Assessment of MRI-Linac Economics under the RO-APM

The implementation of the radiation oncology alternative payment model (RO-APM) has raised concerns regarding the development of MRI-guided adaptive radiotherapy (MRgART). We sought to compare technical fee reimbursement under Fee-For-Service (FFS) to the proposed RO-APM for a typical MRI-Linac (MRL) patient load and distribution of 200 patients. In an exploratory aim, a modifier was added to the RO-APM (mRO-APM) to account for the resources necessary to provide this care. Traditional Medicare FFS reimbursement rates were compared to the diagnosis-based reimbursement in the RO-APM. Reimbursement for all selected diagnoses were lower in the RO-APM compared to FFS, with the largest differences in the adaptive treatments for lung cancer (−89%) and pancreatic cancer (−83%). The total annual reimbursement discrepancy amounted to −78%. Without implementation of adaptive replanning there was no difference in reimbursement in breast, colorectal and prostate cancer between RO-APM and mRO-APM. Accommodating online adaptive treatments in the mRO-APM would result in a reimbursement difference from the FFS model of −47% for lung cancer and −46% for pancreatic cancer, mitigating the overall annual reimbursement difference to −54%. Even with adjustment, the implementation of MRgART as a new treatment strategy is susceptible under the RO-APM.

Parotid sparing adaptive radiotherapy in head and neck cancer patients: A study evaluating resource intensiveness and impact on quality of life.

e24037 Background: Anatomical changes during the course of parotid sparing IMRT for head and neck cancer can lead to an increase in the actual dose absorbed by the parotid glands, which may be controlled with the use of interval adaptive replanning. In this prospective assessment of adaptive replanning for parotid dose changes, we explored the feasibility of carrying out adaptive replanning based on predefined objective dosimetric criteria at specified time points. We sought to assess the impact of this measure using a clinically meaningful endpoint of patient reported quality of life outcomes. Methods: 90 patients with head and neck radiotherapy indicated for definitive management or adjuvant therapy who had at least one parotid gland receiving a mean dose (MD) of between 25-30Gy were accrued in the study. The index parotid was delineated on the images acquired on 14th and 19th day and the MD was determined by overlaying the verification image on the planned CT. If the MD had increased by 2% of the initial intended dose, an adaptive plan was attempted with an aim to reduce MD by 2% without compromising PTV coverage; this plan was then used to deliver the remaining treatment. Patients were invited to complete QoL questionnaires: EORTC-QLQC30 with HN35 module, and XeQoL score at baseline, at 3 and 9 months after completion of treatment. Results: 46 out of 90 patients met the threshold for adaptive replanning and were switched to the new plan during treatment. Adaptive replanning was triggered at D14 for 31 patients and D19 for the remaining 15. Need for adaptive replanning was associated with receipt of concurrent chemotherapy and weight loss in the first two weeks of RT. QoL was evaluable for 50 patients at 3 months post treatment. In patients who required adaptive replanning per protocol, Mean XeQoL scores at 3 months showed significantly worse scores for overall scores (1.1 vs 2.3, p 0.001) and for the component individual physical, pain, psychological, and social domains. EORTC QLQ-C30 and HN35 questionnaires at 3 months also demonstrated significantly worse mean symptom scores of the relevant domains of mouth dryness (39 vs 60), stickiness (32 vs 54) and swallowing (39 vs 60) in patients who required adaptive replanning versus those who did not. No significant QoL trends were observable in the 31 patients who were evaluable at 9 months post treatment. The average time required for each step in the planning process was comparable for both the initial planning workflow and adaptive replanning process. Conclusions: The trigger criteria for replanning identified a population of patients who have significantly worsened quality of life due to radiation induced xerostomia. The benefits of adaptive replanning strategies based on weekly evaluation, binary thresholds and standard planning procedures is doubtful Clinical trial information: CTRI/2017/11/010683.

Benefit of replanning in MR-guided online adaptive radiation therapy in the treatment of liver metastasis

Purpose To assess the effects of daily adaptive MR-guided replanning in stereotactic body radiation therapy (SBRT) of liver metastases based on a patient individual longitudinal dosimetric analysis. Methods Fifteen patients assigned to SBRT for oligometastatic liver metastases underwent daily MR-guided target localization and on-table treatment plan re-optimization. Gross tumor volume (GTV) and organs at risk (OARs) were adapted to the anatomy-of-the-day. A reoptimized plan (RP) and a rigidly shifted baseline plan (sBP) without re-optimization were generated for each fraction. After extraction of DVH parameters for GTV, planning target volume (PTV), and OARs (stomach, duodenum, bowel, liver, heart) plans were compared on a per-patient basis. Results Median pre-treatment GTV and PTV were 14.9 cc (interquartile range (IQR): 7.7–32.9) and 62.7 cc (IQR: 42.4–105.5) respectively. SBRT with RP improved PTV coverage (V100%) for 47/75 of the fractions and reduced doses to the most proximal OARs (D1cc, Dmean) in 33/75 fractions compared to sBP. RP significantly improved PTV coverage (V100%) for metastases within close proximity to an OAR by 4.0% (≤ 0.2 cm distance from the edge of the PTV to the edge of the OAR; n = 7; p = 0.01), but only by 0.2% for metastases farther away from OAR (> 2 cm distance; n = 7; p = 0.37). No acute grade 3 treatment-related toxicities were observed. Conclusions MR-guided online replanning SBRT improved target coverage and OAR sparing for liver metastases with a distance from the edge of the PTV to the nearest luminal OAR < 2 cm. Only marginal improvements in target coverage were observed for target distant to critical OARs, indicating that these patients do not benefit from daily adaptive replanning.

Benefit of Replanning in MR-guided Online Adaptive Radiation Therapy in the Treatment of Liver Metastasis

Purpose: To assess the effects of daily adaptive MR-guided replanning in stereotactic body radiation therapy (SBRT) of liver metastases based on a patient individual longitudinal dosimetric analysis. Methods: Fifteen patients assigned to SBRT for oligometastatic liver metastases underwent daily MR-guided target localization and on-table treatment plan re-optimization. Gross tumor volume (GTV) and organs at risk (OARs) were adapted to the anatomy-of-the-day. A reoptimized plan (RP) and a rigidly shifted baseline plan (sBP) without re-optimization were generated for each fraction. After extraction of DVH parameters for GTV, planning target volume (PTV), and OARs (stomach, duodenum, bowel, liver, heart) plans were compared on a per-patient basis.Results: Median pre-treatment GTV and PTV were 14.9 cc (interquartile range (IQR): 7.7 – 32.85) and 62.7 cc (IQR: 42.4 – 105.5) respectively. SBRT with RP improved PTV coverage (V100%) for 47/75 of the fractions and reduced doses to the most proximal OARs (D1cc, Dmean) in 33/75 fractions compared to sBP. RP significantly improved PTV coverage (V100%) for metastases within close proximity to an OAR by 4.0 % (≤ 0.2 cm distance; n = 7; p = 0.01), but only by 0.2% for metastases farther away from OAR (> 2 cm distance; n = 7; p = 0.37). No acute grade 3 treatment-related toxicities were observed.Conclusion: MR-guided online replanning SBRT improved target coverage and OAR sparing for liver metastases with a distance of more < 2 cm to the nearest luminal OAR. Only marginal improvements in target coverage were observed for target distant to critical OARs, indicating that these patients do not benefit from daily adaptive replanning.