Analysis of real-world (RW) data for metastatic breast cancer (mBC) patients (pts) with somatic BRCA1/2 (sBRCA) or other homologous recombination (HR)-pathway gene mutations (muts) treated with PARP inhibitors (PARPi)

10512

Background: PARPi are approved for treatment of pts w/ HER2-negative mBC and germline BRCA1/2 (g BRCA) pathogenic or likely pathogenic variants (muts); however, clinical benefit has also been demonstrated in mBC pts w/ sBRCA or other HR-pathway gene muts. Using a RW Clinico-Genomic Database (CGDB), we assessed outcomes for pts w/ gBRCA muts compared to pts w/ either s BRCA or other HR-pathway muts treated w/ PARPi. Methods: 6,329 mBC pts from ̃280 US cancer clinics were included in the Flatiron Health (FH) -Foundation Medicine (FM) CGDB, which includes comprehensive genomic profiling (CGP) linked to de-identified, electronic health record (EHR)-derived clinical data. Eligible pts had mBC, received care in the FH network from 1/1/2011-9/1/2020, and had tissue CGP by FM. Pts classified as gBRCA: positive germline result in EHR and BRCA mut predicted germline per FM’s somatic, germline, zygosity algorithm (SGZ) (Sun et al PMID 29415044). Non-g BRCA: negative germline results in EHR and a somatic BRCA (s BRCA) mut per SGZ or BRCA wild-type w/ another HR mut per CGP result. Pts w/o a documented gBRCA result in EHR, unknown FM BRCA SGZ result, or conflicting results were excluded. RW overall survival (rwOS) and RW progression-free survival (rwPFS) from start of PARPi for pts w/ gBRCA and non- gBRCA mBC were compared using Kaplan-Meier analysis and Cox regression adjusted for mBC line number, prior platinum, age at PARPi initiation, race, and receptor status. Results: Among pts who received PARPi in the mBC setting, 44 had gBRCA and 18 had non -gBRCA: 9 s BRCA (5 BRCA1, 4 BRCA2), 4 PALB2, 2 ATM, and 1 each of ATM+CDK12, BARD1+FANCF+RAD54L, and CHEK2. Of HR muts 76% were confirmed biallelic: 33/44 gBRCA (11 unknown), 8/9 sBRCA, 3/4 PALB2, and 3/5 other (1 unknown). Neither median rwPFS nor rwOS from start of PARPi were significantly different between the non-g BRCA and g BRCA cohorts (rwPFS: 7.0 [4.6-11.3] vs 5.5 [4.3-7.2] months (mos), aHR: 1.19 [0.57 – 2.43]; rwOS: 15.0 [7.95-16.3] vs 11.5 [9.46-NA] mos, aHR: 0.85 [0.36-1.98]). For 9 pts w/ sBRCA mut, median rwPFS was 7.1 mos (range 1.4-12.4) and all pts had progressed by data cut off. Conclusions: Despite small pt numbers and limitations from RW data, our results suggest that pts w/ biallelic non-g BRCA mBC may derive similar benefit from PARPi when tumor CGP detects a s BRCA mut or germline or somatic mut in other HR-pathway genes. These findings are consistent w/ the results from TBCRC-048 (Tung et al PMID 33119476) and support further randomized trials exploring the efficacy of PARPi in this population.[Table: see text]

A011801 (CompassHER2 RD): Postneoadjuvant T-DM1 + tucatinib/placebo in patients with residual HER2-positive invasive breast cancer

TPS595

Background: Patients (pts) with HER2+ early breast cancer (EBC) and invasive residual disease (RD) after neoadjuvant therapy (NAT) have a higher risk of relapse than pts with a pathologic complete response (pCR). Post neoadjuvant T-DM1 has improved invasive disease-free survival (iDFS), but pts with estrogen receptor (ER)-negative or nodal RD have suboptimal outcomes and recurrences in the central nervous system are a problem. More effective treatment strategies are needed. The CompassHER2 trials, EA1181 and A011801, leverage pCR to tailor post neoadjuvant therapy in HER2+ EBC. EA1181 is a NAT de-escalation trial of a taxane, trastuzumab and pertuzumab (THP) in clinical stage II-III HER2+ EBC; pts with a pCR complete HP +/- adjuvant radiation (RT) +/- endocrine therapy (ET). A011801 is an escalation trial for pts with high risk HER2+ RD after NAT, examining addition of the HER2 selective tyrosine kinase inhibitor (TKI) tucatinib to adjuvant T-DM1. Methods: Eligibility and Intervention: Pts. with high-risk HER2+ RD (e.g. ER-,node-positive, or both) after a predefined course of neoadjuvant HER2-directed treatment are randomized 1:1 to adjuvant T-DM1+ placebo (pb), vs. T-DM1 and tucatinib with adjuvant RT +/- ET. Eligibility criteria include completion of ≥ 6 cycles of NAT, including ≥ 9 weeks of T and H +/- P. All chemotherapy (CT) must be completed preoperatively unless participating in EA1181 (̃15-30% enrollees); these pts must receive postoperative CT to complete ≥ 6 cycles prior to enrollment on A011801. Pts who received prior HER2-targeted TKIs or antibody-drug conjugates are ineligible. Objectives: The primary objective is to determine if iDFS is higher with addition of T-DM1 to tucatinib in pts with HER2+ EBC with RD after NAT; secondary endpoints include overall survival, breast cancer free survival, distant recurrence-free survival, brain metastases-free survival and disease-free survival. Correlative objectives include the association of i) tumor infiltrating lymphocyte (TILs) levels in the primary tumor and RD with iDFS, ii) TILs with tucatinib benefit, iii) iDFS and circulating tumor cells (CTC) at serial timepoints and iv) the magnitude of benefit of tucatinib (iDFS) in pts with/without detectable pretreatment CTCs. Quality of life and pharmacokinetic endpoints will also be evaluated. Statistics: A011801 is a prospective, double-blind, randomized, phase III superiority trial; stratified by i) receipt of postoperative CT (Y/N), ii) hormone receptor-status (+/-),and iii) pathologic lymph node status (+/-). The study targets an absolute difference of 5% in iDFS (control vs. experimental arm 82% & 87%, HR = 0.7), with a two-sided alpha of 0.05 and power of 80%. The sample size is 981; target accrual = 1031 pts; activation and completion dates are 01/6/21 and ̃ 01/2028. Support: U10CA180821, U10CA180882; Seagen Inc; ClinicalTrials.gov Identifier: NCT04457596 Clinical trial information: NCT04457596.

