(P015) Radiation Biological Responses of MRI-Linac vs Linac in Human Head and Neck and Lung Cancer Cells

April 30, 2015

The 1.5-T MF generated by MRL had no effect on the viability or radioresponses of NSCLC or HNSCC cell lines in vitro. These results suggest that MRL, as a novel cancer treatment technology, has the potential not to influence the radiotherapy outcome of patients. Considering the complicated in vivo microenvironment, further in vivo study is warranted.

Li Wang, Marco van Vulpen, Zhifei Wen, Stan Hoogcarspel, David P. Molkentine, Jan Kok, Steven Hsesheng Lin, R. Broekhuizen, Kie-kian Ang, A.N. Bovenschen, Bas Raaymakers, Steven Jay Frank; UT MD Anderson Cancer Center; University of Utrecht Medical Center

OBJECTIVE: The MRI-Linac (MRL) is a novel radiotherapy technology designed to enable high cure rates with low toxicity and treatment response monitoring. However, the biological influence on radioresponses of human solid tumors within the 1.5-T magnetic field (MF) generated by MRL is unknown. Our hypothesis is that the 1.5-T MF has no influence on cell viability or radiation effects.

METHODS: Two non–small-cell lung carcinoma (NSCLC) lines (H460 and H1299) and two head and neck squamous cell carcinoma (HNSCC) lines (HN-5 and UMSCC-47) were used. The influences of a 1.5-T MF on in vitro cell viability and on cellular radioresponses were determined by cell plate efficiency (PE) and by clonogenic cell survival assay (CSA) after exposing the cells to graded single doses or fractionated 6 MV radiation using Linac (100 MU/min) or MRL (134 MU/min), respectively. The experiments were performed with cell flasks placed inside a 37°C water bath with an optimized radiation dose distribution. The radiation output of Linac and the MRL was measured with a corrected chamber. The physical dose received by the cells was verified using radiation detectors. The results were analyzed by t-test.

RESULTS: Our results supported a very strong trend that MF, as a single factor, had no influence on cell viability. No significant PE change occurred after single exposure or multiple exposures to MF compared with the Linac environment for the four cell lines (12 of 16 experiments; all P > .05) except for one experiment with the H460 cells (borderline; P = .044) andthree experiments withUMSCC-47 cells. Similarly, single exposure or multiple exposures to MF had no influence on cell radioresponse (all P > .05). When the cells were exposed to MRL or Linac treatment for up to four times, no significant changes were observed for the D0s for with MF vs without MF (all P > .05).

CONCLUSIONS: The 1.5-T MF generated by MRL had no effect on the viability or radioresponses of NSCLC or HNSCC cell lines in vitro. These results suggest that MRL, as a novel cancer treatment technology, has the potential not to influence the radiotherapy outcome of patients. Considering the complicated in vivo microenvironment, further in vivo study is warranted.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org