Circulating Cell-free DNA as a Prognostic Biomarker in Patients with Advanced ALK+ Non-small Cell Lung Cancer in the Global Phase III ALEX Trial

PURPOSE

We retrospectively assessed prognostic value of circulating cell-free DNA (cfDNA) using data from the phase III ALEX study in treatment-naïve, advanced ALK+ non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients were randomized to receive twice-daily alectinib 600 mg (n = 152) or crizotinib 250 mg (n = 151). cfDNA was quantified from baseline plasma samples, with patients stratified into ≤median and >median cfDNA biomarker-evaluable populations (BEP). Effect of cfDNA concentration on outcomes was analyzed using a Cox regression model with treatment group as covariate, and in multivariate analyses.

RESULTS

Median cfDNA concentration in the BEP was 11.53 ng/mL (n = 276). A positive correlation was found between cfDNA concentration and number of lesions, organ lesion sites, and tumor size (sum of longest diameter; all P < 0.0001). In both treatment arms, patients in the >median BEP were more likely to experience disease progression than the ≤median BEP [alectinib adjusted HR = 2.04; 95% confidence interval (CI), 1.07-3.89; P = 0.0305 and crizotinib adjusted HR = 1.83; 95% CI, 1.11-3.00, P = 0.0169]. Median progression-free survival was longer with alectinib than crizotinib in both ≤median and >median BEPs (P < 0.0001). Overall survival data remain immature; survival probability was lower in the >median versus ≤median BEP in both treatment arms (alectinib HR = 2.52; 95% CI, 1.08-5.88; P = 0.0333 and crizotinib HR = 2.63; 95% CI, 1.27-5.47; P = 0.0096).

CONCLUSIONS

These data suggest that plasma cfDNA concentration may have prognostic value in advanced ALK+ NSCLC. Prospectively designed studies are warranted to investigate this finding.

Revisiting a lower starting dose of alectinib in ALK-Positive non-small cell lung cancer

We present here a case of ALK-positive lung adenocarcinoma that has been started on Alectinib. Treatment has been initiated at the recommended initial dose, but it subsequently required a dose adjustment following adverse drug events. Alectinib is a second-generation, CNS-active, tyrosine kinase inhibitor used in the treatment of ALK-positive non-small cell lung cancer. Its efficacy as a first-line treatment and as a second-line agent after Crizotinib has been proven across several trials both in terms of overall response rate and progression-free survival. The use of Alectinib is associated with side effects that occasionally lead to treatment discontinuation, interruption, or dose adjustment. Several studies have used two starting doses - 300 mg and 600 mg twice daily - across different populations and have consistently shown efficacy of Alectinib for both treatment doses. Results of these studies have also revealed that body weight, rather than race, affect the pharmacokinetics of Alectinib. Randomized trials have shown that the 600 mg dose is associated with more grade ≥3 adverse events and more changes in treatment in contrast to the 300 mg dose. A lower dose of Alectinib may limit treatment disruptions and dose reductions particularly for specific patient populations-particularly those with a lower body weight.