The Role of Stereotactic Body Radiation Therapy in the Management of Liver Metastases

Enhancing tumor control in liver metastases treated with SBRT: dosimetric predictors and clinical outcomes from a single-center analysis

Liver metastases, a hallmark of systemic disease, carry a poor prognosis despite advancements in systemic therapies. Stereotactic body radiation therapy (SBRT) has emerged as a promising local treatment, offering durable tumor control with minimal toxicity. However, the optimal dosimetric strategies to maximize outcomes remain an area of active investigation. This retrospective study evaluated 76 patients with 101 liver metastases treated with SBRT between November 2012 and June 2024. Dosimetric parameters were analyzed, including prescribed dose (PD) and dose metrics for planning target volume (PTV) and gross tumor volume (GTV), with doses converted to equivalent doses in 2 Gy fractions (EQD2, α/β = 10). Tumor control probability (TCP) models and survival outcomes were assessed, with a focus on the prognostic impact of dosimetric and clinical factors. Median overall survival (OS) was 33 months, with 1-year and 3-year OS rates of 74.1% and 39.4%, respectively. Freedom from local progression (FFLP) was 82.5% at 12 months. PD emerged as the strongest independent predictor of local control, with an optimal threshold of 77.44 Gy EQD2 significantly improving 1-year FFLP rates (96.8% vs. 67.2%; p = 0.007). Advanced motion management techniques, including internal breath-hold (iBH) with image-guided radiotherapy (IGRT), demonstrated superior local control outcomes. Predictive modeling confirmed PD as the most robust dosimetric metric, correlating with a high TCP and outperforming other dose metrics. Toxicity was minimal, with only 3.9% experiencing grade ≥ 3 adverse events. SBRT represents a highly effective and safe approach for liver metastases, with PD and advanced imaging emerging as pivotal determinants of tumor control. These findings underscore the importance of precise dosimetric planning and motion management in optimizing SBRT outcomes. This study provides a robust framework for personalized treatment strategies, contributing to the integration of SBRT as a cornerstone in the multidisciplinary management of liver metastases.

Microwave Ablation of Refractory Oligometastatic Non-Small Cell Lung Cancer in the Liver

PURPOSE

To evaluate safety and effectiveness of microwave ablation (MWA) in the treatment of liver metastases (LMs) secondary to non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

This retrospective study included patients with NSCLC who underwent MWA of LM from March 2015 to July 2022. Local tumor progression-free survival (LTPFS) and overall survival (OS) were estimated using competing risk analysis and the Kaplan-Meier method. Postprocedural adverse events were recorded according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0.

RESULTS

Twenty-three patients with 32 LMs were treated in 27 MWA sessions. The mean dimension of the largest index tumor was 1.96 cm (SD ± 0.75). Technical success was 100%. Technical effectiveness was achieved in 26 (81.3%) of 32 tumors. The median length of follow-up was 37.7 months (interquartile range, 20.5-54.5 months). The median LTPFS was 16.3 months (95% confidence interval [CI], 7.87-44.10 months). The median OS was 31.7 months (95% CI, 11.1-65.8 months). Ablation margin was a significant factor for LTPFS, with tumors ablated without a measurable margin being more likely to progress than those with measurable margins (subdistribution hazard ratios [HRs], 0.008-0.024; P < .001). Older age (HR, 1.18; 95% CI, 1.09-1.28; P < .001) and presence of synchronous lung metastases (HR, 14.73; 95% CI, 1.86-116.95; P = .011) were significant predictors of OS. Serious adverse events (CTCAE Grade ≥3) within 30 days occurred in 2 (7.4%) of 27 sessions, including pulmonary embolus and severe abdominal pain.

CONCLUSIONS

Percutaneous MWA was a safe treatment for NSCLC LM, with longer survival noted in younger patients and those without synchronous lung tumors.

Synchronized Contrast-Enhanced 4DCT Simulation for Target Volume Delineation in Abdominal SBRT

Background/Objectives: To present the technical aspects of contrast-enhanced 4DCT (ce4DCT) simulation for abdominal SBRT. Methods: Twenty-two patients underwent two sequential 4DCT scans: one baseline and one contrast-enhanced with personalized delay time (tdelay) calculated to capture the tumor in the desired contrast phase, based on diagnostic triple-phase CT. The internal target volume (ITV) was delineated on ten contrast phases, and a panel of three experts qualitatively evaluated tumor visibility. Aortic HU values were measured to refine the tdelay for subsequent patients. The commonly used approach of combining triple-phase CT with unenhanced 4DCT was simulated, and differences in target delineation were evaluated by volume, centroid shift, Dice and Jaccard indices, and mean distance agreement (MDA). The margins required to account for motion were calculated. Results: The ce4DCT acquisitions substantially improved tumor visibility over the entire breathing cycle in 20 patients, according to the experts' unanimous evaluation. The median contrast peak time was 54.5 s, and the washout plateau was observed at 70.3 s, with mean peak and plateau HU values of 292 ± 59 and 169 ± 25. The volumes from the commonly used procedure (ITV2) were significantly smaller than the ce4DCT volumes (ITV1) (p = 0.045). The median centroid shift was 4.7 mm. The ITV1-ITV2 overlap was 69% (Dice index), 53% (Jaccard index), and 2.89 mm (MDA), with the liver volumes showing significantly lower indices compared to the pancreatic volumes (p ≤ 0.011). The margins required to better encompass ITV1 were highly variable, with mean values ≥ 4 mm in all directions except for the left-right axis. Conclusions: The ce4DCT simulation was feasible, resulting in optimal tumor enhancement with minimal resource investment, while significantly mitigating uncertainties in SBRT planning by addressing poor visibility and respiratory motion. Triple-phase 3DCT with unenhanced 4DCT led to high variability in target delineation, making the isotropic margins ineffective.

