Showing papers by "Ramesh Rengan published in 2013"

A moving target: Image guidance for stereotactic body radiation therapy for early-stage non-small cell lung cancer

Abstract: Purpose Precise patient positioning is critical due to the large fractional doses and small treatment margins employed for thoracic stereotactic body radiation therapy (SBRT). The goals of this study were to evaluate the following: (1) the accuracy of kilovoltage x-ray (kV x-ray) matching to bony anatomy for pretreatment positioning; (2) the magnitude of intrafraction tumor motion; and (3) whether treatment or patient characteristics correlate with intrafraction motion. Methods and Materials Eighty-seven patients with lung cancer were treated with SBRT. Patients were positioned with orthogonal kV x-rays matched to bony anatomy followed by cone-beam computed tomography (CBCT), with matching of the CBCT-visualized tumor to the internal gross target volume obtained from a 4-dimensional CT simulation data set. Patients underwent a posttreatment CBCT to assess the magnitude of intrafraction motion. Results The mean CBCT-based shifts after initial patient positioning using kV x-rays were 2.2 mm in the vertical axis, 1.8 mm in the longitudinal axis, and 1.6 mm in the lateral axis (n = 335). The percentage of shifts greater than 3 mm and 5 mm represented 39% and 17%, respectively, of all fractions delivered. The mean CBCT-based shifts after treatment were 1.6 mm vertically, 1.5 mm longitudinally, and 1.1 mm laterally (n = 343). Twenty-seven percent and 10% of shifts were greater than 3 mm and 5 mm, respectively. Univariate and multivariable analysis demonstrated a significant association between intrafraction motion with weight and pulmonary function. Conclusions Kilovoltage x-ray matching to bony anatomy is inadequate for accurate positioning when a conventional 3-5 mm margin is employed prior to lung SBRT. Given the treatment techniques used in this study, CBCT image guidance with a 5-mm planning target volume margin is recommended. Further work is required to find determinants of interfraction and intrafraction motion that may help guide the individualized application of planning target volume margins.

Comparison of Intensity Modulated Radiation Therapy, Adaptive Radiation Therapy, Proton Radiation Therapy, and Adaptive Proton Radiation Therapy for Small Cell Lung Cancer

Abstract: Purpose/Objective(s): To evaluate the role of three-dimensional radiation therapy for Non-Small Cell Lung Cancer (NSCLC) patients with bone metastasis. Materials/Methods: Clinical data of 95 NSCLC patients with bone metastases were collected, all patients received radiation to thoracic primary tumor and 2 cycles chemotherapy. The Kaplan-Meier method was used to calculate the OS. The log-rank test was used to compare the survival curves. Multivariate Cox regression analysis was used to test independent significant prognostic factors for OS. Results: For these 95 patients, 47 patients had only bone metastasis, 48 had bone concur with other organ metastasis. The median survival time (MST) was 11.0 months (95% CI, 8.5-13.5), and the 1-, 2and 3-year overall survival rate was 43.6%, 16.8% and 8.5%, respectively. The MST was 15.0 months for patients received radiation dose to primary tumor 63 Gy, whereas 9.0 months for those with dose <63 Gy (chi-squareZ 11.038, p Z 0.001). Patients with treatment response (CR + PR) to primary tumor had longer median OS time than those without response (SD + PD) (13.0 months vs 7.0 months, chi-square Z 4.364, p Z 0.037). Overall survival was significantly prolonged in patients with received 4 cycles chemotherapy vs <4 cycles, the MSTwas 14.0 months vs 8.0 months (chi-square Z 6.800, p Z 0.009), radiation to metastatic sites was not correlated with OS. Radiation dose to primary tumor 63 Gy remained significance when patients with bone metastasis only and those had bone intercurrent with other organ metastasis were analyzed separately. For patients with bone metastasis only, patients with T1-2 tumors had longer OS than those with T3-4 tumors, the 1-, 2and 3-year overall survival rate was 50.0% vs 39.5%, 27.8% vs 9.3%, 18.5% vs 2.3% (chi-square Z 3.912, p Z 0.048), respectively; radiation to metastatic sites was marginally significant correlated with OS (chi-squareZ 2.757, pZ 0.097); and patients received 4 cycles chemotherapy and <4 cycles had similar survival times, the MST was 14.0 months vs 12.0 months (chi-square Z 0.756, p Z 0.385). On multivariate analysis, radiation dose 63 Gy, and bone metastasis only were independent prognostic factors for better OS. Conclusions: Radiation dose to primary tumor 63 Gy and bone metastasis only are associated with better overall survival in NSCLC patients with bone metastasis. For patients with bone metastasis only, besides radiation dose, T status was also correlated with OS, whereas the number of chemotherapy cycles was not, aggressive thoracic radiation play an important role in improving OS. Author Disclosure: S. Su: None. B. Lu: None. W. Ouyang: None. Q. Li: None. Y. Hu: None. Z. Ma: None. H. Li: None.