Could analysis of tumor cells from blood predict therapeutic outcome and challenge previous treatment methods?

Importance of tumor cells circulating in the blood

Many studies are focused on the development of targeted cancer therapies, and research into tyrosine kinase inhibitors and immune checkpoint inhibitors is becoming increasingly important. Nevertheless, cytotoxic chemotherapeutic agents remain the gold standard in the neoadjuvant or adjuvant treatment of tumors at various stages. The choice of mono- or combination therapy is often based on guidelines without any molecular or functional indication, which also reflects the limitations of such non-personalized therapy. For the treatment of metastatic breast cancer, taxol is used as first-line therapy, to which only 30% of patients respond. Another 30% achieve disease stagnation and 40% do not respond at all, still experiencing severe side effects and toxicity of this treatment.

Chemotherapy failure is due to tumor resistance, which is random, unpredictable, and only apparent during clinical evaluation of treatment response. If the resistance and sensitivity profile of the tumor could be recorded before the application of the therapy, it would lead to a significantly higher response rate and consequently a higher cure rate. In earlier attempts to test chemosensitivity from isolated tumor tissue, no clinical correlation could be found with the results. Other attempts, in which chemo and biosensitivity tests were done in the laboratory from circulating tumor cells, failed due to the low content of extracted tumor cells.

Chemotherapy failure is due to tumor resistance, which is random, unpredictable, and only apparent during clinical evaluation of treatment response. If the resistance and sensitivity profile of the tumor could be recorded before the application of the therapy, it would lead to a significantly higher response rate and consequently a higher cure rate. In earlier attempts to test chemosensitivity from isolated tumor tissue, no clinical correlation could be found with the results. Other attempts, in which chemo and biosensitivity tests were done in the laboratory from circulating tumor cells, failed due to the low content of extracted tumor cells. Chemotherapy failure is due to tumor resistance, which is random, unpredictable, and only apparent during clinical evaluation of treatment response.

If it were possible to record the profile of resistance and sensitivity of the tumor before the application of therapy, it would lead to a significantly higher response rate and consequently a higher cure rate. In earlier attempts to test chemosensitivity from isolated tumor tissue, no clinical correlation could be found with the results. Other attempts, in which chemo and biosensitivity tests were done in the laboratory from circulating tumor cells, failed due to the low content of extracted tumor cells. unpredictable and apparent only during clinical evaluation of treatment response. If the resistance and sensitivity profile of the tumor could be recorded before the application of the therapy, it would lead to a significantly higher response rate and consequently a higher cure rate.

In earlier attempts to test chemosensitivity from isolated tumor tissue, it was not possible to find any clinical correlation with the results. Other attempts, in which chemo and biosensitivity tests were done in the laboratory from circulating tumor cells, failed due to the low content of extracted tumor cells. unpredictable and apparent only during clinical evaluation of treatment response. If the resistance and sensitivity profile of the tumor could be recorded before the application of the therapy, it would lead to a significantly higher response rate and consequently a higher cure rate. In earlier attempts to test chemosensitivity from isolated tumor tissue, no clinical correlation could be found with the results.

Further attempts, in which chemo and biological sensitivity tests were done in the laboratory from circulating tumor cells, failed due to the low content of extracted tumor cells. this would lead to significantly higher response rates and consequently higher cure rates. In earlier attempts to test chemosensitivity from isolated tumor tissue, no clinical correlation could be found with the results. Other attempts, in which chemo and biosensitivity tests were done in the laboratory from circulating tumor cells, failed due to the low content of extracted tumor cells. this would lead to significantly higher response rates and consequently higher cure rates.

In earlier attempts to test chemosensitivity from isolated tumor tissue, it was not possible to find any clinical correlation with the results. Other attempts, in which tests for chemo and biological sensitivity from circulating tumor cells were made in the laboratory, failed due to the low content of extracted tumor cells.

The authors of the study "Clinical utility of circulating tumor-associated cells for predicting and monitoring chemo-response in solid tumors" (*) described a method that allows the detection, extraction and recovery of useful circulating tumor cells in the laboratory from the peripheral blood of patients with various solid tumors organs. Using this method, tumor cells were obtained from the blood of 5090 patients with a previous diagnosis of 17 different organ tumors. From this collective, tumor cells were isolated from a previous biopsy of tumor tissue from 230 patients. The chemosensitivity of circulating cancer cells was evaluated to different cytotoxic drugs and the results were tested for agreement with the chemosensitivity results of cells from tumor tissue. Both primary and secondary resistances of untreated and previously treated patients were identified.

