A Durable Response to Pembrolizumab in a Patient with Uterine Serous Carcinoma and Lynch Syndrome due to the MSH6 Germline Mutation.

Pembrolizumab, a programmed death 1 ligand (PD-1) checkpoint inhibitor, has elicited responses in mismatch repair (MMR)-deficient advanced solid tumors, leading to its agnostic approval by the US Food and Drug Administration in 2017 when no other therapeutic options are available. However, there are still insufficient data on the response to checkpoint inhibitors in advanced endometrial cancer related to Lynch syndrome (LS) and, specifically, in uterine serous carcinoma, which is uncommon in LS. Here we report a case of metastatic uterine serous carcinoma due to a germline MSH6 mutation (Lynch syndrome) that was discovered because of a patient's tumor MMR deficiency. The patient was started on first-line pembrolizumab in 2018 and sustained a partial response. She remains asymptomatic and progression free for more than 2 years. Tumor sequencing showed a high mutational burden and an upstream somatic mutation in the same gene, p.F1088fs. Immunohistochemical staining was negative for PD-L1 expression. We discuss clinical characteristics of the patient, molecular features of her tumor, and the mechanism of her tumor response. We also discuss the duration of immunotherapy in her case. Our case demonstrated a partial response and a long-term remission from the frontline single-agent pembrolizumab in a woman with metastatic uterine serous carcinoma and Lynch syndrome due to a germline MSH6 gene mutation. Our experience suggests a potential significant clinical benefit of checkpoint inhibitors used as single agents early on in the treatment of MMR-deficient/high microsatellite instability/hypermutated uterine cancers in women with Lynch syndrome. KEY POINTS: Even though checkpoint inhibitors are effective in mismatch repair-deficient endometrial cancer, it is unknown whether the response to them differs between women with endometrial cancer due to germline mutations in a mismatch repair gene (Lynch syndrome) and women with sporadic endometrial cancer. In our case, a patient with Lynch syndrome and recurrent mismatch repair-deficient serous endometrial cancer achieved a durable remission on the first-line therapy with the checkpoint inhibitor pembrolizumab and remains progression free after more than 2 years. Based on our observation and the data, suggesting the stronger immune activation in women with Lynch syndrome-associated endometrial cancer, we propose to use checkpoint inhibitor monotherapy early in the course of their treatment and stratify patients for the presence of Lynch syndrome in clinical trials.

Paired tumor sequencing and germline testing in breast cancer management: An experience of a single academic center.

BACKGROUND: Genetic testing for cancer predisposition is recommended to women with breast cancer who meet the criteria for such testing. After the FDA approvals of the poly ADP ribose polymerase (PARP) inhibitors, olaparib and talazoparib, for treatment of metastatic breast cancer, carrying germline mutations in BRCA1 and BRCA2 genes, the genetic testing result has become critical in their care. With the recent FDA approval of alpelisib for the treatment of PIK3CA-mutated hormone-receptor positive metastatic breast cancer, tumor molecular profiling to identify somatic mutations and potential molecularly targeted agents is increasingly utilized in the treatment of advanced breast cancer. AIM: Combining germline and somatic sequencing (paired testing) offers an advantage over a single technique approach. Our study evaluates the role of paired testing on the management of breast cancer patients. METHODS AND RESULTS: Forty-three breast cancer patients treated at Rush University Medical Center underwent paired germline and somatic variant testing in 2015 to 2017. A retrospective chart review was conducted with the analysis of demographic, clinical, and genomic data. Three actionable germline variants were found in the CHEK2 (2) and ATM (1) genes. 95% of tumors had somatic mutations. Seventy-seven percent of tumors had genomic alterations targetable with agents approved for breast cancer and 88% had molecular targets for agents approved for other cancers. Clinical examples of such use are described and potential future directions of tumor and paired testing are discussed. CONCLUSIONS: Germline variants were present in a relatively small patient group not routinely tested for inherited alterations. Potentially targetable somatic alterations were identified in the majority of breast cancers. Paired testing is a feasible and efficient approach that delivers valuable information for the care of breast cancer patients and eliminates serial testing.

Exceptional Response to Olaparib in a Patient With Recurrent Ovarian Cancer and an Entire BRCA1 Germline Gene Deletion.

