Breast cancer is the most common cancer in women. Surgery is the main treatment for early stage breast cancer. To treat a possible but undetectable metastasis and, thus, prevent recurrence, most doctors will recommend adjuvant systemic therapy, normally in the form of chemotherapy, following surgical resection. However, for some of these women, adjuvant chemotherapy is unnecessary. For these women, the risks of  chemotherapy-related harms can be higher than the actual cancer-related harms. 

With the evolution of genomic research enabling the genetic and molecular profiling of cancers, in recent years, an increasing number of biomarker-based tests which claim to identify those breast cancer patients who will benefit from adjuvant chemotherapy have entered the healthcare markets. The actual benefit and the reimbursement of such biomarker-based diagnostics for the use in breast cancer treatment is currently under assessment in several European jurisdictions. 

In Germany, the standards for the validation and reimbursement of novel diagnostics are very high, particularly, in case such diagnostics may potentially lead to the complete omission of a necessary standard treatment of a life threatening disease. Unlike companion diagnostics in the traditional sense, which aim to provide essential information for the safe and effective use of a certain corresponding drug, the concerned biomarker-based diagnostics are not related to a particular chemotherapy drug or method. They rather aim to support the treatment decision for or against adjuvant chemotherapy of a certain group of breast cancer patients in general. For a positive benefit assessment of such diagnostics,, the German pricing regulator basically demands data from prospective randomized trials. The standards are different elsewhere in Europe.