Focal versus craniospinal radiation for disseminated atypical teratoid/rhabdoid tumor following favorable response to systemic therapy.

PURPOSE: Radiotherapy (RT) is associated with improved survival in atypical teratoid/rhabdoid tumor (ATRT); however, optimal RT delivery is unknown. A meta-analysis was conducted for disseminated (M+) ATRT receiving focal or craniospinal radiation (CSI). METHODS: After abstract screening, 25 studies (1995-2020) contained necessary patient, disease, and radiation treatment information (N = 96). All abstract, full text, and data capture were independently double-reviewed. The corresponding author was contacted for cases of insufficient information. Response to pre-radiation chemotherapy (N = 57) was categorized as complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD). Univariate and multivariate statistics were performed to investigate survival correlation. Patients with M4 disease were excluded. RESULTS: The 2- and 4-year overall survival (OS) was 63.8% and 45.7%, respectively, with a median follow-up of 2 years (range 0.3-13.5). The median age was 2 years (range 0.2-19.5), and 96% received chemotherapy. On univariate analysis, gross total resection (GTR, p = .0007), pre-radiation chemotherapy response (p < .001), and high-dose chemotherapy with stem cell recuse (HDSCT, p = .002) correlated with survival. On multivariate analysis, pre-radiation chemotherapy response (p = .02) and GTR (p = .012) retained survival significance as compared to a trend for HDSCT (p = .072). Comparisons of focal RT (vs. CSI) and greater than or equal to 5400 cGy primary dose were nonsignificant. Following CR or PR, a statistical trend favored focal radiation (p = .089) over CSI. CONCLUSION: Chemotherapy response prior to RT and GTR correlated with improved survival on multivariate analysis for ATRT M+ receiving RT. No benefit was observed for CSI compared to focal RT among all patients and following favorable chemotherapy response, inviting further study of focal RT for ATRT M+.

Comparative dosimetric analysis of volumetric modulated arc therapy based craniospinal irradiation plans between Halcyon ring gantry and TrueBeam C-arm linear accelerator.

This study evaluates the volumetric modulated arc therapy (VMAT) dosimetric comparison between Halcyon ring gantry and TrueBeam c-arm linear accelerators for craniospinal irradiation (CSI) of the neuro-axis. 25 patients, who received treatment for medulloblastoma and primitive neuro-ectodermal tumors between 2018 and 2021, were planned for VMAT in True Beam (TB), and Halcyon (HAL) linear accelerators using 6 MV unflattened (FFF) photon beams (HALFFF and TBFFF). Dose-volume statistics for the target and organs at risk (OARs) and the total number of monitoring units (MUs) in the treatment plans were compared which included dose received by 95% PTV volume (V95%), volume receiving ≥ 107% dose, homogeneity index (HI), conformity index (PI), MU and dose spillage (D10%, D30%, D50%, D70%, D90%). In all 26 OARs were considered of which five were serial and the remaining were parallel structures. For the former, the dose received by 0.2 cm3, volume = D0.2 cm3) were evaluated and for the latter mean dose were evaluated. Both arms were statistically compared with paired sample t-test with a significant value of ≤ 0.05. 11 patients received treatment with the Halcyon and the rest 14 in the TrueBeam C-arm linear accelerator. Patients in the low- and intermediate-risk category (n = 13) received 23.4 Gy in 13 fractions. The remaining patients were in the high-risk category and received 35 Gy in 21 fractions or 36 Gy in 20 fractions. For HALFFF and TBFFF, PTVV95% were 97.5 ± 0.8% and 97.4 ± 0.9% respectively (p = 0.371) while the V107% were 0.6 ± 0.4% and 0.5 ± 0.5 respectively (p = 0.504). However, the number of monitoring units showed statistical significance (p < 0.001) with values of 1331.9 ± 243.4 MU and 1089 ± 206.7 MU respectively for the HAL and TB plans. The differences in spillage dose were also statistically significant, favouring HAL plans at D30% (p = 0.002), D50% (p < 0.001), D70% (p = 0.039), and D90% (p = 0.01) level except for D10% (p = 0.090). Conformity index also showed statistical significance with PI_HAL = 0.9 ± 0.02 and PI_TB = 0.89 ± 0.03 (p = 0.029). For 10 of the 21 parallel structures, the mean dose differences were statistically significant in favouring of HAL plans. Halcyon based VMAT CSI plans are dosimetrically superior in terms of organ dose, especially for the large organs, and offer lower spillage doses than the TrueBeam plans. Plans generated by both linear accelerators are suitable for the patients' treatments.

