DNA Repair Biomarkers to Guide Usage of Combined PARP Inhibitors and Chemotherapy: a Meta-Analysis and Systematic Review

Purpose The addition of PARP inhibitors to chemotherapy has been assessed in ∼80 clinical trials across multiple malignancies, on the premise that PARP inhibitors will increase chemotherapy effectiveness regardless of whether cancers have underlying disruption of DNA repair pathways. Consequently, the majority of combination therapy trials have been performed on patients without biomarker selection, despite the use of homologous recombination deficiency to dictate use of PARP inhibitors in the maintenance setting. An unresolved question is whether biomarkers are needed to identify patients who respond to combination PARP inhibitors and chemotherapy. Methods A systematic literature review identified studies using PARP inhibitors in combination with chemotherapy versus chemotherapy alone, where the study included a biomarker of DNA repair function ( BRCA1 , BRCA2 , BRCAPRO, ATM, ERCC1, SFLN11). Hazard ratios (HR) were pooled in a meta-analysis using generic inverse-variance and fixed or random effects modelling. Subgroup analyses were conducted on biomarker selection and type of malignancy. Results Nine studies comprising 2,084 patients met the inclusion criteria. Progression-free survival (PFS) was significantly better in patients with a DNA repair biomarker (HR 0.52, 95% confidence interval (CI) 0.43-0.63; p < 0.00001), but there was no benefit in patients who lacked a biomarker (HR 0.94, 95% CI 0.82–1.08; p = 0.38). Subgroup analysis showed that BRCA mutation and SFLN11 biomarkers could predict benefit, and biomarker-driven benefit occurred in ovarian, breast and small cell lung cancers. The addition of PARP inhibitors was associated with increased grade 3/4 side effects, and particularly neutropenia. Conclusions Combination therapy only increases PFS in patients with identifiable DNA repair biomarkers. This indicates that PARP inhibitors do not sensitise patients to chemotherapy treatment, except where their cancer has a homologous recombination defect, or an alternative biomarker of altered DNA repair. While effective in patients with DNA repair biomarkers, there is a risk of high-grade haematological side-effects with the use of combination therapy. Thus, the benefit in PFS from combination therapy must be weighed against potential adverse effects, as individual arms of treatment can also confer benefit. ![Figure][1] GRAPHICAL ABSTRACT ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research was generously supported by the Dr Lee MacCormick Edwards Charitable Foundation. C.E.C. is supported by a Cancer Institute NSW Career Development Fellowship (CDF1071). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Data from published studies was analysed as a meta-analysis, and all publications are appropriately cited in the text. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors. [1]: pending:yes