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To study the feasibility and safety for patients with high-risk (HR) and very high-risk (VHR) prostate cancer treated with adaptive ultra-hypofractionated whole-pelvic radiotherapy (UHF-WPRT) on 1.5 magnetic resonance (MR)-Linac. Sevenpatients with clinical stage T3a-4N0-1M0-1c consecutively treated with UHF-WPRT on a 1.5-T MR-Linac were recruited prospectively in a phase II trial (NCT05183074, ChiCTR2000033382). A 36.25 Gy dose in five fractions was delivered every other day with a boost of 40 Gy to the whole prostate, as well as 25 Gy to whole pelvic nodal area with a concomitant boost of 35 Gy to metastatic regional nodes. To estimate the delivered dose, we collected data by 3D-MR for the following stages: pre-MR, position verification-MR (PV-MR) in the Adapt-To-Shape (ATS) workflow, and 3D-MR during the beam-on phase (Bn-MR) and at the end of RT (post-MR). The target and organ-at-risk contours in the PV-MR, Bn-MR, and post-MR stages were projected from the pre-MR data by deformable image registration and manually adapted by the physician, followed by dose recalculation for the ATS plan. The cumulative acute genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated as per NCI-CTCAE 5.0 criteria. The primary endpoints were acute ≥grade 3 genitourinary (GU) and gastrointestinal (GI) toxicities during the first 3 months. Overall, 133 MR scans were collected (35 pre-MR, 35 PV-MR, 31 Bn-MR and 32 post-MR scans). With a median on-couch time of 61 minutes, the mean prostate and pelvic planning target volume (PTV)-V95% of all scans was 96.98 ± 3.06% and 96.44 ± 2.85%, respectively. The corresponding mean prostate clinical target volume (CTV)-V100% was 99.89 ± 0.32%, 98.71 ± 1.90%, 97.77 ± 2.89%, and 98.56 ± 1.72%, and the mean pelvic CTV-V100% was 97.57% ± 3.70%, 96.54 ± 3.80%, 95.43 ± 4.31%, and 94.39 ± 4.47% on pre-MR, PV-MR, Bn-MR and post-MR scans, respectively. For the 4 patients with positive nodes, the mean V100% of metastatic regional nodes was 99.89 ± 0.81%. The median V29 Gy change in the rectal wall was -1% (-18%–20%). The V29 Gy of the rectal wall increased by >15% was observed in one scan. A slight increase in the high dose of bladder wall was noted due to gradual bladder growth during the workflow. With median follow-up time of 7.3 (4.6-12.2) months, all patients were followed-up for more than 3 months. No patient was observed with acute CTCAE grade 2 or more severe GU or GI toxicities (0%). UHF-RT to prostate and pelvic with ATS workflow is well tolerated by patients with HR and VHR prostate cancer, with only mild GU and GI toxicities. The 3D-MR–based dosimetry analysis demonstrated clinically acceptable estimated dose coverage of target volumes during the beam-on period. [ABSTRACT FROM AUTHOR]

To evaluate the efficacy of partial tumor stereotactic ablative boost radiotherapy (P-SABR) in the treatment of bulky (>8cm) lung cancer. Between January 2013 and October 2022, 57 patients with bulky (>8cm) lung cancer treated with P-SABR technique were analyzed. Thirty-seven (64.9%) of the patients had stage III, 16 (28.1%) had stage IV and 4 (7%) had postoperative recurrence or metastasis. Median tumor diameter treated by P-SABR was 10.01 cm (8.03–22.72 cm) and median tumor volume was 218.5 cm3 (82.40–2041.4 cm3). Twenty-five (43.9%) of the patients were treated with P-SABR alone and 19 (33.3%) were treated with P-SABR combined with conventional fractionation or SABR as definitive treatment. Thirteen (22.8%) patients received palliative treatment with P-SABR. P-SABR consisted of a SABR plan (6- 8 Gy per fraction in 3- 6 fractions) to the boost target volume (BTV) followed by one conventional plan to the planning target volume (PTV). BTV was the max volume within the tumor receiving SABR plan, in which the critical organ-at-risk (OAR) dose was reduced toto about 3 Gy/f. The median total dose of BTV was 76Gy (range: 65-110Gy) and PTV was 60Gy (range: 50-86Gy). With a median follow-up of 32 months (range, 1–75 months), 1-year, 2-year and 3-year overall survival rates were 36.2%, 26.1% and 23.2%, respectively. One-year, 2-year and 3-year local control rates were 81%, 70.8% and 70.8%, respectively. One