OBJECTIVE: We report the use of online adaptive radiotherapy (OART) aiming to improve dosimetric parameters in the prostate cancer patient who had lower urinary tract symptoms that caused him not to adhere to the standard bladder filling protocol.
METHODS: The reference treatment plan for adaptive radiotherapy plan was generated for the pelvis and the solitary bony lesion using the Ethos treatment planning system. For each treatment session, high-quality iterative reconstructed cone beam CT (CBCT) images were acquired, and the system automatically generated an optimal adaptive plan after verification of contours. Image-guided RT (IGRT) plans were also created using the reference plan recalculated on the CBCT scan and were compared with adaptive plans.
RESULTS: The reference bladder volume in the planning CT scan was 173 cc, and the mean bladder volume difference over the course was 25.4% ± 16.6%. The ART offered superior target coverage for PTV 70 Gy over online IGRT (V95: 90.5 ± 3.2 % Vs 97.3 ± 0.4%; p=0.000) and the bladder was also better spared from the high dose (V65 Gy: 17.9 ± 9.1% vs 14.8 ± 3.6%; p=0.03). However, the mean rectum V65 doses were very similar in both plans.
CONCLUSIONS: Managing the inconsistent bladder volume was feasible in the prostate cancer patient using the CBCT-guided OART and our analysis confirmed that adaptive plans offered better target coverage while sparing the bladder from high radiation doses in comparison to online IGRT plans.
BACKGROUND: radiotherapy, CBCT, online adaptive radiotherapy, image-guided RT.

We report our early clinical experience with image-guided, pencil beam scanning proton beam therapy (PBS-PBT) for residual and recurrent craniopharyngioma.
Between September 2019 and January 2023, 19 consecutive patients with residual or recurrent craniopharyngioma, suitable for radiotherapy and treated with image-guided PBS-PBT were analyzed. We documented detailed dosimetric data, acute toxicities, early outcomes, and imaging response on follow-up magnetic resonance imaging scans.
A total of 19 patients (11 males and 8 females) with residual or recurrent craniopharyngioma were treated during the study period. The median age of the cohort was 14 years (range, 3-33 years). The histology of most lesions was the adamantinomatous subtype (95%). The most common clinical presentation (before PBT) and most common endocrine deficit was visual disturbance (79%) and hypocortisolism (74%), respectively. Of the 19 patients, 13 had recurrent craniopharyngioma, and 5 had undergone radiotherapy previously. Five patients (26%) had undergone surgery ≥3 times before proton therapy. The median dose delivered was 54 GyE. The most common acute toxicity was grade 1 alopecia (63%). No patient experienced grade ≥3 acute toxicity. With a median follow-up of 18 months (range, 3-40 months), 12 patients showed shrinkage of the residual tumor and/or cyst, and 4 showed a dramatic cyst reduction at 3-9 months of follow-up. Two patients experienced a reduction in both solid and cystic components, with the remaining experiencing a reduction in the cystic component only. The remaining 8 patients had stable disease on magnetic resonance imaging, with 100% disease control and overall survival. Visual function remained stable after treatment.
Our preliminary experience with modern PBS-PBT and image guidance for craniopharyngioma is encouraging. Proton therapy in our cohort was well tolerated, resulting in limited toxicity and promising early outcomes.

Adrenocortical carcinoma is a malignant tumor with a poor prognosis and a frequent metastatic extension. In very rare cases, a cardiac metastatic disease may occur, and surgical resection is essential for its management. MR-guided stereotactic radiotherapy is an attractive radiotherapy modality for the treatment of mobile thoracic tumors, enabling the target to be monitored continuously during irradiation, while the dosimetric plan can be adapted daily if necessary. We report here the case of a patient with intracardiac metastasis secondary to malignant adrenocortical carcinoma, treated with magnetic resonance imaging-guided stereotactic radiotherapy.