Limitations of direct-to-consumer (DTC) genetic testing for hereditary breast and ovarian cancer

10515

Background: With the advent of DTC genetic testing, individuals have access to genetic testing without input from a healthcare professional. DTC testing now exists for the 3 Ashkenazi Jewish (AJ) BRCA1/2 founder variants. DTC testing may provide false reassurance to individuals that they do not carry a pathogenic or likely pathogenic variant (PLPV) in BRCA1/2 or other cancer-risk genes. Methods: Multi-panel genetic testing was performed in 348,692 individuals for a clinical indication of hereditary breast/ovarian cancer (Clinical cohort) and 7,636 self-referred ostensibly healthy individuals (Healthy cohort) by a clinical testing laboratory. The primary analysis evaluated PLPVs for Group 1 genes: BRCA1/2 AJ founder variants and Group 2: full sequence BRCA1/2. Secondary analyses assessed PLPVs in Group 3: high-risk breast cancer genes ( BRCA1/2, CDH1, PALB2, PTEN, STK11, TP53), Group 4: all breast or ovarian cancer-risk genes (Group 3 genes plus ATM, BARD1, BRIP1, truncating CHEK2, EPCAM, MLH1, MSH2/6, NF1, PMS2, RAD51C/D) and Group 5: 41 cancer-risk genes; these analyses were limited to participants who tested for all 41 genes. Potentially mosaic variants were excluded. Results: Table illustrates PLPVs found in both cohorts. The BRCA1/2 AJ founder variants account for only ̃11% (1513/13,987) and ̃30% (19/64) of the BRCA PLPVs in the Clinical and Healthy cohorts, respectively. Even among AJ individuals, testing only for the 3 founder variants will miss ̃10% (52/513) of all BRCA1/2 PLPVs. Evaluating only the BRCA AJ founder variants missed a higher percentage of PLPVs in other cancer-risk genes. Conclusions: The 3 BRCA1/2 AJ founder variants analyzed by DTC testing account for a small fraction of PLPVs in cancer-risk genes in the general population, and miss 10% of BRCA PLPVs even among AJ individuals. Greater public education is needed to dispel the misconception that DTC tests are equivalent to clinical assessment and comprehensive genetic testing. PLPVs identified in Clinical and Healthy Cohorts.[Table: see text]

Twenty-one-gene recurrence score (RS) in germline (g)CHEK2 mutation-associated versus sporadic breast cancers (BC): A multi-site case-control study

10531

Background: Genomic assays, such as RS, are used to determine chemotherapy benefit in early-stage, estrogen receptor (ER)- and/or progesterone receptor (PR)-positive, HER2 negative BC patients (pts). Currently, guidelines to use pts’ germline genetic testing results to guide adjuvant therapy are lacking. Several reports have indicated worse outcomes for BC pts with g CHEK2 pathogenic variants (PV). We investigated whether PV in CHEK2 were associated with increased RS. Methods: Patient-level clinical data and RS were derived from electronic medical records of seven medical centers between years 2013-17. Confirmation of RS using the Genomic Health provider portal was performed. 38 pts with germline PV in CHEK2 (15 pts/39.5% with c.1100delC mutation) and RS score (cases) were matched with BC pts whose genetic testing did not identify PV (controls) using a 1:2 matching schema. Pts were matched based on age at diagnosis and lymph node (LN) status. LN negative pts were further matched based on T-stage. A multivariate random intercept linear mixed model of CHEK2 mutation status on RS was performed, adjusting for PR. A secondary ordinal univariate analysis was conducted that categorized RS into low, intermediate and high risk ( < 18, 18-30, and > 30, respectively). P-values were reported based on a null hypothesis of no effect against a two-sided alternative. Results: The median RS for cases was 19.5 (interquartile range [IQR]: 15 to 25) and the median RS for controls was 18 (IQR: 12 to 22). A greater proportion of cases were categorized as high risk (10.5%) compared to controls (5.6%), and a smaller proportion of cases were categorized as low risk (36.8%) compared to controls (49.3%). Cases had higher grade and increased proportion of PR-negative BC as compared with controls (grade 1: 12.1% of cases versus 32.4% of controls; PR-negative: 7.9% of cases versus 5.6% of controls). The variables used to match cases and controls (age, lymph node status, and T-stage) had similar summary statistics. The RS was 1.97-point higher in pts with g CHEK2 PV compared to controls, after adjusting for PR (95% confidence interval [CI]: 1.02-point lower to 4.96-point higher; p = 0.194). The secondary analysis of CHEK2 mutation status on an ordinal RS risk group yielded comparable results; on average, the odds of being high risk compared to the combined intermediate/low risk groups was 1.72 times higher in cases compared to controls (95% CI: 0.77 to 3.80; p = 0.181), but these differences were not significant. Conclusions: Our case-control study did not show a statistically higher RS for BC that develops in pts with g CHEK2 PV. Further studies are warranted to evaluate the association between type of CHEK2 PV (frameshift versus missense) and other modifying genetic variables and RS.

