survival in the MV model (HR: 1.89; 95% CI: 1.28-2.79; p = 0.001). Addition of BAP to the MV clinical model increased the area under the receiver operating characteristic curve 2-yr value from 0.667 to 0.755 (p = 0.003).

CONCLUSIONS

Biomarkers of bone formation, especially BAP, have prognostic value in mCRPC patients treated with radium-223. Its predictive value remains to be assessed, ideally in prospective, adequately powered, randomised clinical trials.

PATIENT SUMMARY

In this study, we evaluate the role of bone metabolism biomarkers to help improve the use of radium-223 as therapy for advanced prostate cancer. We found that bone alkaline phosphatase may be a suitable tool.

Assessing Therapeutic Response to Radium-223 with an Automated Bone Scan Index among Metastatic Castration-Resistant Prostate Cancer Patients: Data from Patients in the J-RAP-BSI Trial

To evaluate the usefulness of change in the automated bone scan index (aBSI) value derived from bone scintigraphy findings as an imaging biomarker for the assessment of treatment response and survival prediction in metastatic castration-resistant prostate cancer (mCRPC) patients treated with Ra-223. This study was a retrospective investigation of a Japanese cohort of 205 mCRPC patients who received Ra-223 in 14 hospitals between July 2016 and August 2020 and for whom bone scintigraphy before and after radium-223 treatment was available. Correlations of aBSI change, with changes in the serum markers alkaline phosphatase (ALP) and prostate-specific antigen (PSA) were evaluated. Additionally, the association of those changes with overall survival (OS) was assessed using the Cox proportional-hazards model and Kaplan-Meier curve results. Of the 205 patients enrolled, 165 (80.5%) completed six cycles of Ra-223. Following treatment, ALP decline (%ALP < 0%) was noted in 72.2% (148/205), aBSI decline (%aBSI < 0%) in 52.7% (108/205), and PSA decline (%PSA < 0%) in 27.8% (57/205). Furthermore, a reduction in both aBSI and ALP was seen in 87 (42.4%), a reduction in only ALP was seen in 61 (29.8%), a reduction in only aBSI was seen in 21 (10.2%), and in both aBSI and ALP increasing/stable (≥0%) was seen in 36 (17.6%) patients. Multiparametric analysis showed changes in PSA [hazard ratio (HR) 4.30, 95% confidence interval (CI) 2.32-8.77, p < 0.0001], aBSI (HR 2.22, 95%CI 1.43-3.59, p = 0.0003), and ALP (HR 2.06, 95%CI 1.35-3.14, p = 0.0008) as significant prognostic factors for OS. For mCRPC patients treated with Ra-223, aBSI change is useful as an imaging biomarker for treatment response assessment and survival prediction.

Clinical Translation of Targeted α-Therapy: An Evolution or a Revolution?

The field of radioligand therapy has advanced greatly in recent years, driven largely by β-emitting therapies targeting somatostatin receptor-expressing tumors and the prostate-specific membrane antigen. Now, more clinical trials are under way to evaluate α-emitting targeted therapies as potential next-generation theranostics with even higher efficacy due to their high linear energy and short range in human tissues. In this review, we summarize the important studies ranging from the first Food and Drug Administration-approved α-therapy, ²²³Ra-dichloride, for treatment of bone metastases in castration-resistant prostate cancer, including concepts in clinical translation such as targeted α-peptide receptor radiotherapy and ²²⁵Ac-PSMA-617 for treatment of prostate cancer, innovative therapeutic models evaluating new targets, and combination therapies. Targeted α-therapy is one of the most promising fields in novel targeted cancer therapy, with several early- and late-stage clinical trials for neuroendocrine tumors and metastatic prostate cancer already in progress, along with significant interest and investment in additional early-phase studies. Together, these studies will help us understand the short- and long-term toxicity of targeted α-therapy and potentially identify suitable therapeutic combination partners.

The DASciS Software for BSI Calculation as a Valuable Prognostic Tool in mCRPC Treated with 223RaCl2: A Multicenter Italian Study

BACKGROUND/AIM

Radium-223 dichloride (²²³RaCl₂) represents a therapeutic option for metastatic castration-resistant prostate cancer (mCRPC) patients dealing with symptomatic bone metastases. The identification of baseline variables potentially affecting the life-prolonging role of ²²³RaCl₂ is still ongoing. Bone scan index (BSI) defines the total load of bone metastatic disease detected on a bone scan (BS) and is expressed as a percentage value of the whole bone mass. The aim of this multicenter study was to assess the impact of baseline BSI on overall survival (OS) in mCRPC patients treated with ²²³RaCl₂. For this purpose, the DASciS software developed by the Sapienza University of Rome for BSI calculation was shared between six Italian Nuclear Medicine Units.

METHODS

370 pre-treatment BS were analyzed through the DASciS software. Other clinical variables relevant to OS analysis were taken into account for the statistical analysis.

RESULTS

Of a total of 370 patients, 326 subjects had died at the time of our retrospective analysis. The median OS time from the first cycle of ²²³RaCl₂ to the date of death from any cause or last contact was 13 months (95%CI 12-14 months). The mean BSI value resulted in 2.98% ± 2.42. The center-adjusted univariate analysis showed that baseline BSI was significantly associated with OS as an independent risk factor (HR 1.137, 95%CI: 1.052-1.230, p = 0.001), meaning that patients with higher BSI values had worse OS. When adjusting for other measures on multivariate analysis, in addition to Gleason score and baseline values of Hb, tALP, and PSA, baseline BSI was confirmed to be a statistically significant parameter (HR 1.054, 95%CI: 1.040-1.068, p < 0.001).

CONCLUSIONS

Baseline BSI significantly predicts OS in mCRPC treated with ²²³RaCl₂. The DASciS software was revealed to be a valuable tool for BSI calculation, showing rapid processing time and requiring no more than a single demonstrative training for each participating center.

Novel nomogram developed for determining suitability of metastatic castration-resistant prostate cancer patients to receive maximum benefit from radium-223 dichloride treatment-Japanese Ra-223 Therapy in Prostate Cancer using Bone Scan Index (J-RAP-BSI) Trial

PURPOSE

To develop a novel nomogram for determining radium-223 dichloride (Ra-223) treatment suitability for metastatic castration-resistant prostate cancer (mCRPC) patients.

