Recent studies in advanced prostate cancer have identified emerging treatment targets and mechanisms of treatment resistance. At the 2017 European Society of Medical Oncology (ESMO) Annual Meeting, Dr. Himisha Beltran chaired and moderated a session evaluating the use of liquid biopsies – blood tests used to glean information about tumors – as a useful clinical tool for prostate cancer management.
While there are no formal guidelines on who, when, how and what to test for in prostate cancer, Dr. Beltran’s expertise provided important guidance to the global oncology community on this topic, as the prospect that a blood test might reveal many insights about the cancer and the tumor makeup has led oncologists to feel excited. Several steps are still needed for broad clinical implementation.
As tumors grow, some of their cells may enter into the bloodstream. These cells are known as circulating tumor cells (CTCs) and travel throughout the body along with fragments of tumor cell DNA known as circulating tumor DNA (ctDNA). Compared with traditional biopsies which extract tissue directly from the tumor, liquid biopsies offer a less invasive way for doctors to detect molecular biomarkers and learn more about what’s going on with someone’s cancer. Liquid biopsies can also better capture tumor heterogeneity, as CTCs and ctDNA can provide a window into the entire tumor (and metastatic sites), compared with a traditional biopsy in which typically only one part of the tumor is sampled. Thus, with a simple blood test, doctors can potentially access a more comprehensive view of an individual’s cancer, which can then help them determine the best treatment for that person. Blood testing can also be more easily repeated throughout the course of treatment in order to monitor disease changes in response to therapy, so liquid biopsy offers ways to detect treatment resistance and resistance mutations early on and throughout the course of the disease.
There is an emerging role for molecular testing in advanced prostate cancer since this information can better inform treatment decisions involving targeted therapies, such as PARP inhibitors, platinum-based chemotherapy, and immunotherapies. Liquid biopsies such as ctDNA may provide information about the genomic alterations present in the cancer, which can be used to help predict how people might respond to certain therapies.
Through liquid biopsies, physicians and researchers can also better detect signs of therapy resistance that may be emerging. For example, if a patient has a gene amplification or mutation detected in ctDNA that involves the androgen receptor (AR) gene, or AR splice variants expressed in CTCs, this may indicate that potent AR-targeted therapies may be less likely to work. This is because the cancer cells may develop various ways to reactivate androgen receptor signaling by acquiring extra copies of the AR gene (gene amplification), activating AR mutations, and/or AR splice variants (such as the AR-V7 variant), all of which result in downstream over-activity of the AR-pathway. Knowing this information up front may spare people from the side effects from a treatment likely to be ineffective. Current research is focused on developing more effective AR pathway inhibitors in this setting. CTCs may also identify other features of the cancer such as localization of the AR in response to taxanes as observed in the TAXYNERGY trial, tumor heterogeneity, and expression of emerging therapeutic targets.
Through a grant from the Prostate Cancer Foundation (PCF), Dr. Beltran and colleagues at WCM are working as part of an international consortium to develop, validate, and implement a ctDNA platform for prostate cancer. This targeted genomic sequencing test, called PCF SELECT, identifies tumor mutations in ctDNA from metastatic prostate cancer patients to guide treatment selection based on precision medicine. It is currently undergoing centralized development, and the long-term goal is that this ctDNA test will be widely used by the clinical prostate cancer community for precision medicine applications.
While liquid biopsies do have promise for these indications and can help guide decisions on the most appropriate treatments for prostate cancer patients, it is important that both patients and clinicians understand the advantages and limitations of available and emerging technologies. Undergoing treatment at a center of excellence that contributes to research on emerging trends allows individuals the opportunity to be among the first to access cutting-edge technologies that may benefit them.
Each year, the American Society of Clinical Oncology (ASCO) Annual Meeting brings together more than 30,000 oncology professionals. At this year’s meeting in Chicago, physicians and scientists presented the latest research findings in an effort to bring the best cancer treatments to patients across the United States and the world. We’ve outlined some of the genitourinary (GU) oncology highlights, broken down by disease type.
At this year’s meeting, there was also some important research presented related to communication, quality of life and survival. In a study that involved patients with GU cancers, as well as those with other types of tumors, patients were randomized to two groups: 1) a control group of standard care 2) a group to utilize a web-based patient-reported outcome questionnaire between visits. Results from any answers completed in the online system were sent to the treatment team in real time. In this study, the patients that were randomized to the online questionnaire group experienced better quality of life. In addition, these patients lived longer, with a 17% improvement in survival simply by using the online tracker reporting symptoms to their treatment team between visits. While the study was only conducted at a single institution, it underscores the importance of communicating and relaying any symptoms to your treatment team members responsible for your medical care (generally physicians, nurses and advanced practitioners).
The results from two large phase 3 clinical trials will lead to a change in the standard of care treatment for men with advanced prostate cancer. The LATITUDE and STAMPEDE trials investigated the addition of abiraterone and low dose prednisone to standard androgen deprivation therapy (ADT) for men with advanced prostate cancer. Similar to the unprecedented results presented at ASCO in 2014 (CHAARTED) and 2015 (STAMPEDE) with the use of docetaxel chemotherapy, a major improvement in overall survival was demonstrated, improving length of life by nearly 40%. The results from these studies will provide an additional treatment option for men presenting with advanced prostate cancer.
For men with metastatic castration-resistant prostate cancer (mCRPC), a randomized phase 2 trial demonstrated no significant differences in the efficacy, or effectiveness, of abiraterone or enzalutamide, two of the leading treatments for prostate cancer that is resistant to hormonal therapy. This research finding was consistent with most clinicians’ belief that either drug may be utilized, allowing physician and patient choice. Importantly, the study incorporated a number of interesting biomarkers using circulating tumor cell (CTC) DNA from a liquid biopsy, and the data gleaned from the DNA revealed prognostic insights about disease aggressiveness and biology. Another study showed a lack of utility to continue enzalutamide after disease progression, confirming the current practice of switching treatments after cancer growth.
