Homologous DNA Repair Deficiency Research Articles

BRCA Mutations, Homologous DNA Repair Deficiency, Tumor Mutational Burden, and Response to Immune Checkpoint Inhibition in Recurrent Ovarian Cancer.

Homologous DNA repair-deficient (HRD) ovarian cancers (OCs), including those with BRCA1/2 mutations, have higher levels of genetic instability, potentially resulting in higher immunogenicity, and have been suggested to respond better to immune checkpoint inhibitors (ICIs) than homologous DNA repair-proficient OCs. However, clinical evidence is lacking. The study aimed to evaluate the associations between BRCA1/2 mutations, HRD, and other genomic parameters and response to ICIs and survival in OC. This is a single-institution retrospective analysis of women with recurrent OC treated with ICIs. BRCA1/2 mutation status and clinicopathologic variables were abstracted from the medical records. Targeted and whole-exome sequencing data available for a subset of patients were used to assess tumor mutational burden (TMB), HRD, and fraction of genome altered (FGA). ICI response was defined as lack of disease progression for ≥ 24 weeks. Associations of BRCA1/2 status and genomic alterations with progression-free survival (PFS) and overall survival (OS) were determined using Cox proportional hazards models. Of the 143 women treated with ICIs, 134 had known BRCA1/2 mutation status. Deleterious germline or somatic BRCA1/2 mutations were present in 31 women (24%). There was no association between presence of BRCA1/2 mutations and response (P = .796) or survival. Genomic analysis in 73 women found no association between TMB (P = .344) or HRD (P = .222) and response, PFS, or OS. There were also no significant differences in somatic genetic alterations between responders and nonresponders. High FGA was associated with an improvement in PFS (P = .014) and OS (P = .01). TMB, BRCA1/2 mutations, and HRD are not associated with response or survival, cautioning against their use as selection criteria for ICI in recurrent OC. FGA should be investigated further as a biomarker of response to immunotherapy in OC.

GeparOLA: A randomized phase II trial to assess the efficacy of paclitaxel and olaparib in comparison to paclitaxel/carboplatin followed by epirubicin/cyclophosphamide as neoadjuvant chemotherapy in patients (pts) with HER2-negative early breast cancer (BC) and homologous recombination deficiency (HRD).

506 Background: The efficacy and toxicity of olaparib in early BC pts with homologous DNA repair deficiency (here defined as HRD score high tumors +/- germline (g) or tumor (t) BRCA mutation) is not well described. GeparOLA investigates olaparib in HER2 negative early BC with HRD. Methods: GeparOLA (NCT02789332) randomized 102 pts to either paclitaxel 80 mg/m² weekly (Pw) plus olaparib 100 mg twice daily for 12 weeks (PwO n = 65) or Pw plus carboplatin (Cb) AUC2 weekly for 12 weeks (PwCb n = 37), both followed by EC. Randomization was stratified by hormone receptor-status (HR+ vs HR-) and age ( < 40 vs ≥40 years). Pts with untreated primary cT2 - cT4a-d or cT1c with either cN+ or pNSLN+ or triple negative or Ki-67 > 20% were included, with either g/t BRCA mutation and/or high HRD score. The primary endpoint is pathological complete response (pCR; ypT0/is ypN0). A one group χ2-test was planned to exclude the pCR rate of ≤55% in PwO→EC arm. Secondary endpoints are other pCR definitions, breast conservation rate, clinical and imaging response, tolerability and safety. Results: A total of 107 pts were randomized between 9/2016 and 7/2018; 106 started treatment. Median age was 47.0 years [range 25.0-71.0]; 36.2% of pts had cT1, 61.0% cT2, 2.9% cT3, and 31.8% cN-positive tumors; G3: 86.8%; Ki-67 > 20%: 89.6%; TNBC 72.6%; confirmed g /tBRCA 1/2 mutation: 60.4%. pCR rate with PwO was 55.1% (90%CI 44.5%-65.3%) vs PwCb 48.6% (90%CI 34.3%-63.2%). Analysis for the stratified subgroups showed higher pCR rates with PwO in the cohorts of pts < 40 years and HR+ pts Clinical trial information: NCT02789332. Conclusions: GeparOla could not exclude a pCR rate of ≤55% in the PwO arm. Subgroup analysis is hypothesis generating and need further confirmation.[Table: see text]

A randomized phase II trial to assess the efficacy of paclitaxel and olaparib in comparison to paclitaxel / carboplatin followed by epirubicin / cyclophosphamide as neoadjuvant chemotherapy in patients with HER2-negative early breast cancer and homologous recombination deficiency (HRD): GeparOLA.

506Background: The efficacy and toxicity of olaparib in early BC pts with homologous DNA repair deficiency (here defined as HRD score high tumors +/- germline (g) or tumor (t) BRCA mutation) is not...

Hereditary cancer syndromes: utilizing DNA repair deficiency as therapeutic target.

Human cells have numerous repair mechanisms to counteract various insults incurred on the DNA. Any mutation in these repair mechanisms can lead to accumulation of DNA errors and carcinogenesis. This review aims to discuss the therapeutic options in the two most common DNA repair deficient cancer syndromes, namely Lynch syndrome (hereditary non-polyposis colorectal cancer) and breast cancer susceptibility gene (BRCA) associated ovarian and breast cancer. Deficiency in DNA repair mechanisms renders these tumors with increased sensitivity to platinum agents. There has been increasing amount of information on the utility of the defects in DNA repair as targets for cancer therapy in these syndromes. Novel therapies like poly (ADP-ribose) polymerase (PARP) inhibitors are one of such example where the induction of double stranded breaks in DNA leads to tumoricidal effect in patients with homologous DNA repair deficiency. Interestingly, patients with DNA repair deficiencies tend to have a more favorable prognosis than sporadic malignancies. In microsatellite high colorectal cancer patients, this has been attributed to increased recruitment of CD8+ T lymphocytes in tumor microenvironment. However, these tumors are able to limit the host immune response by activation of immune checkpoints that seem like attractive targets of therapy in the future.

From breaking bad to worse: exploiting homologous DNA repair deficiency in cancer.

DNA repair deficiencies are common among cancer cells and represent a potential vulnerability that might be exploited by targeting compensatory repair pathways. However, the identification of synthetically lethal combinations of DNA repair defects, although of significant clinical relevance, has been somewhat anecdotal. Although numerous models have been proposed to explain synthetic lethality among DNA repair mutations, we have only a limited understanding of why a given mutation should render cells sensitive to another. In this issue of Cancer Discovery, Dietlein and colleagues define a general connection between mutations in genes involved in homologous recombination and sensitivity to inhibitors of non-homologous end joining. In doing so, they provide a mechanism to demarcate a set of seemingly diverse tumors that may be highly responsive to established DNA repair-targeted therapeutics.