Liquid Biopsy
Actionable mutations from circulating tumour DNA, without taking tissue again. Focused by digital PCR for ESR1, PIK3CA, BRAF V600 and RAS-G12 — or broad through the focused panel from blood.
Under endocrine therapy, resistance mutations arise. They are therapeutically addressable, but they do not appear in the report on the primary tumour — they develop under the pressure of treatment, often years later and frequently in only part of the tumour burden.
Liquid biopsy catches this where a re-biopsy is impractical: with multiple lesions, with poorly accessible metastases, in patients for whom a further procedure is unreasonable. And it reflects what is circulating at the moment of sampling, not what stood in the primary tumour three years ago.
From plasma we offer two routes, and which one fits depends on the question.
The focused route: digital PCR. When a single marker touches the therapy, dPCR is the most sensitive choice. At low tumour burden, the fraction of mutated alleles in plasma lies in the per-mille range. This is where the strength of digital PCR lies: it is built for the detection of the smallest allele frequencies. This is how we determine ESR1 and PIK3CA in breast cancer, BRAF V600 and the RAS-G12 variants where they are treatment-decisive.
The broad route: the focused panel from blood. When a single marker is not enough, we also run the focused panel from plasma — circulating DNA and RNA together, around 50 genes, including fusions. This is the route when no tissue is available and the question is broader than a single dPCR can answer.
Digital PCR is validated for the detection of the smallest allele frequencies from plasma down to 0.1 %. From tissue (FFPE) the limit is 5 %. The difference has a reason: in plasma the mutated fraction at low tumour burden is extremely small, and that is exactly where dPCR brings its sensitivity to bear.
With circulating tumour DNA the preanalytics matter more than with tissue. The Streck tube stabilizes the cell-free DNA, but the time between collection and processing remains the critical factor. Hence the cooled return shipping on the day of collection and the four-day window. Discuss the case with us beforehand, and the logistics are right from the first sample on.
The report is issued in English and signed by a specialist in pathology.
One point we state openly: a negative result does not rule out a mutation. At low tumour burden, too little tumour DNA may be circulating to detect it. Liquid biopsy is good at finding a mutation — it is worse at proving its absence. Reading it the other way leads to the wrong conclusion.
Clarify the preanalytics beforehand
With ctDNA, the route from collection to laboratory decides. Talk to us before the first sample is on its way.