Dosimetrical and geometrical parameters in single-fraction lattice radiotherapy for the treatment of bulky tumors: Insights from initial clinical experience.

PURPOSE: This study aims to investigate lattice radiotherapy (LRT) for bulky tumor in 10 patients, analyzing geometrical and dosimetrical parameters and correlations among variables. METHODS: Patients were prescribed a single-fraction of 18 Gy to 50 % of each spherical vertex (1.5 cm diameter). Vertices were arranged in equidistant planes forming a triangular pattern. Center-to-center distance (Dc-c) between vertices was varied from 4 to 5 cm. A new method for calculating the valley-to-peak dose ratio (VPDR) was proposed and compared to other two from existing literature. GTV volumes (VGTV), vertex number (Nvert), low-dose related parameters and vertex D99%, D50%, and D1% were recorded. Beam-on time and Monitor Units (MU) were also evaluated. Correlations were assessed using Spearman's coefficient, with significant differences analyzed using Mann-Whitney U test. RESULTS: Tumor volumes ranged from 417 to 3615 cm3. Median vertex number was 14.5 (IQR:11.3-17.8). VPDR ranged from 0.16 to 0.28. Median D99% spanned from 10.0 to 13.7 Gy, median D50% exceeded 18.0 Gy, and median D1% surpassed 23.3 Gy. Periphery dose remained under 4.0 Gy. Plans exhibited high modulation, with median beam-on time and MU of 8.8 min (IQR:8.2-10.1) and 13,069 MU (IQR:11574-13639). Significant correlations were found between Nvert and VGTV (p < 0.01), MU (p < 0.02) and beam-on time (p < 0.01) and between Dc-c and two VPDR definitions (p < 0.02) and periphery dose (p < 0.01). Significant differences were observed among the three valley dose definitions (p < 0.01) and the three peak dose definitions (p < 0.01). CONCLUSIONS: Reporting geometrical and dosimetrical parameters in LRT is crucial, alongside the need for unified definitions of valley and peak doses.

Acute skin toxicity of ultra-hypofractionated whole breast radiotherapy with simultaneous integrated boost for early breast cancer.

Background: Whole-breast irradiation (WBI) after breast conserving surgery (BCS) is indicated to improve loco-regional control and survival. Former studies showed that addition of tumor bed boost in all age groups significantly improved local control although no apparent impact on overall survival but with an increased risk of worse cosmetic outcome. Even though shortened regimens in 3 weeks are considered the standard, recent studies have shown the non-inferiority of a treatment regimen of 5 fractions in one-week in both locoregional control and toxicity profile, although simultaneous integrated boost (SIB) in this setting has been scarcely studied. Materials and Methods: From March-2020 to March-2022, 383 patients with early breast cancer diagnosis and a median age of 56 years-old (range 30-99)were included in a prospective registry of ultra-hypofractionated WBI up to a total dose of 26 Gy in 5.2 Gy/fraction with a SIB of 29 Gy in 5.8 Gy/fraction in 272 patients (71%), 30-31 Gy in 6-6.2 Gy/fraction in 111 patients (29%) with close/focally affected margins. Radiation treatment was delivered by conformal 3-D technique in 366 patients (95%), VMAT in 16patients (4%) and conformal 3-D with deep inspiration breath hold (DIBH) in 4patients (1%). Ninety-three per cent of patients received endocrine therapy and 43% systemic or targeted chemotherapy. Development of acute skin complications was retrospectively reviewed. Results: With a median follow-up of 18 months (range 7-31), all patients are alive without evidence of local, regional or distant relapse. Acute tolerance was acceptable, with null o mild toxicity: 182 (48%) and 15 (4%) patients developed skin toxicity grade 1 and 2 respectively; 9 (2%) and 2 (0.5%) patients breast edema grade 1and 2 respectively. No other acute toxicities were observed. We also evaluated development of early delayed complications and observed grade 1 breast edema in 6 patients (2%); grade 1 hyperpigmentation in 20 patients (5%); and grade 1 and 2 breast induration underneath boost region in 10(3%) and 2 patients (0.5%) respectively. We found a statistically significant correlation between the median PTVWBI and presence of skin toxicity (p = 0.028) as well as a significant correlation between late hyperpigmentation with the median PTVBOOST (p = 0.007) and the ratio PTVBOOST/PTVWBI (p = 0.042). Conclusion: Ultra-hypofractionated WBI + SIB in 5 fractions over one-week is feasible and well tolerated, although longer follow-up is necessary to confirm these results.

Stereotactic body radiation therapy (SBRT) for spinal metastases: 12 years of a single center experience.

OBJECTIVE: To assess the clinical outcomes of patients with spine metastases treated with SBRT at our institution. MATERIALS AND METHODS: Patients with spine metastases treated with SBRT (1 fraction/18 Gy or 5 fractions/7 Gy) during the last 12 years have been analyzed. All patients were simulated supine in a vacuum cushion or with a shoulder mask. CT scans and MRI image registration were performed. Contouring was based on International Spine-Radiosurgery-Consortium-Consensus-Guidelines. Highly conformal-techniques (IMRT/VMAT) were used for treatment planning. Intra and interfraction (CBCT or X-Ray-ExacTrac) verification were mandatory. RESULTS: From February 2010 to January 2022, 129 patients with spinal metastases were treated with SBRT [1 fraction/18 Gy (75%) or 5 fractions/7 Gy] (25%). For patients with painful metastases (74/129:57%), 100% experienced an improvement in pain after SBRT. With a median follow-up of 14.2 months (average 22.9; range 0.5-140) 6 patients (4.6%) experienced local relapse. Local progression-free survival was different, considering metastases's location (p < 0.04). The 1, 2 and 3 years overall survival (OS) were 91.2%, 85.1% and 83.2%, respectively. Overall survival was significantly better for patients with spine metastases of breast and prostate cancers compared to other tumors (p < 0.05) and significantly worse when visceral metastases were present (p < 0.05), when patients were metastatic de novo (p < 0.05), and in those patients receiving single fraction SBRT (p: 0.01). CONCLUSIONS: According to our experience, SBRT for patients with spinal metastases was effective in terms of local control and useful to reach pain relief. Regarding the intent of the treatment, an adequate selection of patients is essential to propose this ablative approach.