Circulating Tumor DNA as Marker for Response to Antineoplastic Treatment of Metastatic Cancer (FLUIDO)

Patients Patients with metastatic cancer who are treated with antineoplastic treatment are eligible if a molecular marker is either known due to the type of cancer (Case A) or if a molecular marker is known due to routine assessment (Case B). An example for "Case A" is pancreatic cancer, which is known to harbor KRAS-mutations as part of tumorigenesis in more than 90% (8), or multiple cancers harboring methylated WIF(9). A typical example for "Case B" is colorectal or gastric cancer. Systemic treatment requires the knowledge of the mutational status of RAS, EGFR and BRAF, which is assessed routinely from tumor tissue. If a mutation is found the patient qualifies for participation in the project. We finally plan to include at least 40 patients with mPDAC, another 40 patients with mCRC and 20 patients with mGC (100 patients in total at least).

• The inclusion criteria therefore are:

• Metastatic cancer (mPDAC, mGC, mCRC)

• Known mutation of the cancer

• Signed informed consent

• At least 18 years

• Eligible for antineoplastic treatment

• Patient treated at the Ordensklinikum Linz

• Exclusion criteria o Inclusion criteria not met

Treatment monitoring Circulating tumor DNA is analysed from peripheral blood. For this purpose, 30 ml blood is taken at start and during treatment additionally to the blood volume required for analyses in the frame of routine. Therefore, there are no extra blood sampling time points additionally to these required for routine care. Due to that, the time points depend on the cancer type investigated as treatment schedules are different. However, within an entity the time points are homogenous.

Analysis of ctDNA The preparation of ctDNA is done in the Laboratory for Molecular Biology and Tumor Cytogenetics at the Ordensklinikum Linz (Dr. Gerald Webersinke) and digital droplet PCR is performed by the Department of Genetics at the Medical University of Innsbruck (Prof. Johannes Zschoke). The analysis is performed in a batch and not in real time. In detail, ctDNA detection is based on KRAS-screening in mPDAC or by patient specific ddPCR. The latter patient specific ddPCR is based on the mutations found in the tumor by NGS-screening (ARCHER or Truesight 170 or whole-genome sequencing if panels are negative) at the Laboratory in Linz. This is the case for mGC and mCRC, where multiple mutations are possible (KRAS, NRAS, BRAF, TP53). In patients suffering from mCRC, this analysis in performed within routine procedures as such mutations are crucial for treatment decisions. In case of mGC mutations screening is done within the proposed project.