Understanding the Benefit of Magnetic Resonance-guided Adaptive Radiotherapy in Rectal Cancer Patients: a Single-centre Study.

AIMS: Neoadjuvant chemoradiotherapy followed by surgery is the mainstay of treatment for patients with rectal cancer. Standard clinical target volume (CTV) to planning target volume (PTV) margins of 10 mm are used to accommodate inter- and intrafraction motion of target. Treating on magnetic resonance-integrated linear accelerators (MR-linacs) allows for online manual recontouring and adaptation (MRgART) enabling the reduction of PTV margins. The aim of this study was to investigate motion of the primary CTV (CTVA; gross tumour volume and macroscopic nodes with 10 mm expansion to cover microscopic disease) in order to develop a simultaneous integrated boost protocol for use on MR-linacs. MATERIALS AND METHODS: Patients suitable for neoadjuvant chemoradiotherapy were recruited for treatment on MR-linac using a two-phase technique; only the five phase 1 fractions on MR-linac were used for analysis. Intrafraction motion of CTVA was measured between pre-treatment and post-treatment MRI scans. In MRgART, isotropically expanded pre-treatment PTV margins from 1 to 10 mm were rigidly propagated to post-treatment MRI to determine overlap with 95% of CTVA. The PTV margin was considered acceptable if overlap was >95% in 90% of fractions. To understand the benefit of MRgART, the same methodology was repeated using a reference computed tomography planning scan for pre-treatment imaging. RESULTS: In total, nine patients were recruited between January 2018 and December 2020 with T3a-T4, N0-N2, M0 disease. Forty-five fractions were analysed in total. The median motion across all planes was 0 mm, demonstrating minimal intrafraction motion. A PTV margin of 3 and 5mm was found to be acceptable in 96 and 98% of fractions, respectively. When comparing to the computed tomography reference scan, the analysis found that PTV margins to 5 and 10 mm only acceptably covered 51 and 76% of fractions, respectively. CONCLUSION: PTV margins can be reduced to 3-5 mm in MRgART for rectal cancer treatment on MR-linac within an simultaneous integrated boost protocol.

Elective Management of the Neck in Parotid Tumours.

AIMS: Management of the clinically node-negative (cN0) neck for parotid tumours remains controversial. Options include observation, elective neck dissection (END) or elective nodal irradiation (ENI). We reviewed the evidence for ENI on a background of current practice among UK clinical oncologists. MATERIALS AND METHODS: We carried out a systematic search of PubMed between 1 January 1980 and 31 December 2016. Articles on patients treated with parotidectomy and either END or ENI, and studies on nodal patterns of disease, were included. UK clinical oncologists were asked to complete an online questionnaire regarding their use of neck radiotherapy in this setting. RESULTS: From 96 references, 20 studies met the inclusion criteria: 11 reported on END, five on ENI and two on both. Eight studies reported on nodal patterns of disease. The prevalence of occult nodal metastases after END ranged from 0 to 45%. Five year locoregional control was variable (range 64-100%). For ENI, 5 year locoregional control varied from 74 to 100%. High-grade and T3/T4 tumours were factors for nodal relapse after END or ENI, which most commonly occurred in levels I-III. For the survey, 33/50 (66%) of cancer centres responded. Fourteen (42%) centres had guidelines for ENI. Most centres considered high-grade tumours (96%), T3/T4 disease (80%) and lymphovascular invasion (88%) as indications for ENI. Twelve centres (36%) irradiated levels Ib-IV electively; the remaining centres treated other various combinations of nodal levels. CONCLUSION: There is heterogeneity in the use and indications for ENI in the UK. ENI is a reasonable alternative to END as elective management for the cN0 neck in patients with high-grade tumours or T3/T4 disease. The elective clinical target volume should at least encompass nodal levels I-III.

Langerhans cell histiocytosis: old disease new treatment.

Langerhans cell histiocytosis (LCH) has been previously thought of as a rare illness, but is now increasingly diagnosed as a result of the more intensive investigations of patients with cystic pulmonary disease. In recent years, treatments developed from our new understanding of the molecular biology of malignant disease have been applied to patients with LCH, and responses seen. In this review, we describe the origins, presentation and modern treatment of LCH, showing that there is new hope for patients with this condition.