Impact of Different BRCA1/2 Gene Variants on Response to Therapy and Prognosis of Ovarian Cancer

Ovarian carcinoma (OC) is the leading cause of death among gynaecological neoplasms. It is, in fact, a neoplasm that is not very frequent but highly lethal: in Emilia-Romagna, the incidence is about 17 cases per 100,000 inhabitants and the mortality rate is around 15 cases per 100,000, with a very high mortality/incidence ratio (0.83). The high mortality rate is mainly due to the fact that, due to the non-specific and late symptoms, 75-80% of patients arrive at the diagnosis at an advanced stage of the disease (III-IV), characterised by a 5-year survival of less than 25%. The primary therapeutic approach for this tumour is a combination of debulking surgery and platinum-based chemotherapy generally associated with taxanes, while as far as maintenance therapies are concerned, PARP inhibitors (PARPi), drugs capable of blocking a DNA repair mechanism alternative to that of homologous recombination, have been gaining in importance in recent years. They have proved particularly effective in tumours that present alterations in the BRCA1 and BRCA2 genes, which are key players in homologous recombination. For this reason, the detection of mutations in the BRCA1 and BRCA2 genes is predictive of the efficacy of PARPi maintenance therapy and, consequently, as of 2015, the BRCA test has been indicated in all women newly diagnosed with ovarian cancer (excluding borderline and mucinous forms), possibly from tumour tissue, given the evidence that in addition to constitutional (inherited) variants, somatic variants (acquired and tumour-confined), present in about 9%, are also associated with a PARPi benefit. Recent data, however, have challenged the assumption that functionally significant variants for which a predisposing role has been demonstrated for hereditary breast and ovarian cancers are necessarily predictive of drug response. Furthermore, the fact that somatic mutations are present in only a limited fraction of the DNA copies analysed in a tumour suggests that there may be residual BRCA activity that compromises effective PARPi activity.