Re-irradiation after stereotactic body radiotherapy for spine metastases from hepatocellular carcinoma: a case report.

Modern radiotherapy machines with refinements in planning software and image-guidance apparatuses have made stereotactic body radiotherapy (SBRT) more widely available as an effective tool in the management of spine metastases. In conventional palliative radiotherapy, the aim has traditionally been pain relief and short-term local control. In contrast, SBRT aims to deliver an ablative dose to enhance local control, with a smaller number of fractions while sparing the organs at risk (OAR), especially the spinal cord. Recently, trials have asserted the role of spine SBRT as an effective modality for durable local control, in addition to achieving pain relief. The quality of evidence for spine SBRT data is maturing, while prospective published trials on re-irradiation SBRT in spine remain sparse. The purpose of the present case report is to share the challenges faced while salvaging a dorsal spine metastasis and ablating a new right adrenal metastatic lesion in proximity of the transplanted liver.

Hybrid planning techniques for hypofractionated whole-breast irradiation using flattening filter-free beams.

OBJECTIVE: The aim of this study was to assess the feasibility of flattening filter-free (FFF) photon beams in hybrid intensity-modulated radiation therapy (H-IMRT) and hybrid volumetric modulated arc therapy (H-VMAT) for left-sided whole-breast radiation therapy with a boost volume (RT) using a hypofractionated dose regimen. PATIENTS AND METHODS: RT plans of 25 patients with left-sided early-stage breast cancer were created with H­IMRT and H­VMAT techniques under breath-hold conditions using 6­MV FFF beams. In hybrid techniques, three-dimensional conformal radiotherapy (3DCRT) plans were kept as base-dose plans for the VMAT and IMRT plans. In addition, H­IMRT in step-and-shoot mode was also calculated to assess its achievability with FFF beams. RESULTS: All hybrid plans achieved the expected target coverage. H­VMAT showed better coverage and homogeneity index results for the boost target (p < 0.002), while H­IMRT presented better results for the whole-breast target (p < 0.001). Mean doses to normal tissues were comparable between both plans, while H­IMRT reduced the low-dose levels to heart and ipsilateral lung (p < 0.05). H­VMAT revealed significantly better results with regard to monitor units (MU) and treatment time (p < 0.001). CONCLUSION: The 6­MV FFF beam technique is feasible for large-field 3DCRT-based hybrid planning in whole-breast and boost planning target volume irradiation. For breath-hold patients, the H­VMAT plan is superior to H­IMRT for hypofractionated dose regimens, with reduced MU and treatment delivery time.

Hybrid volumetric modulated arc therapy for whole breast irradiation: a dosimetric comparison of different arc designs.

PURPOSE: To find an optimal arc design for hybrid volumetric modulated arc therapy (H-VMAT), a combination of conventional 3DCRT and VMAT plans for left-sided whole breast radiation therapy. METHODS AND MATERIALS: A total of 26 left-sided early-stage breast cancer patients were selected for this study. To find the superior plan, H-VMAT with three different arc designs including, two partial arcs (2A), four partial arcs (4A) and four tangential arcs (TA) were created for each study case by combining 3DCRT and VMAT with 75% 3DCRT/25% VMAT dose proportion of prescription dose. RESULTS: All H-VMAT plans achieved the expected target coverage. A higher conformity index and homogeneity index were achieved for 2A and 4A H-VMAT plans and significantly differ from TA H-VMAT (p < 0.003). The heart and ipsilateral lung dose parameters were comparable among all plans except heart V40Gy which was significantly less in 4A H-VMAT plan (p < 0.05). The contralateral lung, contralateral breast, spinal cord, normal tissue doses and MU were significantly less in TA H-VMAT (p < 0.03). The beam-on time was significantly less in 2A H-VMAT (p < 0.0001). CONCLUSION: 2A and 4A H-VMAT techniques are effective in improving the PTV dosimetric parameters as well as reducing the OAR doses. Further, 2A H-VMAT delivers less MU and beam-on time compared to 4A H-VMAT.

Sparing dysphagia/aspiration related structures using novel hybrid volumetric modulated arc therapy.

PURPOSE: Studies using split field IMRT to spare dysphagia/aspiration related structures (DARS) have raised concern regarding dose uncertainty at matchline. This study explores the utility of hybrid VMAT in sparing the DARS and assesses matchline dose uncertainty in postoperative oral cavity cancer patients and compares it with VMAT. METHODS & MATERIALS: Ten postoperative oral cavity cancer patients were planned with h-VMAT and VMAT using the same planning CT dataset. PTV and DARS were contoured using standard delineation guidelines. In h-VMAT 80% of the neck dose was planned using AP/PA technique and then VMAT optimization was done for the total PTV by keeping the corresponding AP/PA plan as the base dose. Planning goal for PTV was V95%≥95% and for DARS, adequate sparing. Plans and dose volume histograms were analyzed using dosimetric indices. Absolute point and portal dose measurements were done for h-VMAT plans to verify dose at the matchline. RESULTS: Coverage in both the techniques was comparable. Significant differences were observed in mean doses to DARS (Larynx: 24.36±2.51 versus 16.88±2.41Gy; p<0.0006, Pharyngeal constrictors: 25.16±2.41 versus 21.2±2.1Gy; p<0.005, Esophageal inlet: 18.71±2 versus 12.06±0.79Gy; p<0.0002) favoring h-VMAT. Total MU in both the techniques was comparable. Average percentage variations in point dose measurements in h-VMAT done at +3.5 and -3.5 positions were (1.47±1.48 and 2.28±1.35%) respectively. Average gamma agreement for portal dose measured was 97.07%. CONCLUSION: h-VMAT achieves better sparing of DARS with no matchline dose uncertainty. Since these patients have swallowing dysfunction post-operatively, attempts should be made to spare these critical structures as much as possible.

Bilateral Breast Irradiation Using Hybrid Volumetric Modulated Arc Therapy (h-VMAT) Technique: A Planning Case Report.

The purpose of this planning case report is to share the perceived dosimetric benefits of innovative hybrid volumetric modulated arc therapy (h-VMAT) for bilateral breast cancer radiotherapy in two patients with synchronous bilateral breast cancer. Two patients with early bilateral breast cancer after breast conservation surgery and adjuvant chemotherapy were planned for bilateral breast radiotherapy. On the planning computed tomography (CT) dataset, bilateral breast planning treatment volume (PTV) and organs at risk (OARs) were delineated using standard guidelines. Using the same structure set, volumetric modulated arc therapy (VMAT) and h-VMAT plans were generated and compared dosimetrically. The h-VMAT showed comparable target coverage, conformity and homogeneity while sparing of both lungs and heart were better. The dose to heart was reduced with h-VMAT, with a V25Gy and V5Gy of 3.2 & 22.3% for h-VMAT versus 11.6 & 84.9% for the VMAT plan. Similarly, the dose to the total lung was better in h-VMAT with a V20Gy and V5Gy of 12.1 & 46.2 versus 19.9 & 83.3% for VMAT. Overall the results indicate a better sparing of lung and heart at low doses with h-VMAT. Long-term clinical follow-up will give us more insight about the dosimetric benefits of these innovative techniques.