Repetitively dosed docetaxel and ¹⁵³samarium-EDTMP as an antitumor strategy for metastatic castration-resistant prostate cancer

Targeted Radiopharmaceutical Therapy for Bone Metastases

Radiopharmaceutical approaches for targeting bone metastasis have traditionally focused on palliation of pain. Several agents have been clinically used over the last several decades and have proven value in pain palliation providing pain relief and improving quality of life. The role is well established across several malignancies, most commonly used in osteoblastic prostate cancer patients. These agents have primarily based on targeting and uptake in bone matrix and have mostly included beta emitting isotopes. The advent alpha emitter and FDA approval of 223Ra-dichloride has created a paradigm shift in clinical approach from application for pain palliation to treatment of bone metastasis. The approval of 223Ra-dichloride given the survival benefit in metastatic prostate cancer patients, led to predominant use of this alpha emitter in prostate cancer patients. With rapid development of radiopharmaceutical therapies and approval of other targeted agents such as 177Lu-PSMA the approach to treatment of bone metastasis has further evolved and combination treatments have increasingly been applied. Novel approaches are needed to improve and expand the use of such therapies for treatment of bone metastasis. Combination therapies with different targeting mechanisms, combining chemotherapies and cocktail of alpha and beta emitters need further exploration.

Current state of theranostics in metastatic castrate-resistant prostate cancer

Prostate cancer remains one of the leading causes of cancer-related death in the world. There have been significant advances in chemotherapy, hormonal therapy and targeted therapy options for patients with castrate-resistant disease. However, these systemic treatments are often associated with unwanted toxicities. Targeted therapy with radiopharmaceuticals has become of key interest to limit systemic toxicity and provides a more precision oncology approach to treatment. Strontium-89, Samarium-153 EDTMP and Radium-223 have been trialled with mixed results. Strontium-89 and Samarium-153 EDTMP have shown benefits in palliating metastatic bone pain but with no impact on survival outcomes. Early therapeutic radiopharmaceuticals targeting PSMA that were developed were beta-emitting agents, but recently alpha-emitting agents are being investigated as potentially superior options. Radium-223 is the first alpha-particle emitter therapeutic agent approved by the FDA, with phase III trial evidence showing benefits in overall survival and delay in symptomatic skeletal events for patients. Recently, 177-Lutetium-PSMA-617 has demonstrated significant survival advantages in pre-treated metastatic castrate-resistant cancer patients in a number of phase II and III studies. Furthermore, 225-Actinium-PSMA-617 also showed promise even in patients pre-treated with 177-Lutetium-PSMA-617. Hence, there has been an explosion of radiopharmaceutical treatment options for patients with prostate cancer. This review explores past and current theranostic capacities in the radiopharmaceutical treatment of metastatic castrate-resistant prostate cancer.

Myeloma Bone Disease: A Comprehensive Review

Multiple myeloma (MM) is a neoplastic clonal proliferation of plasma cells in the bone marrow microenvironment, characterized by overproduction of heavy- and light-chain monoclonal proteins (M-protein). These proteins are mainly found in the serum and/or urine. Reduction in normal gammaglobulins (immunoparesis) leads to an increased risk of infection. The primary site of origin is the bone marrow for nearly all patients affected by MM with disseminated marrow involvement in most cases. MM is known to involve bones and result in myeloma bone disease. Osteolytic lesions are seen in 80% of patients with MM which are complicated frequently by skeletal-related events (SRE) such as hypercalcemia, bone pain, pathological fractures, vertebral collapse, and spinal cord compression. These deteriorate the patient's quality of life and affect the overall survival of the patient. The underlying pathogenesis of myeloma bone disease involves uncoupling of the bone remodeling processes. Interaction of myeloma cells with the bone marrow microenvironment promotes the release of many biochemical markers including osteoclast activating factors and osteoblast inhibitory factors. Elevated levels of osteoclast activating factors such as RANK/RANKL/OPG, MIP-1-α., TNF-α, IL-3, IL-6, and IL-11 increase bone resorption by osteoclast stimulation, differentiation, and maturation, whereas osteoblast inhibitory factors such as the Wnt/DKK1 pathway, secreted frizzle related protein-2, and runt-related transcription factor 2 inhibit osteoblast differentiation and formation leading to decreased bone formation. These biochemical factors also help in development and utilization of appropriate anti-myeloma treatments in myeloma patients. This review article summarizes the pathophysiology and the recent developments of abnormal bone remodeling in MM, while reviewing various approved and potential treatments for myeloma bone disease.

