Evaluation of the effect of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) techniques on survival response in cell lines with a new radiobiological modeling.

BACKGROUND: The optimal radiobiological model, which assesses the biological effects of novel radiotherapy techniques that concurrently modify multiple physical factors, has not yet been defined. This study aimed to investigate the impact of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) on cellular response in head and neck cancer and melanoma models. METHODS: Clonogenic analysis, DNA double-strand break analysis, apoptosis, and cell cycle analysis were performed on cancer stem cell models, cancer models, and normal tissue cell models to assess radiation sensitivity. RESULTS: The segmented radiation approach used in IMRT applications enhanced radiosensitivity and cytotoxicity in the cancer models, while changes in dose rate had varying effects on cytotoxicity depending on the tumor cell type. VMAT increased cellular resistance, favoring treatment outcomes. CONCLUSIONS: The biological processes were influenced differently by dose rate, IMRT, and VMAT depending on the tumor cell type. The selection of the most appropriate technique is crucial in representing new radiotherapy approaches. The obtained data can serve as a model to address clinical questions in daily practice. The integration of non-standard outcomes with standard applications should be considered in clinical settings.

Dosimetric evaluation of different radiotherapy techniques in mastectomized left-sided breast cancer.

CONTEXT: Inclusion of internal mammary lymph nodes in mastectomized left breast cancer radiotherapy may lead to high dose receiving risk of the heart, lung, and contralateral breast. AIM: The aim of this study is to compare the dosimetric differences of field-in-field (FIF), volumetric-modulated arc therapy (VMAT), seven-field intensity-modulated radiotherapy (7F-IMRT), and helical tomotherapy (HT) planning techniques for mastectomized left breast cancer. MATERIALS AND METHODS: Computed tomography images of ten patients treated with the FIF technique were used to compare four different treatment planning techniques. Planning target volume (PTV) included chest wall and regional lymph nodes. The heart, left anterior descending coronary artery (LAD), left and whole lung, thyroid, esophagus, and contralateral breast were identified as organs-at-risks (OARs). Except for HT, a single isocenter in PTV and bolus of thickness 0.3 cm on the chest wall was used. Complete and directional blocks were applied in HT, and the dosimetric parameters of PTV and OARs for four different techniques were analyzed using the Kruskal-Wallis test. RESULTS: 7F-IMRT, VMAT, and HT were superior to the FIF technique in providing homogeneous dose distribution covering the PTV (P < 0.0001). Mean doses (Dmean) of the contralateral breast and esophagus, lung, and body-PTV V5 (volume receiving 5 Gy) were reduced in FIF, whereas in the HT, Heart Dmean, LAD Dmean , Dmax, healthy tissue (body-PTV) Dmean , heart and left lung V20, and thyroid V30 were significantly reduced (P < 0.0001). CONCLUSIONS: FIF and HT techniques were found to be significantly advantageous over 7F-IMRT and VMAT for OARs. Using those three multiple-beam techniques reduced high-dose volumes of healthy tissues and organs in mastectomized left breast cancer radiotherapy but also increased low-dose volumes and contralateral lung and breast doses. Complete and directional blocks applied in HT reduce heart, lung, and contralateral breast doses.