Functional Interference due to Pain Following Palliative Radiotherapy for Bone Metastases Among Patients in Their Last Three Months of Life

FLASH Radiotherapy for the Treatment of Symptomatic Bone Metastases (FAST-01): Protocol for the First Prospective Feasibility Study

BACKGROUND

In preclinical studies, FLASH therapy, in which radiation delivered at ultrahigh dose rates of ≥40 Gy per second, has been shown to cause less injury to normal tissues than radiotherapy delivered at conventional dose rates. This paper describes the protocol for the first-in-human clinical investigation of proton FLASH therapy.

OBJECTIVE

FAST-01 is a prospective, single-center trial designed to assess the workflow feasibility, toxicity, and efficacy of FLASH therapy for the treatment of painful bone metastases in the extremities.

METHODS

Following informed consent, 10 subjects aged ≥18 years with up to 3 painful bone metastases in the extremities (excluding the feet, hands, and wrists) will be enrolled. A treatment field selected from a predefined library of plans with fixed field sizes (from 7.5 cm × 7.5 cm up to 7.5 cm × 20 cm) will be used for treatment. Subjects will receive 8 Gy of radiation in a single fraction-a well-established palliative regimen evaluated in prior investigations using conventional dose rate photon radiotherapy. A FLASH-enabled Varian ProBeam proton therapy unit will be used to deliver treatment to the target volume at a dose rate of ≥40 Gy per second, using the plateau (transmission) portion of the proton beam. After treatment, subjects will be assessed for pain response as well as any adverse effects of FLASH radiation. The primary end points include assessing the workflow feasibility and toxicity of FLASH treatment. The secondary end point is pain response at the treated site(s), as measured by patient-reported pain scores, the use of pain medication, and any flare in bone pain after treatment. The results will be compared to those reported historically for conventional dose rate photon radiotherapy, using the same radiation dose and fractionation.

RESULTS

FAST-01 opened to enrollment on November 3, 2020. Initial results are expected to be published in 2022.

CONCLUSIONS

The results of this investigation will contribute to further developing and optimizing the FLASH-enabled ProBeam proton therapy system workflow. The pain response and toxicity data acquired in our study will provide a greater understanding of FLASH treatment effects on tumor responses and normal tissue toxicities, and they will inform future FLASH trial designs.

TRIAL REGISTRATION

: ClinicalTrials.gov NCT04592887; http://clinicaltrials.gov/ct2/show/NCT04592887.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/41812.

Prognostic factors and a new scoring system for survival of patients irradiated for bone metastases

Background

Personalized therapy for bone metastases should consider the patients’ remaining lifespan. Estimation of survival can be facilitated with scoring tools. A new tool was developed, specifically designed to estimate 12-month survival.

Methods

In 445 patients irradiated for bone metastases, radiotherapy regimen plus 13 factors (age, gender, Karnofsky performance score (KPS), primary tumor type, interval between cancer diagnosis and RT of bone metastases, visceral metastases, other (non-irradiated) bone metastases, sites of bone metastases, number of irradiated sites, pathological fracture, fractionation of RT, pre-RT surgery, pre-RT administration of bisphosphonates/denosumab, pre-RT systemic anticancer treatment) were retrospectively analyzed for survival. Factors achieving significance (p < 0.05) or borderline significance (p < 0.055) on multivariate analysis were used for the scoring system. Twelve-month survival rates were divided by 10 (factor scores); factor scores were summed for each patient (patient scores).

Results

On multivariate analysis, survival was significantly associated with KPS (hazard ratio (HR) 1.91, p < 0.001) and primary tumor type (HR 1.12, p < 0.001); age achieved borderline significance (HR 1.14, p = 0.054). These factors were used for the scoring tool. Patient scores ranged from 8 to 17 points. Three groups were designated: 8–9 (A), 10–14 (B) and 15–17 (C) points. Twelve-month survival rates were 9, 38 and 72% (p < 0.001); median survival times were 3, 8 and 24 months.

Conclusions

This new tool developed for patients irradiated for bone metastases at any site without spinal cord compression allows one to predict the survival of these patients and can aid physicians when assigning the treatment to individual patients.