A Systematic Review and Meta-Analysis about the Effect of Bisphosphonates on the Risk of Skeletal-Related Event in Men with Prostate Cancer

BACKGROUND

Although the adjuvant therapy of bisphosphonates in prostate cancer is effective in improving bone mineral density, it is still uncertain whether bisphosphonates could decrease the risk of Skeletal- Related Event (SRE) in patients with prostate cancer. We reviewed and analyzed the effect of different types of bisphosphonates on the risk of SRE, defined as pathological fracture, spinal cord compression, radiation therapy to the bone, surgery to bone, hypercalcemia, bone pain, or death as a result of prostate cancer.

METHODS

A systemic literature search was conducted on PubMed and related bibliographies. The emphasis during data extraction was laid on the Hazard Ratio (HR) and the corresponding 95% Confidence Interval (CI) from every eligible Randomized Controlled Trial (RCT). HR was pooled with the fixed effects model, and preplanned subgroup analyses were performed.

RESULTS

5 RCTs (n = 4651) were included and analyzed finally after screening 51 articles. The meta-analysis of all participants showed no significant decrease in the risk of SRE when adding bisphosphonates to control group (HR = 0.968, 95% CI = 0.874 - 1.072, p = 0.536) with low heterogeneity (I2 = 0.0% (d.f. = 4) p = 0.679). There was no significant improvement on SRE neither in the subgroups with Metastases (M1) or Castration-Sensitive Prostate Cancer (CSPC) (respectively HR = 0.968, 95% CI = 0.874 - 1.072, p = 0.536, I2 = 0.0% (d.f. = 4) p = 0.679; HR = 0.954, 95% CI = 0.837 - 1.088, p = 0.484, I2 = 0.0% (d.f. = 3) p = 0.534).

CONCLUSION

Our study demonstrated that bisphosphonates could not statistically significantly reduce the risk of SRE in patients with prostate cancer, neither in the subgroups with M1 or CSPC.

Targeted Palliative Radionuclide Therapy for Metastatic Bone Pain

Bone metastasis develops in multiple malignancies with a wide range of incidence. The presence of multiple bone metastases, leading to a multitude of complications and poorer prognosis. The corresponding refractory bone pain is still a challenging issue managed through multidisciplinary approaches to enhance the quality of life. Radiopharmaceuticals are mainly used in the latest courses of the disease. Bone-pain palliation with easy-to-administer radionuclides offers advantages, including simultaneous treatment of multiple metastatic foci, the repeatability and also the combination with other therapies. Several β¯- and α-emitters as well as pharmaceuticals, from the very first [⁸⁹Sr]strontium-dichloride to recently introduced [²²³Ra]radium-dichloride, are investigated to identify an optimum agent. In addition, the combination of bone-seeking radiopharmaceuticals with chemotherapy or radiotherapy has been employed to enhance the outcome. Radiopharmaceuticals demonstrate an acceptable response rate in pain relief. Nevertheless, survival benefits have been documented in only a limited number of studies. In this review, we provide an overview of bone-seeking radiopharmaceuticals used for bone-pain palliation, their effectiveness and toxicity, as well as the results of the combination with other therapies. Bone-pain palliation with radiopharmaceuticals has been employed for eight decades. However, there are still new aspects yet to be established.

