Clinical Trials: From the Editor
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“Prostate cancer aggressive variants deserve clinical trial attention.”
The most commonly recognized prostate cancer aggressive variant is a high-grade neuroendocrine carcinoma. De novo neuroendocrine prostate cancer (NEPC) is very rare, and it is much more common to see treatment-emergent NEPC arise after treatment with androgen deprivation therapy.1, 2 Some of these tumors may exhibit small cell morphology, although that is not a uniform characteristic. By immunohistochemistry, NEPC typically has low expression of prostate lineage markers (e.g. androgen receptor [AR], NKX3.1, and HOXB13), yet high expression of neuroendocrine markers ( e.g. synaptophysin, chromogranin, and INSM1). For this disease, it is well accepted that platinum chemotherapy is the standard of care. Beyond that, our therapeutic options are limited, without any clear standard in patients who have previously been treated with platinum chemotherapy.
High-Risk, Non-Muscle Invasive Bladder Cancer – Is There Anything We Should Be Adding to BCG?
Non-muscle invasive bladder cancer is a topic that I tackled in previous UroToday Clinical Trials Portal articles, including last month’s discussion. Although transurethral resection is standard of care, recurrence rates are high. Prognostic factors for recurrence include the number of tumors, tumor size, prior recurrence, stage, grade, and concurrent carcinoma in situ (CIS).1 Patients with high risk features have approximately a 60-70% chance of recurrence and a 10-45% chance of progression to muscle invasive bladder cancer over a 5 year period. Intravesical Bacillus Calmette-Guerin (BCG) is the standard for intermediate and high-risk disease, but BCG is not adequate to prevent relapses or frank resistance in approximately 50% of treated patients.2
Pembrolizumab and Beyond for BCG-Unresponsive, High-Risk, Non-Muscle Invasive Bladder Cancer
It has now been over a year since pembrolizumab received FDA approval on January 8, 2020, for treatment for Bacillus Calmette-Guerin (BCG)-unresponsive, high-risk, non-muscle invasive bladder cancer (NMIBC) with carcinoma in situ (CIS) with or without papillary tumors who are ineligible for or who have elected to not undergo radical cystectomy. This approval was a nice step towards expanding treatment options for a patient population that harbors a clear unmet medical need. Intravesical BCG is the standard for intermediate and high-risk disease, but BCG is not adequate to prevent relapses or frank resistance in approximately 50% of patients.1 BCG-unresponsive disease includes both BCG-refractory and BCG-relapse populations. BCG-refractory refers to the presence of persistent high-grade cancer 6 months after the start of induction therapy or cancers that have progressed by either stage or grade 3 months after the initiation of induction therapy.2
Triple Combination Therapy With Chemohormonal Approaches: Paving a Path Forward in Various Disease States With Newer Agents and Even More Treatment Intensification
I recently wrote about “triple combination therapy” with androgen deprivation therapy (ADT), docetaxel, and a novel hormonal agent a few months ago.1 In that article, I described a list of enrolling trials utilizing either novel hormonal, chemotherapy and/or chemohormonal strategies for patients with metastatic castration-sensitive prostate cancer. Yet, we are fortunate, as a field, that the landscape is rapidly changing as new advances continue to be reported.
Can PARP Inhibitors Make It into the Metastatic Castration-Sensitive Prostate Cancer Disease State?
I’m continuing this series focused on metastatic castration-sensitive prostate cancer (mCSPC), as it is a disease state with many upcoming potential changes to standard of care. A couple of months ago, I briefly summarized what is known about the PEACE-1 trial, and I highlighted ongoing chemohormonal therapy trials.1 Since then, there has been a press release that the ARASENS trial with androgen deprivation therapy (ADT) plus docetaxel and darolutamide is superior in overall survival compared to ADT plus docetaxel. We eagerly await the data to be presented at the upcoming 2022 ASCO Genitourinary Cancers Symposium. Additionally, just last month, I summarized the trials that are ongoing using PD-1/PD-L1 antibody inhibition for patients with mCSPC.2 Although single agent PD-1/PD-L1 inhibitors have not shown definitive promise yet in metastatic castration-resistant prostate cancer (mCRPC) for unselected populations, hope remains that earlier use may offer benefit to our patients.
Combination Strategies with PD-1/PD-L1 Inhibition for Patients with Metastatic Castration-Sensitive Prostate Cancer
The clinical data surrounding inhibition of PD-1/PD-L1 in prostate cancer is evolving. In the past, I have written a couple of articles about both single-agent and combination approaches for metastatic castration-resistant prostate cancer (mCRPC).1, 2 The field has evolved to the point where we recognize that single-agent PD-1/PD-L1 inhibition is unlikely to yield a major benefit for an unselected population. In the KEYNOTE-199 trial, pembrolizumab yielded 5% and 3% objective response rates in patients with PD-L1 positive and negative tumors, respectively.3
Metastatic Castration-Sensitive Prostate Cancer, The Advances Keep Coming With Chemohormonal Therapy
The topic of metastatic castration-sensitive prostate cancer has been on the forefront of clinical research in prostate cancer for many years now. In 2017, and again in 2019, I wrote Clinical Trials Portal articles on the topic of metastatic castration-sensitive prostate cancer, summarizing the key ongoing trials during those times.1, 2 We now know that early treatment intensification with the addition of either docetaxel, abiraterone acetate, enzalutamide or apalutamide to androgen deprivation therapy (ADT) offers a significant overall survival benefit. Docetaxel is the only agent that may have questionable benefit for low volume metastatic prostate cancer, with benefit perhaps being restricted to high-volume metastatic disease only, defined as ≥4 bone metastases with at least one in the appendicular skeleton and/or a visceral metastasis.3
Upper Tract Urothelial Carcinoma – A Patient Population That Deserves More Attention in Clinical Trials
The majority of urothelial carcinomas occur in the lower urinary tract, yet 5-10% originate in the upper urinary tract, including the renal calyces, renal pelvis, and ureters.1 Although upper and lower urinary tract urothelial carcinoma may share similar histology, the natural history differs, and upper tract disease often has a higher incidence of local invasion at diagnosis.2 Risk factors for upper tract urothelial carcinoma are similar to those of the lower tract, but there are some unique risk factors are associated with environmental exposures. For example, Taiwan has an extremely high incidence of upper tract urothelial carcinoma, with a counterintuitive 1:2 male-to-female ratio due to arsenic-contaminated water, termed Blackfoot disease. Additionally, in both Taiwan and the Balkan countries, exposure to the Aristolochic herbs (fangchi and clematis) is carcinogenic, leading to progressive renal fibrosis and upper tract urothelial carcinoma.4, 5
Maintenance therapy and beyond with avelumab…
Avelumab initially received regulatory approval for patients with metastatic urothelial carcinoma in the post-platinum chemotherapy setting based on an objective response rate of 16.5%.1 In the post-platinum chemotherapy setting, both nivolumab and pembrolizumab also currently retain their regulatory approval status. However, the situation where avelumab has the strongest data is in the maintenance-switch setting. I initially discussed that topic in a Urotoday Clinical Trials Portal article almost 4 years ago.2 Of course, everything discussed in that article has been completed, and all highlighted trials were positive.
