PARP Inhibitors: A Major Therapeutic Option in Endocrine-Receptor Positive Breast Cancers

Clinical effectiveness and safety of olaparib in BRCA-mutated, HER2-negative metastatic breast cancer in a real-world setting: final analysis of LUCY

PURPOSE

The interim analysis of the phase IIIb LUCY trial demonstrated the clinical effectiveness of olaparib in patients with germline BRCA-mutated (gBRCAm), human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (mBC), with median progression-free survival (PFS) of 8.11 months, which was similar to that in the olaparib arm of the phase III OlympiAD trial (7.03 months). This prespecified analysis provides final overall survival (OS) and safety data.

METHODS

The open-label, single-arm LUCY trial of olaparib (300 mg, twice daily) enrolled adults with gBRCAm or somatic BRCA-mutated (sBRCAm), HER2-negative mBC. Patients had previously received a taxane or anthracycline for neoadjuvant/adjuvant or metastatic disease and up to two lines of chemotherapy for mBC.

RESULTS

Of 563 patients screened, 256 (gBRCAm, n = 253; sBRCAm, n = 3) were enrolled. In the gBRCAm cohort, median investigator-assessed PFS (primary endpoint) was 8.18 months and median OS was 24.94 months. Olaparib was clinically effective in all prespecified subgroups: hormone receptor status, previous chemotherapy for mBC, previous platinum-based chemotherapy (including by line of therapy), and previous cyclin-dependent kinase 4/6 inhibitor use. The most frequent treatment-emergent adverse events (TEAEs) were nausea (55.3%) and anemia (39.2%). Few patients (6.3%) discontinued olaparib owing to a TEAE. No deaths associated with AEs occurred during the study treatment or 30-day follow-up.

CONCLUSION

The LUCY patient population reflects a real-world population in line with the licensed indication of olaparib in mBC. These findings support the clinical effectiveness and safety of olaparib in patients with gBRCAm, HER2-negative mBC.

CLINICAL TRIAL REGISTRATION

Clinical trials registration number: NCT03286842.

Theranostic biomarkers and PARP-inhibitors effectiveness in patients with non-BRCA associated homologous recombination deficient tumors: Still looking through a dirty glass window?

Breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2) deleterious variants were the first and, still today, the main biomarkers of poly(ADP)ribose polymerase (PARP)-inhibitors (PARPis) benefit. The recent, increased, numbers of individuals referred for counseling and multigene panel testing, and the remarkable expansion of approved PARPis, not restricted to BRCA1/BRCA2-Pathogenic Variants (PVs), produced a strong clinical need for non-BRCA biomarkers. Significant limitations of the current testing and assays exist. The different approaches that identify the causes of Homologous Recombination Deficiency (HRD), such as the germline and somatic Homologous Recombination Repair (HRR) gene PVs, the testing showing its consequences, such as the genomic scars, or the novel functional assays such as the RAD51 foci testing, are not interchangeable, and should not be considered as substitutes for each other in clinical practice for guiding use of PARPi in non-BRCA, HRD-associated tumors. Today, the deeper knowledge on the significant relationship among all proteins involved in the HRR, not limited to BRCA, expands the possibility of a successful non-BRCA, HRD-PARPi synthetic lethality and, at the same time, reinforces the need for enhanced definition of HRD biomarkers predicting the magnitude of PARPi benefit.

Progress and prospects in research and clinical practice of hormone receptor-positive, HER-2-negative breast cancer with BRCA1/2 mutations

Breast cancer (BC) is a heterogeneous disease that is the most common cancer in women worldwide. However, precise subtyping and corresponding treatments have improved patient outcomes. Hormone receptor (HR)-positive, human epidermal growth factor receptor type 2 (HER2)-negative (HR+/HER2-) BC with BRCA1 and/or BRCA2 mutations (BRCA1/2m) is a unique BC subset with dual drivers: homologous recombination deficiency and hormone receptor signaling. Wild-type BRCA1/2 suppresses estrogen receptor-mediated signaling. Loss-of-function mutations in BRCA1/2 release estrogen receptor suppression, leading to reduced sensitivity to endocrine therapy. Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPis) exert antitumor effects against this subtype and can be used in combination with endocrine therapy. Although PARPis have been evaluated in metastatic triple-negative breast cancer, their efficacy against HR+/HER2- BC has not been clearly established. The present review summarizes recent advances and prospects in the progress of the HR+/HER2-/BRCA1/2m subgroup. As such, this article provides theoretical guidance for future research and promotes the use of PARPis for the treatment of HR+/HER2-/BRCA1/2m BC.