Spine and Non-spine Bone Metastases - Current Controversies and Future Direction

Bone is a common site of metastases in advanced cancers. The main symptom is pain, which increases morbidity and reduces quality of life. The treatment of bone metastases needs a multidisciplinary approach, with the main aim of relieving pain and improving quality of life. Apart from systemic anticancer therapy (hormonal therapy, chemotherapy or immunotherapy), there are several therapeutic options available to achieve palliation, including analgesics, surgery, local radiotherapy, bone-seeking radioisotopes and bone-modifying agents. Long-term use of non-steroidal analgesics and opiates is associated with significant side-effects, and tachyphylaxis. Radiotherapy is effective mainly in localised disease sites. Bone-targeting radionuclides are useful in patients with multiple metastatic lesions. Bone-modifying agents are beneficial in reducing skeletal-related events. This overview focuses on the role of surgery, including minimally invasive treatments, conventional radiotherapy in spinal and non-spinal bone metastases, bone-targeting radionuclides and bone-modifying agents in achieving palliation. We present the clinical data and their associated toxicity. Recent advances are also discussed.

Effect of bisphosphonates on overall survival in subgroups of patients with prostate cancer

Adjuvant therapy with bisphosphonates in prostate cancer is effective in improving bone mineral density and thus reducing fractures and skeletal-related events. We analyzed the effect of bisphosphonates on overall survival (OS) in subgroups of patients with prostate cancer. A systematic literature search was conducted of the PubMed database and the bibliographies of related studies. The long-term OS rates were extracted from every eligible trial. The hazard ratio (HR) was pooled with the fixed effects model, and preplanned subgroup analyses were performed. The search yielded 112 articles, of which 10 articles with 13 patient subgroups met the eligibility criteria. The meta-analysis of all 13 subgroups showed that adjuvant bisphosphonate therapy did not significantly improve OS versus the control group (HR = 0.961, 95% CI 0.899-1.026, p = 0.233) with low heterogeneity (I² = 13.47%, degrees of freedom = 12, p = 0.336). There was no significant improvement in OS with the addition of bisphosphonates in the major subgroup analyses (metastatic (M1) versus non-metastatic, clodronate versus zoledronic acid, castration-sensitive prostate cancer (CSPC) versus castration-refractory prostate cancer). When the subgroups were further divided, adjuvant bisphosphonate therapy significantly improved OS in patients with CSPC + M1 (HR = 0.874, 95% CI 0.778-0.982, p = 0.023; I² = 0.0%, degrees of freedom = 3, p = 0.579). Our study demonstrated that bisphosphonates do not significantly improve long-term OS in patients with prostate cancer. However, adjuvant bisphosphonate therapy significantly improves OS in the subgroup of patients with CSPC + M1.

Bone-Targeting Radiopharmaceuticals as Monotherapy or Combined With Chemotherapy in Patients With Castration-Resistant Prostate Cancer Metastatic to Bone

In patients with metastatic castration-resistant prostate cancer, bone is the most common site for metastases. Because of their osteoblastic character, these lesions are very suitable for treatment with bone-seeking radiopharmaceuticals (RPs). Nowadays, radium-223-chloride is the only RP with a proven benefit in overall survival, whereas the β-emitting RPs are used for pain palliation. In the past, many trials that investigated RPs alone, or in combination with chemotherapy have been performed. Because of different designs, characteristics of included patients, and chemotherapeutical and RP regimens, interpretation of the promising data and positioning of RPs in the treatment of metastatic prostate cancer has become difficult. In this review, we provide an overview of the existing data per RP with a focus on the different RPs in combination with chemotherapy. Furthermore, we aim to clarify the benefits on pain response and quality of life. Finally, we focus on the optimal timing and use of biomarkers in the treatment of patients with castration-resistant prostate cancer with RPs.

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.

Efficacy and safety of 153Sm-EDTMP as treatment of painful bone metastasis: a large single-center study

PURPOSE

The purpose of this study is to assess the efficacy of ¹⁵³Sm-EDTMP (Quadramet®) in a clinical setting.

METHODS

We have conducted a retrospective study of all consecutive patients (pts) treated with ¹⁵³Sm-EDTMP for painful bone metastases. At each visit (before and after treatment), four parameters were collected: (i) pain assessment according to the 10-step visual analogue scale (VAS), (ii) sleep disturbance related to pain, (iii) dose of analgesic medication, and (iv) answer to the following closed question "Do you think you obtained a benefit from treatment?" Success of treatment was defined by the combination of these four parameters.

