Cardiac radioablation for ventricular tachycardia: Which approach for incorporating cardiorespiratory motions into the planning target volume?

PURPOSE: To evaluate different approaches for generating a cardiorespiratory ITV for cardiac radioablation. METHODS: Four patients with ventricular tachycardia were included in this study. For each patient, cardiac-gated and respiration-correlated 4D-CT scans were acquired. The cardiorespiratory ITV was defined using registrations of the cardiac and respiratory 4D-CT images. Five different approaches, which differed in the number of incorporated cardiac phases (1, 2, 10, or 1 with a fixed 3 mm margin (FM) expansion) and respiratory phases (2 or 10), were evaluated. For each approach, a VMAT treatment plan was simulated. Target coverage (TC) and spill were evaluated geometrically and dosimetrically for each approach. RESULTS: When employing one cardiac phase, the TC did not exceed 85%. Using the two extreme phases of the cardiac and respiratory cycles resulted in a geometric TC < 88% for two patients, with a dosimetric TC of 83% for one patient. An acceptable TC for all patients (geometric TC > 89%, dosimetric TC > 92%) was only achieved when combining 10 respiratory phases with either 2 or 10 cardiac phases or a single cardiac phase with FM. The use of a single cardiac phase with FM combined with 10 respiratory phases lead to a mean geometric and dosimetric spill of 43% and 35%, respectively. CONCLUSION: For cardiac radioablation, the use of two extreme cardiac phases combined with 10 respiratory phases is a robust approach to generate a cardiorespiratory ITV. The use of a single cardiac phase with or without fixed margin expansion is not recommended based on this study.

Cardiac stereotactic ablative radiotherapy for refractory ventricular arrhythmias: A radical alternative? A narrative review of rationale and cardiological aspects.

Ventricular arrhythmias are serious life-threatening cardiac disorders. Despite many technological improvements, a non-negligible number of patients present refractory ventricular tachycardias, resistant to a catheter ablation procedure, placing these patients in a therapeutic impasse. Recently, a cardiac stereotactic radioablative technique has been developed to treat patients with refractory ventricular arrhythmias, as a bail out strategy. This new therapeutic option historically brings together two fields of expertise unknown to each other, pointing out the necessity of an optimal partnership between cardiologists and radiation oncologists. As described in this narrative review, the understanding of cardiological aspects of the technique for radiation oncologists and treatment technical aspects comprehension for cardiologists represent a major challenge for the application and the future development of this promising treatment.

Optimized radiotherapy to improve clinical outcomes for locally advanced lung cancer.

BACKGROUND: We aimed to evaluate the toxicity, loco-regional control (LRC) and overall survival (OS) associated with accelerated intensity-modulated radiotherapy (IMRT) for locally advanced lung cancer. METHODS: Seventy-three patients were consecutively treated with IMRT from November 2011 to August 2016. A total dose of 66 Gy was delivered using two different schedules of radiotherapy: simultaneous modulated accelerated radiotherapy (SMART) (30 × 2.2 Gy, across 6 weeks) with or without chemotherapy, or moderate hypofractionated radiotherapy (HRT) (24 × 2.75 Gy, across 4 weeks) in patients unfit to receive concomitant chemotherapy. Data on esophageal and pulmonary toxicities, LRC and OS were prospectively collected. RESULTS: The median follow-up duration was 44 months. Severe pneumonitis and esophagitis (grade 3-4) were observed in 7% and 1% of patients respectively, with only one case of grade 4 (pneumonitis). Overall, the 1-year and 2-year LRCs were 76% [95 confidence interval (CI)%: 66-87%] and 62% [95 CI%: 49-77%] respectively. The 1 and 2-year OS rates were 72% [95% CI: 63-83%] and 54% [95 CI%: 43-68%] respectively. None parameters were correlated with LRC or OS. In particular, no difference was observed between patients treated with SMART and H-RT (p = 0.26 and 0.6 respectively), with a 1-year LRC of 74% [95 CI%: 62-86%] for SMART and 91% [95 CI%: 74-100%] for H-RT. No significant differences were observed in the toxicity rates associated with each of the RT schedules. CONCLUSIONS: Accelerated IMRT for locally advanced lung cancer is associated with low toxicities and high LRC. Moderate hypofractionated RT, by decreasing the total treatment time, may be promising in improving clinical outcomes.

CBCT-guided evolutive library for cervical adaptive IMRT.

PURPOSE: In the context of adaptive radiation therapy (ART) for locally advanced cervical carcinoma (LACC), this study proposed an original cone-beam computed tomography (CBCT)-guided "Evolutive library" and evaluated it against four other known radiotherapy (RT) strategies. MATERIAL AND METHODS: For 20 patients who underwent intensity-modulated radiation therapy (IMRT) for LACC, three planning CTs [with empty (EB), intermediate (IB), and full (FB) bladder volumes], a CT scan at 20 Gy and bi-weekly CBCTs for 5 weeks were performed. Five RT strategies were simulated for each patient: "Standard RT" was based on one IB planning CT; "internal target volume (ITV)-based RT" was an ITV built from the three planning CTs; "RT with one mid-treatment replanning (MidTtReplan)" corresponded to the standard RT with a replanning at 20 Gy; "Pretreatment library ART" using a planning library based on the three planning CTs; and the "Evolutive library ART", which was the "Pretreatment library ART" strategy enriched by including some CBCT anatomies into the library when the daily clinical target volume (CTV) shape differed from the ones in the library. Two planning target volume (PTV) margins of 7 and 10 mm were evaluated. All the strategies were geometrically compared in terms of the percentage of coverage by the PTV, for the CTV and the organs at risk (OAR) delineated on the CBCT. Inadequate coverage of the CTV and OARs by the PTV was also assessed using deformable image registration. The cumulated dose distributions of each strategy were likewise estimated and compared for one patient. RESULTS: The "Evolutive library ART" strategy involved a number of added CBCTs: 0 for 55%; 1 for 30%; 2 for 5%; and 3 for 10% of patients. Compared with the other four, this strategy provided the highest CTV geometric coverage by the PTV, with a mean (min-max) coverage of 98.5% (96.4-100) for 10 mm margins and 96.2% (93.0-99.7) for 7 mm margins (P < 0.05). Moreover, this strategy significantly decreased the geometric coverage of the bowel. CTV undercoverage by PTV occurred in the anterior and superior uterine regions for all strategies. The dosimetric analysis at 7 mm similarly demonstrated that the "Evolutive library ART" increased the V42.75Gy of the CTV by 27%, 20%, 13%, and 28% compared with "Standard RT", "ITV-based RT", "MidTtReplan", and "Pretreatment library ART", respectively. The dose to the bowel was also decreased by the "Evolutive library ART" compared with that by the other strategies. CONCLUSION: The "Evolutive library ART" is a personalized ART strategy that comprises a pretreatment planning library of three CT scans, enriched for half of the patients by one to three per-treatment CBCTs. This original strategy increased both the CTV coverage and bowel sparing compared with all the other tested strategies and enables us to consider a PTV margin reduction.