Updated Standardized Definitions for Efficacy End Points (STEEP) in Adjuvant Breast Cancer Clinical Trials: STEEP Version 2.0

PURPOSE

The Standardized Definitions for Efficacy End Points (STEEP) criteria, established in 2007, provide standardized definitions of adjuvant breast cancer clinical trial end points. Given the evolution of breast cancer clinical trials and improvements in outcomes, a panel of experts reviewed the STEEP criteria to determine whether modifications are needed.

METHODS

We conducted systematic searches of ClinicalTrials.gov for adjuvant systemic and local-regional therapy trials for breast cancer to investigate if the primary end points reported met STEEP criteria. On the basis of common STEEP deviations, we performed a series of simulations to evaluate the effect of excluding non-breast cancer deaths and new nonbreast primary cancers from the invasive disease-free survival end point.

RESULTS

Among 11 phase III breast cancer trials with primary efficacy end points, three had primary end points that followed STEEP criteria, four used STEEP definitions but not the corresponding end point names, and four used end points that were not included in the original STEEP manuscript. Simulation modeling demonstrated that inclusion of second nonbreast primary cancer can increase the probability of incorrect inferences, can decrease power to detect clinically relevant efficacy effects, and may mask differences in recurrence rates, especially when recurrence rates are low.

CONCLUSION

We recommend an additional end point, invasive breast cancer-free survival, which includes all invasive disease-free survival events except second nonbreast primary cancers. This end point should be considered for trials in which the toxicities of agents are well-known and where the risk of second primary cancer is small. Additionally, we provide end point recommendations for local therapy trials, low-risk populations, noninferiority trials, and trials incorporating patient-reported outcomes.

Germline genetic testing in breast cancer: Rationale for the testing of all women diagnosed by the age of 60 years and for risk-based testing of those older than 60 years

Approximately 5% to 10% of women diagnosed with breast cancer will have a pathogenic variant (PV) in a hereditary cancer susceptibility gene, and this has significant implications for the management of these patients and their relatives. Despite the benefits of genetic testing, many eligible patients with breast cancer never undergo testing because of various barriers, including complicated testing criteria such as those from the National Comprehensive Cancer Network (NCCN). In 2019, the American Society of Breast Surgeons (ASBrS) proposed germline genetic testing for all patients with breast cancer to increase the identification of PV carriers. In 2020, a Mayo Clinic study highlighted the limitations of these 2 genetic testing guidelines (NCCN and ASBrS) and proposed a hybrid approach of testing all women diagnosed with breast cancer by the age of 65 years and using NCCN criteria for older patients. This commentary presents an updated analysis of the Mayo Clinic data and discusses the rationale for using the age of 60 years rather than 65 years as the cutoff for this hybrid approach. Using an age at diagnosis of ≤60 or ≤65 years for the universal testing of patients with breast cancer detected more PVs (11.9% [16 of 134] and 15.7% [21 of 134], respectively) in comparison with using the NCCN criteria. Lowering the age for universal testing from 65 to 60 years maintained the sensitivity of detecting a PV at >90% while sparing testing for an additional 10% of women. Compared with the testing of all patients, the hybrid approach would allow 31% of all women with breast cancer to forgo testing and result in fewer variants of uncertain significance identified and, therefore, would decrease the chance of harm from misinterpretation of these variants.

TBCRC 048: Phase II Study of Olaparib for Metastatic Breast Cancer and Mutations in Homologous Recombination-Related Genes

PURPOSE

Olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor (PARPi), is approved for the treatment of human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) in germline (g)BRCA1/2 mutation carriers. Olaparib Expanded, an investigator-initiated, phase II study, assessed olaparib response in patients with MBC with somatic (s)BRCA1/2 mutations or g/s mutations in homologous recombination (HR)-related genes other than BRCA1/2.

METHODS

Eligible patients had MBC with measurable disease and germline mutations in non-BRCA1/2 HR-related genes (cohort 1) or somatic mutations in these genes or BRCA1/2 (cohort 2). Prior PARPi, platinum-refractory disease, or progression on more than two chemotherapy regimens (metastatic setting) was not allowed. Patients received olaparib 300 mg orally twice a day until progression. A single-arm, two-stage design was used. The primary endpoint was objective response rate (ORR); the null hypothesis (≤ 5% ORR) would be rejected within each cohort if there were four or more responses in 27 patients. Secondary endpoints included clinical benefit rate and progression-free survival (PFS).

