A feasibility study of a modified treatment strategy combined external beam radiation therapy and brachytherapy for cervical cancer.

ABSTRACT

PURPOSE: To evaluate the feasibility of a modified treatment strategy combined external beam radiation therapy (EBRT) and brachytherapy (BT) for cervical cancer through a dosimetry analysis. MATERIAL AND METHODS: This study retrospectively selected 12 cervical cancer patients treated with the conventional treatment strategy, which consisted of 45─50 Gy/25 fractions of EBRT using volumetric-modulated arc therapy (VMAT) and image-guided BT with a fraction dose of 5─7 Gy. The modified treatment strategy decreased the central EBRT dose while increasing the number of BT fractions. New target volumes were additionally contoured, and new VMAT EBRT plans were generated for the modified treatment strategy. The dosimetric parameters for evaluation included the doses to the most irradiated 2 cc (D2cc) of the organs at risk (OARs) and doses to at least 90% (D90) of the gross tumor volume (GTV) and high-risk clinical target volume (HR-CTV). The total doses to OARs and targets obtained by adding the equivalent doses in 2 Gy fraction (EQD2) from the EBRT and BT plans were used for quantitative comparison between the modified and conventional treatment strategies. RESULTS: Comparison to the conventional treatment strategy, the modified treatment strategy resulted in a higher bladder D2cc, a slightly lower rectal D2cc and a similar HR-CTV D90, all with no significant differences (p > 0.05). The GTV D90 of the modified treatment strategy was significantly higher than that of the conventional treatment strategy (p < 0.01). CONCLUSION: The modified treatment strategy can significantly increase the BT dose while remaining the total doses to the bladder and rectum basically unchanged, demonstrating its feasibility and promising prospect in clinical use.