RESULTS

Three hundred seventy consecutive ¹⁵³Sm-EDTMP treatments for painful bone metastases were given. Patients had the following primary tumors: breast carcinoma (153), prostate carcinoma (155), lung carcinoma (27), or other cancers (35). Fifty-eight percent of the patients had received previous external osseous radiotherapy. Ninety-seven percent of the patients were treated with concomitant analgesics and 61% were treated with diphosphonates. A clinical benefit was described in 55.0% of cases at D30. Treatment was more effective in cases of breast and prostate cancers compared with other types of primary cancers. Patients described a benefit at D30 in 62, 58, 6, and 38% of cases of breast, prostate, lung, and other cancers. The subjective efficacy was accompanied by a decrease in analgesic intake in 35.0% of cases.

CONCLUSION

¹⁵³Sm-EDTMP therapy is an effective supportive treatment in patients who suffer from bone metastases, especially in patients with breast or prostate cancer.

Isotope Therapy for Castrate-Resistant Prostate Cancer: Unique Sequencing and Combinations

Radiopharmaceuticals used in the treatment of castrate-resistant prostate cancer are reviewed herein with an emphasis on sequential and combination therapies. Four bone-seeking radiopharmaceuticals had been approved in the United States. Three of these are β-emitters (phosphorus-32, strontium-89, samarium-153-ethylenediaminetetramethylene-phosphonic acid) that are approved for palliative purposes. One α-emitter (radium-223 [Ra]) is approved for prolongation of survival in bone metastatic castrate-resistant prostate cancer. Bone-seeking radiopharmaceuticals have been used in combination therapy with chemotherapy, hormones, and bisphosphonates for decades. Current combinations and clinical trials are primarily focused on Ra, given that overall survival benefit is associated with this radionuclide. Phase III trials with Ra were conducted in combination with a variety of standard hormonal therapies, bisphosphonates, and external beam radiation. Since the phase III Ra trials have been conducted, additional experience has been obtained with newer hormonal therapies such as abiraterone and enzalutamide, as well as with chemotherapies such as docetaxel. These therapies have been used both in combination with Ra and in sequence. Insights have arisen under each condition.A continuous evolution of radiopharmaceuticals is anticipated as these agents evolve in 2 distinct ways. First, current agents will evolve in combination with both current and emerging therapies, to create a better integrated and optimized approach. Second, radiopharmaceuticals that target the tumor (regardless of location) will continuously evolve. Therapies restricted to bone have inherent shortcomings, even in bone-tropic malignancies such as prostate cancer. Preliminary data with prostate-specific membrane antigen targeted β-emitters such as lutetium-177 are promising but need further evaluation. Prostate-specific membrane antigen targeted α-emitters are also in development. Given the molecular heterogeneity of tumor cells and the many shortcomings of molecularly targeted therapy, radiopharmaceuticals represent an attractive alternative approach given their capability of direct antitumor effects as well as their capability of microenvironmental disruption.

Beyond Just Androgen Deprivation Therapy: Novel Therapies Combined With Radiation

External beam radiation therapy (EBRT) combined with androgen deprivation are standard of care for selected patients with prostate cancer. In recent years, multiple therapies have been experimentally combined with EBRT either concomitantly or adjuvantly. These therapies include chemotherapies, immunotherapies, and novel hormones. In addition to EBRT, clinical trials with radiopharmaceuticals are planned or have been performed with concomitant chemotherapy, immunotherapies, novel hormones, and inhibitors of DNA damage repair. Herein we cover the therapeutic landscape of radiation, both EBRT and radiopharmaceuticals, and various novel therapies. Today, these therapies have yet to change the standard of care, but in the future, these combinations may improve upon currently available therapies. Clinical trials with radiation and novel forms of therapy are the key to progress, and newer adaptive clinical trial designs may allow such progress to occur faster.

Treatment of painful bone metastases in prostate and breast cancer patients with the therapeutic radiopharmaceutical rhenium-188-HEDP. Clinical benefit in a real-world study

AIM

Rhenium-188-HEDP ((188)Re-HEDP) is an effective radiopharmaceutical for the palliative treatment of osteoblastic bone metastases. However, only limited data on its routine use are available and its effect on quality of life (QoL) has not been studied. Therefore, we evaluated the clinical benefit of (188)Re-HEDP in routine clinical care.