RESULTS

Fifty-four patients enrolled. Seventy-six percent had estrogen receptor-positive HER2-negative disease. Eighty-seven percent had mutations in PALB2, sBRCA1/2, ATM, or CHEK2. In cohort 1, ORR was 33% (90% CI, 19% to 51%) and in cohort 2, 31% (90% CI, 15% to 49%). Confirmed responses were seen only with gPALB2 (ORR, 82%) and sBRCA1/2 (ORR, 50%) mutations. Median PFS was 13.3 months (90% CI, 12 months to not available/computable [NA]) for gPALB2 and 6.3 months (90% CI, 4.4 months to NA) for sBRCA1/2 mutation carriers. No responses were observed with ATM or CHEK2 mutations alone.

CONCLUSION

PARP inhibition is an effective treatment for patients with MBC and gPALB2 or sBRCA1/2 mutations, significantly expanding the population of patients with breast cancer likely to benefit from PARPi beyond gBRCA1/2 mutation carriers. These results emphasize the value of molecular characterization for treatment decisions in MBC.

Medical Management of newly diagnosed breast cancer in a BRCA1/2 mutation carrier

Germline BRCA1/2 mutations may be infrequent in unselected breast cancer population but are concentrated in those with triple-negative breast cancer or high-risk family history. Insight into the biology of BRCA mutation is now allowing a targeted therapeutic approach to these carriers with breast cancer. Functional BRCA genes play a critical role in DNA damage repair. Agents such as platinum salts and poly (ADP-ribose) polymerase (PARP) inhibitors exploit this vulnerability of impaired DNA damage repair mechanism in BRCA mutant cancers to leverage therapeutic benefit. Research has demonstrated improved response rates to platinum salts in BRCA-mutated compared with non-BRCA-mutated breast cancer, particularly in the metastatic setting. Additionally, clinical trials of single-agent PARP inhibitors have shown encouraging response rates and progression-free survival in patients with BRCA1/2-mutated breast cancer. In this review, we summarize the medical management of BRCA-associated breast cancer.

Management of Hereditary Breast Cancer: American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology Guideline

PURPOSE

To develop recommendations for management of patients with breast cancer (BC) with germline mutations in BC susceptibility genes.

METHODS

The American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology convened an Expert Panel to develop recommendations based on a systematic review of the literature and a formal consensus process.

RESULTS

Fifty-eight articles met eligibility criteria and formed the evidentiary basis for the local therapy recommendations; six randomized controlled trials of systemic therapy met eligibility criteria.

RECOMMENDATIONS

Patients with newly diagnosed BC and BRCA1/2 mutations may be considered for breast-conserving therapy (BCT), with local control of the index cancer similar to that of noncarriers. The significant risk of a contralateral BC (CBC), especially in young women, and the higher risk of new cancers in the ipsilateral breast warrant discussion of bilateral mastectomy. Patients with mutations in moderate-risk genes should be offered BCT. For women with mutations in BRCA1/2 or moderate-penetrance genes who are eligible for mastectomy, nipple-sparing mastectomy is a reasonable approach. There is no evidence of increased toxicity or CBC events from radiation exposure in BRCA1/2 carriers. Radiation therapy should not be withheld in ATM carriers. For patients with germline TP53 mutations, mastectomy is advised; radiation therapy is contraindicated except in those with significant risk of locoregional recurrence. Platinum agents are recommended versus taxanes to treat advanced BC in BRCA carriers. In the adjuvant/neoadjuvant setting, data do not support the routine addition of platinum to anthracycline- and taxane-based chemotherapy. Poly (ADP-ribose) polymerase (PARP) inhibitors (olaparib and talazoparib) are preferable to nonplatinum single-agent chemotherapy for treatment of advanced BC in BRCA1/2 carriers. Data are insufficient to recommend PARP inhibitor use in the early setting or in moderate-penetrance carriers. Additional information available at www.asco.org/breast-cancer-guidelines.

TBCRC 048: A phase II study of olaparib monotherapy in metastatic breast cancer patients with germline or somatic mutations in DNA damage response (DDR) pathway genes (Olaparib Expanded)

1002

Background: Olaparib, a PARP inhibitor, is approved for HER2-negative MBC in g BRCA1/2 mutation carriers. Olaparib Expanded, an investigator-initiated study, assessed the response to olaparib in MBC patients with sBRCA1/2 mutations or g/s mutations in DDR-pathway genes other than BRCA1/2. Methods: Eligibility included: MBC with measurable disease; progression on < 2 metastatic chemotherapy regimens. Prior PARP inhibitor or progression on platinum was not allowed. Cohort 1 included patients with germline mutations in non- BRCA1/2 DDR-pathway genes. In Cohort 2 were those with somatic mutations in these genes or BRCA1/2; germline testing was required only to exclude a gBRCA mutation if a s BRCA mutation was present. Patients received olaparib 300 mg bid until progression or unacceptable toxicity. For each cohort, a single-arm Simon two-stage design was used with 13 then 14 patients in the 1st and 2nd stages, respectively. The null hypothesis within each cohort [≤ 5% objective response rate (ORR)] would be rejected if > 4 responses were seen at the end of stage 2. Secondary endpoints include clinical benefit rate, progression-free survival, and duration of response. Results: 54 patients enrolled from March 2018 to Jan 2020; 1 ineligible s BRCA2 was excluded. Median age was 59 yrs (range: 30-87). 40 patients had ER+ HER2-, 3 HER2+, and 10 TNBC. 87% had a mutation in PALB2, s BRCA1/2, ATM or CHEK2. ORR was 29.6% (8/27, 90%-CI: 15.6%-47.1%) in Cohort 1 and 38.5% (10/26, 90%-CI: 22.5%-56.4%) in Cohort 2. Responses were gene specific (Table): g PALB2 and s BRCA mutations predicted response; no responses were seen with only a CHEK2 or ATM mutation. To date, responses as long as 16.4 months have been observed. Responses were seen in all subtypes: 5/10 TNBC, 1/3 HER2+, 12/40 ER+ HER2-. 11 responses occurred after prior CDK4/6 inhibitor. In June 2020, final data for confirmed ORR and secondary endpoints will be reported. Conclusion: In this proof-of-principle study, single-agent olaparib successfully met its primary endpoint in both cohorts. Activity was seen largely in patients with MBC and s BRCA1/2 or g PALB2 mutations but not with ATM or CHEK2 mutations. Clinical trial information: NCT03344965 . [Table: see text]

