Germline PALB2 Mutation in High-Risk Chinese Breast and/or Ovarian Cancer Patients

The prevalence of the PALB2 mutation in breast cancer varies across different ethnic groups; hence, it is of intense interest to evaluate the cancer risk and clinical association of the PALB2 mutation in Chinese breast and/or ovarian cancer patients. We performed sequencing with a 6-gene test panel (BRCA1, BRCA2, TP53, PTEN, PALB2, and CDH1) to identify the prevalence of the PALB2 germline mutation among 2631 patients with breast and/or ovarian cancer. In this cohort, 39 mutations were identified with 24 types of mutation variants, where the majority of the mutations were frame-shift mutations and resulted in early termination. We also identified seven novel PALB2 mutations. Most of the PALB2 mutation carriers had breast cancer (36, 92.3%) and were more likely to have family history of breast cancer (19, 48.7%). The majority of the breast tumors were invasive ductal carcinoma (NOS type) (34, 81.0%) and hormonal positive (ER: 32, 84.2%; PR: 23, 60.5%). Pathogenic mutations of PALB2 were found in 39 probands with a mutation frequency of 1.6% and 1% in breast cancer and ovarian cancer patients, respectively. PALB2 mutation carriers were more likely have hormonal positive tumors and were likely to have familial aggregation of breast cancer.

PALB2 mutation as a predictive biomarker for immunotherapy in patients with advanced melanoma: Results from (a pooled analysis of) five multicenter, randomized clinical trials.

e21537 Background: PALB2, a gene in the homologous recombination repair (HRR) pathway, has been shown to be associated with the efficacy of platinum based chemotherapy, and PARP inhibitor therapy in breast, prostate, ovarian, and pancreatic cancers. However, their predictive value of PALB2 remained unknown in patients with advanced melanoma. Methods: Five independent cohorts (Miao2018, Samstein2018, Allen 2015, Hugo2016, and Synder2014. study cohort) with data from 672 patients with advanced melanoma were used to analyze the correlation with immunogenic marker, and the prognostic effect of PALB2 on immunotherapy. Results: A pooled analysis of five independent cohorts of 672 advanced patients melanoma show that 31 (4.6%) harbored PALB2 mutation ( PALB2mut). PALB2mut (72.63Muts/Mb) was associated with higher tumor mutation burden (TMB) (P < 0.001) than PALB wild-type ( PALB2wt) (19.71Muts/Mb). The same phenomenon has also been observed in TNB, PALB2mut (1983 counts) was associated with higher tumor neoantigen burden (TNB) than PALB2wt (603.5 counts) (P = 0.0147). The objective response rate (ORR) of immunotherapy was 53.33% for the patients with PALB2mut and 24% for the PALB2wt subgroup (P = 0.027). The PALB2mut patients had significantly improved median overall survival (mOS) than the PALB2wt group (Not reach versus 29 months, hazard ratio (HR) = 0.38, 95%CI 0.19−0.73, P = 0.003). A subgroup analysis of CTLA4 inhibitor treatment found that PALB2mut was associated with better ORR (50% versus 18.3%, P = 0.016) on immunotherapy, and mOS in the PALB2mut group was significantly better than that in the PALB2wt group (Not reach versus 21 months, HR = 0.3, 95%CI 0.13−0.68, P = 0.002). However, in the subgroup receiving PD-L1 inhibitor treatment, no ORR benefit was found in the PALB2mut group (66.67% versus 56.76%, P = 1), and there was no difference on mOS between PALB2mut and PALB2wt (Not reach versus 31 months, HR = 0.45, 95%CI 0.11−1.8, P = 0.254). Conclusions: PALB2 mutations was associated with a higher TMB and TNB level. PALB2 may serve as a positive predictor of immunotherapy (CTLA4 inhibitor therapy) in patients with advanced melanoma and their clinical value warrants further investigation.

A phase II clinical trial of talazoparib monotherapy for PALB2 mutation-associated advanced breast cancer.

