Pancreatic Ductal Adenocarcinoma: Characteristics of Tumor Microenvironment and Barriers to Treatment

Pancreatic ductal adenocarcinoma remains a highly aggressive disease, with a 5-year relative survival rate of 10%. Numerous barriers to treatment exist, such as dense desmoplasia, infiltration of immune suppressor cells, inhibitory cytokines, low effector T-cell infiltration, and low tumor mutational burden. These factors help form a highly suppressive tumor microenvironment unique to pancreatic ductal adenocarcinoma. This review outlines barriers to treatment of pancreatic ductal adenocarcinoma by discussing the unique characteristics of the pancreatic tumor microenvironment and the factors that contribute to making pancreatic ductal adenocarcinoma such a challenging disease to treat.

Efficacy and safety of immune checkpoint blockade in self-identified Black patients with advanced non-small cell lung cancer

BACKGROUND

To the authors' knowledge, race-based differences in efficacy for the treatment of patients with advanced non-small cell lung cancer (NSCLC) have not been studied to date due to the underrepresentation of patients of minority backgrounds in pivotal trials. In the current study, the authors examined real-world differences in outcome in a diverse patient population.

METHODS

The authors retrospectively analyzed the clinical outcomes of patients with advanced NSCLC who were treated with single-agent immune checkpoint blockade (ICB) between 2013 and July 2018 at Winship Cancer Institute of Emory University in Atlanta, Georgia. Primary efficacy comparison between Black patients and White patients was performed using bivariate and multivariate analyses for overall survival (OS) and progression-free survival (PFS).

RESULTS

Data from 257 patients were analyzed. The median age of the patients was 69 years; 50.6% of the patients were female, 63.4% were White, 29.5% were Black, and 7.1% of the patients were of "other" race. ICB was the first-line treatment in 51 patients (19.9%), the second-line treatment in 161 patients (62.6%), and the third-line treatment in 33 patients (12.9%). The most commonly used agents were nivolumab (49.0%), pembrolizumab (25.2%), and atezolizumab (21.3%). No differences with regard to OS (P = .839) and PFS (P = .235) were noted between Black and White patients. The sample overall response rate was 20.6% (15.2% in Black patients and 23.1% in White patients). No differences with regard to OS (P = .081) and PFS (P = .176) were observed between female and male patients. The rate of immune-related adverse events was found to be similar in Black and White patients (20.0% vs 29.9%; P = .148). On multivariate analysis, race was not found to be significantly associated with OS or PFS.

CONCLUSIONS

Real-world analysis of the authors' institutional experience demonstrated similar efficacy and tolerability of ICB in Black versus White patients with advanced NSCLC. Larger multi-institutional studies including other US minority populations would make the findings of the current study more generalizable.

Evaluating the role of race in outcome of advanced non-small cell lung cancer (NSCLC) patients treated with immune checkpoint inhibitor (ICI): Our institutional experience

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Background: Race-based differences in ICI efficacy for advanced NSCLC have not been studied due to under-representation of patients of minority background in pivotal trials. We systematically explored real-world differences in outcome in our diverse patient population. Methods: This is a retrospective review of clinical outcome of patients with advanced NSCLC treated with single-agent ICI between 2013 and July 2018 at the Winship Cancer Institute of Emory University. We performed univariate and multivariate analyses for overall survival (OS) and progression free survival (PFS) patients according to self-reported race and of OS according to gender and PD-L1 expression levels. Results: We analyzed clinical data from 90 eligible patients: Median age of 68.5 yrs, 51% male, White (W)/Black(B)/Asians(A) made up 62.3%/30.7%/5%; 36.5% had brain metastasis at the time of ICI initiation. The majority (85.9%) had ECOG PS ≤2; ICI was 1st line in 15 (16.9%), 2nd line in 59 (66.3%), 3rd line in 12 (13.5%) and nivolumab was the most commonly used agent (41.1%) followed by atezolizumab (32.2%) and pembrolizumab (26.7%). The median OS for the entire population was not reached (NR) (95%CI: 15.6, NR) while 12-month and 24-month OS rates were 63.8% (52.8%, 72.8%) and 53.1% (40.2%, 64.4%). The median OS, 12-month and 24-month OS rates for W and B respectively, were 23.6 months vs. NR; HR: 1.02 (95%CI: 0.51-2.04), p = 0.9571; 61.8% (47.7%, 73.2%) vs. 59.3% (38.6%, 75.0%) and 46.0% (27.9%, 62.4%) vs. 53.9% (32.8%, 70.9%). The overall response rate was 16.7%; 23.8% vs. 11% for B and W respectively. The median duration of response was comparable at 3.36 months vs. 2.94 months for W and B. The median PFS and 12-month PFS rate for W and B respectively were 5.5 (3.2, 14.8) vs. 3.0 (1.4, 10.7) months, p = 0.1350 and 40.0% (27.1%, 52.5%) vs. 29.6% (14.1%, 47.0%). Conclusions: Real-world analysis of our institutional experience showed no significant racial disparity in advanced NSCLC patients treated with ICI. Larger multi-institutional studies to include other US minority population would make our findings generalizable.

