Category: 2019

The National Cancer Institute (NCI) is sponsoring a clinical trial at many locations comparing two types of radiation therapy, stereotactic body radiation therapy (SBRT) with intensity-modulated radiation therapy (IMRT). The former is administered in less than two weeks while the latter is given in five weeks. The aim of the trial is to compare cure rates and side effects. The following video by Dr. Mark Scholz, Executive Director of the Prostate Cancer Research Institute (PCRI) describes the trial now recruiting patients.

Delivering higher doses of radiation therapy over a shorter time period — an approach called stereotactic body radiation therapy (SBRT) — does not worsen side effects in men with localized prostate cancer, compared to conventional radiation therapy, a Phase 3 trial shows. The study also suggests that SBRT delivered through the CyberKnife System is less toxic for the genitourinary system than conventional linear accelerators used for this kind of radiation therapy. The research was published in an article in the journal The Lancet Oncology.

Accuray’s CyberKnife is a robotic system that delivers SBRT to the prostate and other organs. This approach involves very high doses of radiation over a smaller number of treatment sessions compared to conventional radiation therapy. As the prostate can move unpredictably during the course of treatment, tracking its position and correcting the radiation delivery site are key. CyberKnife offers continual imaging and automatic beam delivery corrections through its Synchrony technology, which helps increase treatment efficacy and spare healthy tissue, according to the company.

The international, Accuray-funded PACE-B Phase 3 trial (NCT01584258) was designed to compare SBRT to conventional radiation therapy in men who were ineligible for surgery, had low or intermediate risk cancer, and to determine if the CyberKnife system provided any benefits over other SBRT delivery systems. Patients assigned to SBRT received five sessions over one or two weeks, while those on conventional radiotherapy had either 39 sessions over eight weeks, or 20 sessions over four weeks. The trial included 874 men and took place in the U.K., Ireland, and Canada. In both groups, 90% of the patients had intermediate-risk prostate cancer.

Clinical assessments and patient-completed questionnaires showed that SBRT and conventional radiation therapy resulted in similar levels of acute gastrointestinal and genitourinary side effects over three months. No treatment-related deaths occurred in either group. The researchers also found that moderate or worse genitourinary side effects were less common in CyberKnife users (12%) than in non-users (31%). Gastrointestinal side effects were similar in both groups. In a news release, researchers said the results are “promising, and for the first time show in a large patient group that giving five large doses of SBRT is safe in the short term.” Of note, eight of the study’s authors received grants and/or personal fees from Accuray.

The above information first appeared in the Oct. 3rd e mail edition of Prostate Cancer News Today, by Jose Marques Lopes, Ph.D.

The U.S. Food and Drug Administration (FDA) has approved Erleada (apalutamide) for the treatment of men with metastatic, castration (hormone)-sensitive prostate cancer (mCSPC), or those whose cancer still responds to androgen deprivation (hormonal) therapy (ADT).

The decision is based on the double-blind TITAN Phase 3 trial (NCT02489318), as it showed that adding Janssen’s Erleada to ADT significantly extended both overall survival and progression-free survival (PFS) – the period without cancer progression –, which were the trial’s primary goals. Based on results from the SPARTAN clinical trial, Erleada had already been approved in 2018 as a treatment for patients with non-metastatic (localized) castration (hormone)-resistant prostate cancer in both the United States and the European Union.

Compared to ADT and a placebo, treatment with Erleada and ADT reduced the risk of death by 33%, and the likelihood of disease worsening (as assessed by radiography) or death by 52%. After a median follow-up of 22.7 months, 84% of the patients on Erleada and ADT reached the two-year mark alive, compared to 78% of those on ADT and placebo. In this indication, Earleada decreased the risk of cancer spreading or death by 72 percent compared to a placebo, and delayed the cancer’s metastasis by more than two years. The frequency of serious adverse events was 19.8% for Erleada and 20.3% for placebo.

Erleada is an oral therapy that targets the androgen receptor, blocking its activation by androgens such as testosterone. Its chemical structure and mode of action are similar to that of enzalutamide (Xtandi). In turn, ADT, a mainstay of prostate cancer treatment, reduces the amount of androgens in the body.

TITAN included 1,052 mCSPC patients regardless of extent of disease and of being newly diagnosed or having been treated with up to six cycles of docetaxel (taxotere). It was funded by Johnson & Johnson-owned Aragon Pharmaceuticals and Janssen Research and Development (also owned by Johnson & Johnson). The study’s findings were presented at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting and published in The New England Journal of Medicine.

“Prostate cancer is more difficult to treat once it spreads, and for patients with castration (hormone)-sensitive disease, it is clear that androgen deprivation therapy (ADT) alone is often not enough,” Kim Chi, principal investigator in TITAN and medical oncologist at BC Cancer-Vancouver, said in a press release. “Results from the TITAN study showed that, regardless of the extent of disease, patients with metastatic castration-sensitive prostate cancer have the potential to benefit from treatment with Erleada in addition to ADT.”

Most information in this post appeared in the September 19th, 2019 Prostate Cancer News Today by Jose Marques Lopes, Ph.D.

Tumors with large numbers of prostate cancer cells with mutations in DNA repair genes (e.g. BRCA1 and 2) are easier to target using prostate-specific membrane antigen (PSMA) therapies, and patients with these tumors are more likely to respond to this potential treatment’s use, a study found and published in European Urology.

PSMA is a membrane protein often found at very high levels on the surface of prostate cancer cells, especially among those forming castration (hormone)-resistant prostate cancer (CRPC) tumors, an aggressive form of the disease that no longer responds to hormone therapy.