TPS1109 Background: PALB2 (Partner and Localizer of BRCA2) plays a critical role in the maintenance of genomic integrity through its role in the Fanconi anemia and homologous recombination DNA repair pathways. Our recently reported phase II clinical trial (Gruber, et al. JCO 2019) showed that talazoparib monotherapy was associated with single agent activity in germline PALB2 (gPALB2) mutation-associated advanced breast cancers. Of 5 patients with a germline PALB2 mutation, all 5 had reduction in target lesions > 20% with 3 of 5 achieving a RECIST 1.1 response. All patients had visceral metastases and were heavily pretreated; one response occurred in a patient with 8 prior lines of therapy for metastatic breast cancer. Clinical activity of the PARP inhibitor olaparib was also demonstrated in breast cancer patients with gPALB2 mutations in the Olaparib Expanded trial (TBCRC 048). Thus, we believe there is significant value in generating additional PARP inhibitor monotherapy data in subjects with advanced PALB2 mutation-associated breast cancer. We propose this phase II trial to better estimate the rate of RECIST 1.1 objective response in this patient population. Methods: This is a single-arm, two-stage, non-randomized study to assess the objective response rate (ORR) of talazoparib monotherapy in patients with PALB2 mutation-associated advanced breast cancer. Eligible subjects will be adults with inoperable locally advanced or metastatic breast cancer with a germline or somatic PALB2 mutation with 0-3 prior therapies for advanced disease. Eligible patients must have a deleterious or suspected deleterious mutation in PALB2 on a CLIA approved commercial germline or next generation sequencing tumor assay. Study treatment is talazoparib 1 mg PO daily. In stage 1, ORR will be assessed after 15 patients; if at least 2 responses are observed then an additional 15 patients will be enrolled; if less than 2 responses are observed the study will be terminated. The primary objective is to evaluate whether talazoparib monotherapy can induce a 30% ORR in subjects with advanced breast cancer associated with a PALB2 mutation. Response will be assessed by RECIST 1.1. Secondary objectives include safety, PFS, clinical benefit rate, and patient-reported quality-of-life. Exploratory endpoints will assess for the presence of PALB2 loss-of-heterozygosity, biallelic mutations, correlation of ctDNA profile with treatment response and the correlation of germline versus somatic mutations with response rate. This trial is currently activated and enrolling at Stanford Cancer Center and it is expected that 4 additional sites will be added. Conclusion: This trial will evaluate gPALB2 as a biomarker for PARP inhibitor monotherapy in advanced or metastatic HER2- breast cancer. Clinical trial information: pending .

A Case Report of Breast Implant–Associated Anaplastic Large-Cell Lymphoma in a PALB2 Mutation–Positive Woman

Breast implant–associated anaplastic large-cell lymphoma (BIA-ALCL) is a rare peripheral T-cell lymphoma composed of anaplastic pleomorphic T cells. The first case was reported in 1997 but was not recognized until 2016 by the World Health Organization. The exact incidence is unknown but is estimated to be 0.1 to 0.3 per 100,000 women with implants. Almost every case has been found in women with textured breast implants. The median time of onset after implantation is 10.7 years. Patients presenting with localized disease, most commonly manifesting as breast enlargement, can be managed solely with surgical resection and have a 100% survival rate. This report describes a PALB2 mutation–positive woman with a strong family history of breast cancer who underwent prophylactic bilateral nipple-sparing mastectomy with textured silicone implant placement. She was diagnosed with BIA-ALCL less than 4 years later after seroma aspiration. She was treated with implant removal and capsulectomy; but, surprisingly, final surgical pathology did not show any malignancy.

Solitary Brain Metastasis of Prostate Adenocarcinoma with Normal PSA and PALB2 Mutation

"Prostate cancer is the second most frequent malignancy worldwide, with an increased incidence over the last two decades. Most patients are asymptomatic at diagnosis due to widespread opportunistic prostate-specific antigen-based screening. Cerebral metastases originating from prostatic tumors are rare, occurring in 0.16% to 0.63% of prostate cancer cases, and generally developing in the setting of widespread disease. We report the case of a 62-year-old male with symptomatic isolated brain metastasis as an early clinical presentation of prostate adenocarcinoma in the setting of a normal PSA and digital rectal examination. Next-generation sequencing panel revealed a mutation in the PALB2 gene. Germline mutation in genes involved in homologous recombination repair complex, such as BRCA1, BRCA2, and PALB2 increase the incidence and the aggressiveness of multiple cancer types including prostate cancer, yet can provide alternative treatment options using PARP inhibitors after disease progression for patients previously treated with enzalutamide or abiraterone."

Clinicopathologic features of invasive breast cancer (BC) diagnosed in carriers of germline PALB2, CHEK2 and ATM pathogenic variants.