METHODS

This Japanese Ra-223 Therapy in Prostate Cancer using Bone Scan Index (J-RAP-BSI) Trial was a retrospective multicenter investigation enrolled 258 mCRPC patients in Japan with Ra-223 treatment between June 2016 and August 2020, with bone scintigraphy findings before treatment, clinical data, and survival outcome available. A nomogram was constructed using prognostic factors for overall survival (OS) based on a least absolute shrinkage and selection operator Cox regression model. A sub-analysis was also conducted for patients meeting European Medicines Agency (EMA) guidelines.

RESULTS

Within a median of 17.4 months after initial Ra-223 treatment, 124 patients (48.1%) died from prostate cancer. Predictive factors included (1) sum of prior treatment history (score 0, never prior novel androgen receptor-targeted agents (ARTA) therapy, never prior taxane-based chemotherapy, and ever prior bisphosphonate/denosumab treatment), (2) Eastern Cooperative Oncology Group (ECOG) performance status, (3) prostate-specific antigen doubling time (PSADT), (4) hemoglobin, (5) lactate dehydrogenase (LDH), and (6) alkaline phosphatase (ALP) levels, and (7) automated bone scan index (aBSI) value based on bone scintigraphy. The nomogram using those factors showed good discrimination, with apparent and optimism-corrected Harrell's concordance index values of 0.748 and 0.734, respectively. Time-dependent area under the curve values at 1, 2, and 3 years were 0.771, 0.818, and 0.771, respectively. In 227 patients meeting EMA recommendation, the nomogram with seven factors showed good discrimination, with apparent and optimism-corrected Harrell's concordance index values of 0.722 and 0.704, respectively. Time-dependent area under the curve values at 1, 2, and 3 years were 0.747, 0.790, and 0.759, respectively.

CONCLUSION

This novel nomogram including aBSI to select mCRPC patients to receive Ra-223 with significantly prolonged OS possibility was found suitable for assisting therapeutic decision-making, regardless of EMA recommendation.

Optimization of Radium-223 Treatment of Castration-resistant Prostate Cancer Based on the Burden of Skeletal Metastasis and Clinical Parameters

BACKGROUND

Radium-223 dichloride (Ra-223) is now frequently used to treat prostate cancer that has metastasized to bone, although patient selection continues to be suboptimal for determining who will benefit most from this novel treatment modality.

MATERIALS AND METHODS

Seventy-nine patients with metastatic castration-resistant prostate cancer (mCRPC) were treated with Ra-223 from 2012 to 2016. The burden of skeletal metastasis was determined for each using the Bone Scan Index (BSI) as a ratio of diseased to normal bone. Clinical, laboratory, and survival data were collected and examined for associations with BSI, and treatment tolerability was assessed.

RESULTS

Chemotherapy-naïve patients were significantly more likely to complete the full course of treatment. Median follow-up was 31 months (range 0.7-38.8 months) and median overall survival was 15.4 months (range 9.5-20.6 months). Overall survival was significantly associated with findings on bone scans (P < .05). Patients with higher BSI tended toward poorer outcomes. Nearly half the patients with low baseline BSI survived 3 years or more following Ra-223 treatment. By contrast, only 20% of the patients with high baseline BSI lived for 1 year, and none lived for an additional 3. Baseline BSI was significantly associated with decreased hemoglobin, higher serum PSA and alkaline phosphatase levels, and treatment-associated reductions in platelet and absolute neutrophil counts.

CONCLUSION

Our results suggest better outcomes to Ra-223 therapy for patients who are chemotherapy-naïve and who undergo treatment earlier in the course of their disease as reflected by low BSI and concordant laboratory parameters.

Prostate-specific antigen doubling time following radium-223 treatment as a predictor of the clinical course in patients with metastatic castration-resistant prostate cancer

Objectives

To identify useful biomarkers by reviewing laboratory data for a predictor of the clinical course following treatment with radium-223 dichloride (Ra-223) in patients with metastatic castration-resistant prostate cancer.

Methods

Eighteen metastatic castration-resistant prostate cancer patients who were administered Ra-223 at our hospital were retrospectively enrolled in this study. Prostate-specific antigen doubling times before and after the administration of Ra-223 were evaluated as prognostic factors for metastatic castration-resistant prostate cancer patients treated with Ra-223 using the Kaplan-Meier method and Log-rank test.

Results

Four patients failed to complete the planned six-time Ra-223 treatments with the exacerbation of their condition. In the 14 patients who completed the planned Ra-223 treatment, before the Ra-223 treatment, no significant differences were observed in overall survival between patients with prostate-specific antigen doubling time of 6 months or less and those with prostate-specific antigen doubling time of more than 6 months or stable (p = 0.642). Following the completion of the Ra-223 treatment, overall survival was significantly shorter in patients with prostate-specific antigen doubling time of 6 months or less than in those with prostate-specific antigen doubling time of more than 6 months or stable (p = 0.007).

Conclusion

Prostate-specific antigen doubling time after the Ra-223 treatment is a useful predictor of the clinical course following treatment in metastatic castration-resistant prostate cancer patients.

Real-world effectiveness, long-term safety and treatment pathway integration of radium-223 therapy in patients with metastatic castration-resistant prostate cancer

Radium-223 dichloride (223Ra) is an α-emitter approved for the treatment of metastatic castration-resistant prostate cancer (mCRPC) with bone metastases, but without visceral involvement. Despite being a life-prolonging therapy (LPT), 223Ra remains underutilized. A large body of real-world evidence (RWE) for 223Ra has been published in the decade since the pivotal phase 3 ALSYMPCA study, a period during which the treatment landscape has continued to evolve. How to optimize 223Ra use, including how to integrate it into the mCRPC management pathway amongst other current LPTs (i.e., with respect to timing and concurrent, layered, or sequential use), is therefore of considerable interest. RWE studies lack the conventional restraints of clinical trials and can therefore help to build an understanding of how treatments may be best used in routine practice. Here we review RWE studies investigating the efficacy and safety of 223Ra in mCRPC [including in sequence with the recently approved 177-Lutetium conjugated to the ligand prostate-specific membrane antigen (177Lu-PSMA)], as well as response marker development, imaging techniques, and current clinical practice recommendations.