The BRCA founder outreach study: Initial results of a digital health model

2007

Background: NCCN now endorses BRCA founder mutation genetic testing (GT) via longitudinal studies in all Ashkenazi Jewish (AJ) individuals. The BRCA Founder OutReach (BFOR) study offers pre-GT online education with posttest engagement of primary care providers (PCPs). Methods: The study in 4 US cities enrolls those age > 25 with > 1 AJ grandparent. Participants enroll online with chatbot and video education, have GT at local centers, receive results from their PCP or BFOR staff, and are surveyed 12 weeks post disclosure and annually for 5 years. Univariate analyses and multivariable (MV) logistic regression models were used to evaluate characteristics associated with not completing GT, selecting PCP to disclose GT, and positive GT. Results: As of January 2020, 4754 participants consented (77.5% female, median age 51); 37.7% never previously considered GT. Cancer family histories (FHx) were 56.4% low risk (LR), 36.4% high risk (HR), and 7.2% had a familial mutation (FM). To date, 3658 participants (76.9%) completed and 677 (14.2%) did not complete GT; the remainder are pending. Only 34.8% of participants selected PCP to disclose GT, and 42.6% of PCPs agreed. Of the 124 mutation carriers (3.4%) identified, 60.5% had a FM. At the 12-week survey, 65.4% of mutation carriers planned to proceed with recommended screening or scheduled risk reducing surgery; 3.5% of those with negative GT and HR FHx reported further GT. Satisfaction was high (mean 9.58/10, SD 1.12) and unrelated to result (p>.05). Conclusions: A digital model for founder mutation testing engaged those with LR FHx and no prior experience with GT. Older participants were more likely to complete the study. Males were less likely to enroll but more likely to carry mutations. The majority of those who tested positive had a FM. A minority of results were disclosed by PCPs. Continued follow up is needed to determine long term outcomes. [Table: see text]

Patterns of recurrence and metastasis in BRCA1/BRCA2-associated breast cancers

Background

Breast cancer subtypes are associated with distinct metastatic patterns. Whether germline BRCA1/BRCA2 mutation status is independently associated with central nervous system (CNS) relapse, controlling for tumor subtype, is unknown.

Methods

Patients who were treated at Dana‐Farber Cancer Institute and diagnosed with a first locoregional recurrence (LRR) or metastasis between 1981 and 2014 were identified using 2 institutional registries: 1) patients treated for recurrent breast cancer and 2) patients who underwent BRCA testing. The frequencies of LRR, sites of metastasis, and breast cancer‐specific survival from LRR or metastasis were calculated, and the factors associated with CNS recurrence were evaluated using multivariable logistic regression models.

Results

The final study cohort included 30 BRCA1 mutation carriers, 32 BRCA2 mutation carriers, and 270 noncarriers. Most BRCA1 carriers (73%) had triple‐negative breast cancer; whereas most BRCA2 carriers (72%) had hormone receptor‐positive tumors. BRCA1 carriers frequently experienced lung and distant lymph node metastasis, whereas BRCA2 carriers and noncarriers most often experienced bone metastasis. Although CNS disease occurred frequently in both BRCA1 and BRCA2 carriers (53% BRCA1, 50% BRCA2, 25% noncarriers; P < .001), only BRCA2 mutation (P = .006) was significantly associated with CNS metastasis in multivariable analysis controlling for tumor subtype. BRCA2 mutation (P = .01), triple‐negative subtype (P < .001), and the involvement of CNS (P < .001) and other non‐CNS distant sites (relative to locoregional recurrence or contralateral disease; P < .001) at presentation of recurrent breast cancer were associated with risk for mortality.

Conclusions

CNS involvement is frequent in women with germline BRCA1/BRCA2 mutations who have metastatic breast cancer. BRCA2 mutation carriers had a significantly higher frequency of CNS metastasis than noncarriers when controlling for breast cancer subtype.

Germline BRCA1 or BRCA2 alterations are associated with a high frequency (≥50%) of brain metastases in patients with locoregionally recurrent or metastatic breast cancer. In multivariable analysis, only BRCA2 mutation (P = .006) was significantly associated with central nervous system metastasis when controlling for breast cancer subtype.

