Impacts of different tracking methods on short-term therapeutic effect of cyberknife in treatment of Jung cancer

Objective: To investigate the impacts of fiducial tracking and X-sight tracking on the short-term therapeutic effect of cyberknife in the treatment of lung cancer. Methods: Retrospective analysis was performed on 64 lung cancer patients (72 lesions), including 40 primary tumor patients (41 lesions) and 24 metastatic tumor patients (31 lesions), who were treated with cyberknife. Fiducial tracking was used for 45 lesions, while X-sight tracking was used for 27 lesions. The planning target volume was covered by 70%-94% (median 80%) isodose contour. The irradiation dose was 60 Gy/3 fractions. The relationship between short-term therapeutic effect and tracking method was determined. Results: Overall, the lesions undergoing fiducial tracking showed significantly higher response rate than those undergoing X-sight tracking (93% vs. 74%, χ² = 6.84, P = 0.033), and so was in lower lung lesions (15% vs. 7%, χ² = 7.18, P = 0.028). But the two tracking methods achieved similar effects in upper lung lesions (28% vs. 12%, χ² = 2.36, P = 0.310). In the lesions with treatment volumes smaller than 15 cm³, the fiducial tracking achieved significantly higher response rate than the X-sight tracking (25% vs. 12%, χ² = 6.53, P = 0.038), but the two tracking methods achieved similar effects in the lesions with treatment volumes not smaller than 15 cm³ (17% vs 8%, χ² = 1.57, P = 0.460). Overall, the lesions undergoing X-sight tracking had significantly higher treatment failure rate than fiducial tracking (19 % vs. 2%, χ² = 6.33, P = 0.021). Conclusions: Different tracking methods may lead to different therapeutic effects of cyberknife in the treatment of lung cancer, which are related to lesion location and treatment volume. (authors)