Investigation into the Optimal Strategy of Radium-223 Therapy for Metastatic Castration-Resistant Prostate Cancer

The optimal sequence and combination of radium-223 therapy (Ra-223) for castration-resistant prostate cancer with bone metastasis (mCRPC) remain unclear. This study aimed to explore the prognostic factors after Ra-223 administration and to determine the optimal treatment strategy. We enrolled 64 patients with mCRPC who underwent Ra-223 therapy from June 2016 to July 2022 at a single institution in Japan. Overall survival (OS) and pain progression-free survival (p-PFS), which was proposed as a measure of quality of life (QOL), were analyzed using Cox proportional hazards models and log-rank tests, and between-factor analysis was performed with the Mann–Whitney U (MWU) test. Univariable and multivariable analyses revealed prognostic factors; specifically, early treatment (≤third line), completion of six treatment cycles, low bone scan index (BSI) (<0.61), alkaline phosphatase (ALP) (<140 U/L), prostate-specific antigen (PSA; <22.9 ng/mL), lactate dehydrogenase (LDH; <240 U/L), high hemoglobin (Hb) (≥11.4 g/dL), and prior denosumab use significantly prolonged OS. Low BSI, low ALP, and early Ra-223 treatment also prolonged p-PFS in the log-rank tests. The MWU test showed that high BSI (≥0.61) was associated with high PSA and high ALP and a tendency for Hb to decrease. Late Ra-223 treatment (≥fourth line) was significantly associated with low Hb and high PSA. Early Ra-223 treatment was significantly associated with improved OS, and administering Ra-223 before novel hormonal or anticancer agents may be meaningful.

Role of radium-223 discontinuation due to adverse events in castration-resistant prostate cancer patients. A retrospective monocentric analysis

Background:

Radium 223 (Ra-223) was approved for the treatment of metastatic castration resistant prostate cancer (mCRPC) patients with bone-only disease, following demonstration of significant improvement in overall survival (OS). To date, there are no validated prognostic factors useful in predicting outcome of mCRPC patients treated with Ra-223. Our retrospective study aims to evaluate the prognostic role of treatment discontinuation due to adverse events in mCRPC patients treated with Ra-223, and to identify which factors correlate with the toxicity onset.

Methods:

We performed a retrospective analysis of all consecutive mCRPC patients treated with Ra-223 from September 2013 to December 2019 at our institute. Patients were divided in 2 groups according to the reason of Ra-223 therapy discontinuation: toxicity versus other causes. Outcome measures were progression-free survival (PFS) and OS.

Results:

In the overall population (75 patients) median PFS and OS were 5.46 months and 11.15 months respectively. Patients who discontinued treatment due to toxicity had a lower median PFS (3.49 vs 5.89 months, HR: 1.88, 95% CI: 1.14-3.12, p = 0.014) and OS (8.59 vs 14.7 months HR: 3.33, 95% CI: 1.85-6.01, p < 0.001) than patients who discontinued therapy due to other causes. The risk of Ra-223 discontinuation due to toxicity correlates with the number of previous treatments ( p = 0.002), previous chemotherapy treatment ( p = 0.039), baseline LDH ( p = 0.012), Hb ( p = 0.021) and platelet-to-lymphocyte ratio ( p = 0.024).

Conclusions:

Discontinuation due to toxicity is associated with worse outcomes in mCRPC patients treated with Ra-223. To reduce the risk of developing toxicities that may compromise treatment efficacy, Ra-223 should be used early in mCRPC patients.

Beyond the Prognostic Value of 2-[18F]FDG PET/CT in Prostate Cancer: A Case Series and Literature Review Focusing on the Diagnostic Value and Impact on Patient Management

The role of 2-deoxy-2-[¹⁸F]fluoro-D-glucose Positron Emission Tomography/Computed Tomography (FDG PET/CT) in the management of prostate cancer (PCa) patients is increasingly recognised. However, its clinical role is still controversial. Many published studies showed that FDG PET/CT might have a prognostic value in the metastatic castration-resistant phase of the disease, but its role in other settings of PCa and, more importantly, its impact on final clinical management remains to be further investigated. We describe a series of six representative clinical cases of PCa in different clinical settings, but all characterised by a measurable clinical impact of FDG PET/CT on the patients’ management. Starting from their clinical history, we report a concise narrative literature review on the advantages and limitations of FDG PET/CT beyond its prognostic value in PCa. What emerges is that in selected cases, this imaging technique may represent a useful tool in managing PCa patients. However, in the absence of dedicated studies to define the optimal clinical setting of its application, no standard recommendations on its use in PCa patients can be made.

Biomarkers for Treatment Response in Advanced Prostate Cancer

Simple Summary

Prostate cancer is a leading cause of cancer-related death among males. Many treatments are available to manage the disease, but despite this, ultimately advanced prostate cancer is incurable and fatal. In order to improve survival and minimize side effects from these various treatments, the treatments need to be given in an optimal sequence or combination. This optimal use of therapies must be individualized, and biomarkers can be used for these decisions. Biomarkers can be useful in predicting whether a patient will respond to a treatment option and may help avoid use of therapies that are not expected to be effective. Many biomarkers are already in clinical use while many others are currently being investigated and may become part of clinical practice in future. In this review, we discuss both established and novel biomarkers with a role in management of advanced prostate cancer.

Abstract

Multiple treatment options with different mechanisms of action are currently available for the management of metastatic prostate cancer. However, the optimal use of these therapies—specifically, the sequencing of therapies—is not well defined. In order to obtain the best clinical outcomes, patients need to be treated with the therapies that are most likely to provide benefit and avoid toxic therapies that are unlikely to be effective. Ideally, predictive biomarkers that allow for the selection of the therapies most likely to be of benefit would be employed for each treatment decision. In practice, biomarkers including tumor molecular sequencing, circulating tumor DNA, circulating tumor cell enumeration and androgen receptor characteristics, and tumor cell surface expression (PSMA), all may have a role in therapy selection. In this review, we define the established prognostic and predictive biomarkers for therapy in advanced prostate cancer and explore emerging biomarkers.

