Effectiveness of a Fractionated Therapy Scheme in Tumor Treating Fields Therapy

• Published in: Technology in cancer research & treatment 2019, Vol.18, p.1533033819845008-1533033819845008
• Main Authors: Jo, Yunhui, Sung, Jiwon, Jeong, Hyesun, Hong, Sunghoi, Jeong, Youn Kyoung, Kim, Eun Ho, Yoon, Myonggeun
• Format: Article
• Language: English
• Subjects: Apoptosis - radiation effects; Biomarkers; Brain cancer; Cell Cycle - radiation effects; Cell Line, Tumor; Dose Fractionation, Radiation; Head & neck cancer; Head and Neck Neoplasms - diagnosis; Head and Neck Neoplasms - etiology; Head and Neck Neoplasms - metabolism; Head and Neck Neoplasms - radiotherapy; Humans; Immunohistochemistry; Original; Radiation therapy; Radiotherapy Planning, Computer-Assisted; Treatment Outcome; Tumors
• ISSN: 1533-0346; 1533-0338
• DOI: 10.1177/1533033819845008

This study aimed to evaluate the biological effectiveness of cancer therapy with tumor treating fields using a fractionated treatment scheme that was originally designed for radiotherapy. Discontinuous fractional tumor treating fields of an intensity of 0.9 to 1.2 V/cm and a frequency of 150 KHz were applied to U373 cancer cells and IEC6 normal cells for 3 days, with durations of 3, 6, 12, or 24 h/d. As the treatment duration of the tumor treating fields increased from 3 to 24 h/d, the relative tumor cell (U373) number (% of control) reduced in proportion to the treatment duration. Compared to a 25% cell number reduction (75% of control) for the group of 6 h/d treatment at 1.2 V/cm, only 5% (70% of control) and 8% (67% of control) of additional reductions were observed for the group of 12 and 24 h/d treatment, respectively. This experimental result indicates that the dependence on treatment duration in tumor cell inhibition was weakened distinctly at treatment duration over 6 h/d. For normal cells (IEC6), the relative cell number corresponding to the treatment time of the tumor treating fields at 1.2 V/cm of electric field strength was not decreased much for the treatment times of 3, 6, and 12 h/d, revealing 93.3%, 90.0%, and 89.3% relative cell numbers, respectively, but it suddenly decreased to ∼73% for the 24 h/d treatment. Our results showed that the effects of tumor treating fields on tumor cells were higher than on normal cells for treatment duration of 3 to 12 h/d, but the difference became minimal for treatment duration of 24 h/d. The fractionated scheme, using tumor treating fields, reduced the treatment time while maintaining efficacy, suggesting that this method may be clinically applicable for cancer treatment.