Li-Fraumeni syndrome: not a straightforward diagnosis anymore-the interpretation of pathogenic variants of low allele frequency and the differences between germline PVs, mosaicism, and clonal hematopoiesis

The introduction of next-generation sequencing has resulted in testing multiple genes simultaneously to identify inherited pathogenic variants (PVs) in cancer susceptibility genes. PVs with low minor allele frequencies (MAFs) (< 25-35%) are highlighted on germline genetic test reports. In this review, we focus on the challenges of interpreting PVs with low MAF in breast cancer patients undergoing germline testing and the implications for management.The clinical implications of a germline PV are substantial. For PV carriers in high-penetrance genes like BRCA1, BRCA2, and TP53, prophylactic mastectomy is often recommended and radiation therapy avoided when possible for those with Li-Fraumeni syndrome (LFS). For germline PV carriers in more moderate-risk genes such as PALB2, ATM, and CHEK2, annual breast MRI is recommended and prophylactic mastectomies considered for those with significant family histories. Detection of PVs in cancer susceptibility genes can also lead to recommendations for other prophylactic surgeries (e.g., salpingo-oophorectomy) and increased surveillance for other cancers. Therefore, recognizing when a PV is somatic rather than germline and distinguishing somatic mosaicism from clonal hematopoiesis (CH) is essential. Mutational events that occur at a post-zygotic stage are somatic and will only be present in tissues derived from the mutated cell, characterizing classic mosaicism. Clonal hematopoiesis is a form of mosaicism restricted to the hematopoietic compartment.Among the genes in multi-gene panels used for germline testing of breast cancer patients, the detection of a PV with low MAF occurs most often in TP53, though has been reported in other breast cancer susceptibility genes. Distinguishing a germline TP53 PV (LFS) from a somatic PV (TP53 mosaicism or CH) has enormous implications for breast cancer patients and their relatives.We review how to evaluate a PV with low MAF. The identification of the PV in another tissue confirms mosaicism. Older age, exposure to chemotherapy, radiation, and tobacco are known risk factors for CH, as is the absence of a LFS-related cancer in the setting of a TP53 PV with low MAF. The ability to recognize and understand the implications of somatic PVs, including somatic mosaicism and CH, enables optimal personalized care of breast cancer patients.

Early results from the BRCA Founder Outreach (BFOR) Study: Population genetic screening using a medical model

1578

Background: Barriers to population screening for BRCA mutations include access, availability of counseling, and readiness of care providers to participate in this process. The BRCA Founder OutReach (BFOR) study evaluates a digital approach to genetic testing of a defined population using a medical model and risk-adapted follow-up. Methods: The BFOR study (Bforstudy.com) includes web-based enrollment open to individuals in four US cities who are age 25 or older and have at least one grandparent of Ashkenazi Jewish (AJ) ancestry. Participants receive web-based education, provide consent, complete questionnaires, and note their preference for receiving results either from their primary care provider (PCP) or BFOR staff. BRCA AJ founder mutation results are disclosed by (e)mail or phone, depending on need for additional counseling/genetic testing. Participants will be surveyed by email for up to 5 years; a subset of PCPs is also being surveyed. Results: From March 2018 to January 2019, 2562 participants enrolled: 78% female; < 30 years old, 8%; 30-50 years, 39%; > 50 years, 53%. At enrollment, 33% requested disclosure of results by PCP. Among 847 PCPs invited to disclose results, 45% accepted, 50% declined and 5% have yet to respond. 69 (3.2%) participants tested positive for a BRCA founder mutation, of whom 8 (12%) had no significant family history. 2087 participants tested negative, of whom 6% reported a known family mutation, 38% reported a family history of breast/ovarian cancer, and 56% no such history. The most common reason for study participation was referral by a friend. One individual with a distant history of breast cancer tested positive for a BRCA2 mutation and underwent risk reducing surgery that identified an early stage fallopian tube carcinoma. Her daughter then tested positive and underwent prophylactic surgeries. Conclusions: Population screening of individuals at higher risk for cancer-predisposing mutations is feasible and identifies individuals who would not have been tested using clinical criteria. Preliminary findings reveal challenges for engaging PCPs and at-risk individuals, particularly men. Ongoing follow-up and a second phase of the study will address these barriers to testing. Clinical trial information: NCT03351803.

TBCRC 030: A randomized phase II study of preoperative cisplatin versus paclitaxel in TNBC—Evaluating the homologous recombination deficiency (HRD) biomarker

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Background: Cisplatin (C) and paclitaxel (T) have activity in TNBC, however predictive biomarkers are lacking. The HRD assay detects impaired dsDNA break repair and may identify BRCA1/2-proficient tumors for treatment with DNA targeting therapies. TBCRC 030 was designed to determine the association between HRD and response to preoperative chemotherapy (CT) in TNBC. Methods: This phase II study randomized patients (pts) with BRCA1/2-proficient/unknown stage I-III TNBC to 12 weeks (wks) of preoperative C or T, followed by surgery. HRD was performed on baseline tissue, with positive scores > 33. Non-responders at 12 wks could crossover to alternative CT. The co-primary objectives were to detect a positive association of HRD with pathologic response (RCB 0-1) vs not (RCB 2-3) to C and a negative association to T. Target accrual of 160 pts was planned to yield 140 evaluable specimens for HRD, providing 90% power for the primary objectives. Analyses used logistic models and likelihood ratio tests with one-sided Type I errors of alpha = 0.05. Results: 140 pts initiated treatment, (72 Arm C, 68 Arm T; 81% T1-2, 62% node negative); 138 were evaluable for response at 12 wks. Post-enrollment testing showed 8 pts (5.8%) with germline DNA-repair pathway mutations. HRD results were available for 95 pts (68.8%, 23 inadequate tissue, 22 pending); 68 (71.6%) were HRD positive: 38 in Arm C, 30 in Arm T. In response-evaluable pts, 87 (63.0%) had surgery at 12 wks, and 51 (37.0%) crossed over. Response outcomes are shown in the Table. No association was seen between HRD score and RCB response to either neoadjuvant C (OR 2.78, [CI 0.61, 17.74]) or T (OR 0.98, CI [0.20, 5.06]). There was no evidence of an interaction between HRD and CT arms. Similarly, no association was observed between HRD score and pCR to either C (OR 1.47, CI [0.40, 5.59]) or T (OR 0.61, CI [0.14, 2.52]). There were no new safety signals. Conclusions: In this mostly BRCA1/2 proficient TNBC cohort, 12 wks of preoperative C or T led to a similar response rate of about 40%; baseline HRD was not predictive of response to preoperative CT, defined either by RCB 0-1 or pCR. Further data will be presented. Correlative analyses of research tissues for markers predictive of response to specific CT in TNBC is ongoing. Clinical trial information: NCT01982448. [Table: see text]