Automating the treatment planning process for 3D-conformal pediatric craniospinal irradiation therapy.

PURPOSE: Pediatric patients with medulloblastoma in low- and middle-income countries (LMICs) are most treated with 3D-conformal photon craniospinal irradiation (CSI), a time-consuming, complex treatment to plan, especially in resource-constrained settings. Therefore, we developed and tested a 3D-conformal CSI autoplanning tool for varying patient lengths. METHODS AND MATERIALS: Autocontours were generated with a deep learning model trained:tested (80:20 ratio) on 143 pediatric medulloblastoma CT scans (patient ages: 2-19 years, median = 7 years). Using the verified autocontours, the autoplanning tool generated two lateral brain fields matched to a single spine field, an extended single spine field, or two matched spine fields. Additional spine subfields were added to optimize the corresponding dose distribution. Feathering was implemented (yielding nine to 12 fields) to give a composite plan. Each planning approach was tested on six patients (ages 3-10 years). A pediatric radiation oncologist assessed clinical acceptability of each autoplan. RESULTS: The autocontoured structures' average Dice similarity coefficient ranged from .65 to .98. The average V95 for the brain/spinal canal for single, extended, and multi-field spine configurations was 99.9% ± 0.06%/99.9% ± 0.10%, 99.9% ± 0.07%/99.4% ± 0.30%, and 99.9% ± 0.06%/99.4% ± 0.40%, respectively. The average maximum dose across all field configurations to the brainstem, eyes (L/R), lenses (L/R), and spinal cord were 23.7 ± 0.08, 24.1 ± 0.28, 13.3 ± 5.27, and 25.5 ± 0.34 Gy, respectively (prescription = 23.4 Gy/13 fractions). Of the 18 plans tested, all were scored as clinically acceptable as-is or clinically acceptable with minor, time-efficient edits preferred or required. No plans were scored as clinically unacceptable. CONCLUSION: The autoplanning tool successfully generated pediatric CSI plans for varying patient lengths in 3.50 ± 0.4 minutes on average, indicating potential for an efficient planning aid in a resource-constrained settings.

Salvage craniospinal irradiation for recurrent intracranial germinoma: a single institution analysis.

This study investigated the effectiveness and safety of low-dose salvage craniospinal irradiation (CSI) for recurrent germinoma. We retrospectively reviewed long-term tumor control and late adverse effects in 15 recurrent germinoma patients treated at our hospital between 1983 and 2019. Following the first recurrence of germinoma, seven were treated with 24-30 Gy of salvage CSI, three underwent non-CSI, and five were treated with only chemotherapy. CSI achieved a significantly better recurrence-free survival rate after the first recurrence compared to other strategies (100% vs 33%, p < 0.001: log-rank test). To evaluate the safety of salvage CSI, we assessed the outcomes at the final follow-up of seven patients who received salvage CSI at first recurrence and three patients who received salvage CSI at second recurrence. The median follow-up period was 220 months after initial treatment. Five patients who received 40-50 Gy of radiation therapy or underwent multiple radiation therapy before salvage CSI were classified into Group A, whereas five patients treated with platinum-based chemotherapy and 24-32 Gy of radiation therapy to the primary site, whole ventricle, or whole brain were classified into Group B. In Group A, one had endocrine dysfunction and the other had visual dysfunction. None were socially independent. Meanwhile, in Group B, no endocrine or visual dysfunction was found, and three patients were socially independent. Salvage CSI achieved excellent tumor control in recurrent germinoma and was safe in patients initially treated with low-dose radiation therapy and chemotherapy.

