Author: John T Barrett, Dan Heo, Chulhaeng Huh, Farshad Mostafaei 👨🔬
Affiliation: Department of Radiation Oncology, Medical College of Georgia, Augusta University, Department of Radiation Oncology, Augusta University 🌍
Purpose: This study aimed to compare the tumor control probability (TCP) of radiation therapy (RT) and magnetic hyperthermia combined with RT (MHRT) in the human prostate cancer cells based on radiobiological modeling.
Methods: Biological modeling was conducted to estimate the radiobiological responses of PC3 and LNCaP cells. The initial values were obtained from in vitro experiments on RT, MHRT, and RT combined with conventional hyperthermia (HTRT). To describe both the direct cytotoxic and radiosensitizing effects simultaneously, the Arrhenius equation and the linear-quadratic model were employed, respectively. TCP was estimated using a Poisson TCP model, incorporating assumptions about target tumor volume, clonogenic cell density within the tumor, and the Lea-Catcheside protection factor. For TCP estimation, the clinical scenario was set to 20 fractions of RT with a dose of 1.0 Gy per fraction. Radiation doses that achieved 50% TCP (TCP50) were calculated to compare the treatment approaches.
Results: PC3 cells were more sensitive to both HTRT and MHRT than LNCaP cells, while PC3 exhibited higher radioresistance to RT. When HTRT was applied at 43oC for 30 minutes, the α/β ratio increased 13-fold in PC3 and 4-fold in LNCaP cells compared to RT alone. The additional therapeutic effect of magnetic hyperthermia was similar in both cell lines. TCP50 values were significantly reduced in both PC3 and LNCaP when HTRT or MHRT was applied. Specifically, TCP50 decreased approximately 4-fold and 5-fold in PC3 when HTRT and MHRT were applied, respectively, compared to RT. In LNCaP, TCP50 decreased approximately 2-fold.
Conclusion: The therapeutic enhancement induced by HTRT and MHRT was clearly demonstrated through TCP estimation. While there was only a small difference between HTRT and MHRT in both cell lines, MHRT is expected to yield better therapeutic outcomes in clinical practice due to its precise temperature and margin control capabilities.