Stereotactic ablative radiotherapy for early stage non-small cell lung cancer: A critical literature review of predictive factors of relapse

Stereotactic ablative radiation therapy (SABR) has become the standard treatment for peripheral medically non-operable patients with early stage non-small cell lung cancer (NSCLC). Previous attempts of trials to compare SABR and surgery have failed and new randomized studies (SABRtooth, STABLEMATES, and VALOR) are ongoing. While predictive factors of relapse have been extensively studied in patients receiving surgery, there is scarce data on such putative factors in SABR patients. The purpose of this review is to analyze such predictive factors through a critical review of the literature.     

Stereotactic body radiation therapy for liver metastases

Over the years, early diagnosis of metastatic disease has improved and the prevalence of oligometastatic patients is increasing. Liver is a most common site of progression from gastrointestinal, lung and breast cancer and in the setting of oligometastatic patients, surgical resection is associated with increased survival. Approximately 70-90% of liver metastases, however, are unresectable and an effective and safe alternative therapeutic option is necessary for these patients. The role of stereotactic body radiation therapy (SBRT) was investigated in the treatment of oligometastatic patients with promising results, thanks to the ability of this procedure to deliver a conformal high dose of radiation to the target lesion and a minimal dose to surrounding critical tissues. This paper was performed to review the current literature and to provide the practice guidelines on the use of stereotactic body radiotherapy in the treatment of liver metastases. We performed a literature search using Medical Subject Heading terms “SBRT” and “liver metastases”, considering a period of ten years.     

Comparative study of respiratory motion correction techniques in cone-beam computed tomography

Background and purpose

To validate the clinical usefulness of motion-compensated (MC) cone-beam (CB) computed tomography (CT) for image-guided radiotherapy (IGRT) in comparison to four-dimensional (4D) CBCT and three-dimensional (3D) CBCT.

Material and methods

Forty-eight stereotactic body radiation therapy (SBRT) patients were selected. Each patient had 5-12 long CB acquisitions (4 min) and 1-7 short CB acquisitions (1 min), with a total of 349 and 150 acquisitions, respectively. 3D, 4D and MC CBCT images of every acquisition were reconstructed. Image quality, tumor positioning accuracy and tumor motion amplitude were quantified.

Results

The mean image quality of long short acquisitions, measured using the correlation ratio with the planning CT, was 74%/70%, 67%/47% and 79%/74% for 3D, 4D and MC CBCT, respectively; both 4D and MC CBCT were corrected for respiratory motion artifacts but 4D CBCTs suffered from streak artifacts. Tumor positioning with MC CBCT was significantly closer to 4D CBCT than 3D CBCT (p < 0.0001). Detailed patient analysis showed that motion correction was not required for tumors with less than 1 cm motion amplitude.

Conclusions

4D and MC CBCT both allow accurate tumor position analysis under respiratory motion but 4D CBCT requires longer acquisition time than MC CBCT for adequate image quality. MC CBCT can therefore advantageously replace 4D CBCT in clinical protocols for patients with large motion to improve image quality and reduce acquisition time.     

Stereotactic body radiation therapy (SBRT) for early-stage lung cancer in the elderly

Early-stage non-small cell lung cancer (NSCLC) is on the rise due to the implementation of screening guidelines for patients at risk for developing lung cancer. It is anticipated that as the US population continues to age, there will be a higher percentage of medically inoperable early-stage lung cancer patients. For this reason, noninvasive ablative therapies are necessary. Stereotactic body radiation therapy (SBRT) is an effective modality in addressing early-stage NSCLC. SBRT consists of high-dose radiation delivered over 3–5 treatments. Several randomized trials comparing surgery to SBRT in early-stage operable patients have unfortunately closed early due to poor accrual. However, a recent pooled analysis from 2 randomized trials (StereoTActic Radiotherapy and Radiosurgery Or Surgery for operable Early-stage non–small cell Lung cancer) comparing surgery to SBRT did show comparable local control and overall survival rates between surgery and SBRT, offering a very effective, noninvasive modality for older adult patients with early-stage NSCLC. In this review, we summarize the role of SBRT in early-stage NSCLC, in particularly applied to the older adult population.     

