Pembrolizumab monotherapy for previously treated metastatic triple-negative breast cancer: cohort A of the phase II KEYNOTE-086 study

ABSTRACT Background Treatment options for previously treated metastatic triple-negative breast cancer (mTNBC) are limited. In cohort A of the phase II KEYNOTE-086 study, we evaluated pembrolizumab as second or later line of treatment for patients with mTNBC. Patients and methods Eligible patients had centrally confirmed mTNBC, ≥1 systemic therapy for metastatic disease, prior treatment with anthracycline and taxane in any disease setting, and progression on or after the most recent therapy. Patients received pembrolizumab 200 mg intravenously every 3 weeks for up to 2 years. Primary end points were objective response rate in the total and PD-L1–positive populations, and safety. Secondary end points included duration of response, disease control rate (percentage of patients with complete or partial response or stable disease for ≥24 weeks), progression-free survival, and overall survival. Results All enrolled patients (N = 170) were women, 61.8% had PD-L1–positive tumors, and 43.5% had received ≥3 previous lines of therapy for metastatic disease. ORR (95% CI) was 5.3% (2.7–9.9) in the total and 5.7% (2.4–12.2) in the PD-L1–positive populations. Disease control rate (95% CI) was 7.6% (4.4–12.7) and 9.5% (5.1–16.8), respectively. Median duration of response was not reached in the total (range, 1.2+–21.5+) and in the PD-L1–positive (range, 6.3–21.5+) populations. Median PFS was 2.0 months (95% CI, 1.9–2.0), and the 6-month rate was 14.9%. Median OS was 9.0 months (95% CI, 7.6–11.2), and the 6-month rate was 69.1%. Treatment-related adverse events occurred in 103 (60.6%) patients, including 22 (12.9%) with grade 3 or 4 AEs. There were no deaths due to AEs. Conclusions Pembrolizumab monotherapy demonstrated durable antitumor activity in a subset of patients with previously treated mTNBC and had a manageable safety profile. Clinical trial registration ClinicalTrials.gov, NCT0244700

Serial analysis of circulating tumor cells in metastatic breast cancer receiving first-line chemotherapy

Background: We examined the prognostic significance of circulating tumor cell (CTC) dynamics during treatment in metastatic breast cancer (MBC) patients receiving first-line chemotherapy. Methods: Serial CTC data from 469 patients (2,202 samples) were used to build a novel latent mixture model to identify groups with similar CTC trajectory (tCTC) patterns during the course of treatment. Cox regression was used to estimate hazard ratios for progression-free survival (PFS) and overall survival (OS) in groups based on baseline CTCs (bCTC), combined CTC status at baseline to the end of cycle 1 (cCTC), and tCTC. Akaike Information Criterion (AIC) was used to select the model that best predicted PFS and OS. Results: Latent mixture modeling revealed 4 distinct tCTC patterns: undetectable CTCs (tCTCneg, 56.9% ), low (tCTClo, 23.7%), intermediate (tCTCmid, 14.5%), or high (tCTChi, 4.9%). Patients with tCTClo, tCTCmid and tCTChi patterns had statistically significant inferior PFS and OS compared to those with tCTCneg (P<.001). AIC indicated that the tCTC model best predicted PFS and OS when compared to bCTC and cCTC models. Validation studies in an independent cohort of 1,856 MBC patients confirmed these findings. Further validation using only a single pretreatment CTC measurement confirmed prognostic performance of the tCTC model. Conclusions: We identified four novel prognostic groups in MBC based on similarities in CTC trajectory patterns during chemotherapy. Prognostic groups included patients with very poor outcome (tCTCmid+tCTChi, 19.4%) who could benefit from more effective treatment. Our novel prognostic classification approach may be utilized for fine-tuning of CTC-based risk-stratification strategies to guide future prospective clinical trials in MBC

Serial Analysis of Circulating Tumor Cells in Metastatic Breast Cancer Receiving First-Line Chemotherapy