patient (1.8%) had complete response (CR), 16 patients (28.1%) had partial response (PR), 7 patients (12.3%) had stable disease (SD) and 30 patients (52.6%) had progressive disease (PD). Of the 30 patients who had progressive disease, 25(83.3%) had local response but systemic progression, only 4 (13.3%) were presented with a RT-in-field- progression and 1 (3.3%) had both local recurrence and distant metastasis. For acute side effects, 2 (3.5%) patients developed grade III myelosuppression and 1 (1.8%) developed grade IV myelosuppression. One (1.8%) patient developed grade V radiation pneumonitis. No late severe toxicities (>CTCAE grade II) were reported. Partial stereotactic ablative boost radiotherapy could improve the local control rate of bulky lung tumors larger than 8cm and the toxicities were well tolerated. P-SABR might be a new choice for the treatment of bulky tumors. [ABSTRACT FROM AUTHOR]

To quantitatively characterize the dosimetric effects of long on-couch time of adaptive radiotherapy for prostate cancer patients on 1.5-T MR-Linac. Seventeen patients consecutively treated with ultra-hypofractionated radiotherapy (UHF-RT) on 1.5-T MR-Linac were recruited from an on-going prospective phase II trial (NCT05183074). UHF-RT with dose of 36.25Gy in 5 fractions to whole prostate w/o seminal vesicles (SVs) (N=12) was delivered every other day, with a boost dose of 40Gy to whole prostate (CTV4000, N=16). Except the Pre-MR for registration and re-contouring and Position Verification-MR (PV-MR) for dose/position check which were conventionally used in Adapt-To-Shape (ATS) workflow, we also collected 3D-MR during beam-on phase (Bn-MR) and after RT (Post-MR). For each fraction, the contours of targets and organs-at-risk (OARs) on PV-MR, Bn-MR and Post-MR were projected from the Pre-MR by deformable registration, and manually adapted by the physician, followed by dose-recalculation of the ATS plan. The dose parameters of target volumes and OARs on each scan were generated in a commercially available software for final analysis. In total, 290 MR-scans were collected, including 85 Pre-MR, 85 PV-MR, 49 Bn-MR and 71 Post-MR scans, respectively. For each fraction, the volume differences of prostate and CTV on different scans were less than 3.0cc, indicating good alignment of target contouring. With median 49 (24-78) minutes of on-couch time, the mean PTV-V95% (34.4Gy) of plans on PV-MR, Bn-MR and Post-MR was 97.69±2.03%, 97.04±2.29%, and 96.82±2.59%, respectively, compared with 99.27±0.75% of ATS plan. Furthermore, the mean CTV-V100% (36.25Gy) of plans on PV-MR, Bn-MR and Post-MR was 99.32±1.20%, 98.59±1.84% and 98.65±1.87, respectively, compared with 99.93±0.30% of ATS plan. With excellent dose coverage of prostate-V100% (36.25Gy) (99.73±0.79% on PV-MR, 99.41±1.35% on Bn-MR and 99.38±1.35% on post-MR), the main reason of lower CTV-V100% was due to mild underdose of SVs (96.97±6.26% on PV-MR, 93.62±12.94% on Bn-MR and 94.69±9.22% on post-MR). With comparison to values of ATS plan, the actual dose of rectum wall during the whole workflow also varied, with mean △V38 Gy of 0.23±0.28cc on PV-MR, 0.41±0.51cc on Bn-MR and 0.39±0.52cc on post-MR, with mean △V36 Gy of 0.27±0.57cc on PV-MR, 0.39±0.71cc on Bn-MR and 0.30±0.68cc on post-MR, respectively. However, the V29 Gy of rectum wall increased by >15% was only observed in one scan. On the contrary, no obvious increase of bladder wall dose was seen due to gradual growth of bladder over the workflow. This dosimetry analysis demonstrated reliable dose coverage of target volumes during beam-on period with adaptive ATS workflow on 1.5-T MR-Linac. The 3 mm CTV-PTV margin applied in our study have proven to be large enough for prostate irradiation, but might be insufficient for SVs incidentally. More attention should be paid to restrict the rectum wall high dose when optimizing ATS plan. [ABSTRACT FROM AUTHOR]

