Geographical miss and overdosing of organs at risk (OAR) due to tumor & organ mobility is a concern for cervix cancer IMRT. Exploring the dose consequence of such organ dynamics might allow refinement of current IMRT strategies. The aim of this study was to simulate the accumulated dose of whole pelvis IMRT in a cohort of cervix cancer patients, determine where underdosing occurred & what influenced it. We also assessed what improvements a mid-course replan provided. 30 pts with stage IB-IVA cervix cancer, receiving standard chemoRT & brachy, had baseline & weekly MRI scans of the pelvis during treatment. The clinical target volume (CTV = GTV + cervix + parametria + upper vagina + 2cm uterus) & OARs were contoured on the fused axial MR-CT images and on each weekly MRI. Patient anatomy at each fraction was deformably mapped to the baseline case, thereby modeling the dosimetric impact of inter-fraction motion. A 3mm PTV margin (smallest limit of what might be clinically feasible with modern image-guided (IG) RT) was used as our prior work showed 5 mm PTV margins to be adequate. Perfect daily IG set up to bone was assumed. Prescribed dose was 50 Gy. CTV D98 ≥47.5 Gy was considered acceptable. We compared baseline dose of tumor & OARs to delivered dose (incorporating organ motion) at the end of treatment and to delivered dose that included a mid-course replan. Without replan, delivered dose to the CTV relative to the planned dose in all patients was significantly reduced (p < 0.0001). However, the delivered CTV D98 was <47.5 Gy (mean 46.3 Gy) in only 4 patients. The anterior parametria & CTV extensions to the lower uterus & upper vagina were most frequently underdosed. Tumor regression in one patient altered uterus flexion from upright to anteverted. Influencing factors were changes in bladder, rectum & tumor volume, uterus position, & movement of small bowel. Delivered OAR doses were similar to the planned doses. A mid-course replan improved the delivered dose to >47.5 Gy (mean 48.1 Gy) in 3 of these 4 patients. The replan reduced V45 for rectum, sigmoid, and bladder by 18% (p < 0.001), 11% (p < 0.03), and 14% (p < 0.007), relative to planned doses, respectively. Tumor & organ dynamics influence delivered dose compared to planned dose. Individual patients may exhibit more target motion and potentially significant reductions in target dose. The influences on this motion are complex and multifactorial. While stringent preparation may control bladder & bowel filling, other factors like tumor regression, changing uterus flexion, or movement of bowel between bladder & uterus are unpredictable. A single mid-course replan can improve target coverage and substantially reduce the dose to critical OARs.

The purpose of this study was to document how radiation oncology departments in Australia and New Zealand manage extended waiting lists by prioritizing patients for radiotherapy and how these centres define the ‘waiting time’. A literature search on strategies for management of waiting lists in radiotherapy, both locally and internationally, was performed. A collaborative survey of all the radiotherapy departments in Australia and New Zealand was then undertaken. Of the 32 centres surveyed around Australia and New Zealand, 25 (77%) responded. There was considerable variation in the definitions used for ‘waiting times’. Eleven of the 25 centres had formally documented protocols. New Zealand has a national policy for prioritization of patients for radiotherapy. Six centres had verbal protocols. Four centres had no significant waiting times and did not require a protocol for prioritization. One centre prioritized according to clinician discretion, two centres used a first-come, first-served basis. One centre replied but their protocol was missing. The variation in the definition of waiting time reduces its usefulness as an indirect measure of resources and as a method of comparing centres. There is also wide variation in the management of waiting lists, particularly in the prioritization schedules used by different centres. The major factor contributing to waiting lists at present is a shortage of radiation oncology staff, particularly radiation therapists. The implementation of standardized protocols for prioritizing patients may be useful in helping to manage scarce resources not withstanding the need to increase the resource base. However, the existence of such protocols should not give legitimacy to undue delays in commencing radiation treatment.