Outcomes of Infants and Young Children With Relapsed Medulloblastoma After Initial Craniospinal Irradiation-Sparing Approaches: An International Cohort Study.

PURPOSE: Infant and young childhood medulloblastoma (iMB) is usually treated without craniospinal irradiation (CSI) to avoid neurocognitive late effects. Unfortunately, many children relapse. The purpose of this study was to assess salvage strategies and prognostic features of patients with iMB who relapse after CSI-sparing therapy. METHODS: We assembled a large international cohort of 380 patients with relapsed iMB, age younger than 6 years, and initially treated without CSI. Univariable and multivariable Cox models of postrelapse survival (PRS) were conducted for those treated with curative intent using propensity score analyses to account for confounding factors. RESULTS: The 3-year PRS, for 294 patients treated with curative intent, was 52.4% (95% CI, 46.4 to 58.3) with a median time to relapse from diagnosis of 11 months. Molecular subgrouping was available for 150 patients treated with curative intent, and 3-year PRS for sonic hedgehog (SHH), group 4, and group 3 were 60%, 84%, and 18% (P = .0187), respectively. In multivariable analysis, localized relapse (P = .0073), SHH molecular subgroup (P = .0103), CSI use after relapse (P = .0161), and age ≥ 36 months at initial diagnosis (P = .0494) were associated with improved survival. Most patients (73%) received salvage CSI, and although salvage chemotherapy was not significant in multivariable analysis, its use might be beneficial for a subset of children receiving salvage CSI < 35 Gy (P = .007). CONCLUSION: A substantial proportion of patients with relapsed iMB are salvaged after initial CSI-sparing approaches. Patients with SHH subgroup, localized relapse, older age at initial diagnosis, and those receiving salvage CSI show improved PRS. Future prospective studies should investigate optimal CSI doses and the role of salvage chemotherapy in this population.

Robustly optimized hybrid intensity-modulated proton therapy for craniospinal irradiation.

Aim: The aim of the study was to investigate the hybrid robust optimization planning approach in intensity-modulated proton therapy (IMPT) of craniospinal irradiation (CSI). Subjects and Methods: Five IMPT-based adult CSI plans in supine position were created using Raystation treatment planning system (TPS) modelled for Proteus plus proton therapy system. A hybrid planning strategy was implemented, where clinical target volume was robustly optimized (RB) for set up uncertainties and planning target volume was optimized for target coverage using minimax algorithm in the TPS. Beam angle selection, optimization, and dose calculation approach were carefully performed to ensure optimum organ at risk (OAR) sparing, even with potential setup and range errors. The complementary dose gradients in junctions were generated using spot assignment and RB technique. Dosimetric outcomes in both nominal plan and the 16 error scenarios (±3 mm setup and 3.5% range) were analyzed using standard dose volume histogram. Results: This planning approach resulted in a homogeneous dose distribution in the target volume of CSI, including the junction regions, by explicitly reducing number of robust optimization scenarios. The proposed technique was also able to achieve excellent coverage to cribriform plate with lower lens doses and minimal dose to other OARs. Target and OAR doses in the nominal plans as well as in the worst case scenarios with setup and range errors were able to meet the predefined clinical goal. Conclusions: This proposed planning technique is efficient, robust against the uncertainties. It could be adopted in other proton therapy centers.

Successful treatment with tirabrutinib for relapsed Bing-Neel syndrome following high-dose methotrexate and craniospinal irradiation.