BACKGROUND: We examined the prognostic significance of circulating tumor cell (CTC) dynamics during treatment in metastatic breast cancer (MBC) patients receiving first-line chemotherapy. METHODS: Serial CTC data from 469 patients (2202 samples) were used to build a novel latent mixture model to identify groups with similar CTC trajectory (tCTC) patterns during the course of treatment. Cox regression was used to estimate hazard ratios for progression-free survival (PFS) and overall survival (OS) in groups based on baseline CTCs, combined CTC status at baseline to the end of cycle 1, and tCTC. Akaike information criterion was used to select the model that best predicted PFS and OS. RESULTS: Latent mixture modeling revealed 4 distinct tCTC patterns: undetectable CTCs (56.9% ), low (23.7%), intermediate (14.5%), or high (4.9%). Patients with low, intermediate, and high tCTC patterns had statistically significant inferior PFS and OS compared with those with undetectable CTCs (P < .001). Akaike Information Criterion indicated that the tCTC model best predicted PFS and OS compared with baseline CTCs and combined CTC status at baseline to the end of cycle 1 models. Validation studies in an independent cohort of 1856 MBC patients confirmed these findings. Further validation using only a single pretreatment CTC measurement confirmed prognostic performance of the tCTC model. CONCLUSIONS: We identified 4 novel prognostic groups in MBC based on similarities in tCTC patterns during chemotherapy. Prognostic groups included patients with very poor outcome (intermediate + high CTCs, 19.4%) who could benefit from more effective treatment. Our novel prognostic classification approach may be used for fine-tuning of CTC-based risk stratification strategies to guide future prospective clinical trials in MBC

A genetic variant in a PP2A regulatory subunit encoded by the PPP2R2B gene associates with altered breast cancer risk and recurrence.

A recent candidate gene association study identified a single nucleotide polymorphism (SNP) in the PPP2R2B gene (rs319217, A/G) that manifests allelic differences in the cellular responses to treatment with chemotherapeutic agents (Vazquez et al., Nat Rev Drug Discov 2008;7:979-87). This gene encodes a regulatory subunit of protein phosphatase 2A (PP2A), one of the major Ser/Thr phosphatases implicated in the negative control of cell growth and division. Given the tumor suppressor activities of PP2A, here we evaluate whether this genetic variant associates with the age of diagnosis and recurrence of breast cancer in women. To investigate the linkage disequilibrium in the vicinity of this SNP, PPP2R2B haplotypes were analyzed using HapMap data for 90 Caucasians. It is found that the A variant of rs319217 tags a haplotype that appears tobe under positive selection in the Caucasian population, implying that this SNP is functional. Subsequently, associations with cellular responses were investigated using data reported by the NCI anticancer drug screen and associations with breast cancer clinical variables were analyzed in a cohort of 819 Caucasian women. The A allele associates with a better response of tumor derived cell lines, lower risk of breast cancer recurrence, later time to recurrence, and later age of diagnosis of breast cancer in Caucasian women. Taken together these results indicate that the A variant of the rs319217 SNP is a marker of better prognosis in breast cancer

Breast cancer in young women (YBC): Prevalence of BRCA1/2 mutations and risk of secondary malignancies across diverse racial groups

Background: Despite significant differences in age of onset and incidence of breast cancer between Caucasian (CA), African-American (AA) and Korean (KO) women, little is known about differences in BRCA1/2 mutations in these populations. The purpose of this study is to evaluate the prevalence of BRCA1/2 mutations and the association between BRCA1/2 mutation status and secondary malignancies among young women with breast cancer in these three racially diverse groups. Methods: Patients presenting to our breast cancer follow-up clinics selected solely on having a known breast cancer diagnosis at a young age (YBC defined as age \u3c45 years at diagnosis) were invited to participate in this study. A total of 333 eligible women, 166 CA, 66 AA and 101 KO underwent complete sequencing of BRCA1/2 genes. Family history (FH) was classified as negative, moderate or strong. BRCA1/2 status was classified as wild type (WT), variant of uncertain significance (VUS) or deleterious (DEL). Results: DEL across these three racially diverse populations of YBC were nearly identical: CA 17%, AA 14% and KO 14%. The type of DEL differed with AA having more frequent mutations in BRCA2, compared with CA and KO. VUS were predominantly in BRCA2 and AA had markedly higher frequency of VUS (38%) compared with CA (10%) and KO (12%). At 10-year follow-up from the time of initial diagnosis of breast cancer, the risk of secondary malignancies was similar among WT (14%) and VUS (16%), but markedly higher among DEL (39%). Conclusions: In these YBC, the frequency of DEL in BRCA1/2 is remarkably similar among the racially diverse groups at 14%-17%. VUS is more common in AA, but aligns closely with WT in risk of second cancers, age of onset and FH. © The Author 2009. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved

Polymorphic variants in TSC1 and TSC2 and their association with breast cancer phenotypes

