Radiosensitivity Differences between EGFR Mutant and Wild-Type Lung Cancer Cells are Larger at Lower Doses

In the era of precision medicine, radiotherapy strategies should be determined based on genetic profiles that predict tumor radiosensitivity. Accordingly, pre-clinical research aimed at discovering clinically applicable genetic profiles is needed. However, how a given genetic profile affects cancer cell radiosensitivity is unclear. To address this issue, we performed a pilot in vitro study by utilizing EGFR mutational status as a model for genetic profile. Clonogenic assays of EGFR mutant (n = 6) and wild-type (n = 9) non-small cell lung carcinoma (NSCLC) cell lines were performed independently by two oncologists. Clonogenic survival parameters SF(2), SF(4), SF(6), SF(8), mean inactivation dose (MID), D(10), D(50), α, and β were obtained using the linear quadratic model. The differences in the clonogenic survival parameters between the EGFR mutant and wild-type cell lines were assessed using the Mann–Whitney U test. As a result, for both datasets, the p values for SF(2), SF(4), D(50), α, and α/β were below 0.05, and those for SF(2) were lowest. These data indicate that a genetic profile of NSCLC cell lines might be predictive for their radiation response; i.e., EGFR mutant cell lines might be more sensitive to low dose- and low fraction sized-irradiation.