PROfound Trial With Olaparib Shows Feasibility of Personalizing Care in mCRPC

Olaparib (Lynparza) significantly improved overall survival (OS) versus enzalutamide (Xtandi) or abiraterone acetate (Zytiga) in patients with metastatic castration-resistant prostate cancer (mCRPC) who harbor BRCA1, BRCA2, and/or ATM aberrations, according to results from the final OS analysis of the pivotal phase 3 PROfound trial (NCT02987543).¹

In the trial, patients with mCRPC who progressed on previous treatment with a new hormonal agent and harbored BRCA1, BRCA2, or ATM aberrations (n = 245; cohort A) or other alterations in the homologous recombination repair (HRR) pathway (n = 142; cohort B) were randomized 2:1 to receive either olaparib or enzalutamide or abiraterone acetate.

Final OS data from cohorts A and B were presented during the 2020 ESMO Virtual Scientific Program. Results showed that the median OS in cohort A was significantly longer with olaparib than with physician’s choice (HR 0.69; 95% CI 0.50-0.97; P = .0175).1 In cohort B, the median OS was 14.1 months with olaparib versus 11.5 months with the control (HR, 0.96; 95% CI, 0.63-1.49). 

“What is exciting about this particular trial is that it showed the feasibility of personalizing care and using precision medicine strategies to preselect patients to maximize the chance of benefit for those who are candidates for these treatments,” said Maha H.A. Hussain, MD, FACP, FASCO. “We can also help patients avoid unnecessary exposure to ineffective treatments.”

Previously published data showed that olaparib resulted in a 66% reduction in the risk of disease progression or death compared with abiraterone or enzalutamide (HR, 0.34; 95% CI, 0.25-0.47; P <.0001).² Based on these results, the FDA approved olaparib in May 2020 for the treatment of adult patients with deleterious or suspected deleterious germline or somatic HRR gene–mutated mCRPC who have progressed following prior treatment with enzalutamide or abiraterone.

In an interview with OncLive, Hussain, the Genevieve E. Teuton Professor of Medicine in the Department of Medicine of the Division of Hematology Oncology and the deputy director at the Robert H. Lurie Comprehensive Cancer Center of the Northwestern University Feinberg School of Medicine, further discussed the updated findings from the PROfound trial, its clinical significance in the treatment of patients with mCRPC, and the promise of precision medicine.

OncLive: Could you first provide some background of this trial? 

Hussain: PROfound is a randomized phase 3 clinical trial. It is one of the first precision medicine clinical trials to complete; patients were preselected based on specific genomic alterations and then randomized accordingly. Patients with mutations in the HRR genes or DNA damage repair genes were assigned to 2 different cohorts. The primary cohort was [comprised of] patients who had BRCA1/2 or ATM mutations, while cohort 2 included [those who harbored] other genes that are involved in the HRR pathway. Patients were randomized 2:1 to olaparib or standard of care per physician’s choice of either abiraterone and prednisone or enzalutamide. The primary end point [of the trial] was radiographic progression-free survival (rPFS), which is a meaningful clinical end point, while OS was one of the several key secondary end points [examined].

What was the rationale for targeting the DNA repair pathway in prostate cancer?

Data from the Stand Up to Cancer highlighted the fact that over 20% of patients with mCRPC have significant mutations in the DNA repair pathway or the HRR genes. That [research] underscored the fact that this is a clinically relevant pathway to go after. At the time that [the PROfound trial was being designed] we saw evidence of benefit [with this approach] in other tumors [such as] breast and ovarian cancers, and then subsequently, in pancreatic cancer. 

The specific pathway relevance is that both normal cells and cancer cells need to repair themselves when there is damage; the HRR pathway is involved in that repair process. However, are alterations or mutations [are present], the cells are not able to repair themselves and they fall back into a different pathway, which is the PARP pathway. Basically, PARP agents tend to inhibit that enzyme so that the [cancer] cells cannot repair themselves.

What results were presented at the 2020 ESMO Virtual Congress?

[Earlier data from the trial were previously published] this past summer. Johann de Bono, MB, ChB, PhD, of The Institute of Cancer Research was the first author on the publication in the New England Journal of Medicine, which highlighted [data regarding] the primary end point of rPFS. In this particular presentation delivered at the 2020 ESMO Virtual Congress, [investigators] reported OS [data from] cohorts A and B. 

We saw that the benefit [with olaparib is] not only in terms of rPFS; the benefit translated into a median OS benefit of over 4 months between the arms, despite crossover from the control arm to the olaparib arm at time of progression. Additionally, the risk of death was reduced by 31%, which is very clinically significant. In [the cohort of patients who harbored the] other 12 genes, other than BRCA1/2 and ATM, we saw a trend in OS improvement but it was not statistically significant. The trend was about a little bit over 2 months of a difference. When adjusting for crossover, the trend improved although it was still not statistically significant. However, several patients in cohort B experienced clinical benefits from treatment. The primary benefit [with olaparib] still seems to be driven by BRCA primarily.

Were any new safety signals observed?

No; the overall safety was very much consistent with what was known about olaparib. The most common adverse effects observed included anemia, nausea, and fatigue. Most of these were low-grade events, aside from the anemia. Many of these patients were heavily pretreated; while they might have previously received abiraterone or enzalutamide, they would have also received chemotherapy and other potential anticancer treatment and be fairly advanced in the course of their disease. The findings, overall, are really not surprising and the safety profile very much consistent with what has been observed with the agent in other tumors.

What should your colleagues take away from this research?

We have reached a major benchmark in the management of this disease. Ever since the original observations regarding androgen deprivation [therapy] in prostate cancer and subsequent treatments, and certainly since the time I entered the field in the early 1990s, prostate cancer management has been more of a one-size-fits-all approach. In fact, when we give chemotherapy and hormone treatment we don't preselect [patients].

We still have [a lot of work to do]. Patients with metastatic castration-resistant disease continue to die from prostate cancer; they also suffer from pain and other factors involved with this disease. This [research] highlights the feasibility of performing precision medicine trials. It also shows us that meaningful clinical benefits could be achieved in these patients. I would hope that our partners across the spectrum will invest further in conducting more clinical trials. 

The observation that we've seen with olaparib also opens up the door for potential combination clinical trials, both in castration-resistant disease and potentially in earlier stages of disease, where we might get a better return on investment from a clinical perspective.

What does this work underscore about germline testing?

Genomic profile evaluation for patients is critical moving forward, not only for the purpose of treatment for the patient. Conducting or counseling the patient regarding germline testing and tumor genomics evaluation in preparation for future treatment is also very critical. Obviously, genetic testing is associated with genetic counseling, [which may allow patients] and potential blood relatives [to get ahead of the game].

Tissue-based genomic evaluation will open the door for the patient to explore different treatments, and [certain] genomic alterations might qualify them for different clinical trials opportunities. [This work] underscores the hope for patients that their cancer can be managed better with genomically targeted treatments, specifically, in this case, the PARP inhibitor. [Now we can build on] these observations in terms of different treatment strategies and combinations.

References

1. De Bono JS, Mateo J, Fizazi K, et al. Final overall survival (OS) analysis of PROfound: Olaparib vs physician’s choice of enzalutamide or abiraterone in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) gene alterations. Presented at: 2020 ESMO Virtual Congress; September 19-21, 2020; Virtual. Abstract: 610O.
2. De Bono JS, Mateo J, Fizazi K, et al. Olaparib for metastatic castration-resistant prostate cancer. N Eng J Med. 2020;382:2091-2102. doi:10.1056/NEJMoa1911440