Plasma pre-treatment T790M relative allelic frequency in patients with advanced EGFR-mutated non-small cell lung cancer predicts treatment response to subsequent-line osimertinib

Background

Approximately half of all patients with advanced EGFR-mutant NSCLC will develop acquired resistance to first or second-generation EGFR tyrosine kinase inhibitors (EGFR-TKIs) with a T790M mutation. In the AURA3 trial, patients with a T790M mutation had a response rate of 71% to osimertinib, a third-generation EGFR-TKI. The response to osimertinib may vary according to plasma T790M mutation frequency. Our aim was to determine the effect of plasma T790M mutation load on treatment response to osimertinib in an Australian multi-institutional cohort.

Methods

We performed a retrospective study on patients treated with osimertinib in the second-line setting and beyond between 2016-2018 from ten centres in Australia, who had T790M mutations detected in tumour or plasma. The primary objective was to investigate if there was a difference in disease control rate (DCR) between patients with high vs. low T790M relative allelic frequency (RAF) as detected in plasma, using a 0.3 RAF cut-off, as determined by ddPCR or BEAMing PCR. Secondary objective was to determine the survival outcomes according to high versus low plasma T790M RAF. Additional analyses were performed to investigate the survival outcome for patients with plasma versus tissue T790M positivity.

Results

A total of 139 patients were included in this study. Patients with higher RAF demonstrated higher DCR (74% vs. 36%, P=0.02), however there was no statistically significant difference in survival outcomes in the two groups. Exploratory analysis showed that patients with tissue T790M+ had improved DCR compared with those with plasma T790M+ (89% vs. 68%, P=0.01) and longer progression free survival (median 15.4 vs. 9.7 months; HR 0.51, 95% CI: 0.34 to 0.77, P=0.003) and overall survival (median not reached, HR 0.51, 95% CI: 0.30 to 0.86, P=0.02). Patients who were tissue T790M+ demonstrated superior survival compared to plasma T790M+ after correcting for confounding variables in a multivariate model.

Conclusions

DCR was superior in patients with higher plasma T790M mutation load versus lower plasma T790M mutational load, without significant survival benefit. Plasma T790M RAF is a potential predictive biomarker which should be investigated and validated in larger prospective studies.

Severe infusion reaction due to nivolumab: A case report

BACKGROUND

Nivolumab is an anti-PD1 immune checkpoint inhibitor commonly used for the treatment of solid organ and hematological malignancies. Severe infusion reaction due to nivolumab is quite rare.

CASE

We report a case of severe infusion reaction due to nivolumab necessitating ICU admission and withdrawal of further nivolumab use in a patient with metastatic non-small cell lung cancer.

CONCLUSION

Our knowledge and expertise with the use of immune checkpoint inhibitors are still evolving. This report highlights one of the rare possible side-effects that clinicians and patients may have to face with increasing indications and use of nivolumab in day to day practice.

Plasma next generation sequencing and droplet digital PCR-based detection of epidermal growth factor receptor (EGFR) mutations in patients with advanced lung cancer treated with subsequent-line osimertinib

BACKGROUND

Gene mutation analysis from plasma circulating tumor DNA (ctDNA) can provide timely information regarding the mechanism of resistance that could translate to personalised treatment. We compared concordance rate of next generation sequencing (NGS) and droplet digital polymerase chain reaction (ddPCR) in the detection of the EGFR activating and T790M mutation from plasma ctDNA with diagnostic tissue biopsy-based assays. The second objective was to test whether putative osimertinib resistance associated mutations were detectable from plasma using NGS.

METHODS

From January 2016 to December 2017, we prospectively collected plasma samples from patients prior to commencement of second- or third-line osimertinib therapy and upon disease progression, in a single tertiary hospital in South Western Sydney, Australia. Amplicon-based NGS and ddPCR assays were used to detect activating epidermal growth factor receptor (EGFR) and T790M mutations in 18 plasma samples from nine patients; all patients were required to have tissue biopsies with known EGFR status.

