Content of circulating tumor DNA depends on the tumor type and the dynamics of tumor size, but is not influenced significantly by physical exercise, time of the day or recent meal.

Purpose: This study aimed to investigate factors, which influence the content of circulating tumor DNA (ctDNA).

Methods: 398 serial plasma samples were collected within 1-7 consecutive days from patients with EGFR-mutated lung cancer (n = 13), RAS/RAF-mutated colorectal cancer (n = 54) and BRAF-mutated melanoma (n = 17), who presented with measurable tumor disease. The amount of ctDNA was determined by ddPCR.