Linac-based stereotactic arrhythmia radioablation of paroxysmal atrial fibrillation in elderly patients

Background

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, occurring in 1–2% of the general population. Patients affected by AF have an increased risk of stroke and heart failure and European guidelines recommend catheter ablation of AF in symptomatic patients refractory to antiarrhythmic therapy. In elderly patients, the AF ablation procedure is associated with a higher rate of overall complications. Recently, stereotactic arrhythmia radioablation (STAR) with precise high-dose of radiation was used to treat ventricular arrhythmias.

Purpose

No data were reported in literature about the use of Linac-based STAR, so a prospective phase-II trial was designed to evaluate safety of Linac-based STAR in elderly patients with paroxysmal AF.

Methods

Fourteen patients (mean age 78±6 years; 57% male) were enrolled in the study. All patients had symptomatic paroxysmal AF refractory to antiarrhythmic drugs. All patients performed 1-week ECG-Holter monitoring (ECG-HM) and transthoracic echocardiogram before and after STAR. Primary end-point was defined as all the adverse events of special interest related to STAR treatment; secondary end-point was defined as AF recurrence after the treatment. The study was approved by the local Ethics Committee and all patients signed informed consent.

Results

All patients performed STAR with a mean overall treatment time of 3 minutes. No serious adverse events were documented acutely and after 6 months of follow up. Transthoracic echocardiogram did not show cardiac damage after STAR. The 1-week ECG-HM performed before STAR documented symptomatic AF episodes in all patients. The 1-week ECG-HM performed 1-month after procedure documented frequent symptomatic atrial ectopy and atrial tachycardias without AF recurrences. The 1-week ECG-HM performed 3 and 6 months after procedure did not revealed AF recurrences. Two patients had a single episode of sustained atrial tachycardia 6 months after STAR. Both patients performed a left atrial mapping using CARTO system and Pentaray mapping catheter documenting PV isolation without vein stenosis (figure); no phrenic nerve damage was documented in both patients. All patients had an improvement in quality of life.

Conclusion

Our preliminary data reported for the first time that the LINAC-based STAR approach could represent a valid alternative to perform PVI in elderly patients with paroxysmal AF.

Funding Acknowledgement

Type of funding sources: None.

Toxicity after moderately hypofractionated versus conventionally fractionated prostate radiotherapy: A systematic review and meta-analysis of the current literature

BACKGROUND

Moderately hypofractionated radiotherapy (RT) currently represents the standard RT approach for all prostate cancer (PCa) risk categories. We performed a systematic review and meta-analysis of available literature, focusing on acute and late genitourinary (GU) and gastrointestinal (GI) adverse events (AEs) of moderate hypofractionation for localized PCa.

MATERIALS AND METHODS

Literature search was performed and two independent reviewers selected the records according to the following Population (P) Intervention (I) Comparator (C) and Outcomes (O) (PICO) question: "In patients affected by localized PCa (P), moderately hypofractionated RT (defined as a treatment schedule providing a single dose per fraction of 3-4.5 Gy) (I) can be considered equivalent to conventionally fractionated RT (C) in terms of G > 2 GI and GU acute and late adverse events (O)?". Bias assessment was performed using Cochrane Cochrane Collaboration's Tool for Assessing Risk of Bias.

RESULTS

Thirteen records were identified and a meta-analysis was performed. Risk of acute GI and GU > 2 adverse events in the moderately hypofractionated arm was increased by 9.8 % (95 %CI 4.8 %-14.7 %; I² = 57 %) and 1.5 % (95 % CI -1.5 %-4.4 %; I² = 0%), respectively.

DISCUSSION

Overall, majority of trials included in our meta-analysis suggested that moderately hypofractionated RT is equivalent, in terms of GI and GU adverse events, to conventional fractionation. Pooled analysis showed a trend to increased GI toxicity after hypofractionated treatment, but this might be related to dose escalation rather than hypofractionation.

Linac-based STereotactic Arrhythmia Radioablation (STAR) for ventricular tachycardia: a treatment planning study

OBJECT

To analyze geometrical approaches, prescription modalities, and delivery efficiency for linear accelerator (Linac)-based STereotactic Arrhythmia Radioablation (STAR) for ventricular tachycardia.

METHODS

The anatomy and planning target volume (PTV) of the first Italian STAR patient were used. To assess geometrical approaches, 3 plans prescribed to 75% isodose-line, differing for number, length of arcs, and couch rotations, were generated and compared (Plans#1-3). Volumetric-arc with 6-MV flattening-filter-free (FFF) was employed. To evaluate prescription modality and delivery, the best geometrical plan was compared with other plans prescribed on 70%, 65%, and 60% isodose-line and with another one using 10MV-FFF beams (Plans#4-7).

RESULTS

For Plans#1-3, PTV coverage, mean cardiac dose, monitor units (MUs), and beam-delivery-time (BDT) were 96-98.5%, 4.9-5.2 Gy, 7047-7790, and 5-6 min, respectively. Plans#4-7 were similar in terms of mean cardiac dose, MUs and BDT to Plans#1-3, except in maximum dose and lower time for 10MV-FFF plan.

CONCLUSION

Linac-based STAR is safe and efficient in terms of BDT and MUs. To ensure high dose to PTV, different dose prescription modalities should be evaluated. The 10FFF approach was the faster but not suitable in patient with cardiac implantable electronic devices.