Feasibility and Early Clinical Experience of Online Adaptive MR-Guided Radiotherapy of Liver Tumors

Abstract

Purpose: To assess the feasibility and early results of online adaptive MR-guided radiotherapy (oMRgRT) of liver tumors. Methods: We retrospectively examined consecutive patients with primary or secondary liver lesions treated at our institution using a 0.35T hybrid MR-Linac (Viewray Inc., Mountain View, CA, USA). Online-adaptive treatment planning was used to account for interfractional anatomical changes, and real-time intrafractional motion management using online 2D cine MRI was performed using a respiratory gating approach. Treatment response and toxicity were assessed during follow-up. Results: Eleven patients and a total of 15 lesions were evaluated. Histologies included cholangiocarcinomas and metastases of neuroendocrine tumors, colorectal carcinomas, sarcomas and a gastrointestinal stroma tumor. The median BED10 of the PTV prescription doses was 84.4 Gy (range 59.5–112.5 Gy) applied in 3–5 fractions and the mean GTV BED10 was in median 147.9 Gy (range 71.7–200.5 Gy). Online plan adaptation was performed in 98% of fractions. The median overall treatment duration was 53 min. The treatment was feasible and successfully completed in all patients. After a median follow-up of five months, no local failure occurred and no ≥ grade two toxicity was observed. OMRgRT resulted in better PTV coverage and fewer OAR constraint violations. Conclusion: Early results of MR-linac based oMRgRT for the primary and secondary liver tumors are promising. The treatment was feasible in all cases and well tolerated with minimal toxicity. The technique should be compared to conventional SBRT in further studies to assess the advantages of the technique.

Magnetic Resonance-Guided Stereotactic Body Radiotherapy of Liver Tumors: Initial Clinical Experience and Patient-Reported Outcomes

“…One of the previously mentioned US-American studies provided data on treatment outcome: Rosenberg et al reported a LC of 80% at the median follow-up of 21.2 months (40). Furthermore, Rogowski et al described a local control rate of 100%, however with a median follow-up of 5 months (41). Preliminary LC results are therefore so far comparable to non-MRI-guided liver SBRT, as recently described in a systematic review by Ohri et al with a LC after 1and 2-years of 90 and 79% (43).…”

“…Furthermore, Rogowski et al. described a local control rate of 100%, however with a median follow-up of 5 months ( 41 ). Preliminary LC results are therefore so far comparable to non-MRI-guided liver SBRT, as recently described in a systematic review by Ohri et al.…”

HDR Brachytherapy and SBRT as Bridging Therapy to Liver Transplantation in HCC Patients: A Single-Center Experience

“…The increasing use of SBRT has led to accumulating evidence suggesting that SBRT is an effective and safe treatment option for HCC. Other, more elaborate radiation-based techniques, such as proton radiotherapy ( 18 ) or MR-guided radiation therapy ( 19 , 20 ), are currently emerging in the treatment of liver tumors. However, access to these treatments is still limited today.…”

ESTRO-ACROP recommendations on the clinical implementation of hybrid MR-linac systems in radiation oncology

“…In addition to physical compatibility, the radiation oncologists should carefully evaluate the general clinical status of the patient, especially with regard to the required degree of compliance and in consideration of the clinical benefits expected from the use of oMRgRT. Treatment slots for online adaptive treatments using full online replanning are significantly longer than on conventional linacs and can last up to 60 minutes [30,31,36,49,58,59]. Elderly age and frailty do not represent direct exclusion criteria, and specific scoring systems can be used as decisional support systems [50].…”