Toxicity outcome of endorectal brachytherapy boost in medically inoperable patients.

AIM: This communication reviews results and toxicity of image-guided high-dose-rate endorectal brachytherapy (HDREBT) boost after external beam radiotherapy (ERT) in medically inoperable patients with rectal cancer. MATERIALS AND METHODS: A total of 18 patients with rectal cancer and clinical stage T2-4N0­2 treated with HDREBT boost after ERT were retrospectively reviewed. RESULTS: Following treatment with a median total dose (EQD2, α/ß = 10) of 66 Gy (range 48-92 Gy), the incidence of early and late rectal grade 3 toxicity was 11% and 19%, respectively. There was no correlation between the occurrence of acute and late toxicity. CONCLUSION: With proper technique, a combined approach using EBRT and HDREBT was associated with acceptable toxicity in medically inoperable rectal cancer patients.

Single fraction computed tomography-guided high-dose-rate brachytherapy or stereotactic body radiotherapy for primary and metastatic lung tumors?

PURPOSE: To provide a pilot dosimetric study of computed tomography (CT)-guided high-dose-rate (HDR) brachytherapy (BRT) and stereotactic body radiotherapy (SBRT) for primary and metastatic lung lesions. MATERIAL AND METHODS: For nine lung primary and metastasis patients, 3D image-based BRT plan using a single virtual catheter was planned for 34 Gy in single fraction to the gross tumor volume (GTV) + 3 mm margin to account for tumor deformation. These plans were compared to margin-based (MB-) and robustness optimized (RO-) SBRT, assuming the same tumor deformation under real-time tumor tracking. Consistent dose calculation was ensured for both BRT and SBRT plans using the same class of collapsed cone convolution superposition algorithm. Plan quality metrics were compared by Friedman tests and Wilcoxon t-tests. RESULTS AND CONCLUSIONS: Brachytherapy plans showed significant higher GTV mean dose compared to MB- and RO-SBRT (122.2 Gy vs. 50.4 and 44.7 Gy, p < 0.05), and better dose gradient index (R50) = 2.9 vs. 4.3 and 8.4 for MB- and RO-SBRT, respectively. Dose constraints per the RTOG 0915 protocol were achieved for all critical organs except chest wall in BRT. All other dose-volume histograms (DVH) metrics are comparable between BRT and SBRT. Treatment delivery time of BRT and SBRT plans significantly increased and decreased with increasing GTV size, respectively. SBRT using advanced MLC tracking technique and non-coplanar VMAT can achieve comparable dosimetric quality to HDR BRT. Whether or not, the significantly higher GTV dose can increase killing of radioresistant tumor cells and offset the effect of tumor reoxygenation in single fraction BRT, requires further clinical investigation.