Population-Based Genetic Testing for BRCA1 and BRCA2

Precision Medicine for BRCA/PALB2-Mutated Pancreatic Cancer and Emerging Strategies to Improve Therapeutic Responses to PARP Inhibition

Simple Summary

For the small subset of pancreatic ductal adenocarcinoma (PDAC) patients with loss-of-function mutations to BRCA1/2 or PALB2, both first-line and maintenance therapy differs significantly. These mutations confer a loss of double-strand break DNA homologous recombination (HR), substantially altering drug sensitivities. In this review, we discuss the current treatment guidelines for PDAC tumors deficient in HR, as well as newly emerging strategies to improve drug responses in this population. We also highlight additional patient populations in which these strategies may also be effective, and novel strategies aiming to confer similar drug sensitivity to tumors proficient in HR repair.

Abstract

Pancreatic cancer is projected to become the second leading cause of cancer-related death by 2030. As patients typically present with advanced disease and show poor responses to broad-spectrum chemotherapy, overall survival remains a dismal 10%. This underscores an urgent clinical need to identify new therapeutic approaches for PDAC patients. Precision medicine is now the standard of care for several difficult-to-treat cancer histologies. Such approaches involve the identification of a clinically actionable molecular feature, which is matched to an appropriate targeted therapy. Selective poly (ADP-ribose) polymerase (PARP) inhibitors such as Niraparib, Olaparib, Talazoparib, Rucaparib, and Veliparib are now approved for several cancers with loss of high-fidelity double-strand break homologous recombination (HR), namely those with deleterious mutations to BRCA1/2, PALB2, and other functionally related genes. Recent evidence suggests that the presence of such mutations in pancreatic ductal adenocarcinoma (PDAC), the most common and lethal pancreatic cancer histotype, significantly alters drug responses both with respect to first-line chemotherapy and maintenance therapy. In this review, we discuss the current treatment paradigm for PDAC tumors with confirmed deficits in double-strand break HR, as well as emerging strategies to both improve responses to PARP inhibition in HR-deficient PDAC and confer sensitivity to tumors proficient in HR repair.

Adherence to NCCN Guidelines for Genetic Testing in Breast Cancer Patients: Who Are We Missing?

BACKGROUND

Genetic predisposition accounts for 5-10% of all breast cancers (BC) diagnosed. NCCN guidelines help providers identify appropriate candidates for counseling and testing. Concerns about underutilization of genetic testing have spurred interest in broader peri-diagnostic testing. We evaluated surgeon adherence to NCCN guidelines and studied patterns of testing in newly diagnosed BC patients.

METHODS

A total of 397 patients were identified with newly diagnosed BC treated at our institution between 2016 and 2017 with no prior genetic testing. Eligibility for genetic testing based on NCCN criteria, referral, and patient compliance were recorded.

RESULTS

In total, 212 of 397 (53%) met NCCN testing criteria. Fifty-nine of 212 (28%) patients went untested despite meeting one or more criteria. Fourteen of 59 (24%) of these were referred but did not comply. Most common criteria for meeting eligibility for testing both in the overall cohort and among missed patients were family history-based. Age > 45 years old and non-Ashkenazi Jewish descent were predictive of missed referral (p < 0.01). We identified pathogenic mutations in 16 of 153 (10%) patients who did undergo testing (11 (7%) BRCA1 or 2 and 5 (3%) with other predisposition gene mutations) or 16 of 397 (4%) among the overall group.

CONCLUSIONS

Our data highlight the underutilization of genetic testing. Even in the setting of a full-service breast center with readily available genetic counseling, there is a substantial miss rate for identifying eligible patients, related to assessment of family history, patient age, and ethnicity, as well as patient compliance. Broader peri-diagnostic testing should be considered, and higher compliance rates with patients referred should be sought.

Genetic Testing and Results in a Population-Based Cohort of Breast Cancer Patients and Ovarian Cancer Patients

PURPOSE

Genetic testing for cancer risk has expanded rapidly. We examined clinical genetic testing and results among population-based patients with breast and ovarian cancer.

METHODS

The study included all women 20 years of age or older diagnosed with breast or ovarian cancer in California and Georgia between 2013 and 2014 and reported to the SEER registries covering the entire state populations. SEER data were linked to results from four laboratories that performed nearly all germline cancer genetic testing. Testing use and results were analyzed at the gene level.

RESULTS

There were 77,085 patients with breast cancer and 6,001 with ovarian cancer. Nearly one quarter of those with breast cancer (24.1%) and one third of those with ovarian cancer (30.9%) had genetic test results. Among patients with ovarian cancer, testing was lower in blacks (21.6%; 95% CI, 18.1% to 25.4%; v whites, 33.8%; 95% CI, 32.3% to 35.3%) and uninsured patients (20.8%; 95% CI, 15.5% to 26.9%; v insured patients, 35.3%; 95% CI, 33.8% to 36.9%). Prevalent pathogenic variants in patients with breast cancer were BRCA1 (3.2%), BRCA2 (3.1%), CHEK 2 (1.6%), PALB2 (1.0%), ATM (0.7%), and NBN (0.4%); in patients with ovarian cancer, prevalent pathogenic variants were BRCA1 (8.7%), BRCA2 (5.8%), CHEK2 (1.4%), BRIP1 (0.9%), MSH2 (0.8%), and ATM (0.6%). Racial/ethnic differences in pathogenic variants included BRCA1 (ovarian cancer: whites, 7.2%; 95% CI, 5.9% to 8.8%; v Hispanics, 16.1%; 95% CI, 11.8% to 21.2%) and CHEK2 (breast cancer: whites, 2.3%; 95% CI, 1.8% to 2.8%; v blacks, 0.1%; 95% CI, 0% to 0.8%). When tested for all genes that current guidelines designate as associated with their cancer type, 7.8% of patients with breast cancer and 14.5% of patients with ovarian cancer had pathogenic variants.

CONCLUSION

Clinically-tested patients with breast and ovarian cancer in two large, diverse states had 8% to 15% prevalence of actionable pathogenic variants. Substantial testing gaps and disparities among patients with ovarian cancer are targets for improvement.

The uptake of presymptomatic genetic testing in hereditary breast-ovarian cancer and Lynch syndrome: a systematic review of the literature and implications for clinical practice

Following the identification in a proband of a germline BRCA1/BRCA2 mutation in hereditary breast-ovarian cancer (HBOC) or a DNA mismatch repair gene mutation in Lynch syndrome (LS) he or she will be asked to inform at-risk family members about the option for presymptomatic DNA testing. However, in clinical practice multiple factors may complicate the process of information sharing. We critically evaluated studies on the uptake of presymptomatic genetic testing in both syndromes. A search of relevant MeSH terms and key words in PubMed, Embase and PsycINFO yielded 795 articles published between 2001 and 2017. Thirty of these publications included outcome measures relevant for the current study. Based on information provided by the proband (15 studies) the uptake of presymptomatic genetic testing ranged from 15 to 57% in HBOC, while one study in LS kindreds reported an uptake of 70%. Based on information provided by genetics centres (the remaining 15 studies) the uptake ranged from 21 to 44% in HBOC and from 41 to 94% in LS. However, when genetics centres contacted relatives directly a substantial number of additional family members could be tested. Proband-mediated provision of information to at-risk relatives is a standard procedure in hereditary breast-ovarian cancer and Lynch syndrome. However, the resulting uptake of presymptomatic testing is disappointing-an issue that is now urgent due to the increased use of genetic testing in clinical oncology. We propose that additional strategies should be introduced including the geneticist directly contacting relatives. The outcomes of these strategies should be carefully monitored and evaluated.