Quantitative assessment of dosimetric parameters of the radiation treatment plan for unplanned changes in the fractionation scheme

Changes in the fractionation scheme of the radiotherapy course have an impact on the results of treatment of cancer patients. If changes in the fractionation scheme are not taken into account, this leads to under-irradiation of tumor cells and a possible occurrence of subsequent relapses. There are radiobiological models in order to take into account the errors in the radiation dose delivered to the tumor. They allow predicting the tumor control, as well as the toxicity level in normal tissues after traditional RT.The objective of the work is to assess the effectiveness of the absorbed dose in the event, if the fractionation scheme in the RT course changes, and to develop an algorithm that takes into account breaks between treatment sessions.In the study, the effectiveness of the radiation dose delivered to the tumor due to a change in the total treatment time is assessed analytically, a graphical dependence of the radiation dose efficiency on the duration of the unplanned interruption in the treatment of patients is built for the most common oncological localizations, an algorithm for radiotherapy procedures taking into account deviations from the standard radiation treatment pattern is developed.

A Retrospective Cohort Study of Longitudinal Audiologic Assessment in Single and Fractionated Stereotactic Radiosurgery for Vestibular Schwannoma

BACKGROUND Fractionated stereotactic radiosurgery (SRS) for vestibular schwannomas (VS) has been theorized to allow for tumor control with higher rates of hearing preservation in selected patients with useful hearing. However, there is a paucity of literature with formal audiologic measures of hearing preservation to support the standard use of fractionated SRS in VS. We hypothesized that fractionation would diminish the amount of hearing damage. OBJECTIVE To evaluate the relationship between audiologic performance and SRS fractionation scheme. METHODS We performed an IRB-approved retrospective review of patients treated with 1, 3, or 5 fraction SRS for VS at our institution from 1998 to 2016. Pre- and post-SRS audiograms with speech awareness threshold (SAT) in treated and contralateral ears were obtained. Contralateral ear measurements were used for hearing normalization to account for presbycusis. RESULTS Fifty-six patients with median audiologic follow-up 2.0 yr (mean 2.66 yr, min-max 0.50-9.45 yr) were included. Patients treated with single fractionation had a significantly worsened SAT (dB) compared to patients treated with 5 fractions (P = .008) and compared to all multifraction patients (P = .009) at 12 to 24 mo follow-up. CONCLUSION This retrospective analysis supports the use of fractionated SRS to preserve hearing in patients with VS. SAT can be used as an objective metric of hearing response to radiosurgery.

The financial impact of fractionation scheme and treatment planning method for rectal cancer in the United States.

6518 Background: Preoperative long-course chemoradiotherapy (CRT) and short-course radiotherapy (SCR) for locally advanced rectal cancer (LARC) were found to have equivalent outcomes in three randomized trials. SCR may have lower acute toxicity and the down-staging following CRT is more well-established. At present, SCR is frequently used in Europe but has not been widely adopted in the United States (US). It is standard to deliver radiotherapy by 3D planning, while the use of Intensity-modulated radiotherapy (IMRT) is controversial. In recent years there has been an increasing focus on understanding the cost and value of cancer care. In this study we aimed to assess the economic impact of fractionation scheme and treatment planning method for payers in the US. Methods: We performed a population-based analysis of the total cost of radiotherapy for LARC in the US annually. The national annual target population of patients was calculated using the Surveillance, Epidemiology, and End Results (SEER) database. Treatment costs for various fractionation schemes were based on billing codes and 2018 pricing by Medicare's Hospital Outpatient Prospective Payment System (OPPS). The cost of chemotherapy was based on the Payment Allowance Limits for Medicare Part B Drugs by Centers for Medicare and Medicaid Services (CMS). Results: We estimate that 12,945 patients with LARC are treated with radiotherapy annually in the US. The cost of CRT with 3-D or IMRT is US$ 15,881.76 and US$ 23,744.82 per patient, respectively. With 3-D SCR the cost is US$ 5,457 per patient. The use of SCR would lead to 64-77% annual savings of US$ 125,701,387 - US$ 236,727,934 in the US compared with 3-D and IMRT based CRT, respectively. IMRT based planning increases the total cost of CRT by 49% and if adopted widely would lead to an excess cost of US$ 101,787,312 annually. Conclusions: SCR may have the potential to save in the region of US$ 0.12-0.23 billion annually in the US, likely without impacting outcomes. Lack of evidence showing benefit with costly IMRT should limit its use to clinical trials. SCR may also lead to lower personal financial toxicity. It would be reasonable for public and private payers to consider which type of radiation is most suited to reimbursement.