Radium-223 Treatment of Patients with Metastatic Castration Resistant Prostate Cancer: Biomarkers for Stratification and Response Evaluation

Simple Summary

Radium-223 dichloride ([²²³Ra]RaCl₂; Ra-223) is an alpha-emitting radiopharmaceutical treatment for patients with metastatic castration resistant prostate cancer (mCRPC) with predominantly bone metastases. While responses to chemotherapeutic and antihormonal mCRPC treatments can be assessed by serum PSA levels, a decrease of serum PSA levels is not expected during Ra-223 therapy. Moreover, radiographic evaluation of bone metastases response is challenging. Therefore, novel biomarkers to select patients for Ra-223 treatment and monitoring response are urgently needed. In this review, we discuss the currently used and exploratory biomarkers for this purpose, including soluble and cellular factors detected in the peripheral blood, genetic defects and radiographic assessments. We conclude that some biomarkers, including metabolic products of collagen degradation and novel PET scan techniques, might hold promise as predictors of response to Ra-223 treatment. However, these biomarkers have not been extensively studied. Consequently, currently, no biomarker has established a place in patient stratification and response evaluation.

Abstract

Radium-223 dichloride ([²²³Ra]RaCl₂; Ra-223) is a targeted alpha-emitting radiopharmaceutical which results in an overall survival and health related quality of life (HRQoL) benefit in symptomatic patients with metastatic castration resistant prostate cancer (mCRPC) and predominantly bone metastasis. Although effective, options to select patients who will derive treatment benefit and to monitor and predict treatment outcomes are limited. PSA response and radiographic evaluation are commonly used in mCRPC treatment assessment but are not informative in Ra-223 treated patients. Consequently, there is a clear need for predictive and prognostic tools. In this review, we discuss the physiology of bone metastases and the mechanism of action and efficacy of Ra-223 treatment, as well as offering an outline of current innovative prognostic and predictive biomarkers.

Pretreatment PSA levels affects the completion rate of Ra-223 treatment

The aim of this study was to review our initial experience of using radium 223 (Ra-223) for metastatic castration-resistant prostate cancer (CRPC) and to evaluate whether pretreatment PSA levels correlate with completion of Ra-223 treatment. In addition, we examined change ratios of PSA, ALP and BAP after the third administration to evaluate the correlation of these change ratios with completion of the subsequent Ra-223 treatment. Forty patients were enrolled in this retrospective study. Ra-223 treatment was considered completed in patients who received five or six administrations. Patient backgrounds and changes in biomarkers were compared between patient groups (complete vs. incomplete Ra-223 treatment). PSA levels before treatment were significantly lower in the complete compared with the incomplete group (cutoff value; 21.7). ALP and BAP levels had decreased after the third administration in the complete group, compared with baseline levels, while levels in the incomplete group had increased. Significant difference was seen in ALP levels, while was not seen in BAP levels between the two groups. Ra-223 treatment should be considered for CRPC with low PSA levels. Changes in PSA and ALP during Ra-223 treatment might provide markers to identify patients likely to complete Ra-223 treatment, with implications for prognosis.

Quantifying the survival benefit of completing all the six cycles of radium-223 therapy in patients with castrate-resistant prostate cancer with predominant bone metastases

A retrospective analysis was performed of epidemiological data assessing the survival of patients who had received radium-223 for castrate-resistant metastatic prostate cancer treated at a regional tertiary referral center over a 5-year period. The patients' age, date of first treatment, and the number of cycles of radium-223 given were obtained from the patients' electronic patient record (EPR). Data on the date of death were provided by national death registrations which update the EPR via a unique national health service number. A total of 187 patients (mean age on the date of first treatment: 73 years; range: 56-93) were treated from April 1, 2014, to June 30, 2019. The median overall survival of the 119 patients (71%) who had died by December 31, 2019, was 15 months. There was no significant age difference between those who had died and survivors (72 vs. 74 years). On a further analysis, it was found that the median overall survival of the 107 patients who had received all the six cycles of radium-223 was 31 months, significantly longer than the median overall survival of only 6 months for those eighty patients who had received less than the full course of six cycles of radium-223 (P = 0.001). Of those who received all the six cycles of treatment, 58 patients had died (58%) and the 1-year survival was 87%. This was compared to the group of patients receiving <6 cycles of radium-223 where 61 patients (76%) had died and the 1-year survival was 30%. Therefore, the hazard ratio of dying before 1 year if the patient did not receive all the six cycles of treatment was 2.9. Where the reason for stopping treatment was recorded on the EPR the most common cause for the cessation of treatment was because of the side effects caused by the treatment itself. Other causes were hospitalization with comorbidities, disease progression, or patient choice. Given the survival advantage of receiving the full course of all the six cycles of treatment, this should be administered if possible and the patients should be managed in such a way as to allow the complete treatment course to be given.

Clinical indicators for predicting prognosis after radium-223 administration in castration-resistant prostate cancer with bone metastases

BACKGROUND

Radium-223 (Ra-223) is a targeted alpha therapy that has been shown to prolong overall survival (OS) in patients with metastatic castration-resistant prostate cancer (mCRPC) with bone metastases. However, prognosis after Ra-223 administration varies among patients. The aim of the present study was to assess risk factors associated with the poor prognosis of patients treated with Ra-223.

METHODS

We retrospectively reviewed patients' records of treatment with Ra-223 between October 2016 and December 2019. All patients had mCRPC, bone metastasis, and no known visceral metastases, and received up to six cycles of Ra-223 (55 kBq/kg). Prognostic factors for OS were analyzed by Cox proportional hazards model and log-rank test.

RESULTS

We identified 42 patients who received at least one cycle of Ra-223 (median six cycles, range 1-6). Approximately two-thirds of patients had received at least two lines of therapy for mCRPC. The median age was 74 years, and the median follow-up duration was 13.6 months. The median OS time was 16.6 months. On multivariate analysis, PSA doubling time (PSADT) (0-3 months) at baseline, number of bone metastases (≥ 20), and treatment line of Ra-223 (4th-5th line) remained significantly correlated with the poor OS (HR 4.354, P = 0.003; HR 2.855, P = 0.020; and HR 4.871, P = 0.001, respectively).