TSC1 acts coordinately with TSC2 in a complex to inhibit mTOR, an emerging therapeutic target and known promoter of cell growth and cell cycle progression. Perturbation of the mTOR pathway, through abnormal expression or function of pathway genes, could lead to tumorigenesis. TSC1 and TSC2 expression is reduced in invasive breast cancer as compared with normal mammary epithelium. Because single nucleotide polymorphisms (SNPs) in regulatory genes have been implicated in risk and age at diagnosis of breast cancers, systematic SNP association studies were performed on TSC1 and TSC2 SNPs for their associations with clinical features of breast cancer. TSC1 and TSC2 haplotypes were constructed from genotyping of multiple loci in both genes in healthy volunteers. SNPs were selected for further study using a bioinformatics approach based on SNP associations with drug response in NCI-60 cell lines and evidence of selection bias based on haplotype frequencies. Genotyping for five TSC1 and one TSC2 loci were performed on genomic DNA from 1,137 women with breast cancer. This study found that for TSC1 rs7874234, TT variant carriers had a 9-year later age at diagnosis of estrogen receptor positive (ER+), but not ER-, ductal carcinomas (P = 0.0049). No other SNP locus showed an association with age at diagnosis, nor any other breast cancer phenotype. TSC1 rs7874234 is hypothesized to be functional in ER+ breast cancer because the T allele, but not the C allele, may create an estrogen receptor element (ERE) site, resulting in increased TSC1 transcription and subsequent inhibition of mTOR. © 2010 Springer Science+Business Media, LLC

5-year Update of a Multi Institution Prospective Phase II Hypofractionated Post-Mastectomy Radiation Therapy Trial.

PURPOSE: Hypofractionation in the setting of postmastectomy radiation (PMRT) is not currently the standard of care in most countries. Here we present a 5-year update of our multi-institutional, phase 2 prospective trial evaluating a novel 15-day hypofractionated PMRT regimen. METHODS AND MATERIALS: Patients were enrolled to receive 3.33 Gy daily to the chest wall (or reconstructed breast) and regional lymphatics in 11 fractions with an optional 4-fraction mastectomy scar boost. The primary endpoint was freedom from grade 3 or higher late non–reconstruction-related radiation toxicities. Toxicities were scored using Common Terminology Criteria for Adverse Events v4.0. Secondary endpoints included local and locoregional recurrence rates, cosmesis, and reconstruction complications. RESULTS: After enrolling 69 patients with stage II-IIIa breast cancer, 67 women were eligible for analysis. At a median follow up of 54 months, there were no acute or late grade 3 and 4 nonreconstruction reported toxicities. The grade 2 or greater late toxicity rate was only 12% and comprised grade 2 pain, fatigue, and lymphedema that persisted beyond 6 months after completion of radiation therapy. Only 3 women (4.6%) experienced a chest wall or nodal recurrence as a first site of relapse. Freedom from local failure, including local failure after distant relapse, was 92% at 5 years, and the 5-year overall survival was 90%. CONCLUSIONS: This is the first prospective trial conducted in the United States to demonstrate the safe and effective use of hypofractionated PMRT. We have demonstrated a low complication rate while achieving excellent local control. Toxicity was better than anticipated based on previously published series of PMRT toxicities. Although our fractionation was novel, the radiobiological equivalent dose is similar to other hypofractionation schedules. This trial was the basis for the creation of Alliance A221505 (RT CHARM), which is currently accruing patients in a phase 3 randomized design

MDM2 SNP309 accelerates tumor formation in a gender-specific and hormone-dependent manner.

The importance of the p53 stress response pathway in the suppression of tumor formation is well documented. In a previous report, a single nucleotide polymorphism (SNP309 T/G) was found in the promoter of the MDM2 gene resulting in higher levels of MDM2 RNA and protein and, consequently, in the attenuation of the p53 pathway both in vitro and in vivo. As the SNP309 locus is found in a region of the MDM2 promoter, which is regulated by hormonal signaling pathways, and the G-allele of SNP309 increases the affinity of a well-described cotranscriptional activator of nuclear hormone receptors (i.e., Sp1), the hypothesis that the SNP309 locus could alter the effects of hormones on tumorigenesis was tested in vivo in humans. Data obtained from patients with three different sporadic cancers, from four independent case studies, support this hypothesis, providing an example for the genetic basis of gender differences in cancer and showing that the genotype at a specific locus can affect how hormones, like estrogen, affect tumorigenesis in humans