Current practices of craniospinal irradiation techniques in Turkey: a comprehensive dosimetric analysis.

OBJECTIVE: This study evaluates various craniospinal irradiation (CSI) techniques used in Turkish centers to understand their advantages, disadvantages and overall effectiveness, with a focus on enhancing dose distribution. METHODS: Anonymized CT scans of adult and pediatric patients, alongside target volumes and organ-at-risk (OAR) structures, were shared with 25 local radiotherapy centers. They were tasked to develop optimal treatment plans delivering 36 Gy in 20 fractions with 95% PTV coverage, while minimizing OAR exposure. The same CT data was sent to a US proton therapy center for comparison. Various planning systems and treatment techniques (3D conformal RT, IMRT, VMAT, tomotherapy) were utilized. Elekta Proknow software was used to analyze parameters, assess dose distributions, mean doses, conformity index (CI), and homogeneity index (HI) for both target volumes and OARs. Comparisons were made against proton therapy. RESULTS: All techniques consistently achieved excellent PTV coverage (V95 > 98%) for both adult and pediatric patients. Tomotherapy closely approached ideal Dmean doses for all PTVs, while 3D-CRT had higher Dmean for PTV_brain. Tomotherapy excelled in CI and HI for PTVs. IMRT resulted in lower pediatric heart, kidney, parotid, and eye doses, while 3D-CRT achieved the lowest adult lung doses. Tomotherapy approached proton therapy doses for adult kidneys and thyroid, while IMRT excelled for adult heart, kidney, parotid, esophagus, and eyes. CONCLUSION: Modern radiotherapy techniques offer improved target coverage and OAR protection. However, 3D techniques are continued to be used for CSI. Notably, proton therapy stands out as the most efficient approach, closely followed by Tomotherapy in terms of achieving superior target coverage and OAR protection.

Frameless Hypofractionated Gamma Knife Radiosurgery for Residual or Recurrent Craniopharyngioma.

BACKGROUND: The management of craniopharyngiomas is challenging, usually requiring multidisciplinary care. Gamma Knife radiosurgery (GKRS) is an essential technique for residual/recurrent craniopharyngiomas. OBJECTIVE: To evaluate the efficacy of frameless hypofractionated GKRS (hfGKRS) for craniopharyngioma and factors which affect tumor control and complications. METHODS: This retrospective study involved 24 patients managed with hfGKRS. Clinical and radiological data, tumor characteristics, and procedural details were analyzed. RESULTS: There were 15 (62.5%) female patients. The median age was 38.5 years (range, 3-66 years). The mean tumor volume was 2.4 (1.93) cm 3 , with a mean solid volume of 1.6 (1.75) cm 3 . The median marginal dose was 20 Gy (range, 18-25 Gy) delivered in a median of 5 fractions (range, 3-5). During a median radiological follow-up of 23.5 months (range, 12-50 months), tumor progression was noted in 5 (20.8%) patients. The 2-year and 4-year progression-free survival were 81.8% and 61.4%, respectively. No deaths were identified at a median clinical follow-up of 31.3 months (range, 12-54 months). Visual deficits attributable to progression were noted in 3 (12.5%) patients with pre-GKRS visual field defects. An additional 4 (16.7%) patients with pre-GKRS visual deficit developed new minor visual field defects. Four (16.7%) patients showed improvement of vision after GKRS. There were no new-onset post-GKRS hormonal deficits. CONCLUSION: The management of craniopharyngioma requires a multidisciplinary approach, and irradiation represents effective treatment option for residual/recurrent tumors after surgery. To the best of our knowledge, this is the first study that addresses the efficacy of frameless hfGKRS in managing craniopharyngiomas over sufficient follow-up.

Novel Clinically Weight-Optimized Dynamic Conformal Arcs (WO-DCA) for Liver SBRT: A Comparison with Volumetric Modulated Arc Therapy (VMAT).

PURPOSE: To evaluate the feasibility of shortening the duration of liver stereotactic radiotherapy (SBRT) without jeopardizing dosimetry or conformity by utilizing weight-optimized dynamic conformal arcs (WO-DCA) as opposed to volumetric modulated arc therapy (VMAT) for tumors away from critical structures. METHODS: Nineteen patients with liver metastasis were included, previously treated with 50 Gy in 4 fractions with VMAT technique using two partial coplanar arcs of 6 MV beams delivered in high-definition multi-leaf collimator (HD-MLC). Two coplanar partial WO-DCA were generated on Pinnacle treatment planning system (TPS) for each patient; and MLC aperture around the planning target volume (PTV) was automatically generated at different margins for both arcs and maintained dynamically around the target during arc rotation. Weight of the two arcs using optimization method was adjusted between the arcs to maximize tumor coverage and protect organs at risk (OAR) based on the RTOG-0438 protocol. RESULTS: The WO-DCA plans successfully "agreed" with the standard VMAT for OAR (liver, spinal cord, stomach, duodenum, small bowel, and heart) and PTV (Dmean, D98%, D2%, CI, and GI), with superior mean quality assurance (QA) pass rate (97.06 vs 93.00 for VMAT; P < 0.001 and t = 8.87). Similarly, the WO-DCA technique additionally reduced the beam-on time (3.26 vs 4.43; P < 0.001) and monitor unit (1860 vs 2705 for VMAT; P < 0.001) values significantly. CONCLUSION: The WO-DCA plans might minimize small-field dosimetry errors and defeat patient-specific VMAT QA requirements due to the omission of MLC beam modulation through the target volume. The WO-DCA plans may additionally enable faster treatment delivery times and lower OAR without sacrificing target doses in SBRT of liver tumors away from critical structures.