CONCLUSIONS

Our study demonstrated that a shorter PSADT, a heavier volume of bone metastases, and a later treatment line before Ra-223 are poor prognostic factors for mCRPC patients. These newly discovered risk factors may help select patients who potentially have long-term OS after Ra-223 treatment.

The Prognostic Value of Quantitative Bone SPECT/CT Before 223Ra Treatment in Metastatic Castration-Resistant Prostate Cancer

Radiolabeled bisphosphonates such as ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (^99mTc-DPD) typically show intense uptake in skeletal metastases from metastatic castration-resistant prostate cancer (mCRPC). Extensive bone involvement is regarded as a risk factor for mCRPC patients treated with ²²³Ra-dichloride (²²³Ra). The aim of this study was to quantify ^99mTc-DPD uptake by means of SPECT/CT before ²²³Ra and compare the results with the feasibility of treatment and overall survival (OS). Methods: Sixty consecutive mCRPC patients were prospectively included in this study. SPECT/CT of the central skeleton covering the skull to the mid-femoral level was performed before the first cycle of ²²³Ra. The bone compartment was defined by means of low-dose CT. Emission data were corrected for scatter, attenuation, and decay supplemented by resolution recovery using dedicated software. The Kaplan-Meier estimator, U test, and Cox regression analysis were used for statistics. Results: Total ^99mTc-DPD uptake of the central skeleton varied between 11% and 56% of injected dose (%ID) or between 1.8 and 10.5 %ID/1,000 mL of bone volume (%ID/L). SUV_mean ranged from 1.9 to 7.4, whereas the SUV_max range was 18-248. Patients unable to complete ²²³Ra treatment because of progression and/or cytopenia (n = 23) showed significantly higher uptake (31.9 vs. 25.4 %ID and 6.0 vs. 4.7 %ID/L; P < 0.02). OS after ²²³Ra (median, 15.2 mo) was reduced to 7.3 mo in cases of skeletal uptake that was 26 %ID or higher, as compared with 30.8 mo if lower than 26 %ID (P = 0.008). Similar results were obtained for %ID/L and SUV_mean SUV_max did not correlate with survival. %ID/L was identified as an independent prognostic factor for OS (hazard ratio, 1.381 per unit), along with number of previous treatment lines. Conclusion: Quantitative SPECT/CT of bone scans performed at baseline is prognostic for survival in mCRPC patients treated with ²²³Ra.

Role of Baseline and Post-Therapy 18F-FDG PET in the Prognostic Stratification of Metastatic Castration-Resistant Prostate Cancer (mCRPC) Patients Treated with Radium-223

Radium-223 dichloride (Ra223) represents the unique bone-directed treatment option that shows an improvement in overall survival (OS) in metastatic castrate resistant prostate cancer (mCRPC). However, there is an urgent need for the identification of reliable biomarkers to non-invasively determine its efficacy (possibly improving patients’ selection or identifying responders’ after therapy completion). 18F-Fluorodeoxyglucose (FDG)-avidity is low in naïve prostate cancer, but it is enhanced in advanced and chemotherapy-refractory mCRPC, providing prognostic insights. Moreover, this tool showed high potential for the evaluation of response in cancer patients with bone involvement. For these reasons, FDG Positron Emission Tomography (FDG-PET) might represent an effective tool that is able to provide prognostic stratification (improving patients selection) at baseline and assessing the treatment response to Ra223. We conducted a retrospective analysis of 28 mCRPC patients that were treated with Ra223 and submitted to bone scan and FDG-PET/CT for prognostic purposes at baseline and within two months after therapy completion. The following parameters were measured: number of bone lesions at bone scan, SUVmax of the hottest bone lesion, metabolic tumor volume (MTV), and total lesion glycolysis (TLG). In patients who underwent post-therapy 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (FDG-PET/CT), (20/28), PET Response Criteria in Solid Tumors (PERCIST), and European Organization for Research and Treatment of Cancer (EORTC) criteria were applied to evaluate the metabolic treatment response. The difference between end of therapy and baseline values was also calculated for Metabolic Tumor Volume (MTV), TLG, prostate-specific antigen (PSA), alkaline phosphatase (AP), and lactate dehydrogenase (LDH) (termed deltaMTV, deltaTLG, deltaPSA, deltaAP and deltaLDH, respectively). Predictive power of baseline and post-therapy PET- and biochemical-derived parameters on OS were assessed by Kaplan–Meier, univariate and multivariate analyses. At baseline, PSA, LDH, and MTV significantly predicted OS. However, MTV (but not PSA nor LDH) was able to identify a subgroup of patients with worse prognosis, even after adjusting for the number of lesions at bone scan (which, in turn, was not an independent predictor of OS). After therapy, PERCIST criteria were able to capture the response to Ra223 by demonstrating longer OS in patients with partial metabolic response. Moreover, the biochemical parameters were outperformed by PERCIST in the post-treatment setting, as their variation after therapy was not informative on long term OS. The present study supports the role of FDG-PET as a tool for patient’s selection and response assessment in mCRPC patients undergoing Ra223 administration.

Scintigraphic load of bone disease evaluated by DASciS software as a survival predictor in metastatic castration-resistant prostate cancer patients candidates to 223RaCl treatment

Background

Aim of our study was to assess the load of bone disease at starting and during Ra-223 treatment as an overall survival (OS) predictor in metastatic castration-resistant prostate cancer (mCRPC) patients. Bone scan index (BSI) is defined as the percentage of total amount of bone metastasis on whole-body scintigraphic images. We present a specific software (DASciS) developed by an engineering team of “Sapienza” University of Rome for BSI calculation.

Patients and methods

127 mCRPC patients bone scan images were processed with DASciS software, and BSI was tested as OS predictor.

Results

546 bone scans were analyzed revealing that the extension of disease is a predictor of OS (0–3% = 28 months of median survival (MoMS]; 3%–5% = 11 MoMS, > 5% = 5 MoMS). BSI has been analyzed as a single parameter for OS, determining an 88% AUC. Moreover, the composition between the BSI and the 3-PS (3-variable prognostic score) determines a remarkable improvement of the AUC (91%), defining these two parameters as the best OS predictors.