International trends in the uptake of cancer risk reduction strategies in women with a BRCA1 or BRCA2 mutation

BACKGROUND

Women with a BRCA1 or BRCA2 mutation face high risks of breast and ovarian cancer. In the current study, we report on uptake of cancer screening and risk-reduction options in a cohort of BRCA mutation carriers from ten countries over two time periods (1995 to 2008 and 2009 to 2017).

METHODS

Eligible subjects were identified from an international database of female BRCA mutation carriers and included women from 59 centres from ten countries. Subjects completed a questionnaire at the time of genetic testing, which included past use of cancer prevention options and screening tests. Biennial follow-up questionnaires were administered.

RESULTS

Six-thousand two-hundred and twenty-three women were followed for a mean of 7.5 years. The mean age at last follow-up was 52.1 years (27-96 years) and 42.3% of the women had a prior diagnosis of breast cancer. In all, 27.8% had a prophylactic bilateral mastectomy and  64.7% had a BSO. Screening with breast MRI increased from 70% before 2009 to 81% at or after 2009. There were significant differences in uptake of all options by country.

CONCLUSION

For women who received genetic testing more recently, uptake of prophylactic mastectomy and breast MRI is significantly higher than those who received genetic testing more than 10 years ago. However, uptake of both BSO and breast MRI is not optimal, and interventions to increase uptake are needed.

Abstract P1-17-02: Outcomes and safety of paclitaxel and granulocyte-colony stimulating factor (GCSF) in breast cancer in pregnancy (BCP) - A multi-institutional retrospective analysis

Background

BCP is uncommon; however, the frequency is increasing due to trends in delayed childbearing. Studies have suggested that some systemic therapies, including doxorubicin and cyclophosphamide, can be delivered safely during pregnancy after the first trimester, whereas agents such as trastuzumab and endocrine therapy are contraindicated due to risk to the fetus. Data remain limited on the efficacy and safety of administering taxane chemotherapy or growth factor support during pregnancy. We retrospectively evaluated the safety of systemic therapies, including paclitaxel and GCSF, as well as clinical outcomes, in a multi-institutional cohort of patients (pts) with BCP.

Methods

Pts treated for BCP from 1996-2018 from 3 large academic institutions were included. Demographic, oncologic treatment, and obstetric/neonatal outcomes data were obtained from medical records. Disease-free survival (DFS) and overall survival (OS) were estimated by Kaplan-Meier; Log-rank test were used to compare different groups/outcomes. Associations were calculated by Fisher's exact test.

Results

A total of 114 pts diagnosed with BCP were included. The median age was 35 years (range 25-44) and median gestational age at diagnosis was 18 weeks (range 2-38). BCP was predominantly early stage at diagnosis (stage I 28.0%, stage II 53.5%) and ER+/HER2- negative (48.2%). Sixty-three (55.2%) women received chemotherapy, 13 (11.4%) received paclitaxel and 11 (9.6%) GCSF (daily or depot injections) while pregnant. A total of 78% of pts with HER-2-positive BCP (28/36) received trastuzumab after delivery (11% were treated before 2005 and 5.5% were T1a). With median follow-up of 67.7 months, median DFS (stage I-III) was 212.8 months (CI 95% 108.4-317.1), and median OS (stage I-IV) was not reached. Subgroup analysis suggested a higher DFS for pts diagnosed in the 1sttrimester compared to the 3rdtrimester among women with stage II-III (HR 0.25 CI 95% 0.09-0.70, p= 0.03). Among women who received paclitaxel, there was no significant increase in adverse obstetrical/neonatal outcomes: preterm delivery (23.1% vs 13.1%, p 0.39), low weight newborn (7.7% vs 9.1 %, p 1.0), congenital malformations (0% vs 6.1%, p 1.0) or acute neonatal adverse outcomes (7.7% vs 4.0%, p 0.51), which include NICU need and Apgar 5'&lt;7, compared to pts who did not receive paclitaxel. Among pts who received GCSF during pregnancy, adverse outcomes were numerically but not statistically higher than women who did not receive growth factor: preterm delivery (36.3% vs 11.0%, p 0.051), low weight newborn (27.3% vs 6.9%, p 0.058), congenital malformations (9.1% vs 1.0%, p 0.18) or acute neonatal adverse outcomes (18.2% vs 3.0%, p 0.07).

