The role of positron emission tomography following radiosurgical treatment of malignant lung lesions.

OBJECTIVE: To establish response patterns in PET following stereotactic body radiotherapy (SBRT) of malignant lung lesions. METHODS: Patients with malignant lung lesions treated with SBRT were retrospectively reviewed. All patients received 40-52 Gy in three to five equal fractions. An independent, blinded radiologist reassessed all 18F-fluoro-deoxy-glucose PET/computed tomography scans to determine the tumor maximum standardized uptake value (SUVmax) and size changes. RESULTS: Thirty-nine patients were included in this study. Of the 47 lesions treated, there were 22 primary and 25 metastatic lung lesions. In total, 86 PET/computed tomography studies were reviewed. The mean SUVmax values decreased markedly and stabilized after 6 months following the treatment of primary lesions. Metastatic lesions showed greater variability, with an overall increase in SUVmax values until 6 months and decrease thereafter. Of the eight local failures, the mean SUVmax and size change from nadir values to biopsy-proven failure were 117 and 215%; however, it was difficult to measure the size of five lesions because of fibrotic changes. Statistical analysis revealed metastatic tumors to be associated with poorer local control (P=0.028). No correlation was found between size or pretreatment SUVmax and outcome. CONCLUSION: Anticipated SUVmax and size patterns following SBRT remain a challenge due to surrounding tissue reactions. Nonetheless, marked SUVmax changes can aid in determining local failure. Increases in size were also observed in local failures; however, localized fibrosis challenges its utility in distinguishing failures from a normal tissue response. A larger series needs to be examined to better establish the correlation of PET responses to overall survival and local control.

Frameless image-guided stereotactic body radiation therapy for lung tumors with 4-dimensional computed tomography or 4-dimensional positron emission tomography/ computed tomography.

BACKGROUND/PURPOSE: To augment the accuracy of stereotactic body radiation therapy (SBRT), a variety of image guidance systems are used for patient positioning and target localization. Clinical outcomes evaluating these systems, especially frameless image-guided systems, are still limited. This article aims to describe and evaluate our frameless image-guided SBRT technique for lung tumors. METHODS: Between 2007 and 2009, 85 pulmonary tumors (50 primaries and 35 metastases) were treated with SBRT using daily image guidance for patient positioning and target localization in lieu of a body frame. Four-dimensional computed tomography (4DCT) or an in-house protocol for integrated 4D positron emission computed tomography (4DPET/CT) was used for planning simulation. RESULTS: Median follow-up was 17 months (range, 4-42). Median overall survival (OS) was 31 months (95% CI, 26-34), and median local failure-free survival was 30 months (95% CI, 18-32). At last follow-up, 9 of 83 evaluable lesions failed locally. Actuarial local control at 24 months was 87% (95% CI, 75-98) and was significantly worse for metastatic lesions (95% vs. 74%; P = .045; log-rank test). No acute or late toxicities (grade ≥ 4) were observed. CONCLUSIONS: Frameless image-guided SBRT is a feasible, safe, and effective treatment for lung tumors.

Locoregional and distant failure following image-guided stereotactic body radiation for early-stage primary lung cancer.

PURPOSE: To report our institutional experience using image-guided stereotactic body radiation therapy (SBRT) for early stage lung cancer, including an analysis into factors associated with nodal and distant failures (NF, DF). METHODS: Forty-eight patients with early-stage primary lung cancer were treated with image-guided SBRT between 2007 and 2009. Median prescription dose was 48 Gy in 4 fractions. Toxicity was graded according to the NCI CTCAE v3.0 scale. RESULTS: Local failure was detected in two lesions and actuarial 24-month local control was 95%. At 24 months, the cumulative incidence of NF was 6%, and DF was 29%. Larger lesions (>3 cm) and younger age (<70 years) were the only factors found to be significantly correlated with increased DF (p=0.005 and p=0.015, respectively). A single grade ≥ 3 toxicity was observed. After adjusting for age and lesion size, distant failure was significantly associated with a poorer OS (Cox regression, p=0.0059). CONCLUSION: Image-guided SBRT can produce excellent LC rates with minimal toxicity. Distant failure was a major determinant of OS and the most common pattern of failure, indicating a potential role for systemic therapy in younger patients with large lesions.

Toxicity analysis of postoperative image-guided intensity-modulated radiotherapy for prostate cancer.

PURPOSE: To report on the acute and late gastrointestinal (GI) and genitourinary (GU) toxicity associated with a unique technique of image-guided radiotherapy (IGRT) in patients undergoing postprostatectomy irradiation. METHODS AND MATERIALS: Fifty patients were treated with intensity-modulated radiation therapy (IMRT) after radical prostatectomy. Daily image guidance was performed to localize the prostate bed using kilovoltage imaging or cone-beam computed tomography. The median prescription dose was 68 Gy (range, 62-68 Gy). Toxicity was graded every 3 to 6 months according to the Common Terminology Criteria for Adverse Events version 3.0. RESULTS: The median follow-up was 24 months (range, 13-38 months). Grade 2 acute GI and GU events occurred in 4 patients (8%) and 7 patients (14%), respectively. No Grade 3 or higher acute GI or GU toxicities were observed. Late Grade 2 GI and GU events occurred in 1 patient (2%) and 8 patients (16%), respectively. Only a single (2%) Grade 3 or higher late toxicity was observed. CONCLUSIONS: Image-guided IMRT in the postprostatectomy setting is associated with a low frequency of acute and late GI/GU toxicity. These results compare more favorably to radiotherapy techniques that do not use in-room image-guidance, suggesting that daily prostate bed localization may reduce the incidence of adverse events in patients undergoing postprostatectomy irradiation.