PARP inhibitors are known to be effective in patients with ovarian cancer (OC) and germline mutations in BRCA1 and BRCA2 genes (BRCA mutations). Little is known, however, about any correlation between the deletion size and location of the BRCA mutation and the response to PARP inhibitors. Women with OC commonly undergo genetic testing because the presence of a germline BRCA mutation impacts therapeutic decisions and is important for cancer surveillance in patients and their family members. This report presents a case of a rare entire germline BRCA1 gene deletion and an exceptional response to a PARP inhibitor, olaparib, in a heavily pretreated patient with OC. Her disease course was also remarkable for complete responses to platinum-based chemotherapy and long chemotherapy-free intervals. Interestingly, the deletion of the entire BRCA1 gene was found after previously negative BRCA test results and is associated with a deletion of 6 adjacent genes without known clinical significance. She has remained progression-free and asymptomatic for >3 years on olaparib, with an overall survival of >12 years. We postulate that this unusually favorable response and prolonged overall survival is related to the cancer cells' inability to reverse the entire gene deletion to wild-type (a common mechanism of resistance to PARP inhibition). This case shows the value of genetic testing for patients with OC and highlights the utility of additional testing with previously negative results and limited genetic testing. It also provides insight into a potential mechanism of an exceptional response to PARP inhibition.

Somatic variants of potential clinical significance in the tumors of BRCA phenocopies.

BACKGROUND: BRCA phenocopies are individuals with the same phenotype (i.e. cancer consistent with Hereditary Breast and Ovarian Cancer syndrome = HBOC) as their affected relatives, but not the same genotype as assessed by blood germline testing (i.e. they do not carry a germline BRCA1 or BRCA2 mutation). There is some evidence of increased risk for HBOC-related cancers in relatives of germline variant carriers even though they themselves test negative for the familial variant (BRCA non-carriers). At this time, BRCA phenocopies are recommended to undergo the same cancer surveillance as individuals in the general population. This raises the question of whether the increased cancer risk in BRCA non-carriers is due to alterations (germline, somatic or epigenetic) in other cancer-associated genes which were not analyzed during BRCA analysis. METHODS: To assess the nature and potential clinical significance of somatic variants in BRCA phenocopy tumors, DNA from BRCA non-carrier tumor tissue was analyzed using next generation sequencing of 572 cancer genes. Tumor diagnoses of the 11 subjects included breast, ovarian, endometrial and primary peritoneal carcinoma. Variants were called using FreeBayes genetic variant detector. Variants were annotated for effect on protein sequence, predicted function, and frequency in different populations from the 1000 genomes project, and presence in variant databases COSMIC and ClinVar using Annovar. RESULTS: None of the familial BRCA1/2 mutations were found in the tumor samples tested. The most frequently occurring somatic gene variants were ROS1(6/11 cases) and NUP98 (5/11 cases). BRCA2 somatic variants were found in 2/6 BRCA1 phenocopies, but 0/5 BRCA2 phenocopies. Variants of uncertain significance were found in other DNA repair genes (ERCC1, ERCC3, ERCC4, FANCD2, PALB2), one mismatch repair gene (PMS2), a DNA demethylation enzyme (TET2), and two histone modifiers (EZH2, SUZ12). CONCLUSIONS: Although limited by a small sample size, these results support a role of selected somatic variants and epigenetic mechanisms in the development of tumors in BRCA phenocopies.

Misdiagnosis of Li-Fraumeni Syndrome in a Patient With Clonal Hematopoiesis and a Somatic TP53 Mutation.