Study design: description of patients

The study results come from an observational study and three interventional studies, all of which compare personalized therapy using molecular chemosensitivity analysis from tumor cells in blood or directly from tumor tissue and conventional therapeutic approaches with cytotoxic chemotherapeutics. 5090 patients were retrospectively divided into three study populations. Population 1 consists of 230 patients who first received a blood sample and then a tumor biopsy. Some of these patients have already been treated.

The second population consists of 2201 patients whose blood was taken and who were already treated with a cytotoxic chemotherapeutic agent. Population 3 consists of 2734 patients whose blood was drawn and whose tumor had not yet been treated. There is some overlap between the populations. All mononuclear cells from blood samples were epigenetically treated, after which cell death was induced in healthy cells with an intact apoptosis signaling cascade. The cells associated with the tumor thus remained. The obtained tumor cells could now be immunohistochemically typed and assigned to different organs and carcinomas.

The chemosensitivity test was performed on microtitre plates with a specific number of cells and one chemotherapeutic agent per dish. Sensitivity is tested using light transmittance, which correlates with the rate of apoptosis. Thus, the highest and lowest sensitivity could be tested for each tumor cell line. In population 1, the chemosensitivity of different chemotherapeutic agents was first tested on tumor biopsy cells and then compared with the results from circulating cancer cells. In populations 2 and 3, only those chemotherapeutic agents used according to the guidelines for the respective cancer types were tested. A chemotherapeutic agent was considered sensitive if cell death was detected in more than 50% of cells 12 h after initial exposure.

Results of different groups of patients

In population 1, the resistance and sensitivity results of tumor cells circulating in the blood and cells taken directly from the tumor tissue were compared. The results match at 93.7%.

In population 3, resistance to cytotoxic chemotherapeutic substances was detected in 58.9%, which points to the innate internal resistance of tumor cells. Out of 2734 patients, 77 people underwent a follow-up radiological examination after six months. In the 33 patients who showed high sensitivity to the tested chemotherapeutic agents, a complete or partial response to treatment could be determined by PET-CT in 32 (97%) patients. The in-vitro/in-vivo agreement is therefore 97%. In 18 cases (41%) of 44 patients in whom sensitivity was not determined chemically, even radiological examination showed no improvement.

In population 2, resistance to cytotoxic chemotherapeutics was found in 77.8% of patients. As a result, many tumor cells develop acquired resistance to chemotherapeutic agents that have already been used. In this population, 143 patients were radiologically monitored. All of them showed a worsening of the cancer and the condition of the disease. Laboratory analyzes showed a chemical match with drug resistance in 124 patients. The in vitro/in vivo agreement here is 86.7%.

Conclusion: A promising therapeutic approach in cancer patients

Although the identification of resistance is of great importance for optimal cancer treatment, no technology has yet been established to identify innate and prospective resistance. Today's methods have a long turnaround time, show low clinical consistency, and are highly invasive, requiring a large amount of tissue biopsy. The high invasiveness and rapid progression of the tumor make these methods obsolete.

This study shows a method by which a chemosensitivity profile can be quickly and non-invasively created. In addition, not only tumor cells are recorded, but also tumor-related cells such as macrophages and fibroblasts. They significantly contribute to tumor progression, for example by suppressing antitumor immunity. Thanks to epigenetic modification, it is possible to quickly obtain tumor cells and then directly test chemotherapy substances.

The study also confirms that the tumor cells circulating in the blood adequately represent the tumor present. It was also possible to determine significant correspondences between therapeutic response rates in radiology and chemosensitivity profiles. Thus, chemosensitivity tests can accurately predict the success or failure of chemotherapy and are used for long-term follow-up of cancer patients.

In addition, the study authors found high variability between patients within different types of cancer. Therefore, it is advisable to create a chemosensitivity profile before starting therapy to avoid therapy failures, rapid spread of cancer, and unnecessary administration of toxic substances with significant side effects. Knowledge of the in vitro susceptibility profile enables rapid identification of resistance and may provide significantly improved and personalized therapeutic approaches. The presented method is non-invasive and cost-effective. In addition, it provides real-time synchronous information during diagnosis and continuously during therapy.