A 63-year-old man was diagnosed with Waldenström's macroglobulinemia (WM). Six courses of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone) resulted in complete remission, but WM relapsed three years after R-CHOP. After six courses of BR (bendamustine, rituximab), the serum IgM level and CRP normalized. Four years after BR, the patient presented with muscle weakness, sensory disturbance, and myoclonus of lower limbs. T2-weighted magnetic resonance imaging (MRI) showed areas of signal hyperintensity with contrast enhancement in the right temporal and parietal lobes in brain parenchyma, medulla, bilateral basal ganglia, white matter of occipital lobe, and thoracic spinal cord at the Th2-11 levels. Open brain biopsy revealed diffuse proliferation of small lymphocytes and plasmacytoid lymphocytes on the brain surface and around cerebral blood vessels, resulting in a diagnosis of Bing-Neel syndrome (BNS). Two courses of R-MPV (rituximab, methotrexate, procarbazine, and vincristine) resulted in progressive disease, but the neurological symptoms and MRI findings improved following craniospinal irradiation of 30.6 Gy. Three years after craniospinal irradiation, T2-weighted MRI showed recurrence of BNS with progression of myoclonus of lower limbs and IgM elevation. Tirabrutinib was started for the second recurrence of WM and progression of BNS. Two months after the initiation of treatment with tirabrutinib, the myoclonus of lower limbs disappeared and the MRI findings showed improvement. Serum IgM levels decreased and no adverse events were observed. Tirabrutinib shows promise as a therapeutic option for relapsed BNS.

Progression-Free Survival of LM Is Improved by Proton Craniospinal Irradiation.

pCSI improved central nervous system progression-free survival of LM as compared to standard of care.

WNT Medulloblastoma Limbo: How Low Can We Go?

Survival rates for average-risk medulloblastoma exceed 80%; however, long-term sequelae are substantial. A study from Mumbai, India evaluated the role of omission of craniospinal irradiation. Albeit unsuccessful, this study raises the crucial question of how low therapy can be safely de-escalated with the intent of improving quality of survival. See related article by Gupta et al., p. 4180.

Randomized Phase II Trial of Proton Craniospinal Irradiation Versus Photon Involved-Field Radiotherapy for Patients With Solid Tumor Leptomeningeal Metastasis.

PURPOSE: Photon involved-field radiotherapy (IFRT) is the standard-of-care radiotherapy for patients with leptomeningeal metastasis (LM) from solid tumors. We tested whether proton craniospinal irradiation (pCSI) encompassing the entire CNS would result in superior CNS progression-free survival (PFS) compared with IFRT. PATIENTS AND METHODS: We conducted a randomized, phase II trial of pCSI versus IFRT in patients with non-small-cell lung cancer and breast cancers with LM. We enrolled patients with other solid tumors to an exploratory pCSI group. For the randomized groups, patients were assigned (2:1), stratified by histology and systemic disease status, to pCSI or IFRT. The primary end point was CNS PFS. Secondary end points included overall survival (OS) and treatment-related adverse events (TAEs). RESULTS: Between April 16, 2020, and October 11, 2021, 42 and 21 patients were randomly assigned to pCSI and IFRT, respectively. At planned interim analysis, a significant benefit in CNS PFS was observed with pCSI (median 7.5 months; 95% CI, 6.6 months to not reached) compared with IFRT (2.3 months; 95% CI, 1.2 to 5.8 months; P < .001). We also observed OS benefit with pCSI (9.9 months; 95% CI, 7.5 months to not reached) versus IFRT (6.0 months; 95% CI, 3.9 months to not reached; P = .029). There was no difference in the rate of grade 3 and 4 TAEs (P = .19). In the exploratory pCSI group, 35 patients enrolled, the median CNS PFS was 5.8 months (95% CI, 4.4 to 9.1 months) and OS was 6.6 months (95% CI, 5.4 to 11 months). CONCLUSION: Compared with photon IFRT, we found pCSI improved CNS PFS and OS for patients with non-small-cell lung cancer and breast cancer with LM with no increase in serious TAEs.