Safety and Effectiveness of Stereotactic Ablative Radiotherapy for Ultra-Central Lung Lesions: A Systematic Review

IntroductionThe safety and effectiveness of stereotactic ablative radiotherapy (SABR) in patients with ultra-central lung tumors is currently unclear. We performed a systematic review to summarize existing data and identify trends in treatment-related toxicity and local control following SABR in patients with ultra-central lung lesions.MethodsWe performed a systematic review based on the Preferred Reporting Items for Systemic Reviews and Meta-Analyses guidelines using the PubMed and Embase databases. The databases were queried from dates of inception until September 27, 2018. Studies in the English language that reported treatment-related toxicity and local control outcomes post-SABR for patients with ultra-central lung lesions were included. Guidelines, reviews, non–peer reviewed correspondences, studies focused on re-irradiation, and studies with fewer than five patients were excluded.ResultsA total of 446 studies were identified, with 10 meeting all criteria for inclusion. The total sample size from the identified studies was 250 ultra-central lung patients and all studies were retrospective in design. Radiotherapy dose and fractionation ranged from 30 to 60 Gy in 3 to 12 fractions, with biologically effective doses (BED₁₀) ranging from 48 to 138 Gy₁₀ (median, 78–103 Gy₁₀). Median treatment-related grade 3 or greater toxicity was 10% (range, 0–50%). Median treatment-related mortality was 5% (range, 0–22%), most commonly from pulmonary hemorrhage (55%). High-risk indicators for SABR-related mortality included gross endobronchial disease, maximum dose to the proximal bronchial tree greater than or equal to 180 Gy₃ (BED₃, corresponding to 45 Gy in 5 fractions or 55 Gy in 8 fractions), peri-SABR bevacizumab use, and antiplatelet/anticoagulant use. Median 1-year local control rate was 96% (range, 63%–100%) and 2-year local control rate was 92% (range, 57%–100%).ConclusionsSABR for ultra-central lung lesions appears feasible but there is a potential for severe toxicity in patients receiving high doses to the proximal bronchial tree, those with endobronchial disease, and those receiving bevacizumab or anticoagulants around the time of SABR. Prospective studies are required to establish the optimal doses, volumes, and normal tissue tolerances for SABR in this patient population.     

Assessment of residual error in liver position using kV cone-beam computed tomography for liver cancer high-precision radiation therapy

PURPOSE: To evaluate the residual error in liver position using breath-hold kilovoltage (kV) cone-beam computed tomography (CT) following on-line orthogonal megavoltage (MV) image-guided breath-hold liver cancer conformal radiotherapy. METHODS AND MATERIALS: Thirteen patients with liver cancer treated with 6-fraction breath-hold conformal radiotherapy were investigated. Before each fraction, orthogonal MV images were obtained during exhale breath-hold, with repositioning for offsets>3 mm, using the diaphragm for cranio-caudal (CC) alignment and vertebral bodies for medial-lateral (ML) and anterior posterior (AP) alignment. After repositioning, repeat orthogonal MV images, orthogonal kV fluoroscopic movies, and kV cone-beam CTs were obtained in exhale breath-hold. The cone-beam CT livers were registered to the planning CT liver to obtain the residual setup error in liver position. RESULTS: After repositioning, 78 orthogonal MV image pairs, 61 orthogonal kV image pairs, and 72 kV cone-beam CT scans were obtained. Population random setup errors (sigma) in liver position were 2.7 mm (CC), 2.3 mm (ML), and 3.0 mm (AP), and systematic errors (Sigma) were 1.1 mm, 1.9 mm, and 1.3 mm in the superior, medial, and posterior directions. Liver offsets>5 mm were observed in 33% of cases; offsets>10 mm and liver deformation>5 mm were observed in a minority of patients. CONCLUSIONS: Liver position after radiation therapy guided with MV orthogonal imaging was within 5 mm of planned position in the majority of patients. kV cone-beam CT image guidance should improve accuracy with reduced dose compared with orthogonal MV image guidance for liver cancer radiation therapy.