1549 Background: While germline pathogenic variants (PVs) in BRCA1/2 account for a large proportion of hereditary breast cancer (BC), PVs in PALB2, CHEK2 and ATM are increasingly detected. However, the phenotype and clinical features of invasive BC with these PVs have not been fully described. Methods: We identified patients with a PV or likely PV in PALB2, CHEK2 or ATM tested clinically at Stanford between 2014 - 2019 who provided informed consent to be included in a prospective cancer genetics registry. Data on baseline demographics, genetic testing history, and clinicopathologic features of diagnosed BC were collected. For patients with a subsequent diagnosis of metastatic BC, we calculated disease-free interval (DFI). Results: 130 patients met inclusion criteria for analysis: ATM (N=39), CHEK2 (N=58), PALB2 (N=33). Nearly all (98.5%) were women, with 2 male BC in ATM carriers. Non-Hispanic White ethnicity was most common in ATM (64.1%, 95% CI 48.4%-77.3%) and CHEK2 carriers (69.0%, 95% CI 56.1%-79.4%), but comprised only 39.4% (95% CI 24.7%-56.4%) in PALB2 carriers. Asian/Pacific Islander (24.2%, 95% CI 12.6%-41.3%) and Hispanic (30.3%, 95% CI 17.3%-47.5%) ethnicities were enriched among PALB2 mutation carriers. In total, 97.7% learned of their PV status only after a preceding diagnosis of BC and 43.1% were diagnosed with BC at age ≤ 45. Data regarding invasive BC subtypes, incidence of subsequent primary BC, and metastatic recurrence are listed below in the table. Additional data on stage, grade and sites of metastatic spread will be presented. Conclusions: We observed clinically important differences in the spectrum of BC subtypes among carriers of ATM, CHEK2 and PALB2 PVs, in addition to racial/ethnic differences with Asian/Pacific Islander and Hispanic ethnicity enriched among carriers of PALB2 PVs. [Table: see text]

Randomized, Multicenter, Phase II Trial of Gemcitabine and Cisplatin With or Without Veliparib in Patients With Pancreas Adenocarcinoma and a Germline BRCA/PALB2 Mutation

PURPOSE Five percent to 9% of pancreatic ductal adenocarcinomas (PDACs) develop in patients with a germline BRCA1/2 or PALB2 (g BRCA/PALB2+) mutation. Phase IB data from a trial that used cisplatin, gemcitabine, and veliparib treatment demonstrated a high response rate (RR), disease control rate (DCR), and overall survival (OS) in this population. We designed an open-label, randomized, multicenter, two-arm phase II trial to investigate cisplatin and gemcitabine with or without veliparib in g BRCA/PALB2+ PDAC. PATIENTS AND METHODS Eligible patients had untreated g BRCA/PALB2+ PDAC with measurable stage III to IV disease and Eastern Cooperative Oncology Group performance status of 0 to 1. Treatment for patients in arm A consisted of cisplatin 25 mg/m2 and gemcitabine 600 mg/m2 intravenously on days 3 and 10; treatment for patients in arm B was the same as that for patients in arm A, and arm A also received veliparib 80 mg orally twice per day on days 1 to 12 cycled every 3 weeks. The primary end point was RRs of arm A and arm B evaluated separately using a Simon two-stage design. Secondary end points were progression-free survival, DCR, OS, safety, and correlative analyses. RESULTS Fifty patients were evaluated by modified intention-to-treat analysis. The RR for arm A was 74.1% and 65.2% for arm B ( P = .55); both arms exceeded the prespecified activity threshold. DCR was 100% for arm A and 78.3% for arm B ( P = .02). Median progression-free survival was 10.1 months for arm A (95% CI, 6.7 to 11.5 months) and 9.7 months for arm B (95% CI, 4.2 to 13.6 months; P = .73). Median OS for arm A was 15.5 months (95% CI, 12.2 to 24.3 months) and 16.4 months for arm B (95% CI, 11.7 to 23.4 months; P = .6). Two-year OS rate for the entire cohort was 30.6% (95% CI, 17.8% to 44.4%), and 3-year OS rate was 17.8% (95% CI, 8.1% to 30.7%). Grade 3 to 4 hematologic toxicities for arm A versus arm B were 13 (48%) versus seven (30%) for neutropenia, 15 (55%) versus two (9%) for thrombocytopenia, and 14 (52%) versus eight (35%) for anemia. CONCLUSION Cisplatin and gemcitabine is an effective regimen in advanced g BRCA/PALB2+ PDAC. Concurrent veliparib did not improve RR. These data establish cisplatin and gemcitabine as a standard approach in g BRCA/ PALB2+ PDAC.