Closer Look, Better Care: Revolutionizing Cancer Treatment with Cutting-Edge Radiotherapy Trial

Study Overview

This study was conducted to evaluate the feasibility of managing intra-fractional respiratory motion during Ethos-based CT-STAR and CT-SBRT using a combination of optical surface imaging and onboard CBCT (Cone Beam Computed Tomography) (1). This Phase I clinical trial involved ten cancer patients diagnosed with mobile lower lung or upper abdominal malignancies. The primary aim was to investigate the effectiveness of this combined approach in controlling tumor movement during breath-hold radiotherapy sessions.

In terms of study design, the trial utilized a pre-configured gating window on optical surface imaging for manually triggering intra-fractional CBCT acquisition and treatment beam irradiation during breath-hold. This process was carried out in two distinct patterns: seven patients were monitored at the end of exhalation and three at the end of inhalation. Additionally, to verify the primary direction and range of tumor or imaging-surrogate movement, two inter-fractional CBCTs were acquired at the ends of exhalation and inhalation in each fraction.

The population under investigation comprised cancer patients, specifically those with mobile tumors in the lower lung or upper abdominal regions. The intervention under investigation was the use of optical surface image-guided Ethos CT-STAR/SBRT. Regarding the control group, this aspect was not explicitly mentioned in the abstract. In total, fifty fractions of Ethos RT were delivered, with thirty-two being CT-STAR (adaptive RT) and eighteen CT-SBRT (non-adaptive RT).

The study involved the analysis of 46 fractions for intra-fractional residual motion and 43 fractions for inter-fractional motion analysis. This analysis was due to certain constraints within the study. The residual motion of the tumor was quantified through variations in the tumor centroid position, and the impact of this motion on target coverage was calculated.

Regarding the results, the primary motion observed was 16.6 ± 9.2 mm in the SI direction for tumors and 15.5 ± 7.3 mm in the AP direction for the imaging-surrogate. The residual motion of the tumor during intra-fractional breath-hold CBCTs was measured at 2.2 ± 2.0 mm for SI, 1.4 ± 1.4 mm for RL, and 1.3 ± 1.3 mm for AP directions. The ratio of the actual dose coverage to the target volume decreased by 0.95 ± 0.11, 0.96 ± 0.10, and 0.99 ± 0.05 for 99%, 90%, and 50% of the target volume, respectively. Furthermore, the mean percentage of the target volume covered by the prescribed dose decreased by 2.8 ± 4.4%.

The clinical significance of these findings lies in demonstrating that while the controlled residual tumor motion measured at 3.5 mm exceeded the predetermined setup value of 2 mm, it remained within the clinically acceptable range defined by the PTV margin of 5 mm. This suggests that the intra-fractional motion-managed treatment strategy in breath-hold Ethos CT-STAR/SBRT using optical surface imaging and CBCT is feasible, although additional caution is warranted in its application.

Standard Treatment

The current standard treatment for mobile lower lung or upper abdominal malignancies typically involves a combination of radiotherapy and, in some cases, chemotherapy, depending on the specific type, stage, and location of the cancer. Stereotactic body radiotherapy (SBRT) is often used for treating small, localized lung tumors. SBRT delivers high-dose radiation with precision, minimizing exposure to surrounding healthy tissue. For abdominal malignancies, the approach might vary but generally includes more conventional forms of radiotherapy and chemotherapy.

The significance of this study lies in its exploration of an advanced technique combining optical surface imaging with CBCT (Cone Beam Computed Tomography) for intra-fractional motion management during breath-hold radiotherapy sessions. This approach is particularly relevant for tumors that move due to breathing, as in the case of lung and upper abdominal cancers.

The potential impact of the study's results on the current standard treatment includes:

  1. Improved Precision in Radiotherapy: The combination of optical surface imaging and CBCT could allow for more precise targeting of the tumor, accounting for its movement due to breathing. This could lead to better sparing of surrounding healthy tissues.

  2. Enhanced Adaptability: The use of adaptive radiotherapy (CT-STAR) as part of this approach allows for adjustments to be made based on the tumor's position at each treatment session, potentially increasing the treatment's effectiveness.

  3. Potential for Reduced Side Effects: By more accurately targeting the tumor and reducing exposure to surrounding tissues, this method might lead to fewer side effects and complications.

  4. Feasibility in Clinical Practice: The study demonstrates the feasibility of this approach in a clinical setting, which is an essential step before any new technique can become part of standard treatment.

  5. Setting New Standards for Tumor Motion Management: The findings highlight the importance of managing intra-fractional motion, which could lead to new protocols and standards in treating mobile tumors.

  6. Need for Further Research: While the study shows promise, it also indicates the need for further research, particularly in ensuring that the motion management technique does not compromise the radiation dose received by the tumor.

In conclusion, if these results are further validated and supported by larger-scale studies, they could lead to refinements in the standard treatment protocols, especially for cancers where tumor motion due to respiration is a significant concern. This could ultimately result in more effective, tailored, and safer treatment options for patients with these types of malignancies.

Clinical Impact Potential

The clinical impact potential of this trial can be assessed as medium. This assessment is based on several key factors:

  1. Innovative Approach: The trial investigates a novel approach combining optical surface imaging with CBCT for managing intra-fractional respiratory motion in radiotherapy. This method addresses a significant challenge in treating mobile tumors in the lower lung and upper abdominal areas, suggesting a potential for meaningful improvement in radiotherapy precision.

  2. Limited Scope and Early Phase: As a Phase I trial involving only ten patients, the study is preliminary in nature. While it demonstrates feasibility and potential benefits, Phase I trials are primarily designed to evaluate safety, not efficacy. The results need to be replicated and validated in larger, more diverse patient populations and in later-phase trials to truly gauge the impact.

  3. Incremental Improvement: The approach studied aims to enhance existing treatment methods rather than revolutionize them. It focuses on improving precision and reducing side effects in current radiotherapy practices, which is an important but incremental advancement.

  4. Clinical Relevance: Managing intra-fractional motion is crucial for certain types of cancers. This trial's focus on better targeting of mobile tumors during radiotherapy is clinically relevant and could lead to improved outcomes for a specific patient group.

  5. Potential for Integration into Standard Care: The technology and techniques used in the trial are not radically different from current practices, which suggests a smoother pathway for integration into standard care if proven effective in subsequent studies.

  6. Need for Further Evidence: The medium impact assessment is tempered by the need for further evidence demonstrating significant improvements in patient outcomes, such as survival rates or quality of life, and the need to establish the cost-effectiveness of the new approach.

In summary, the trial shows promising potential to improve the precision and effectiveness of radiotherapy for mobile tumors, which is a significant issue in oncology. However, its impact is currently medium due to the early stage of research, the limited scope of the study, and the need for further validation through more extensive clinical trials.

Reference

Kim T, Laugeman E, Kiser K, Schiff J, Marasini S, Price A, Gach HM, Knutson N, Samson P, Robinson C, Hatscher C, Henke L. Feasibility of surface-guidance combined with CBCT for intra-fractional breath-hold motion management during Ethos RT. J Appl Clin Med Phys. 2024 Jan 4:e14242. doi: 10.1002/acm2.14242. Epub ahead of print. PMID: 38178622.