Prostate-Specific Membrane Antigen (PSMA) PET for Initial Staging of Prostate Cancer – Now That It’s Regulatory Approved, What’s Next?
PSMA PET imaging has now achieved regulatory approval in the United States. On December 1, 2020, the United States (US) Food and Drug Administration (FDA) granted a limited approval to the University of California, Los Angeles and the University of California, San Francisco, for 68Ga-PSMA-11 PET imaging for patients “with suspected prostate cancer metastasis who are potentially curable by surgery or radiation therapy” and for patients with “suspected prostate cancer recurrence based on elevated serum PSA levels.”1 More recently, on May 27, 2021, a second PSMA imaging agent, PYLARIFY® (piflufolastat F 18) injection (also known as 18F-DCFPyL or PyL), received FDA approval for the exact same indication.2 Although neither 68Ga-PSMA-11 and PYLARIFY® (piflufolastat F 18) injection (also known as 18F-DCFPyL or PyL) are widely available yet, both likely soon will be, and they will change how we think about and treat patients with prostate cancer and both high-risk localized disease and biochemical recurrence.
Abscopal Effect for Prostate Cancer? Does This Really Hold Promise?
The “abscopal effect” in cancer is frequently discussed, although very rarely seen. While the term is used quite loosely, it technically is a situation where an untreated metastatic tumor will shrink concurrently while another site is undergoing a localized treatment. Most commonly, radiation therapy is referenced as that local treatment. Although the exact mechanism is unknown, it is postulated that the immune system is responsible for such an effect.1
177Lutetium-PSMA-617, the Newest Life-Prolonging Therapy for Patients With Metastatic Castration-Resistant Prostate Cancer
Adenosine Triphosphate (ATP), Energy for Your Cells, but Inflammatory Towards Cancer
Partnering up with Abiraterone Acetate – Potentials for a Harmonious Relationship
Is Adjuvant Therapy a New Standard for Urothelial Carcinoma?
Sacituzumab Govitecan – Another Antibody Drug Conjugate Carving out a Path in Genitourinary Oncology
PI3K/AKT/mTOR Inhibitors for Prostate Cancer – Finally Hints of a Breakthrough
Activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway has been strongly linked with prostate cancer progression and metastatic potential.1 Loss of the inhibitory phosphatase, PTEN, leading to hyperactivation of PI3K/AKT/mTOR oncogenic signaling, occurs in 40-50% of metastatic castration-resistant prostate cancer.1,2 Not surprising is the fact that PTEN loss in patients with metastatic castration-resistant prostate cancer is associated with a worse prognosis and less benefit from androgen receptor (AR) blockade.3 Likewise, PTEN loss and subsequent Akt activation confer radiation4 and chemotherapy5, 6 resistance.
Cabozantinib for Prostate Cancer - A Renewed Hope
Cabozantinib, an oral tyrosine kinase inhibitor against MET and vascular endothelial growth factor receptor 2 (VEGFR2), is an agent that was initially met with enormous enthusiasm by the prostate cancer community. The early data showed dramatic bone scan responses, where bone metastases would almost magically disappear after cabozantinib treatment on subsequent restaging bone scans. As this was an unfamiliar, yet welcome phenomenon, the field eagerly began working on the development of this agent.
Erdafitinib, Potential for Expanding Indications for the Future
It has now been approximately a year and a half since the United States Food and Drug Administration (FDA) granted accelerated approval to erdafitinib for patients with locally advanced or metastatic urothelial carcinoma, with susceptible fibroblast growth factor receptor 3 (FGFR3) or FGFR2 genetic alterations after progression during or following platinum chemotherapy.1 The label is inclusive of patients within 12 months of neoadjuvant or adjuvant platinum chemotherapy. Additionally, the label includes companion diagnostic information for a jointly approved therascreen® FGFR RGQ RT-PCR kit, for this specific therapeutic indication.
What’s the Rationale for Adding PARP Inhibitors to Androgen Pathway Inhibitors for Patients with Prostate Cancer?
The TRITON2 trial demonstrated a 43.5% objective response rate with rucaparib in patients with metastatic castration-resistant prostate cancer (mCRPC) and a deleterious BRCA1 or BRCA2 alteration.3 This trial led to the United States Food and Drug Administration (FDA) granting accelerated approval to rucaparib for the
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