4-D CT Based and Daily In-room CT-guided Stereotactic Body Radiotherapy (SBRT) for Lung Cancer

Article Outline

• Purpose/Objective(s)
• Materials/Methods
• Results
• Conclusions
• Copyright

Back to Article Outline

Purpose/Objective(s) 

To evaluate the therapeutic efficacy of image-guided SBRT and treatment-related toxicities in patients with peripherally or centrally located, medically inoperable stage I or isolated recurrent NSCLC.

Back to Article Outline

Materials/Methods 

113 patients with NSCLC who underwent 4-D CT based planning and daily CT-on-rail guided SBRT were studied. The internal gross target volume (IGTV) was delineated and verified for each respiratory phase of the 4D CT data set. The clinical target volume consisted of the IGTV plus an 8-mm margin. A 3-mm setup uncertainty margin was added to the planning target volume (PTV). Daily alignments, range of shifts from the external setup marks were analyzed. The GTV position in daily CT scan was aligned and compared to the aligned bony reference structure.

Among 73 patients with clinical outcome data, 46 had stage I disease and 27 had isolated recurrent disease. 21 patients had centrally located lesions, defined as within 2 cm of the bronchial tree, major vessels, esophagus, heart, or other mediastinal structures, but no direct invasion. The prescribed dose was 50 Gy (40 Gy for in-field recurrent disease) to the PTV delivered in 4 consecutive days. Dosing to the major mediastinal critical organs was restricted to 40 Gy delivered to less than 10 cc except for the esophagus, for which dosing was restricted to no more than 1 cc at 40 Gy.

Back to Article Outline

Results 

Daily shifts (mean 3D vector: 0.9 ± 0.6 cm; range 0–3.3 cm) from the external marks to the final treatment position were required. Statistically significant inter-fractional GTV shifts relative to the bone happened in 30% of cases and systematic trend of more than 5 mm occurred in 10% of cases. Daily CT on-rail provides the advantage of 3-D bony alignment and soft tissue visibility that guided the decision of the final treatment position.

With 3 to 28 months follow-up, the overall progression-free survival rate at the treated site was 95.9%. For stage I disease, the complete response (CR), partial response (PR), and stable disease (SD) rates were 43.5%, 33.3%, and 21.0%, respectively. No significant differences in response rate were seen between stage Ia (n = 39) and Ib (n = 7) disease. Two (4.3%) and three patients (6.5%) with stage I disease developed mediastinal lymph node or distant metastasis respectively. For patients with isolated recurrent disease, the CR, PR, and SD rates were 51.9%, 25.9%, and 15.8%, respectively. Three (11.1%) and five (18.5%) of these patients experienced mediastinal lymph node metastasis or distant metastasis respectively. In stage I disease, 6.5% (three patients) had grade 2 but no grade 3 or above radiation pneumonitis. In three patients with recurrent disease, dyspnea worsened after SBRT, and one patient needed nasal oxygenation/hospitalization. No esophagitis was noted in all patients. Grade 2 and 3 dermatitis developed in 22.8%, 4.1% respectively of patients at the treated site, which appeared to be related to the dose (>35 Gy) and volume of skin treated. Three patients developed chronic skin scar, and five had chronic mild neurogenic chest pain due to intercostal nerve injury. No increased toxicity was noted in centrally located lesions than in peripherally located lesions.

Back to Article Outline

Conclusions 

Image-guided SBRT using 50 Gy delivered in four fractions resulted in excellent local progression-free survival rates with minimal toxicity in both peripherally and centrally located stage I or recurrent NSCLC.