How ten-years of reirradiation for paediatric high-grade glioma may shed light on first line treatment.

PURPOSE: Recurrence incidence for paediatric/adolescent high-grade glioma (HGG) exceeds 80%. Reirradiation (reRT) palliates symptoms and delays further progression. Strategies for reRT are scarce: we retrospectively analysed our series to develop rational future approaches. METHODS: We re-evaluated MRI + RT plans of 21 relapsed HGG-patients, accrued 2010-2021, aged under 18 years. All underwent surgery and RT + chemotherapy at diagnosis. Pathologic/molecular re-evaluation allowed classification based on WHO 2021 criteria in 20/21 patients. Survival analyses and association with clinical parameters were performed. RESULTS: Relapse after 1st RT was local in 12 (7 marginal), 4 disseminated, 5 local + disseminated. Re-RT obtained 8 SD, 1 PR, 1PsPD, 1 mixed response, 10 PD; neurological signs/symptoms improved in 8. Local reRT was given to 12, followed again by 6 local (2 marginal) and 4 local + disseminated second relapses in 10/12 re-evaluated. The 4 with dissemination had 1 whole brain, 2 craniospinal irradiation (CSI), 1 spine reRT and further relapsed with dissemination and local + dissemination in 3/four assessed. Five local + disseminated tumours had 3 CSI, 1 spine reRT, further progressing locally (2), disseminated (1), n.a. (1). Three had a third RT; three were alive at 19.4, 29, 50.3 months after diagnosis. Median times to progression/survival after re-RT were 3.7 months (0.6-16.2 months)/6.9 months (0.6-17.9 months), improved for longer interval between 1st RT and re-RT (P = 0.017) and for non-PD after reRT (P < 0.001). First marginal relapse showed potential association with dissemination after re-RT (P = 0.081). CONCLUSIONS: This is the biggest series of re-RT in paediatric HGG. Considering the dissemination observed at relapse, our results could prompt the investigation of different first RT fields in a randomized trial.

Omission of Upfront Craniospinal Irradiation in Patients with Low-Risk WNT-Pathway Medulloblastoma Is Associated with Unacceptably High Risk of Neuraxial Failure.

PURPOSE: Medulloblastoma is a heterogenous disease comprising four molecular subgroups: wingless (WNT), sonic hedgehog (SHH), group 3, and group 4, respectively. Excellent long-term outcomes have prompted deintensification of therapy in WNT-pathway medulloblastoma. We assessed the safety of avoiding upfront craniospinal irradiation (CSI) in children with low-risk WNT-pathway medulloblastoma. PATIENTS AND METHODS: Children with low-risk WNT-pathway medulloblastoma were treated with postoperative focal conformal radiotherapy, avoiding upfront CSI, followed by six cycles of adjuvant systemic chemotherapy. A group-sequential design (triangular test) with predefined stopping rules if the rate of relapse exceeded 15% at 2 years was incorporated to ensure the safety of study participants. RESULTS: 7 children with low-risk WNT-pathway medulloblastoma were accrued after written informed consent/assent and treated as per protocol. One child died of neutropenic sepsis and multiorgan dysfunction during chemotherapy. Three children were detected with neuraxial failure (supratentorial brain and/or spine) on surveillance neuro-imaging within 2 years from index diagnosis, leading to premature study termination. At relapse, children were treated with salvage CSI plus boost irradiation of metastatic deposits followed by second-line chemotherapy. Two of them continue to be in remission (32 and 26 months after first relapse), while one child developed a second relapse, necessitating further systemic chemotherapy and craniospinal reirradiation, resulting in excellent clinico-radiologic response. At a median follow-up of 42 months, the 2-year Kaplan-Meier estimates of event-free survival, recurrence-free survival, and overall survival were 42.9%, 50%, and 85.7% respectively. CONCLUSIONS: Omission of upfront CSI in low-risk WNT-pathway medulloblastoma is associated with an unacceptably high risk of neuraxial failure. See related commentary by Remke and Ramaswamy, p. 4161.