Li-Fraumeni syndrome (LFS) is a rare genetic disorder that confers a high risk of developing certain malignancies at a young age. It is caused by germline mutations in the TP53 gene and is typically diagnosed by sequencing this gene in blood cells. The presence of a mutation in approximately half of the DNA reads (allelic fraction of 50%) is an indicator of a germline mutation, such as that in LFS. Clonal hematopoiesis (CH) is an expansion of a hematopoietic clone containing a somatic driver mutation with a low allelic fraction, usually not more than 10% to 20%. This report presents a patient with fallopian tube carcinoma who underwent multigene panel testing for cancer predisposition and was found to have a mutation in the TP53 gene, c.733G>T (p.Gly245Cys). Since the TP53 mutation had an allelic fraction of approximately 50%, it was interpreted as being germline, and the patient was diagnosed as having LFS. A year later, she developed acute myelogenous leukemia. Subsequent mutational analysis showed that the TP53 mutation was absent in her benign tissue sample but present in leukemic cells. Furthermore, sequencing of the fallopian tube tumor tissue revealed a different TP53 gene mutation, c.818G>T (p.Arg273Leu). These observations confirmed that the previously identified mutation in her blood was somatic rather than germline and that she had CH at the time of genetic testing. CH can occasionally lead to a misdiagnosis of a germline mutation and a cancer predisposition syndrome that has significant implications for patients and their families. Therefore, the abnormal result of genetic testing for hereditary cancer susceptibility should be carefully interpreted when the clinical presentation is atypical, when the patient is older, when the gene in question is known to have potential germline and somatic mutations such as the TP53 gene, and when the allelic fraction is approximately 50%.

Can chimerism explain breast/ovarian cancers in BRCA non-carriers from BRCA-positive families?

Hereditary breast and ovarian cancer syndrome (HBOC) is most frequently caused by mutations in BRCA1 or BRCA2 (in short, BRCA) genes. The incidence of hereditary breast and ovarian cancer in relatives of BRCA mutation carriers who test negative for the familial mutation (non-carriers) may be increased. However, the data is controversial, and at this time, these individuals are recommended the same cancer surveillance as general population. One possible explanation for BRCA phenocopies (close relatives of BRCA carriers who have developed cancer consistent with HBOC but tested negative for a familial mutation) is natural chimerism where lack of detectable mutation in blood may not rule out the presence of the mutation in the other tissues. To test this hypothesis, archival tumor tissue from eleven BRCA phenocopies was investigated. DNA from the tumor tissue was analyzed using sequence-specific PCR, capillary electrophoresis, and pyrosequencing. The familial mutations were originally detected in the patients' first-degree relatives by commercial testing. The same testing detected no mutations in the blood of the patients under study. The test methods targeted only the known familial mutation in the tumor tissue. Tumor diagnoses included breast, ovarian, endometrial and primary peritoneal carcinoma. None of the familial mutations were found in the tumor samples tested. These results do not support, but do not completely exclude, the possibility of chimerism in these patients. Further studies with comprehensive sequence analysis in a larger patient group are warranted as a chimeric state would further refine the predictive value of genetic testing to include BRCA phenocopies.

Hereditary diffuse gastric cancer and lynch syndromes in a BRCA1/2 negative breast cancer patient.

INTRODUCTION: Genetic counseling and testing is recommended for women with a personal and/or family history of breast and other cancers (ovarian, pancreatic, male breast and others). Mutations in the BRCA1 and BRCA2 genes (BRCA1/2) are the most common causes of hereditary breast and ovarian cancer. Additional genetic counseling and testing with a multi-gene panel may be considered in breast cancer patients who tested negative for mutations in these two genes. In about 11% of BRCA1/2-negative patients, further genetic testing reveals pathogenic mutations in other high or moderate cancer risk genes. In 0.2% of cases, an individual may carry pathogenic mutations in more than one high penetrance gene (a double heterozygote). Finding one or more pathogenic mutations is important for cancer prevention in patients and/or their families. CASE PRESENTATION: Here we present a case of a breast cancer patient who did not have a pathogenic mutation in BRCA1/2 and had a family history of breast and stomach cancers. On an additional multi-gene panel testing, she was found to carry pathogenic mutations in the CDH1 and PMS2 genes, which cause Hereditary Diffuse Gastric Cancer and Lynch syndromes, respectively. To our knowledge, this is the first description of such a double heterozygote. DISCUSSION: Clinical manifestations, genetics, and management of both syndromes are reviewed, including prophylactic surgery and screening for unaffected family members. Management challenges for a mutation carrier with advanced breast cancer are discussed. Our case supports the clinical utility of additional multi-gene panel testing for breast cancer patients who do not have a pathogenic mutation in BRCA1/2 genes.