BACKGROUND: Online adaptive stereotactic radiotherapy allows for improved target and organ at risk (OAR) delineation and inter-fraction motion management via daily adaptive planning. The use of adaptive SBRT for the treatment of pancreatic cancer (performed until now using only MRI or CT on rails-guided adaptive radiotherapy), has yielded promising outcomes. Herein we describe the first reported case of cone beam CT-guided stereotactic adaptive radiotherapy (CT-STAR) for the treatment of pancreatic cancer.
METHODS: A 61-year-old female with metastatic pancreatic cancer presented for durable palliation of a symptomatic primary pancreatic mass. She was prescribed 35 Gy/5 fractions utilizing CT-STAR. The patient was simulated utilizing an end-exhale CT with intravenous and oral bowel contrast. Both initial as well as daily adapted plans were created adhering to a strict isotoxicity approach in which coverage was sacrificed to meet critical luminal gastrointestinal OAR hard constraints. Kilovoltage cone beam CTs were acquired on each day of treatment and the radiation oncologist edited OAR contours to reflect the patient\'s anatomy-of-the-day. The initial and adapted plan were compared using dose volume histogram objectives, and the superior plan was delivered. Use of the initial treatment plan would have resulted in nine critical OAR hard constraint violations. The adapted plans achieved hard constraints in all five fractions for all four critical luminal gastrointestinal structures.
CONCLUSIONS: We report the successful treatment of a patient with pancreatic cancer treated with CT-STAR. Prior to this treatment, the delivery of ablative adaptive radiotherapy for pancreatic cancer was limited to clinics with MR-guided and CT-on-rails adaptive SBRT technology and workflows. CT-STAR is a promising modality with which to deliver stereotactic adaptive radiotherapy for pancreatic cancer.

BACKGROUND: Tenosynovial giant cell tumor (TGCT) is a neoplastic, inflammatory disease with a benign but aggressive course that often presents as localized (TGCT-L) and diffuse (TGCT-D) forms based on the growth pattern and clinical behavior. For TGCT-L, simple excision of the diseased synovial tissue is the preferred treatment option, while for TGCT-D, adequate synovectomy is usually tricky but is essential. However, approximately 44% of TGCT-D cases will relapse after surgery alone. Thus, the optimal treatment strategy in patients with TGCT-D is evolving, and standalone surgical resection can no longer be regarded as the only treatment. The previous studies have shown that postoperative adjuvant radiotherapy can reduce recurrence in TGCT, especially in patients with incomplete synovectomy.
UNASSIGNED: In the first case, a 54-year-old male presented with recurrent pain and swelling of the right knee with a protracted disease course (≥10 years). The other patient is a 64-year-old male who developed swelling, pain, abnormal bending, and limited movement of the left knee without obvious inducement.
UNASSIGNED: Clinical and imaging examinations can provide a definitive diagnosis, and pathology is the gold standard. TGCT-D was confirmed by postoperative pathology. After the operation, the patients underwent an MRI re-examination and showed that the lesions of the knee were not completely resected.
METHODS: Arthroscopic synovectomy was performed on the patients, and postoperative pathology was confirmed as TGCT-D. Because of incomplete synovectomy, the 2 cases received image-guided, intensity-modulated radiotherapy (IG-IMRT) after the operation.
RESULTS: The follow-up time was 1 year, no evidence of disease progression was found in MRI. No obvious adverse effects associated with radiotherapy were detected during the follow-up period.
CONCLUSIONS: These cases and reviews illustrate the necessity of radiotherapy for TGCT-D and that IG-IMRT is a safe and effective method for treating TGCT-D of the knee.

The integration of magnetic resonance (MR) imaging into radiotherapy through new technology, including the MR -linear accelerator (MRL), has allowed further advancements into image guided radiotherapy (IGRT). Better soft tissue visualisation has led to some unusual findings.
A patient with T1c N0 M0 prostate adenocarcinoma received 60Gy in 20# radiotherapy on the MRL. Radiotherapy planning (RTP) scans were completed on both CT and MR (using T2 and T1 weighted three-dimensional turbo spin echo sequences, reconstructed transaxially (TRA). The MR scans revealed atypical oedema in the right peripheral zone, visualised on T2-weighted (T2w) MR Images as an accumulation of high signal intensity fluid. Daily MRL treatment includes a (T2w 3D Tra) sequence with which oedematous changes could be monitored. The images demonstrated an increase in oedematous volume over fractions 1-10 causing the prostate contour variations from the initial planning scans. Despite the prostate volume variations PTV coverage was never breached and dose constraints were always met for both PTV and surrounding organs at risk (OAR\'s), excluding the need for oncologist input. A single Therapeutic Radiographer (RTT) experienced in MRL delivery, contoured the prostate and oedematous volumes on the radiotherapy plan (RTP) MR and all on-treatment MR images to assess change over the radiotherapy course. The initial volumes were 53.4 cm3 and 8.3 cm3 for the prostate plus oedema and oedema alone respectively. The most significant change was seen for both the prostate and oedema on fraction nine (68.0 cm3 and 10.1 cm3, respectively). Reductions were noted after this with final (fraction 20) volumes of 55.2 cm3 and 0.58 cm3 respectively.
The ability to visualise prostatic oedema was new to the radiotherapy treatment team due to better soft tissue visualisation than standard radiotherapy. The results from contouring the prostate and oedema volumes confirmed radiographer observations and demonstrated how oedema impacted the overall prostate volume by quantifying the oedematous variations over time. The changes in oedema volume are presumed to be in response to radiotherapy.
Further adaptive radiotherapy work-flow developments, utilising an \"Adapt to Shape\" model will allow real-time re-contouring of the prostate to ensure tumour control is not compromised. Further work investigating the frequency and impact of oedemotous changes to external beam prostate patients will help to inform practice.