RESULTS

High concordance of allelic fractions were seen in matched plasma NGS and ddPCR for activating EGFR mutations and T790M mutations (R² = 0.92, P < 0.0001). Using tissue biopsies as reference standard, sensitivity was 100% for NGS and 94% for ddPCR. Several possible osimertinib resistance associated mutations, including PIK3CA, BRAF and TP53 mutations, were detected by NGS in samples upon progression on osimertinib therapy.

CONCLUSION

ddPCR assays for EGFR mutations appear to be as sensitive and highly concordant as amplicon-based NGS. NGS has the ability to detect novel resistance mutations.

Clinical outcomes in patients with advanced epidermal growth factor receptor-mutated non-small-cell lung cancer in South Western Sydney Local Health District

BACKGROUND

Epidermal growth factor receptor (EGFR)-mutated non-small-cell lung cancer (NSCLC) is a subgroup of oncogene addicted lung cancer that predicts response to tyrosine kinase inhibitors (TKI). However, there is variability in response and survival outcomes in patients with EGFR mutation treated with TKI.

AIM

To describe clinical characteristics, treatment patterns and factors influencing outcomes in patients with EGFR-mutated NSCLC in South Western Sydney Local Health District.

METHODS

Retrospective review of patients with EGFR-mutated NSCLC diagnosed between January 2010 and June 2016.

RESULTS

A total of 85 EGFR-mutated NSCLC patients was identified; 80 (94%) received first-line treatment with EGFR-TKI. The median follow-up was 10.7 months with a median duration of treatment of 9 months. On disease progression (n = 44), 37% had best supportive care only, 30% received chemotherapy, 23% participated in clinical trials, 7% continued on a first generation EGFR-TKI and 3% received afatinib. Overall response rate to first-line EGFR-TKI was 66%. Median progression-free survival (PFS) was 10.7 months (range 2.7-55.9 months) and median overall survival (OS) was 23 months (range 0.4-35.8 months). Multivariate Cox regression analysis showed that patients with lower disease burden (<4 sites) had longer PFS (hazard ratio (HR) 0.36, 95% confidence interval (CI) 0.18-0.72, P = 0.004) but not OS. Good performance status predicts longer OS (HR 0.33, CI 0.14-0.77, P = 0.01). Lower (<5) pre-treatment neutrophil-to-lymphocyte ratio (NLR) was associated with better PFS (HR 0.40, 95% CI 0.18-0.87, P = 0.02) and OS (HR 0.43, 95% CI 0.19-0.94, P = 0.04). There were no survival differences when patients were stratified by age, baseline albumin level and types of EGFR mutation.

CONCLUSION

Results from this community-based cohort confirm known prognostic factors in patients with EGFR-mutated NSCLC receiving TKI and suggest the negative influence of a heightened host systemic inflammatory response on patient outcomes.

CTC-mRNA (AR-V7) Analysis from Blood Samples-Impact of Blood Collection Tube and Storage Time

Circulating tumour cells (CTCs) are an emerging resource for monitoring cancer biomarkers. New technologies for CTC isolation and biomarker detection are increasingly sensitive, however, the ideal blood storage conditions to preserve CTC-specific mRNA biomarkers remains undetermined. Here we tested the preservation of tumour cells and CTC-mRNA over time in common anticoagulant ethylene-diamine-tetra-acetic acid (EDTA) and acid citrate dextrose solution B (Citrate) blood tubes compared to preservative-containing blood tubes. Blood samples spiked with prostate cancer cells were processed after 0, 24, 30, and 48 h storage at room temperature. The tumour cell isolation efficiency and the mRNA levels of the prostate cancer biomarkers androgen receptor variant 7 (AR-V7) and total AR, as well as epithelial cell adhesion molecule (EpCAM) were measured. Spiked cells were recovered across all storage tube types and times. Surprisingly, tumour mRNA biomarkers were readily detectable after 48 h storage in EDTA and Citrate tubes, but not in preservative-containing tubes. Notably, AR-V7 expression was detected in prostate cancer patient blood samples after 48 h storage in EDTA tubes at room temperature. This important finding presents opportunities for measuring AR-V7 expression from clinical trial patient samples processed within 48 h-a much more feasible timeframe compared to previous recommendations.