For that reason, PSMA has become a promising target of researchers working to develop a new class of medications that combine an anti-PSMA antibody with a radioactive moiety. Such medications, like lutetium (Lu)177-PSMA, use the anti-PSMA antibody to specifically spot and deliver the radioactive lutetium-177 conjugate to prostate cancer cells which produce PSMA in large amounts.

But this type of targeted radiation therapy does not work for all patients, and the rates of those failing to respond have amounted to about 30% in studies. Between 30% to 60% of patients with metastatic CRPC (mCRPC) treated with these therapies, however, have reported reductions of more than 50% in PSA levels (a biomarker of prostate cancer).

Prior studies used antibodies that target the intracellular (not the surface) part of PSMA, which has no clinical value for estimating PSMA levels. A team of investigators at the Institute of Cancer Research in London set out to characterize the levels of PSMA found specifically on the surface of prostate cancer cells — called membranous PSMA (mPMSA) — in a group of men with mCRPC. Because mutations in DNA repair genes lead to a high genetic variability within a single tumor, researchers also examined if these mutations affect PSMA levels and could be used to guide PSMA-directed therapies.

The study involved two groups of patients: a test group of 60 patients who provided mCRPC tissue samples, including 38 people with matched, castration (hormone)-sensitive prostate cancer (CSPC) diagnostic samples; and a confirmation group of 10 patients whose tumors contained a high number of mutations in DNA repair genes.

Despite the high degree of variability in membranous PSMA levels evident among different patients and even between samples obtained from the same patient, high levels of mPSMA at diagnosis generally associated with greater cancer aggressiveness (based on the Gleason score) and poorer patient survival.

In addition, researchers found that membranous PSMA (mPSMA) levels tended to be higher in metastatic hormone-resistant prostate cancer samples compared to hormone-sensitive samples, or samples from patients whose tumors respond to hormone therapies.

Investigators also found that mPSMA levels were more than four times higher in tumors containing numerous mutations in DNA repair genes, compared to those with no mutations. These findings were confirmed in the second group of study patients.

Testing for DNA repair defects was a good indication of which tumors had high levels of PSMA — and so would be expected to respond to these PSMA-targeted therapies like lutetium-177-PSMA. Identifying patients with DNA repair mutations could be useful in design of clinical trials to identify likely responders to PSMA treatments. (I was recently informed that genetic testing for DNA repair mutations is commercially available from the company Invitae.)

For additional details see the Aug. 22 Prostate Cancer News Today.

Men with metastatic hormone-resistant prostate cancer (mCRPC) given Lynparza® (olaparib), a breast and ovarian cancer treatment, lived a clinically meaningful longer time without disease progression or death compared to those given standard treatment with Xtandi® (enzalutamide) or Zytiga® (abiraterone) in a Phase 3 trial. These eligible patients had a mutation in one of 15 DNA repair genes involved in the homologous recombination (HR) pathway. Specifically, these positive benefits were seen in patients with mutations in BRCA1, BRCA2, or ATM, the most common among HR gene mutations; the first two are also strongly linked with familial breast and ovarian cancers. Overall, HR mutations occur in approximately 25% of men diagnosed with mCRPC.

The multicenter, open-label PROfound study (NCT02987543) compared the efficacy and safety of Lynparza® to that of Xtandi® (from Astellas and Pfizer Oncology) and Zytiga® (from Janssen) in mCRPC patients whose disease had progressed while on these newer hormone treatments.

Lynparza®, an oral PARP (poly ADP-ribose polymerase) enzyme inhibitor marketed by AstraZeneca and Merck, is intended to prevent cancer cells from repairing their DNA errors, thereby causing their death. It is approved for some breast and ovarian cancers.

Patients in PROfound were treated with 300 mg twice daily of Lynparza®, or investigators’ choice of Xtandi® (160 mg daily) or Zytiga® (1,000 mg daily, plus prednisone). Lynparza’s safety and tolerability results were generally consistent with previous trials. The PROfound trial is expected to fully conclude in February 2021.

“This is the only positive Phase 3 trial of any PARP inhibitor in metastatic hormone-resistant prostate cancer, where the need for new, effective therapies is high,” according to José Baselga, AstraZeneca’s executive vice president, Oncology R&D. “The PROfound trial also demonstrates the potential value of genomic testing in this at-risk patient population.”  Roy Baynes, senior vice president, head of global clinical development and chief medical officer at Merck Research Laboratories, said trial results “represent the potential for a new, oral, and targeted treatment option for this patient population.”

Lynparza® is being tested in other prostate cancer trials, including the international PROpel Phase 3 study testing the addition of Lynparza® to Zytiga® as a first-line treatment of mCRPC patients who have not been given chemotherapy or newer hormonal agents (NCT03732820). PROpel is currently enrolling up to 720 men at sites across the U.S., Canada, Europe and elsewhere.

The material above was summarized from an article appearing in Prostate Cancer News Today, August 12, 2019 to which an e mail subscription is highly recommended.

 

Additional note on how PARP inhibitors work. DNA is damaged thousands of times during each cell multiplication cycle, and that damage must be repaired, including in normal as well as in cancer cells (which multiply and grow faster than normal cells). Otherwise, if DNA damage is not repaired, cells may die due to this damage. BRCA1, BRCA2 and PALB2 are proteins in cells that are important for the repair of double-strand DNA breaks by the error-free homologous recombinational repair, or HRR, pathway. PARP1 is a protein that is important for repairing single-strand breaks (‘nicks’ in the DNA). Drugs that inhibit PARP1 cause multiple double strand DNA breaks to form in this way, and in tumors with BRCA1, BRCA2 or PALB2  mutations, these double strand breaks cannot be efficiently repaired, leading to the death of the cells. Normal cells that don’t replicate their DNA as often as cancer cells, and that lack any mutated BRCA1 or BRCA2 still have homologous repair system operating, which allows them to survive the inhibition of PARP by drugs like Lynparza®.