Conclusions

This study suggests that OS is inversely correlated with the load of bone disease in mCRPC Ra-223-treated subjects. DASciS software appears a promising tool in identifying mCRPC patients that more likely take advantage from Ra-223 treatment. BSI is proposed as a predictive variable for OS and included to a multidimensional clinical evaluation permits to approach the patients’ enrollment in a rational way, allowing to enhance the treatment effectiveness together with cost optimization.

Assessing Radiographic Response to 223Ra with an Automated Bone Scan Index in Metastatic Castration-Resistant Prostate Cancer Patients

For effective clinical management of patients being treated with ²²³Ra, there is a need for radiographic response biomarkers to minimize disease progression and to stratify patients for subsequent treatment options. The objective of this study was to evaluate an automated bone scan index (aBSI) as a quantitative assessment of bone scans for radiographic response in patients with metastatic castration-resistant prostate cancer (mCRPC). Methods: In a multicenter retrospective study, bone scans from patients with mCRPC treated with monthly injections of ²²³Ra were collected from 7 hospitals in Sweden. Patients with available bone scans before treatment with ²²³Ra and at treatment discontinuation were eligible for the study. The aBSI was generated at baseline and at treatment discontinuation. The Spearman rank correlation was used to correlate aBSI with the baseline covariates: alkaline phosphatase (ALP) and prostate-specific antigen (PSA). The Cox proportional-hazards model and Kaplan-Meier curve were used to evaluate the association of covariates at baseline and their change at treatment discontinuation with overall survival (OS). The concordance index (C-index) was used to evaluate the discriminating strength of covariates in predicting OS. Results: Bone scan images at baseline were available from 156 patients, and 67 patients had both a baseline and a treatment discontinuation bone scan (median, 5 doses; interquartile range, 3-6 doses). Baseline aBSI (median, 4.5; interquartile range, 2.4-6.5) was moderately correlated with ALP (r = 0.60, P < 0.0001) and with PSA (r = 0.38, P = 0.003). Among baseline covariates, aBSI (P = 0.01) and ALP (P = 0.001) were significantly associated with OS, whereas PSA values were not (P = 0.059). After treatment discontinuation, 36% (24/67), 80% (54/67), and 13% (9/67) of patients demonstrated a decline in aBSI, ALP, and PSA, respectively. As a continuous variable, the relative change in aBSI after treatment, compared with baseline, was significantly associated with OS (P < 0.0001), with a C-index of 0.67. Median OS in patients with both aBSI and ALP decline (median, 134 wk) was significantly longer than in patients with ALP decline only (median, 77 wk; P = 0.029). Conclusion: Both aBSI at baseline and its change at treatment discontinuation were significant parameters associated with OS. The study warrants prospective validation of aBSI as a quantitative imaging response biomarker to predict OS in patients with mCRPC treated with ²²³Ra.

Bone scan index can be a useful biomarker of survival outcomes in patients with metastatic castration-resistant prostate cancer treated with radium-223

BACKGROUND

Bone metastasis of prostate cancer is associated with pain and reduced overall survival (OS). Radium-223, which is expected to reduce bone pain and prolong OS, was recently approved in Japan.

AIM

The aim of this study was to investigate the usefulness of the bone scan index by comparing the outcomes and factors according to response in Japanese patients treated with radium-223.

METHODS AND RESULTS

Twenty patients receiving radium-223 were divided into two groups according to whether they did or did not achieve a bone scan index decrease of at least one point (beneficial and non-beneficial groups, respectively). The clinical characteristics at baseline and after three and six treatment cycles were compared using χ² tests and Student's t-tests or Mann-Whitney U tests, and survival was estimated and compared using the Kaplan-Meier method and log-rank test, respectively. Fourteen (70%) and six patients (30%) were categorized into the beneficial and non-beneficial groups, respectively. Patients in the former group were significantly more likely to have a higher Eastern Cooperative Oncology Group performance status score and receive a greater number of radium-223 injections (P < 0.05). Furthermore, patients in the beneficial group had a significantly longer OS (P < 0.05). Regarding safety, one and three patients in the beneficial and non-beneficial groups, respectively, prematurely discontinued radium-223 because of an increased prostate-specific antigen level, decreased hemoglobin level, or femoral fracture.

CONCLUSION

Radium-223 appears generally safe in this population. Patients with good bone scan index response have better performance status, receive more injections of radium-223, and achieve OS prolongation. Bone scan index is a useful biomarker of survival outcomes and can be a valuable assessment tool in patients with metastatic castration-resistant prostate cancer who are treated with radium-223.

Automated Definition of Skeletal Disease Burden in Metastatic Prostate Carcinoma: A 3D Analysis of SPECT/CT Images

To meet the current need for skeletal tumor-load estimation in castration-resistant prostate cancer (CRPC), we developed a novel approach based on adaptive bone segmentation. In this study, we compared the program output with existing estimates and with the radiological outcome. Seventy-six whole-body single-photon emission computed tomographies/x-ray computed tomography with 3,3-diphosphono-1,2-propanedicarboxylic acid from mCRPC patients were analyzed. The software identified the whole skeletal volume (S_Vol) and classified the voxels metastases (M_Vol) or normal bone (B_Vol). S_Vol was compared with the estimation of a commercial software. M_Vol was compared with manual assessment and with prostate specific antigen (PSA) levels. Counts/voxel were extracted from M_Vol and B_Vol. After six cycles of ²²³RaCl2-therapy every patient was re-evaluated as having progressive disease (PD), stable disease (SD), or a partial response (PR). S_Vol correlated with that of the commercial software (R = 0.99, p < 0.001). M_Vol correlated with the manually-counted lesions (R = 0.61, p < 0.001) and PSA (R = 0.46, p < 0.01). PD had a lower counts/voxel in M_Vol than PR/SD (715 ± 190 vs. 975 ± 215 and 1058 ± 255, p < 0.05 and p < 0.01) and B_Vol (PD 275 ± 60, PR 515 ± 188 and SD 528 ± 162 counts/voxel, p < 0.001). Segmentation-based tumor load correlated with radiological/laboratory indices. Uptake was linked with the clinical outcome, suggesting that metastases in PD patients have a lower affinity for bone-seeking radionuclides and might benefit less from bone-targeted radioisotope therapies.