PALB2 germline mutations in a large cohort of Middle Eastern breast-ovarian cancer patients

The PALB2 gene is a breast cancer (BC) and ovarian cancer (OC) predisposition gene involved in the homologous recombination repair pathway. However, the prevalence and clinicopathological association of PALB2 pathogenic/likely pathogenic (PV/LPV) variants in Middle East is still not fully explored. Total 918 BC/OC patients from Saudi Arabia were selected for PALB2 mutations screening using capture sequencing technology. Five heterozygous PVs or LPVs were identified in six cases, accounting for 0.65% (6/918) of entire cohort. Two cases (33.3%) harbored PVs and four cases (66.7%) carried LPVs. Four PVs/LPVs (80%) were frameshift along with one novel splicing LPV (c.2835-2_2835-1delinsTT). One recurrent LPV (c.3425delT: p.L1142fs) was identified in two cases. All six affected carriers have breast cancer diagnosis with median age of 39.5 years (range 34-49 years). Only two cases (33%) have documented family history of cancer. Breast cancer phenotype was invasive ductal unilateral cancer in all cases with 66.7% of hormone receptor positive and 16% of triple negative tumors. Germline PVs/LPVs in the PALB2 gene were observed in low frequency of 0.65% in Saudi BC and/or OC. Our study confirms one recurrent LPV and one novel LPV in Saudi breast cancer patients.

Predominance of BRCA2 Mutation and Estrogen Receptor Positivity in Unselected Breast Cancer with BRCA1 or BRCA2 Mutation

Simple Summary

We performed a meataanalysis of BRCA1 or BRCA2 germline pathogenic or likely pathogenic variant (gBRCA) in 108,699 unselected breast cancer patients and in 238,972 unaffected individuals. The metanalysis shows that 3.4% unselected breast cancer patients have a gBRCA. In unselected breast cancer patients with gBRCA, more than half of tumors are estrogen receptor-positive. 0.5% of unaffected individuals of the studied populations are gBRCA carriers. The frequency of gBRCA2 and gBRCA1 heterozygosity is estimated at 1/288 and 1/434, respectively. In unselected breast cancer and in unfafected individuals gBRCA2 is more frequent than gBRCA1.

Abstract

Background: Poly(ADP-ribose) polymerase 1 inhibitor (PARPi) agents can improve progression-free survival of patients with breast cancer who carry a germline BRCA1 or BRCA2 pathogenic or likely pathogenic variant (gBRCA) in both the metastatic and adjuvant setting. Therefore, we need to reassess the frequency of gBRCA1 and gBRCA2 in order to redefine the criteria for women and tumor phenotype that should be tested. Objective: We studied the relative distribution of gBRCA1 and gBRCA2 in unselected populations of women with breast cancer and in unaffected individuals. We also analyzed the proportion of estrogen receptor (ER)-positive (ER+) tumors in unselected breast cancer patients with gBRCA. Design: We performed a meta-analysis of studies of unselected breast cancer that analyzed the relative contribution of gBRCA1 versus gBRCA2 among unselected breast cancer cases in gBRCA carriers. We then performed a meta-analysis of gBRCA carriage in unaffected individuals from genome-wide population studies, the gnomAD databank, and case–control studies. Results: The BRCA2 gene was involved in 54% of breast cancer cases in unselected patients with gBRCA (n = 108,699) and 60% of unaffected individuals (n = 238,973) as compared with 38% of the largest gBRCA family cohort (n = 29,700). The meta-analysis showed that 1.66% (95% CI 1.08–2.54) and 1.71% (95% CI 1.33–2.2) of unselected breast cancer patients carried gBRCA1 and gBRCA2, respectively. In a population of unaffected individuals, the frequency of heterozygosity for gBRCA1 and gBRCA2 was estimated at 1/434 and 1/288, respectively. Nearly 0.5% of unaffected individuals in the studied populations carried a gBRCA. Carriage of a gBRCA was 2.5% for patients with ER+ tumors (95% CI 1.5–4.1) and 5.7% (95% CI 5.1–6.2) for those with ER- tumors. Overall, 58% of breast tumors occurring in women carrying a gBRCA were ER+ (n = 86,870). Conclusions: This meta-analysis showed that gBRCA2 carriage is predominant in unselected breast cancer patients and unaffected individuals. ER+ tumors among women with gBRCA-related breast cancer are predominant and have been underestimated. Because PARPi agents improve progression-free survival with ER+ gBRCA breast cancer in most clinical trials, breast cancer should be considered, regardless of ER status, for BRCA1/2 screening for therapeutic purposes.

DNA Methylation Malleability and Dysregulation in Cancer Progression: Understanding the Role of PARP1

Mammalian genomic DNA methylation represents a key epigenetic modification and its dynamic regulation that fine-tunes the gene expression of multiple pathways during development. It maintains the gene expression of one generation of cells; particularly, the mitotic inheritance of gene-expression patterns makes it the key governing mechanism of epigenetic change to the next generation of cells. Convincing evidence from recent discoveries suggests that the dynamic regulation of DNA methylation is accomplished by the enzymatic action of TET dioxygenase, which oxidizes the methyl group of cytosine and activates transcription. As a result of aberrant DNA modifications, genes are improperly activated or inhibited in the inappropriate cellular context, contributing to a plethora of inheritable diseases, including cancer. We outline recent advancements in understanding how DNA modifications contribute to tumor suppressor gene silencing or oncogenic-gene stimulation, as well as dysregulation of DNA methylation in cancer progression. In addition, we emphasize the function of PARP1 enzymatic activity or inhibition in the maintenance of DNA methylation dysregulation. In the context of cancer remediation, the impact of DNA methylation and PARP1 pharmacological inhibitors, and their relevance as a combination therapy are highlighted.