Additional data was presented on genomic signatures from prostate tissue, which in combination with clinical data, are more powerful in indicating prognosis in men who receive treatment for clinically localized (low stage / early) prostate cancer.
Prostate cancer acquires resistance to systemic treatment as a result of tumor evolution and selection, but repeat biopsies to study how cancers evolve are challenging, invasive, and may be confounded by tumor heterogeneity. Dr. Himisha Beltran evaluated a non-invasive approach: whole exome sequencing of circulating tumor DNA in the blood. Additional data utilizing circulating tumor cell (CTC) counts as an early indicator of response may speed drug development. Clinical trials are currently evaluating measuring circulating tumor cell counts as a biomarker for whether or not treatments are working. This may be a better indicator than measuring levels of prostate specific antigen (PSA), the current indicator for response.
Dr. Scott Tagawa presented a trial-in-progress update about the clinical trial he is leading at Weill Cornell Medicine and NewYork-Presbyterian utilizing the small molecule lutetium 177Lu-PSMA-617 to target prostate-specific membrane antigen (PSMA). PSMA is a protein abundantly expressed in 85-90 percent of metastatic prostate cancer cells, and this is the first U.S. trial of its kind. Learn more about this radionuclide therapy-based clinical trial and the eligibility criteria.
Additionally, there were many research updates presented in the area of neuroendocrine prostate cancer (NEPC), an aggressive subtype of prostate cancer that is resistant to many traditional treatment types. Dr. Loredana Puca received a Merit Award from the Conquer Cancer Foundation for her research examining the potential use of antibody-drug conjugate rovalpituzumab tesirine for treatment of NEPC. View the abstract and learn more about our open clinical trial using this antibody-drug conjugate. Dr. Himisha Beltran highlighted the significance of the loss of tumor suppressor ZFP36 in prostate cancer patients.
Prostate cancer was the first tumor type to have a cancer vaccine (sipuleucel-T) lead to longer survival, but the drug’s activity may be limited on its own. In a randomized phase 2 trial, receiving sipuleucel-T in combination with indoximod – a drug with the potential to improve immune response – kept the cancer at bay more than twice as long compared to those who received sipuleucel-T plus a placebo. This was an exciting research update showing promise for patients with prostate cancer.
New research using tumor and liquid (blood-based) biopsies demonstrated that a majority of tumors and circulating tumor cells in men with metastatic castration-resistant prostate cancer express a protein called Trop-2, justifying a targeted treatment approach. With this knowledge, we are now evaluating the safety and efficacy of IMMU-132, an immunotherapy-based drug that targets Trop-2, in an open clinical trial for men with prostate cancer.
Bladder Cancer and Other Urothelial Cancers:
Dr. Bishoy Faltas was invited to present at the ASCO Clinical Science Symposium entitled “Expanding the Actionable Landscape: Bladder Cancer Genomics — Unlocking the Genome: Insights Into Risk and Response in Bladder Cancer.”
During this session, Dr. Faltas discussed the genomics of urothelial cancer, and highlighted the latest research describing new data on the frequency of inherited (germline) mutations as well as tumor (somatic) genomics and relationship to response to chemotherapy and immunotherapy. Patients with “upper tract” urothelial cancer (tumors arising in the kidney or ureter) in particular have a higher chance of harboring an inherited mutation. Different genomic alterations in the tumors may be separated into groups that are associated with better responses to chemotherapy and immunotherapy. This is becoming more clinically relevant as we can test for these genes and the number of treatment options is expanding.
Additionally, updated results of the KEYNOTE-045 study confirmed the overall survival benefit of the anti-PD1 immune checkpoint inhibitor pembrolizumab (Keytruda) compared to second-line chemotherapy in patients with prior platinum-based chemotherapy. Importantly, this was the first head-to-head trial to demonstrate the superiority of immunotherapy over chemotherapy in urothelial cancer.
Several different combination studies for the treatment of advanced renal cell carcinoma (RCC) were presented at the 2017 ASCO Annual Meeting. While some studies demonstrated promising response data, significant toxicity of some combinations underscored the importance of clinical trials and the recommendation to avoid combinations outside of the research setting, which is regulated and in which these types of side effects can be monitored. Several randomized phase III trials testing combination therapy are ongoing with results anticipated to lead to changes in standard of care.
Unfortunately, despite imaging that indicates no evidence of cancer metastases (spread), many patients are not cured with surgery alone. Treatment of many cancers incorporate the use of systemic (medical) therapy in addition to surgery to increase cure rates. For the most part, this strategy has not been overwhelmingly successful in the setting of renal cell carcinoma (RCC). Unfortunately, another “negative” phase III trial showed that the addition of pazopanib (Votrient) to surgery did not improve cure rates for patients with RCC. Additional data was presented utilizing either clinical or genomic biomarkers that may assist physicians in choosing patients that might benefit from the addition of the oral drugs following surgery. We continue to await the results of additional completed studies and some currently enrolling studies utilizing immunotherapy before/after surgery.
April brings more than just showers – the month kicks off with a very important cancer research conference. Tomorrow we are headed to Washington, DC for the American Association for Cancer Research (AACR) annual meeting held April 1-5, 2017.
Our team will be joining approximately 20,000 cancer researchers from across the country and around the world for this important meeting. Several physicians and scientists from Weill Cornell Medicine, NewYork-Presbyterian, and the Meyer Cancer Center again served on the scientific program committee, including our own Dr. Scott Tagawa.