A randomized phase II study of tremelimumab and durvalumab with or without radiation for patients with relapsed small cell lung cancer (SCLC)

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Background: The combination of PD-1 and CTLA-4 inhibition has demonstrated activity in the second line therapy setting for SCLC. Radiotherapy enhanced the effectiveness of immunotherapy in NSCLC. We conducted this signal finding study to assess the efficacy of combined ICI with or without radiation in relapsed SCLC. Methods: Patients with relapsed SCLC who have received not more than 2 lines of therapy were enrolled and randomized to either Arm A: [Tremelimumab (T) 1500mg/durvalumab (D) 75mg i.v. every 4 weeks without SBRT] or Arm B: T/D with immune sensitizing SBRT to one selected tumor site (9 Gy x 3 fractions). Treatment continued until progression or maximum of 2 years. Paired tumor biopsies and serial samples of peripheral blood were employed for correlative endpoints (changes in intratumoral and circulating lymphocyte repertoire and immune cytokines). The study was designed to show a promising efficacy signal in either Arm with a hypothesized median PFS of 7 months (10 patients give 87% power at 1-sided alpha of 0.1). Results: Study randomized 17 patients to Arm A (8 patients) or B (9 patients); median age of 70 yrs; females 41.2%; White, 70%, Black 17.6%. Best response in 14 overall evaluable patients was PD in 9 (64.3%), PR in 2 (14%) and SD in 3 (21.4%); median PFS of 2.76 months and OS of 4.47 months. There was no significant difference in efficacy between Arms A and B but a trend of improved PFS and OS with T/D plus SBRT (see table): Median PFS of 2.1 vs. 3.3 months [HR: 2.44 (0.75-7.93); p = 0.122] and median OS of 2.6 vs. 5.7 months [HR: 1.50 (0.45-4.99); p = 0.5068]. Observed grade ≥ 3 adverse events were: Cytopenia (4), Dyspnea (1), and endocrine disorders (3) in Arm A; diarrhea (3) and cytopenias (1) in Arm B. There was an increase in circulating CD8(+) lymphocytes on treatment versus baseline in patients with objective tumor response. Conclusions: The study did not show sufficient signal of efficacy for ICI with or without SBRT in relapsed SCLC. Detailed result of the biomarker analysis will be available at the meeting. Clinical trial information: NCT02701400. [Table: see text]

PCBs and their putative effects on polecat (Mustela putorius) populations in Central Europe

In Europe polecat populations are declining for unknown reasons during the last decades. Data on the river otter, another mustelid predator, indicate that PCB levels are high enough in some populations to interfere with the reproduction of this aquatic species. Since the diet of the polecats consists to a large amount of aquatic prey (amphibians) it appears reasonable to assume that PCBs ingested with the prey are a factor in the decline of polecats. To test this assumption PCB residues in amphibians and in adipose tissue and liver of polecats from Southwest Germany were quantified and the results were compared with literature data on the reproductive toxicity of PCBs in feral mink. According to the current data total PCB levels in polecats (adipose tissue, mean 1244 ng/g lipids; liver, mean 1677 ng/g lipids) and their prey (frogs, mean 9279 ng/kg fresh weight; toads, 4948 ng/kg fresh weight) are comparatively low. Using the toxic equivalent approach, it was calculated that polecats could feed exclusively on amphibians without consuming a harmful amount of PCBs. Therefore, PCBs cannot be an agent currently affecting polecat populations in Central Europe. Other environmental factors like habitat destruction or road accidents are more likely to have a negative impact on polecat populations.

The olfactory system as a portal of entry for airborne polychlorinated biphenyls (PCBs) to the brain?

Ferrets, mammalian carnivores, kept in an indoor enclosure were continuously exposed to low concentrations of polychlorinated biphenyls (PCBs) in the ambient air for 5 years. After that time PCB concentrations were quantified in the olfactory bulbs and in the remaining brain, adipose tissue and liver. The results revealed unexpectedly high PCB concentrations in the olfactory bulbs, surpassing those in the remaining brain and the peripheral tissues. The PCB congener pattern in the olfactory bulbs resembled that found in the ambient air and the less chlorinated volatile PCBs were found in higher concentrations. We, therefore, assume that airborne PCBs enter directly via the olfactory system and are transported through the axons to the olfactory bulbs where they accumulate.

Occurrence of non-ortho, mono-ortho and di-ortho substituted PCB congeners in polecats, stone martens and badgers from the state of Baden-Württemberg, Germany

The concentrations of non-ortho, mono-ortho and di-ortho substituted PCB congeners in tissues of three European mustelid species--polecat, stone marten and badger--were determined. Median congener concentrations are comparable in the three species and are lower than in previous studies on polecats. In all samples PCB-126 contributes most to the TCDD-TEQ; it occurs in considerably higher concentrations in polecats. Additionally, amphibs, the main prey of polecats, were analysed. The total PCB intake of polecats feeding solely on amphibs would be below a critical level, considering the NOAEL for the reproduction of mink, a closely related species.