Chemotherapy side effects occur as a result of affecting the rapidly dividing normal physiology cells in the body and can reach levels that threaten the life of the person.

As cancer-targeting treatment methods will not only avoid the problems caused by side effects but also provide cancer-specific treatment, more effective and cancer-specific treatment methods such as “smart drug therapies” and “immunotherapy” have begun to be developed as a result of extensive research in this field in recent years. Thanks to cancer-specific biomarker discoveries, questions about the details of why the disease occurs, what to expect in the follow-up of the disease (prognosis), and how the treatment response will be, have begun to be answered.

“Tumor mutation burden (TMB), a new concept noticed in the results of biomarker and cancer relationship research, refers to the total number of mutations in a tumor. “Somatic mutations”, which are mutations that do not exist in our genome from birth but only occur in tumor cells, can be analyzed and calculated with new generation methods using many genomic data and algorithms.

It has been found that immunotherapy response is better in tumors with tumor mutation burden above a certain level. Although our immune system cells act for good purposes in the fight against cancer during the development and spread of cancer cells, they can also have negative effects depending on the molecules produced by the immune cells. The amount of somatic mutations reflects the burden of neoantigens, that is, when TMB is high, the expression of neoantigens is also high.

“Foundation Medicine”, an international organization, has so far conducted research on more than 1300 patients for 21 types of cancer. First, in non-small cell lung cancer (NSCCA), combined immunotherapy was observed to increase progression-free survival in patients with increased tumor burden.

PD-L1 (programmed cell death ligand): It is a molecule that allows healthy cells to escape from the immune system. It suppresses the immune system from overreacting. Tumor cells have the ability to block this checkpoint and evade immune cells (T cells). With immunotherapy, checkpoint inhibitors work, reducing PD-L1 activity, T cells are reactivated and directed towards cancer cells. PD-L1 expression can be examined by immunohistochemistry analysis. If the score is high, it means that immunotherapy may benefit. The disadvantage of this analysis performed by immunohistochemistry is that it is difficult to prepare and the interpretation of the results is subjective.