Numerous studies have shown that cell-free DNA (cfDNA) levels may serve as a non-invasive biomarker of a broad spectrum of acute and chronic pathologies. However, in order to make clinical decisions based on cfDNA measurements, it is essential to understand the magnitude of biological variation so this variation is not confused with a variation that actually represent a clinically relevant change. The present study was designed to evaluate the biological variation of cfDNA in healthy subjects and lung cancer patients. Plasma samples were collected from 33 healthy subjects and ten lung cancer patients over three days, as well as during the same day. CfDNA was quantified using droplet digital PCR. Biological variation data was estimated using mixed models. The within-subject variation was 25% and the between-subject variation was 30%. The reference change value for the healthy subjects was 70%. There was no systematic difference in cfDNA levels from day-to-day (p = 0⋅61), but there was a significant decline during the day (p0⋅3). Our findings show that cfDNA levels fluctuate significantly during the day and exhibit considerable within-subject variation. Thus, the data presented offer a substantial contribution to the interpretation of the clinical significance of cfDNA. Læge Sofus Carl Emil Friis og hustru Olga Doris Friis' Legat, Harboefonden, and Dagmar Marshalls Fond.

Objectives: The neurofilament light chain (NfL) has emerged as a versatile biomarker for CNS-diseases and is approaching clinical use. The observed changes in NfL levels are frequently of limited magnitude and in order to make clinical decisions based on NfL measurements, it is essential that biological variation is not confused with clinically relevant changes. The present study was designed to evaluate the biological variation of serum NfL. Methods: Apparently healthy individuals (n=33) were submitted to blood draws for three days in a row. On the second day, blood draws were performed every third hour for 12 h. NfL was quantified in serum using the Simoa™ HD-1 platform. The within-subject variation (CV_I) and between-subject variation (CV_G) were calculated using linear mixed-effects models. Results: The overall median value of NfL was 6.3 pg/mL (range 2.1–19.1). The CV_I was 3.1% and the CV_G was 35.6%. An increase in two serial measurements had to exceed 24.3% to be classified as significant at the 95% confidence level. Serum NfL levels remained stable during the day (p=0.40), whereas a minute variation (6.0–6.6 pg/mL) was observed from day-to-day (p=0.02). Conclusions: Serum NfL is subject to tight homeostatic regulation with none or neglectable semidiurnal and day-to-day variation, but considerable between-subject variation exists. This emphasizes serum NfL as a well-suited biomarker for disease monitoring, but warrants caution when interpreting NfL levels in relation to reference intervals in a diagnosis setting. Furthermore, NfL’s tight regulation requires that the analytical variation is kept at a minimum.

Background: Mutated circulating cell-free DNA (cfDNA) has been suggested as a surrogate marker of tumour burden and aggressiveness of disease. We examined the association between the level of plasma mutant cfDNA and metabolic tumour burden (MTB) measured by ¹⁸F-fluoro-D-glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT). Furthermore, the presence of mutant cfDNA was correlated with patient survival. Methods: Forty-six advanced non-small cell lung cancer (NSCLC) patients were included. At the time of inclusion, blood sampling and a PET/CT scan were performed. cfDNA was isolated and next-generation sequencing (NGS) was performed (Ion AmpliSeq Colon and Lung Cancer panel v2). MTB was defined by a volumetric PET parameter. Results: NGS succeeded in 41 patients. Mutations were detected in the blood of 24 patients. A significant correlation between the allele frequency of the most frequent mutation and MTB was found (P=0.001). Patients with detectable mutated cfDNA had a significantly shorter median overall survival compared with patients without (3.7 versus 10.6 months, P=0.019). This impact on survival was independent of the MTB. Conclusions: Level of mutated cfDNA tends to correlate with MTB in advanced-stage NSCLC patients. Patients with detectable mutant DNA in plasma had an inferior survival, indicating that this could be an important predictor of survival.

Background: Inflammation-scores based on general inflammation markers are suggested as prognostic markers of overall survival (OS) in lung cancer. However, whether these inflammation-scores improves the prognostication performed by well-established prognostic markers is unsettled. In a large register-based lung cancer patient cohort, nine different inflammation-scores were compared, and their ability to optimize the prognostication of OS was evaluated. Methods: Lung cancer patients diagnosed from 2009–2018 in The Central Denmark Region were identified in the Danish Lung Cancer Registry. Pre-treatment inflammation markers were extracted from the clinical laboratory information system. Prognostication of OS was evaluated by Cox proportional hazard models. Comparison of the inflammation-scores and their added value to established prognostic markers were assessed by Akaike's information criteria and Harrel's C-index. Results: In total, 5,320 patients with non-small cell lung cancer (NSCLC) and 890 patients with small cell lung cancer (SCLC) were identified. In NSCLC, the Aarhus composite biomarker score (ACBS), including albumin, C-reactive protein, neutrophil count, lymphocyte count and haemoglobin, and the neutrophil-lymphocyte-ratio (NLR) were superior. Furthermore, they improved the prognostication of OS significantly (p <0.0001) (ACBS: HR: 2.24 (95%CI: 1.97–2.54); NLR: HR: 1.58 (95%CI: 1.47 – 1.69)). In SCLC, three scores were equally superior and improved the prognostication of OS p < 0.0001): neutrophil–lymphocyte-ratio (HR:1.62 (95%CI: 1.38–1.90)), modified Glasgow Prognostic Score (mGPS) (HR:1.70 (95%CI: 1.55–1.86) and the Combined NLR and GPS (CNG) (HR:2.10 (95%CI: 1.77–2.49). Conclusions: The ACBS was the optimal score in NSCLC, whereas neutrophil–lymphocyte-ratio, mGPS and CNG were equally superior in SCLC. Additionally, these inflammation-scores all optimised the prognostication of OS and added value to well-established prognostic markers.

Background: Brain metastases are feared complications in cancer. Treatment by neurosurgical resection and stereotactic radiosurgery are only available when metastatic lesions are limited and early detection is warranted. The neurofilament light chain (NfL) is a sensitive neuron-specific biomarker released following neuronal decay. We explored serum NfL as a biomarker of brain metastases. Methods: Serum was collected from 43 stage IV lung cancer patients with brain metastases and 25 stage I lung cancer patients. Serum was collected at time of cancer diagnosis and at time of brain metastasis diagnosis. In nine patients with brain metastases, additional samples were available between the two time points. NfL was quantified by Single Molecule Array (Simoa)™. Results: The median NfL level was significantly higher in patients with brain metastases than in patients without (35 versus 16 pg/mL, p = 0.001) and separated patients with an area under the curve of 0.77 (0.66–0.89). An increase in NfL could be measured median 3 months (range: 1–5) before the brain metastasis diagnosis. Further, a high level of NfL at time of brain metastasis diagnosis correlated with an inferior survival (hazard ratio: 2.10 (95% confidence interval: 1.11–3.98)). Conclusions: This study implies that NfL could be a potential biomarker of brain metastases.