Measuring the unmeasurable: automated bone scan index as a quantitative endpoint in prostate cancer clinical trials

BACKGROUND

Up to 90% of men with metastatic castration-resistant prostate cancer (mCRPC) will have a distribution of disease that includes bone metastases demonstrated on a Technetium-99m (^99mTc-MDP) bone scan. The Prostate Cancer Working Group 2 and 3 Consensus Criteria standardized the criteria for assessing progression based on the development of new lesions. These criteria have been recognized by regulatory authorities for drug approval. The bone scan index (BSI) is a method to quantitatively measure the burden of bony disease, and can assess both disease progression and regression. The automated BSI (aBSI) is a method of computer analysis to assess BSI, and is being qualified as a clinical trials endpoint.

METHODS

Manual searching was used to identify the literature on BSI and aBSI. We summarize the most relevant aspects of the retrospective and prospective studies evaluating aBSI measurements, and provide a critical discussion on the potential advantages and caveats of aBSI.

RESULTS

The development of neural artificial networks (EXINI boneBSI) to automatically determine the BSI reduces the turnaround time for assessing BSI with high reproducibility and accuracy. Several studies showed that the concordance between aBSI and BSI, as well as the interobserver concordance of aBSI, was >0.95. In a phase 3 assessment of aBSI, a doubling value increased the risk of death in 20%, pre-treatment aBSI values independently correlated with overall survival (OS) and time to symptomatic progression. Retrospective studies suggest that a decrease in aBSI after treatment may correlate with higher survival when compared with increasing aBSI.

CONCLUSIONS

aBSI provides a quantitative measurement that is feasible, reproducible, and in analyses to date correlates with OS and symptomatic progression. These findings support the aBSI to risk-stratify men with mCRPC for clinical trial enrollment. Future studies quantifying aBSI change over time as an intermediate endpoint for evaluating new systemic therapies are needed.

Evaluating radium-223 response in metastatic castration-resistant prostate cancer with imaging

Radium-223 is a first-in-class targeted alpha therapy indicated for treating bone metastases from metastatic castration-resistant prostate cancer (mCRPC) without visceral metastases. Imaging plays an important role in the selection of patients eligible for radium-223 therapy. In the ALSYMPCA trial protocol, bone scintigraphy was used to detect lesions, essentially osteoblastic bone metastases, whereas computed tomography (CT) was used to exclude visceral metastases, with no interim imaging until treatment completion unless clinically indicated. Yet, questions remain: How can we monitor treatment progress more closely and evaluate treatment response more precisely? In the cases discussed herein, interim evaluation of response to radium-223 showed discordance between bone scintigraphy and ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in the patterns of bone lesions observed, that is more lesions were detected on PET/CT. It is postulated that the additional lesions may be attributed to bone marrow metastases that were not effectively targeted by radium-223 as its alpha radiation do not reach deep into the bone marrow. Although the clinical significance of the discordance requires further clarification, it makes sense to consider radium-223 early on in the course of mCRPC, when marrow involvement is minimal, so as to optimize treatment outcomes.

Patient Selection for Radium-223 Therapy in Patients With Bone Metastatic Castration-Resistant Prostate Cancer: New Recommendations and Future Perspectives

Radium-223 therapy was registered in 2013 as a new life-prolonging therapeutic option for patients with symptomatic bone metastatic castration-resistant prostate cancer after the phase 3 ALSYMPCA study. Postregistration reports on the use of radium-223 in real-world populations demonstrate that appropriate selection of patients for radium-223 therapy is challenging. While primarily retrospective and post hoc studies identified prognostic variables associated with overall survival, validated predictive biomarkers are still lacking. Important pretherapeutic prognostic variables include the number of prior therapies, baseline Eastern Cooperative Oncology Group performance status, baseline extent of bone metastatic disease, and baseline alkaline phosphatase, prostate-specific antigen, and lactate dehydrogenase levels. We reviewed the currently available literature to provide recommendations on patient selection for radium-223 therapy in patients with bone metastatic castration-resistant prostate cancer. In addition, the recent evidence from the report of the European Medicines Agency's Pharmacovigilance Risk Assessment Committee regarding the restricted use of radium-223 after interim data analysis of the ERA-223 trial has been incorporated into our recommendations. Future perspectives are also discussed, including radium-223 re-treatment, the use of concomitant therapies, and the implementation of pretherapeutic molecular analysis for treatment stratification.

18F-NaF/223RaCl2 theranostics in metastatic prostate cancer: treatment response assessment and prediction of outcome

Theranostics refers to companion agents with identical or similar structure targeted to a specific biological entity for imaging and treatment. Although the concept has a long history with radioiodine in thyroidology, but it has experienced remarkable recent renaissance in management of neuroendocrine tumors and prostate cancer. Bone scintigraphy based on osteoblastic reaction and targeted radionuclide therapy with the alpha-particle calcium-mimetic agent, 223RaCl2, also form a theranostic model for imaging and treatment of osseous metastatic disease. Since the regulatory approval of 223RaCl2 in 2013, there has been accumulating evidence on the potential use of 18F-NaF PET scintigraphy in the assessment of response and prediction of outcome in males with metastatic castrate-resistant prostate cancer who undergo 223RaCl2 therapy. We review the 18F-NaF/223RaCl2 as theranostic companion in the management of prostate cancer with emphasis on the utility of 18F-NaF and other relevant PET radiotracers in the therapy response and prognosis assessments.

Radionuclide Therapy for Bone Metastases: Utility of Scintigraphy and PET Imaging for Treatment Planning

The skeleton is a common site for cancer metastases. Bone metastases are a major cause of morbidity and mortality and associated with pain, pathologic fractures, spinal cord compression, and decreased survival. Various radionuclides have been used for pain therapy. Recently, an α-emitter has been shown to improve overall survival of patients with bone metastases from castration-resistant prostate cancer and was approved as a therapeutic agent. The aim of this article is to provide an overview regarding state of the art radionuclide therapy options for bone metastases, with focus on the role of PET imaging in therapy planning.

