Optimal management in optic nerve sheath meningioma - A multicentre study and pooled data analysis.

Optic nerve sheath meningiomas (ONSMs) are rare, benign neoplasms of the anterior visual pathway. The optimal modality of radiotherapy for treatment has not yet been established. This is the first study to show significant difference in visual outcomes between radiotherapy subtypes in the management of ONSM. We performed a retrospective analysis of visual outcomes and side effects in ONSM patients treated with radiotherapy at three centres in Sydney, Australia, between 2000 and 2016. 15 patients with ONSM were included, and visual outcomes (visual acuity, visual fields, colour vision, OCT retinal nerve fibre layer thickness and radiological tumour response) and treatment toxicities were assessed. Pooled data analysis of available studies was also performed. Statistical analysis was performed with binomial, two-tailed chi-squared tests and Fisher exact tests. In our cohort a significant majority experienced improved visual field (p = 0.046), stable or improved visual acuity (p = 0.0017) and colour vision (p = 0.015) after fractionated radiotherapy. Pooled analysis with strict inclusion criteria found 3D conformal radiotherapy to offer significantly poorer visual acuity compared to fractionated stereotactic radiotherapy (p = 0.008). When all published studies were included, stereotactic radiosurgery was superior to 3D conformal methods (p = 0.035), and equivalent to other fractionated methods. 3D conformal methods also had significantly higher rates of long-term side effects. These results support the use of fractionated radiotherapy and radiosurgery for ONSM treatment, however 3D conformal methods cannot be recommended.

The impact of contour variation on tumour control probability in anal cancer.

BACKGROUND: While intensity modulated radiotherapy (IMRT) has been widely adopted for the treatment of anal cancer (AC), the added contour complexity poses potential risks. This study investigates the impact of contour variation on tumour control probability (TCP) when using IMRT for AC. METHODS: Nine Australian centres contoured a single computed tomography dataset of a patient with AC. The same optimised template-based IMRT planning protocol was applied to each contour set to generate nine representative treatment plans and their corresponding dose volume histograms. A geometric analysis was performed on all contours. The TCP was calculated for each plan using the linear quadratic and logitEUD model. RESULTS: The median concordance index (CI) for the bladder, head and neck of femur, bone marrow, small bowel and external genitalia was 0.94, 0.88, 0.84, 0.65 and 0.65, respectively. The median CI for the involved nodal, primary tumour and elective clinical target volumes were 0.85, 0.77 and 0.71, respectively. Across the nine plans, the TCP was not significantly different. Variation in TCP between plans increased as tumour cell load increased or radiation dose decreased. CONCLUSIONS: When using IMRT for AC, contour variations generated from a common protocol within the limits of minor deviations do not appear to have a significant impact on TCP. Contouring variations may be more critical with increasing tumour cell load or reducing radiotherapy dose.