The Landmark Series: Multimodal Management of Oligometastatic Sarcoma

The concept of "oligometastatic" disease suggests the presence of intermediate states between localized disease and widespread metastases, which may be potentially treatable with curative therapeutic strategies. Metastases local therapy (MLT) can be accomplished through various techniques such as stereotactic ablative radiotherapy (SABR), radiofrequency ablation (RFA), microwave ablation (MWA), cryoablation, or surgical metastasectomy. The incorporation of MLT in the multidisciplinary treatment of patients with metastatic sarcoma is complex. Retrospective studies support consideration of MLT for selected patients based on factors such as patient condition, disease biology, histologic type, and disease burden. Decisions regarding type and timing of MLT should be made after multidisciplinary discussion including radiation oncologists, surgical and orthopedic oncologists, medical oncologists, and interventional radiology to explore all options before treatment decsions. All MLT techniques have advantages and disadvantages and should be performed in centers specialized in the care of complex oncology patients where various options can be explored concurrently or sequentially for each patient. Future studies evaluating quality of life and patient-reported outcomes are necessary to adequately align patient goals and optimal outcomes. This article reviews the medical scenarios that may benefit the use of MLT, evaluates the distinct advantages and disadvantages associated with these various techniques, and analyzes the findings from pivotal series to provide a comprehensive understanding of its role in clinical practice.

Preoperative imaging of colorectal liver metastases: what the radiologist and the multidisciplinary team need to know

The management of patients with colorectal liver metastases (CRLM) has transformed over the past 2 decades. Advances in surgical techniques, systemic therapies, and local treatments have resulted in a paradigm shift. Disease that would once have been considered terminal is now frequently treated aggressively with both a disease-free and overall survival benefit. In line with the expanding range of treatment options, there has been an increase in the volume and complexity of imaging required in the management of these patients to ensure optimal patient selection and outcome. The radiologist plays a pivotal role in interpreting these studies, conveying the relevant information and informing the discussion at multidisciplinary team meetings. The purpose of this review is to provide an update for radiologists on the current surgical management of patients with CRLM highlighting specific imaging information that is required by the multidisciplinary team when assessing resectability and/or the need for additional liver-directed therapies.

Optimization of collimator angle combined island blocking with parked gap achieves superior normal tissue sparing in SBRT planning of multiple liver lesions

PURPOSE

To propose an efficient collimator angle optimization method by combining island blocking (IB) and parked gap (PG) problem to reduce the radiotherapy dose for normal tissue. The reduction will be done with single-isocenter multi-lesion volumetric modulated arc therapy (VMAT) for the stereotactic body radiation therapy (SBRT) of liver cancer.

METHODS

A novel collimator angle optimization algorithm was developed based on the two-dimensional projection of targets on a beam's eye view (BEV) plane as a function of gantry and collimator angle. This optimization algorithm minimized the sum of the combined IB and PG (IB & PG) areas from all gantry angles for each arc. For comparison, two SBRT plans were respectively generated for each of the 20 retrospective liver cancer cases with multiple lesions. One plan was optimized using the IB & PG algorithm, and the other plan was optimized with a previously reported optimization algorithm that only considered the IB area. Plans were then evaluated and compared using typical dosimetric metrics.

RESULTS

With the comparable target coverage, IB & PG plans had significantly lower D500cc, D700cc, mean dose (Dmean), and V15 of normal liver tissues when compared to IB plans. The median percent reductions were 3.32% to 5.36%. The D1cc, D5cc, and Dmean for duodenum and small intestine in IB & PG plans were significantly reduced in a range from 7.60% up to 16.03%. Similarly, the median integral dose was reduced by 3.73%. Furthermore, the percentage of normal liver Dmean sparing when IB & PG plans compared to IB plans, was found to be positively correlated (ρ = 0.669, P = 0.001) with the inter-target distance.

CONCLUSION

The proposed IB & PG algorithm has been demonstrated to outperform the IB algorithm in almost all normal tissue sparing, and the magnitude of liver sparing was positively correlated with inter-target distance.

Interventional radiological therapies in colorectal hepatic metastases

Colorectal malignancy is the third most common cancer and one of the prevalent causes of death globally. Around 20-25% of patients present with metastases at the time of diagnosis, and 50-60% of patients develop metastases in due course of the disease. Liver, followed by lung and lymph nodes, are the most common sites of colorectal cancer metastases. In such patients, the 5-year survival rate is approximately 19.2%. Although surgical resection is the primary mode of managing colorectal cancer metastases, only 10-25% of patients are competent for curative therapy. Hepatic insufficiency may be the aftermath of extensive surgical hepatectomy. Hence formal assessment of future liver remnant volume (FLR) is imperative prior to surgery to prevent hepatic failure. The evolution of minimally invasive interventional radiological techniques has enhanced the treatment algorithm of patients with colorectal cancer metastases. Studies have demonstrated that these techniques may address the limitations of curative resection, such as insufficient FLR, bi-lobar disease, and patients at higher risk for surgery. This review focuses on curative and palliative role through procedures including portal vein embolization, radioembolization, and ablation. Alongside, we deliberate various studies on conventional chemoembolization and chemoembolization with irinotecan-loaded drug-eluting beads. The radioembolization with Yttrium-90 microspheres has evolved as salvage therapy in surgically unresectable and chemo-resistant metastases.