Stereotactic Body Radiotherapy re-irradiation for locally recurrent rectal cancer: outcomes and toxicity

Background: Stereotactic body radiotherapy (SBRT) has emerged as a potential therapeutic option for locally recurrent rectal cancer (LRRC) but contemporaneous clinical data is limited. We aimed to evaluate the local control, toxicity and survival outcomes in a cohort of patients previously treated with neoadjuvant pelvic radiotherapy for non-metastatic LRRC, now treated with SBRT. Methods: Inoperable rectal cancer patients with ≤ 3 sites of pelvic recurrence and > 6 months since prior pelvic radiotherapy were identified from a prospective registry over 4 years. SBRT dose was 30Gy in 5 fractions, daily or alternate days, using cumulative organ at risk dose constraints. Primary outcome was local control (LC). Secondary outcomes were progression free survival (PFS), overall survival (OS), toxicity and patient reported Quality of Life scores (QoL) using EQ-VAS tool. Results: 30 patients (35 targets) were included. Median GTV size was 14.3cm3. 27/30 (90%) previously received 45-50.4Gy in 25/28 fractions, with 10% receiving an alternative prescription. All patients received the planned re-irradiation SBRT dose. The median FU was 24.5 months (IQR 17.8 – 28.8). The 1-year LC was 84.9% (95% CI 70.6 – 99) and a 2-year LC was 69% (95% CI 51.8 – 91.9). The median PFS was 12.1 months (95% 8.6 – 17.66) and median OS was 28.3 months (95% CI 17.88 – 39.5 months). No patient experienced >G2 acute toxicity and only 1 patient experienced late G3 toxicity. Patient reported QoL outcomes were improved at 3 months following SBRT (Δ EQ-VAS, +10 points, Wilcoxon signed rank, p=0.009). Conclusion: Our study demonstrates that, for small volume pelvic disease relapses from rectal cancer, re-irradiation with 30Gy in 5 fractions is well tolerated and achieves an excellent balance between high local control rates with limited toxicity

Assessment of contour variability in target volumes and organs at risk in lung cancer radiotherapy

Aims This study aimed to examine whether any significant differences existed in trial protocol compliance in target volumes (TV) and organs at risk (OARs) contouring amongst clinical oncologists specialised in lung cancer radiotherapy. Materials/methods Two lung radiotherapy trials that require all prospective investigators to submit pre-trial outlining quality assurance (QA) benchmark cases were selected. The contours from the benchmark cases were compared against a set of reference contours which were defined by the trial management group (TMG). In order to quantify the degree of variation in TV and OARs contouring, the matching index (MI), Dice coefficient (DICE), Jaccard index (JI), Van‘t Riet Index and geographical miss index (GMI) were calculated. Results A total of 198 structures contoured by 21 clinicians were collected from the outlining benchmark cases. There were 40 clinical target volumes (CTV), 32 spinal cord, 36 oesophagus, 36 heart and 54 lungs volumes included in the study. Analysis of the pre-trial benchmark cases revealed statistically significant differences (p ≤ 0.05) in trial protocol compliances between clinical oncologists’ target volume and organs at risk contours. Our results demonstrated that the lung contours had the highest level of conformity, followed by heart, CTV, spinal cord and oesophagus respectively. Conclusions This study showed that there was a statistically significant difference in trial protocol compliance for lung clinical oncologists’ TV and OARs contouring within the pre-trial QA benchmark cases. Trial protocol compliances of TV and OARs delineation can be identified through assessing outlining QA benchmark cases

RTT advanced practice and how it can change the future of radiotherapy

The radiation therapy (RT) landscape is continuously evolving, necessitating adaptation in roles and responsibilities of radiation therapists (RTTs). Advanced Practice Radiation Therapists (APRTs) have taken on a proactive role in expanding services and assuming responsibilities within multi-professional teams. A European Society for Radiotherapy and Oncology (ESTRO) brought geographically diverse and experienced RTTs together, to discuss how advanced practice (AP) in the RTT profession should be future-proofed and create a global platform for collaboration. Challenges in achieving consensus and standardisation of APRT was identified across jurisdictions, emphasising the importance of international collaboration. Whilst highlighting the pivotal role of APRTs in driving innovation, improving patient care, and navigating the complexities of modern RT practice, this position paper presents outcomes and recommendations from the workshop. Discussions highlighted the need for standardised role definitions, education frameworks, regulatory support, and career development pathways to enable the advancement of APRT effectively. Increasing networks and collaboration is recommended to ensure APRTs can shape the future of RT

Superior outcomes of nodal metastases compared to visceral sites in oligometastatic colorectal cancer treated with stereotactic ablative radiotherapy