Conclusion

In this multi-institution cohort of BCP pts, despite a small number of pts, exposure to contemporary therapies including paclitaxel was not associated with unfavorable obstetrical/neonatal outcomes and these results suggest it is safe to administer during pregnancy under the care of a multidisciplinary team. Although not statistically significant, GCSF presented numerical worse outcomes and combining data from several cohorts would be helpful to provide confirmation of these findings.

Citation Format: Exman P, Freret TS, Economy KE, Chen WY, Parsons HA, Lin NU, Moy B, Tung NM, Partridge AH, Mayer EL. Outcomes and safety of paclitaxel and granulocyte-colony stimulating factor (GCSF) in breast cancer in pregnancy (BCP) - A multi-institutional retrospective analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-17-02.

Multicenter Phase II Study of Lurbinectedin in BRCA-Mutated and Unselected Metastatic Advanced Breast Cancer and Biomarker Assessment Substudy

PURPOSE

This multicenter phase II trial evaluated lurbinectedin (PM01183), a selective inhibitor of active transcription of protein-coding genes, in patients with metastatic breast cancer. A unicenter translational substudy assessed potential mechanisms of lurbinectedin resistance.

PATIENTS AND METHODS

Two arms were evaluated according to germline BRCA1/2 status: BRCA1/2 mutated (arm A; n = 54) and unselected ( BRCA1/2 wild-type or unknown status; arm B; n = 35). Lurbinectedin starting dose was a 7-mg flat dose and later, 3.5 mg/m² in arm A. The primary end point was objective response rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST). The translational substudy of resistance mechanisms included exome sequencing (n = 13) and in vivo experiments with patient-derived xenografts (n = 11) from BRCA1/2-mutated tumors.

RESULTS

ORR was 41% (95% CI, 28% to 55%) in arm A and 9% (95% CI, 2% to 24%) in arm B. In arm A, median progression-free survival was 4.6 months (95% CI, 3.0 to 6.0 months), and median overall survival was 20.0 months (95% CI, 11.8 to 26.6 months). Patients with BRCA2 mutations showed an ORR of 61%, median progression-free survival of 5.9 months, and median overall survival of 26.6 months. The safety profile improved with lurbinectedin dose adjustment to body surface area. The most common nonhematologic adverse events seen at 3.5 mg/m² were nausea (74%; grade 3, 5%) and fatigue (74%; grade 3, 21%). Neutropenia was the most common severe hematologic adverse event (grade 3, 47%; grade 4, 10%). Exome sequencing showed mutations in genes related to the nucleotide excision repair pathway in four of seven tumors at primary or acquired resistance and in one patient with short-term stable disease. In vivo, sensitivity to cisplatin and lurbinectedin was evidenced in lurbinectedin-resistant (one of two) and cisplatin-resistant (two of three) patient-derived xenografts.

CONCLUSION

Lurbinectedin showed noteworthy activity in patients with BRCA1/2 mutations. Response and survival was notable in those with BRCA2 mutations. Additional clinical development in this subset of patients with metastatic breast cancer is warranted.

Multicenter Phase II Study of Lurbinectedin in BRCA-Mutated and Unselected Metastatic Advanced Breast Cancer and Biomarker Assessment Substudy

Purpose

This multicenter phase II trial evaluated lurbinectedin (PM01183), a selective inhibitor of active transcription of protein-coding genes, in patients with metastatic breast cancer. A unicenter translational substudy assessed potential mechanisms of lurbinectedin resistance.

Patients and Methods

Two arms were evaluated according to germline BRCA1/2 status: BRCA1/2 mutated (arm A; n = 54) and unselected (BRCA1/2 wild-type or unknown status; arm B; n = 35). Lurbinectedin starting dose was a 7-mg flat dose and later, 3.5 mg/m² in arm A. The primary end point was objective response rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST). The translational substudy of resistance mechanisms included exome sequencing (n = 13) and in vivo experiments with patient-derived xenografts (n = 11) from BRCA1/2-mutated tumors.

Results

ORR was 41% (95% CI, 28% to 55%) in arm A and 9% (95% CI, 2% to 24%) in arm B. In arm A, median progression-free survival was 4.6 months (95% CI, 3.0 to 6.0 months), and median overall survival was 20.0 months (95% CI, 11.8 to 26.6 months). Patients with BRCA2 mutations showed an ORR of 61%, median progression-free survival of 5.9 months, and median overall survival of 26.6 months. The safety profile improved with lurbinectedin dose adjustment to body surface area. The most common nonhematologic adverse events seen at 3.5 mg/m² were nausea (74%; grade 3, 5%) and fatigue (74%; grade 3, 21%). Neutropenia was the most common severe hematologic adverse event (grade 3, 47%; grade 4, 10%). Exome sequencing showed mutations in genes related to the nucleotide excision repair pathway in four of seven tumors at primary or acquired resistance and in one patient with short-term stable disease. In vivo, sensitivity to cisplatin and lurbinectedin was evidenced in lurbinectedin-resistant (one of two) and cisplatin-resistant (two of three) patient-derived xenografts.

Conclusion

Lurbinectedin showed noteworthy activity in patients with BRCA1/2 mutations. Response and survival was notable in those with BRCA2 mutations. Additional clinical development in this subset of patients with metastatic breast cancer is warranted.