3D-image-guided HDR-brachytherapy versus 2D HDR - brachytherapy after external beam radiotherapy for early T-stage nasopharyngeal carcinoma

Background: Two-dimensional high-dose-rate brachytherapy (2D-HDR-BT) is an effective method of dose escalation for local tumor control in early T-stage nasopharyngeal carcinoma (NPC). Treatment outcomes for 3D-image-guided high-dose-rate brachytherapy (3D-image-guided-HDR-BT) after external beam radiotherapy (ERT) have not been examined in early T-stage NPC patients. The current study was designed to evaluate whether addition of 3D-HDR-BT to ERT showed further improvement in treatment outcomes in patients with early T-stage NPC when compared to 2D-HDR-BT after ERT. Methods: The current study retrospectively analyzed and compared treatment outcomes for patients with nonmetastatic stage T1-2b NPC treated with 2D-HDR-BT (n = 101) or 3D-HDR-BT (n = 118) after ERT. Patients in both groups were treated with ERT at a mean dose of 60 Gy and a brachytherapy dose of 12Gy (8 similar to 20Gy), 2.5 similar to 5Gy per fraction under local anesthesia. Results: Compared to patients treated with 2D-HDR-BT after ERT, patients treated with 3D-HDR-BT after ERT showed improvement in five-year actuarial local control survival rates (p = 0.024), local/regional relapse-free survival rates (p = 0.038), and disease-free survival rates (p = 0.021). Multivariate analysis showed that NPC patients treated with 3D-HDR-BT had improved local control survival (p = 0.042). The incidence rates of acute or chronic complications were similar between two groups. Conclusions: The current study showed that 3D-image-guided HDR-BT after ERT was an effective treatment modality for patients with stage T1-2 NPC with acceptable complications. The improvement in local tumor control and disease free survival is likely due to improved conformal dose distributions.