Long-term outcomes and late toxicity of adult medulloblastoma treated with combined modality therapy: A contemporary single-institution experience.

BACKGROUND: Medulloblastoma (MB) is a rare central nervous system malignancy of adults, with limited contemporary studies to define treatment guidelines and expected late toxicity. METHODS: A single-center, retrospective study was conducted of patients age ≥18 years from 1997-2019 with MB and who were treated with postoperative radiotherapy. Late toxicity was defined as a minimum of 18 months from diagnosis. Overall survival (OS) and progression-free survival (PFS) were characterized using Kaplan-Meier and Cox regression analyses. RESULTS: Fifty-nine patients met criteria, with median age of 25 years (range 18-62 y) and median follow-up of 6.5 years (range 0.7-23.1 y). At diagnosis, 68% were standard-risk, 88% Chang M0, and 22% with anaplastic histology. Gross total resection was achieved in 75%; median craniospinal irradiation dose was 30.6 Gy (relative biological effectiveness [RBE]), median total dose was 54.0 Gy (RBE), 80% received proton radiotherapy; 81% received chemotherapy. 5 year PFS and OS were 86.5% and 95.8%, respectively; 10 year PFS and OS were 83.9% and 90.7%, respectively. Anaplastic histology was associated with worse PFS (P = .04). Among eight recurrences, 25% presented after 5 years. Most common grade ≥2 late toxicities were anxiety/depressive symptoms (30%), motor dysfunction (25%), and ototoxicity (22%). Higher posterior fossa radiation dose was associated with increased risk of late toxicity, including worse cognitive dysfunction (P = .05). CONCLUSIONS: Adults with MB have favorable survival outcomes, but late failures and toxicity are not uncommon. Better understanding of prognostic factors, possibly from molecular subtyping, may help to define more personalized treatments for patients with high risk of recurrence and long-term treatment sequelae.

Encouraging early outcomes with image guided pencil beam proton therapy for cranio-spinal irradiation: first report from India.

BACKGROUND: To report our experience with image guided pencil beam proton beam therapy (PBT) for craniospinal irradiation (CSI). MATERIALS AND METHODS: Between January 2019 and December 2021, we carried out a detailed audit of the first forty patients treated with PBT. We had recorded acute toxicities, reporting early outcomes and discuss limitations of current contouring guidelines during CSI PBT planning. RESULTS: Median age of the patient cohort was 8 years, and histologies include 20 medulloblastoma, 7 recurrent ependymoma, 3 pineoblastoma, 3 were germ cell tumors and remaining 7 constituted other diagnoses. Forty percent patients received concurrent chemotherapy. Median CSI dose was 23.4 Gy (Gray; range 21.6-35 Gy). Thirty-five patients (87.5%) completed their CSI without interruption, 5 required hospital admission. No patient had grade 2/ > weight loss during the treatment. Forty-five percent (18) developed grade 1 haematological toxicities and 20% (8) developed grade 2 or 3 toxicities; none had grade 4 toxicities. At median follow up of 12 months, 90% patients are alive of whom 88.9% are having local control. Special consideration with modification in standard contouring used at our institute helped in limiting acute toxicities in paediatric CSI patients. CONCLUSION: Our preliminary experience with modern contemporary PBT using pencil beam technology and daily image guidance in a range of tumours suitable for CSI is encouraging. Patients tolerated the treatment well with acceptable acute toxicity and expected short-term survival outcome. In paediatric CSI patients, modification in standard contouring guidelines required to achieve better results with PBT.

Medulloblastoma and Down Syndrome: An Extremely Rare Association.