Spinal metastasis are a daily challenge in clinical practice. Stereotactic body radiotherapy (SBRT) allows delivery of definitive treatment with excellent long-term control rates. Its implementation needs dedicated devices and day-to-day image-guided radiotherapy (IGRT). The XSight™ spine tracking system, integrates with the CyberKnife® (Accuray™), provides a fiducial-free tracking system for spinal SBRT. We report a rare case of tracking failure during treatment due to the occurrence of a vertebral compression fracture (VCF).

OBJECTIVE: Sampling theory and operator characteristic curves are methods that can determine an optimal schedule for quality control tests. We apply this method to positional data for whole breast radiotherapy since several surveys report inconsistent image guidance practice for this technique.
METHODS: Positional errors were defined, for 55 consecutive breast cancer patients, by comparing the central lung distance measured on portal images with that obtained from the corresponding digitally reconstructed radiograph. From the distribution of positional errors, the probability of a setup error >5 mm in the direction of the mediastinum was established. Using operator characteristic curves, we compared the effectiveness of various image-guidance schedules in dealing with such errors. We also calculated the dosimetric impact of undetected errors.
RESULTS: Setup errors >5 mm towards the mediastinum for this cohort were unlikely, at 2.7%. Imaging half of the fractions protects most patients against three or more undetected errors. Undetected, such an error increases, on average, the maximum dose to 10 cm3 of the heart by 50 cGy, the mean heart dose by 4 cGy, and the left lung V20Gy by 0.2%; therefore, the clinical impact is minute. Given that detected positional errors outside of tolerance are corrected, their residual likelihood decreases with the ratio of fractions being imaged.
CONCLUSIONS: For most tangential breast radiotherapy patients, setup errors >5 mm towards the mediastinum are unlikely, and their dosimetric impact is remote. Imaging half of the fractions of a course of whole breast radiotherapy prevents these errors to occur more than twice.

Eighty percent of hepatocarcinomas are inoperable at the moment of diagnosis. Liver transplantation is the treatment of choice in these cases, but local therapies are another alternative. Among these, Image-Guided BrachyAblation is a safe choice. We report a 76-year-old male with a hepatocarcinoma, who was considered inoperable due to the high surgical risk of the patient. A local treatment with Image-Guided BrachyAblation was decided. A brachytherapy needle was placed in the tumor under computed tomography guidance and a 15 Gy single dose was delivered from an Iridium-192 source. The patient had no immediate complications and at one month of follow up he continued without incidents.

Knowledge models in radiotherapy capture the relation between patient anatomy and dosimetry to provide treatment planning guidance. When treatment schemes evolve, existing models struggle to predict accurately. We propose a case-based reasoning framework designed to handle novel anatomies that are of same type but vary beyond original training samples. A total of 105 pelvic intensity-modulated radiotherapy cases were analyzed. Eighty cases were prostate cases while the other 25 were prostate-plus-lymph-node cases. We simulated 4 scenarios: Scarce scenario, Semiscarce scenario, Semiample scenario, and Ample scenario. For the Scarce scenario, a multiple stepwise regression model was trained using 85 cases (80 prostate, 5 prostate-plus-lymph-node). The proposed workflow started with evaluating the feature novelty of new cases against 5 training prostate-plus-lymph-node cases using leverage statistic. The case database was composed of a 5-case dose atlas. Case-based dose prediction was compared against the regression model prediction using sum of squared residual. Mean sum of squared residual of case-based and regression predictions for the bladder of 13 identified outliers were 0.174 ± 0.166 and 0.459 ± 0.508, respectively (P = .0326). For the rectum, the respective mean sum of squared residuals were 0.103 ± 0.120 and 0.150 ± 0.171 for case-based and regression prediction (P = .1972). By retaining novel cases, under the Ample scenario, significant statistical improvement was observed over the Scarce scenario (P = .0398) for the bladder model. We expect that the incorporation of case-based reasoning that judiciously applies appropriate predictive models could improve overall prediction accuracy and robustness in clinical practice.