Background: Stereotactic ablative radiotherapy (SBRT) is a radical option for oligometastatic colorectal cancer (CRC) patients, but most data relate to visceral metastases. Methods: A prospective, multi-centre database of CRC patients treated with SBRT was interrogated. Inclusion criteria were ECOG PS 0–2, ≤3 sites of disease, a disease free interval of >6 months unless synchronous liver metastases. Primary endpoints were local control (LC), progression free survival (PFS) and overall survival (OS). Results: 163 patients (172 metastases) were analysed. The median FU was 16 months (IQR 12.2–22.85). The LC at 1 year was 83.8% (CI 76.4%−91.9%) with a PFS of 55% (CI 47%−64.7%) respectively. LC at 1 year was 90% (CI 83%−99%) for nodal metastases (NM), 75% (63%−90%) for visceral metastases (VM). NM had improved median PFS (9 vs 19 months) [HR 0.6, CI 0.38–0.94, p = 0.032] and median OS (32 months vs not reached) [HR 0.28, CI 0.18–0.7, p = 0.0062] than VM, regardless of whether the NM were located inside or outside the pelvis. On multivariate analysis, NM and ECOG PS 0 were significant good prognostic factors. An exploratory analysis suggests KRAS WT is also a good prognostic factor. Conclusion: Nodal site is an important prognostic determinant of SBRT that should incorporated into patient selection. We hypothesise this may have an immunoediting basis

The use of Log-file analysis within VMAT audits

OBJECTIVE: This work investigated the delivery accuracy of different Varian linear accelerator models using log file-derived multileaf collimator (MLC) root mean square (RMS) values. METHODS: Seven centres independently created a plan on the same virtual phantom using their own planning system, and the log files were analyzed following delivery of the plan in each centre to assess MLC positioning accuracy. A single standard plan was also delivered by the seven centres to remove variations in complexity, and the log files were analyzed for Varian TrueBeams and Clinacs (2300IX or 2100CD models). RESULTS: Varian TrueBeam accelerators had better MLC positioning accuracy (<1.0 mm) than the 2300IX (<2.5 mm) following delivery of the plans created by each centre and also the standard plan. In one case, log files provided evidence that reduced delivery accuracy was not associated with the linear accelerator model but was due to planning issues. CONCLUSION: Log files are useful in identifying differences between linear accelerator models and isolate errors during end-to-end testing in volumetric-modulated arc therapy (VMAT) audits. Log file analysis can rapidly eliminate the machine delivery from the process and divert attention with confidence to other aspects. ADVANCES IN KNOWLEDGE: Log file evaluation was shown to be an effective method to rapidly verify satisfactory treatment delivery when a dosimetric evaluation fails during end-to-end dosimetry audits. MLC RMS values for Varian TrueBeams were shown to be much smaller than those for Varian Clinacs for VMAT deliveries

The role of complexity metrics in a multi-institutional dosimetry audit of VMAT

OBJECTIVE: To demonstrate the benefit of complexity metrics such as the modulation complexity score (MCS) and monitor units (MUs) in multi-institutional audits of volumetric-modulated arc therapy (VMAT) delivery. METHODS: 39 VMAT treatment plans were analysed using MCS and MU. A virtual phantom planning exercise was planned and independently measured using the PTW Octavius(®) phantom and seven29(®) 2D array (PTW-Freiburg GmbH, Freiburg, Germany). MCS and MU were compared with the median gamma index pass rates (2%/2 and 3%/3 mm) and plan quality. The treatment planning systems (TPS) were grouped by VMAT modelling being specifically designed for the linear accelerator manufacturer's own treatment delivery system (Type 1) or independent of vendor for VMAT delivery (Type 2). Differences in plan complexity (MCS and MU) between TPS types were compared. RESULTS: For Varian(®) linear accelerators (Varian(®) Medical Systems, Inc., Palo Alto, CA), MCS and MU were significantly correlated with gamma pass rates. Type 2 TPS created poorer quality, more complex plans with significantly higher MUs and MCS than Type 1 TPS. Plan quality was significantly correlated with MU for Type 2 plans. A statistically significant correlation was observed between MU and MCS for all plans (R = −0.84, p < 0.01). CONCLUSION: MU and MCS have a role in assessing plan complexity in audits along with plan quality metrics. Plan complexity metrics give some indication of plan deliverability but should be analysed with plan quality. ADVANCES IN KNOWLEDGE: Complexity metrics were investigated for a national rotational audit involving 34 institutions and they showed value. The metrics found that more complex plans were created for planning systems which were independent of vendor for VMAT delivery