Medulloblastoma has a reduced incidence in Down syndrome (DS). This protective characteristic has not been clarified yet. Here, we report the second case of SHH medulloblastoma and DS documented in the literature. A complete surgery was performed followed by reduced craniospinal irradiation dose and adjuvant chemotherapy. No evidence of tumor recurrence was observed. The overall survival was 9.1 years. No family history or physical stigma of other hereditary predisposition syndrome was found. In the elucidation of this extremely rare association, future case reports play an important role in defining the spectrum of brain tumors and their peculiar features in DS.

A review of long-term deficits in memory systems following radiotherapy for pediatric posterior fossa tumor.

INTRODUCTION: In recent years, progress in pediatric posterior fossa tumor (PFT) treatments has improved survival rates. However, the majority of survivors present neurocognitive sequelae that impact academic achievement. METHODS: This review examines the literature from 2000 to 2020 on long-term outcomes in different memory systems for survivors of pediatric PFT, considering the impact of radiotherapy which is a well-known prognostic factor for global neurocognitive function. RESULTS: Of the 43 articles selected, 31 explored working memory, 19 episodic memory, 9 semantic memory and 2 procedural memory. Irradiated survivors had scores of <-2 standard deviation (SD) (n = 4 studies/25) or between -2SD and -1SD (n = 7 studies/25) for working memory; <-1SD for anterograde memory (n = 11/13), with a progressive decline in these two memory systems; <-1SD (n = 4/7) in semantic memory, and a deficit in perceptual-motor procedural learning (n = 1/1). Reducing craniospinal irradiation dose, limiting tumor bed boosts, and using proton therapy seem to have had a beneficial effect with better preservation of the memory score and a reduction in the decline over time. Non-irradiated survivors had memory systems that were less affected, with preservation of anterograde memory and maintenance of long-term stability. CONCLUSION: Memory deficits are a core feature in survivors of pediatric PFT, especially when treatment requires radiotherapy. To limit these effects, dose constraints for specific brain areas involved in memory should be defined. During long-term follow-up, specific attention is essential to identify these deficits in order to limit their impact on the quality of life.

Modified volumetric modulated arc therapy technique with reduced planning and treatment time for craniospinal irradiation utilising two isocentres.

INTRODUCTION: Paediatric patients (individuals below 18 years of age) requiring cranial-spinal irradiation (CSI) at our institution are commonly planned and treated using a three isocentre (3-ISO) volumetric modulated arc therapy (VMAT) technique. A modified two isocentre (2-ISO) VMAT technique was investigated with the aim to improve workflow and reduce planning and treatment time. METHODS: Five CSI paediatric patients previously treated with a 3-ISO VMAT technique were retrospectively replanned using a 2-ISO VMAT technique. The 2-ISO VMAT plans were reviewed and approved by a radiation oncologist (RO) before undergoing patient-specific quality assurance (QA) procedures, performed by a radiation oncology medical physicist (ROMP). Planning target volume (PTV) coverage, organ-at-risk (OAR) dose as well as planning and treatment durations of the first five patients utilising 2-ISO technique were compared with 3-ISO technique. RESULTS: The average percentage difference in PTV coverage by 95% reference dose between the 2-ISO and 3-ISO is 0.14%, and the average difference in OAR median dose is 0.68 Gy. Conformity and homogeneity indices have the same averages at 1.18 and 0.4 respectively. Patient-specific physics QA results were all comparable with the 3-ISO averages at 98.84% and the 2-ISO at 98.71%. Planning duration for the 2-ISO was reduced by up to 75%, and daily treatment duration was reduced by up to 50%. Of all the previously treated CSI patients using a 3-ISO technique, 45% were suitable for the 2-ISO technique. CONCLUSION: The 2-ISO VMAT technique provided comparable dose distribution based on PTV coverage, OAR dose and plan metric indices. Reduced planning and treatment duration with the 2-ISO technique facilitated improved workflow with decreased sedation time for paediatric patients requiring a general anaesthesia.