Validation of the Semiautomatic Quantification of 18F-Fluoride PET/CT Whole-Body Skeletal Tumor Burden

Our purpose was to validate a semiautomatic quantification of the skeletal tumor burden on ¹⁸F-fluoride PET/CT using manual quantification as a reference. Methods: We quantified 51 ¹⁸F-fluoride PET/CT examinations performed on female breast cancer patients. Clinical information (age; time of disease presentation; presence of visceral metastases; and time to death, progression, or a bone event) was recorded. The total volume of ¹⁸F-fluoride-avid skeletal metastases and the total activity of ¹⁸F-fluoride-avid metastases were calculated manually and semiautomatically. Results: Manual and semiautomatic metrics correlated strongly (P < 0.0001; 95% confidence interval, 0.9300-0.9769). On multivariable analysis, the semiautomatic measures of total activity for ¹⁸F-fluoride-avid metastasis correlated significantly with overall survival (P = 0.0001) and progression-free survival (P = 0.0006). Approximate times for calculating skeletal tumor burden (semiautomatic vs. manual) were, respectively, 30 s versus 321 s in patients with fewer than 5 metastases, 120 s versus 640 s in patients with 5-10 metastases, and 240 s versus 1207s in patients with more than 10 metastases. Conclusion: Semiautomatic quantification of whole-body ¹⁸F-fluoride PET/CT skeletal tumor burden can replace manual quantification in breast cancer patients and is a strong independent biomarker of prognosis.

Assessment of Skeletal Tumor Load in Metastasized Castration-Resistant Prostate Cancer Patients: A Review of Available Methods and an Overview on Future Perspectives

Metastasized castration-resistant prostate cancer (mCRPC), is the most advanced form of prostate neoplasia, where massive spread to the skeletal tissue is frequent. Patients with this condition are benefiting from an increasing number of treatment options. However, assessing tumor response in patients with multiple localizations might be challenging. For this reason, many computational approaches have been developed in the last decades to quantify the skeletal tumor burden and treatment response. In this review, we analyzed the progressive development and diffusion of such approaches. A computerized literature search of the PubMed/Medline was conducted, including articles between January 2008 and March 2018. The search was expanded by manually reviewing the reference list of the chosen articles. Thirty-five studies were identified. The number of eligible studies greatly increased over time. Studies could be categorized in the following categories: automated analysis of 2D scans, SUV-based thresholding, hybrid CT- and SUV-based thresholding, and MRI-based thresholding. All methods are discussed in detail. Automated analysis of bone tumor burden in mCRPC is a growing field of research; when choosing the appropriate method of analysis, it is important to consider the possible advantages as well as the limitations thoroughly.

Fluorine-18-fluorocholine PET/CT parameters predictive for hematological toxicity to radium-223 therapy in castrate-resistant prostate cancer patients with bone metastases: a pilot study

PURPOSE

This study aims to predict hematological toxicity induced by Ra therapy. We investigated the value of metabolically active bone tumor volume (MBTV) and total bone lesion activity (TLA) calculated on pretreatment fluorine-18-fluorocholine (F-FCH) PET/CT in castrate-resistant prostate cancer (CRPC) patients with bone metastases treated with Ra radionuclide therapy.

PATIENTS AND METHODS

F-FCH PET/CT imaging was performed in 15 patients with CRPC before treatment with Ra. Bone metastatic disease was quantified on the basis of the maximum standardized uptake value (SUV), total lesion activity (TLA=MBTV×SUVmean), or MBTV/height (MBTV/H) and TLA/H. F-FCH PET/CT bone tumor burden and activity were analyzed to identify which parameters could predict hematological toxicity [on hemoglobin (Hb), platelets (PLTs), and lymphocytes] while on Ra therapy. Pearson's correlation was used to identify the correlations between age, prostate-specific antigen, and F-FCH PET parameters.

RESULTS

MBTV ranged from 75 to 1259 cm (median: 392 cm). TLA ranged from 342 to 7198 cm (median: 1853 cm). Patients benefited from two to six cycles of Ra (n=56 cycles in total). At the end of Ra therapy, five of the 15 (33%) patients presented grade 2/3 toxicity on Hb and lymphocytes, whereas three of the 15 (20%) patients presented grade 2/3 PLT toxicity.Age was correlated negatively with both MBTV (r=-0.612, P=0.015) and TLA (r=-0.596, P=0.018). TLA, TLA/H, and MBTV/H predicted hematological toxicity on Hb, whereas TLA/H and MBTV/H predicted toxicity on PLTs at the end of Ra cycles. Receiver operating characteristic curve analysis allowed to define the cutoffs for MBTV (915 cm) and TLA (4198 cm) predictive for PLT toxicity, with an accuracy of 0.92 and 0.99.

CONCLUSION

Tumor bone burden calculation is feasible with F-FCH PET/CT with freely available open-source software. In this pilot study, baseline F-FCH PET/CT markers (TLA, MBTV) have shown abilities to predict Hb and PLT toxicity after Ra therapy and could be explored for patient selection and treatment optimization.

Hematologic Toxicity From Radium-223 Therapy for Bone Metastases in Castration-Resistant Prostate Cancer: Risk Factors and Practical Considerations

Radium-223 dichloride is an α-emitting radiopharmaceutical that localizes to bone matrix and is approved for the treatment of patients with metastatic castration-resistant prostate cancer (CRPC) and symptomatic bone metastases. The cumulative impact of Ra-223 and other therapeutic agents for metastatic CRPC on myelosuppression in bone marrow is unknown. The phase 3 randomized, double-blind, placebo-controlled ALSYMPCA trial of Ra-223 in patients with CRPC and symptomatic bone metastases demonstrated a significant improvement in overall survival. Of the 571 patients subsequently followed for 3 years, few in either the Ra-223 or placebo arm experienced hematologic adverse events. Little evidence shows secondary malignancies associated with Ra-223 treatment; only 2 cases of secondary leukemia after Ra-223 treatment were found in the literature. The goals of this review were to summarize safety and efficacy results from clinical trials and institutional safety data pertaining to hematologic adverse events occurring with Ra-223, and to discuss practical management issues.