Stereotactic body radiotherapy (SBRT) in liver tumors has been a challenging treatment due to the diaphragm-induced motion. Optical surface monitoring system (OSMS) provides the functions of positioning and motion management, which has been widely used in recent years because it is non-ionizing, non-invasive and contactless. The purpose of this study was to explore the application of OSMS in liver metastasis patients. 33 liver metastasis SBRT patients, who were treated between August 2019 to September 2021, were divided into two groups. 14 patients in Group A were aligned using skin marking (1 anterior and 2 laterals). 19 patients in Group B were aligned near to the skin marking at the initial step. Next, the 'move couch' function on OSMS was applied if the patient's body rotations were less than 1 degrees according to the OSMS deltas value. The setup errors and setup time were recorded in both groups. Total of 88 and 106 CBCT images in group A and B were analyzed. The absolute setup errors for Groups A and B were (0.21 ± 0.15) cm, (0.37 ± 0.38) cm, (0.35 ± 0.33) cm, (0.8 ± 0.3), (1.2±0.5), (1.8 ± 0.7), and (0.04 ± 0.02) cm, (0.28 ± 0.13) cm, (0.03 ± 0.02) cm, (0.1 ± 0.2), (0.1 ± 0.2), and (0.3 ± 0.4) in vertical, longitudinal, lateral, rotation, pitch and roll directions respectively. Positioning accuracy in Group B is far superior to Group A especially in rotational directions. The difference was statistically significant (p<0.05). The average setup time was 2.8 minutes and 3.0 minutes for Group A and B. There was no significant difference in mean setup time. Setup time using OSMS was gradually improved as more experiences gained by the therapist. The study has proven that OSMS is an effective and efficient tool for liver metastasis patients. It can increase the setup accuracy and reduce repeated setup. Continuous real time monitoring is of high clinical value for liver tumor motion management. [ABSTRACT FROM AUTHOR]

Postoperative radiotherapy (PORT) is necessary in patients with locally advanced esophageal squamous cell carcinoma (LA-ESCC) who have not received neoadjuvant chemoradiotherapy (NCRT). However, the optimal clinical target volume has under hot debate for decades. This clinical trial aims to estimate the optimal radiation volume of PORT for patients with LA-ESCC. Patients confirmed LA-ESCC (pT3-4N0-3M0) after esophagectomy without NCRT were randomly assigned to either large-field irradiation (LFI, primary lesion and lymph node tumor bed plus elective nodal irradiation) arm or small-field irradiation (SFI, primary lesion and lymph node tumor bed alone) arm with a ratio of 1:1, stratified by T stage and number of lymph node metastasis (LN<3 vs LN≥3). The primary endpoint was disease-free survival (DFS); secondary endpoints included overall survival (OS), adverse events and first failure patterns. The log-rank test was used to estimate the survival differences. The Chi-square test was used to compare adverse events and failure patterns between groups. In the intention-to-treat analysis, a total of 401 patients with LA-ESCC were randomly assigned to the LFI arm (n=210) and the SFI arm (n=191). With a median follow-up of 38.9 months, the DFS and OS rates of the whole population at 1-year and 3-year were 72.9% and 51.8%, 88.4% and 61.7%, respectively, which were close to patients who received NCRT. Patients in the two irradiation arms had similar DFS (LFI vs SFI, 46.6 vs 48.1 months; HR=0.92, 95% CI, 0.68-1.25; p=0.60). The difference of OS between the two arms did not reach significant (NR vs 73.5 months, HR=0.82, 95% CI, 0.59-1.14; p=0.26). The locoregional recurrence-free survival (HR=0.57, 95% CI 0.35-0.92; p=0.022) and the failure patterns (p=0.021) between two arms were significantly different. Locoregional failure occurred in 12.9% and 20.4% of patients in the LFI arm and SFI arm, respectively; The differences of distant diseases and distant metastasis-free survival of patients between the two arms had no significance. The most frequent toxicity was grade 2 esophagitis (LFI vs SFI, 22.9% vs 16.8%). Grade 3 acute adverse events occurred in 6.7% and 2.6% of patients in the LFI and SFI arms, respectively. No toxicity of grade 4 or 5 was recorded in this study. Both postoperative irradiation fields are alternatives for LA-ESCC patients without NCRT with the promising survival outcomes comparable to CROSS study. Patients in the LFI arm achieved better locoregional control with a safety profile consistent with the SFI arm. [ABSTRACT FROM AUTHOR]