PATIENTS AND METHODS

Prostate or breast cancer patients with painful bone metastases receiving (188)Re-HEDP as a routine clinical procedure were eligible for evaluation. Clinical benefit was assessed in terms of efficacy and toxicity. Pain palliation and QoL were monitored using the visual analogue scale (VAS), corrected for opioid intake, and the EORTC QLQ-C30 Global health status/QoL-scale. Thrombocyte and leukocyte nadirs were used to assess haematological toxicity.

RESULTS

45 and 47 patients were evaluable for pain palliation and QoL, respectively. After a single injection of (188)Re-HEDP, the overall pain response rate was 69% and mean VAS-scores decreased relevantly and significantly (p < 0.05). Repeated treatment resulted in similar pain response. The overall QoL response rate was 68% and mean Global health status/QoL-scores increased relevantly and significantly. Haematological side effects were mild and transient.

CONCLUSION

The clinically relevant response on pain and quality of life and the limited adverse events prove clinical benefit of treatment with (188)Re-HEDP and support its use in routine clinical care. Its effectiveness appears comparable to that of external beam radiotherapy.

Myeloma bone disease: pathogenesis, current treatments and future targets

INTRODUCTION

Patients with myeloma develop localized and generalized bone loss leading to hypercalcaemia, accelerated osteoporosis, vertebral wedge fractures, other pathological fractures, spinal cord compression and bone pain. Bone loss is mediated by a variety of biological modifiers including osteoclast-activating factors (OAF) and osteoblast (OB) inhibitory factors produced either directly by malignant plasma cells (MPCs) or as a consequence of their interaction with the bone marrow microenvironment (BMM). Raised levels of OAFs such as receptor activator of nuclear factor-kappa B ligand (RANKL), macrophage inflammatory protein 1 alpha, tumour necrosis factor-alpha and interleukin 6 stimulate bone resorption by recruiting additional osteoclasts. Via opposing mechanisms, increases in OB inhibitory factors, such as dickkopf-1 (Dkk-1), soluble frizzled-related protein-3 and hepatocyte growth factor (HGF), suppress bone formation by inhibiting the differentiation and recruitment of OBs. These changes result in an uncoupling of physiological bone remodelling, leading to myeloma bone disease (MBD). Moreover, the altered BMM provides a fertile ground for the growth and survival of MPCs. Current clinical management of MBD is both reactive (to pain and fractures) and preventive, with bisphosphonates (BPs) being the mainstay of pharmacological treatment. However, side effects and uncertainties associated with BPs warrant the search for more targeted treatments for MBD. This review will summarize recent developments in understanding the intimate relationship between MBD and the BMM and the novel ways in which they are being therapeutically targeted.

SOURCES OF DATA

All data included were sourced and referenced from PubMed.

AREAS OF AGREEMENT

The clinical utility of BP therapy is well established. However, there is general acknowledgement that BPs are only partially successful in the treatment of MBD. The number of skeletal events attributable to myeloma are reduced by BPs but not totally eliminated. Furthermore, existing damage is not repaired. It is widely recognized that more effective treatments are needed.

AREAS OF CONTROVERSY

There remains controversy concerning the duration of BP therapy. Whether denosumab is a viable alternative to BP therapy is also contested. Many of the new therapeutic strategies discussed are yet to translate to clinical practice and demonstrate equal efficacy or superiority to BP therapy. It also remains controversial whether reported anti-tumour effects of bone-modulating therapies are clinically significant.

GROWING POINTS

The potential clinical utility of bone anabolic therapies including agents such as anti-Dkk-1, anti-sclerostin and anti-HGF is becoming increasingly recognized.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further research effectively targeting the mediators of MBD, targeting both bone resorption and bone formation, is urgently needed. This should translate promptly to clinical trials of combination therapy comprising anti-resorptives and bone anabolic therapies to demonstrate efficacy and improved outcomes over BPs.