Double isocenter optimization with HD-MLC linear accelerator to treat extended fields in patients with head and neck cancers.

PURPOSE: For departments with a congested patient burden or with a limited number of eligible LINACs, we investigated whether LINACS dedicated for SRS-SBRT with limited field high-definition (HD) multi-leaf collimator (MLC) could help to carry this load, and utilized a double-isocenter (DI) optimization with a limited field size of HD-MLC to defeat the craniocaudal field size restriction to match treated plans in a wide-field MLC LINAC for head and neck cancer patients. METHODS: Fourteen patients with locally advanced head and neck cancers were included, previously treated with simultaneous integrated boost volumetric modulated arc treatment (VMAT) in 33 fractions of clinical target volumes (CTV) of 70Gy, 63Gy, and 57Gy, via single isocenter (SI) plans in Millennium MLC-120 of Varian Trilogy. The DI plans were generated on Pinnacle TPS to be delivered in HD 120 leaves MLC on Varian Truebeam. The organs at risk (OAR) doses and the prescription volume parameters were compared. RESULTS: The DI plans in HD-MLC LINACs were successfully matching the previously treated plans for OAR and CTV constraints. The CI (1.18 versus 1.26; p=0.004) and HI (0.23 versus 0.29; p<0.001) were significantly improved with DI, while the MUs (1321.5 versus 800.3; p<0.001) and the treatment delivery times (6.1 versus 3.7 min; p<0.001) per fraction increased modestly with DI compared to SI, respectively. CONCLUSIONS: We revealed that DI optimization plans prepared for HD-MLC could effectively accomplish our goal dosimetrically in locoregionally advanced head and neck cases, despite a modest increase in the MU and treatment delivery times per fraction. This technique may provide an alternative in case of downtimes of standard MLC systems or a standalone treatment machine in case of high volumes requiring extended-field IMRT procedures, or possibly shorten the lengthy waiting times in facilities with limited SRS or SBRT patients.

Single-fraction versus hypofractionated gamma knife radiosurgery for small metastatic brain tumors.

Stereotactic radiosurgery (SRS) has become a standard of care for the treatment of metastatic brain tumors (METs). Although a better balance of tumor control and toxicity of hypofractionated SRS (hfSRS) compared with single-fraction SRS (sfSRS) was demonstrated in large METs, there is no data comparing two approaches for small METs (< 4 cm3). It was aimed to compare clinical outcomes between sfSRS versus hfSRS Gamma Knife radiosurgery (GKRS) in a series of patients with unresected, small METs. Patients (n = 208) treated with sfGKRS or hfGKRS between June 2017 and May 2020 were retrospectively examined in a single center. The co-primary endpoints of local control (LC) and toxicity were estimated by applying the Kaplan-Meier method. Multivariate analysis using Cox proportional hazards (HR) modeling was used to assess the effect of independent variables on the outcomes. The actuarial LC rate was 99.7% at six months and 98.8% at 18 months in the sfGKRS group, and 99.4% and 94.3% in the hfGKRS group (p = 0.089), respectively. In multivariate analysis, MET volume (p = 0.023, HR 2.064) and biologically effective dose (BED10) (p < 0.0001, HR 0.753) was associated with LC. In total, treatment-related toxicity was observed in 13 (8.7%) patients during a median period of 10 weeks (range 1-31). Radiation necrosis was observed in four patients (1.9%), and all patients were in the sfGKRS group (p = 0.042). Only the maximum dose was associated with toxicity (p = 0.032, HR 1.047). Our current results suggest that hfGKRS is advantageous and beneficial also in patients with unresected, small METs.

Dosimetric comparison of modern radiotherapy techniques for gastric cancer after total gastrectomy.

PURPOSE: The purpose of this study is to investigate the optimal radiotherapy technique for postoperative irradiation of gastric cancer treated with total gastrectomy. MATERIALS AND METHODS: The database of ten patients was used for this study. Three-dimensional (3D) conformal radiotherapy, intensity-modulated therapy (IMRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) plans were created for each dataset. The prescription dose was 45 Gy in 25 fractions. Comparative analyses of the target volume coverage and the doses of organs at risk were performed. RESULTS: HT was significantly provided more homogeneity. The best conformal plans were achieved with VMAT. Both kidneys were better preserved with HT and VMAT. HT significantly lowered the V13 of the left kidney and VMAT significantly lowered V20. However, the mean left kidney doses were not statistically different. The lowest liver V30 was obtained with VMAT but not with statistically different than IMRT and HT. Mean liver doses were statistically inferior with 3D. The worst spinal cord doses were seen with 3D. The integral dose of the body did not differ among the techniques. CONCLUSION: In comparison of the four techniques, 3D seems to be the most unsuitable method regarding sparing the normal tissues. According to availability, HT and VMAT should be primarily preferred. IMRT can also be used with carefully paying attention to the clinical condition of the patient.