Evaluation of QA software system analysis for the static picket fence test.

Intensity modulation treatments are widely used in radiotherapy because of many known advantages. In this context, the picket fence test (PF) is a relevant test to check the Multileaf Collimator (MLC) performances. So this work compares and evaluates three analysis platforms for the PF used routinely by three different institutions. This study covers two linear accelerators (Linac) with two MLC types, a Millenium 120 MLC and Millenium 120 High Definition MLC respectively on a Varian Truebeam and Truebeam STx. Both linacs include an As 1200 portal imager (EPID). From a reference PF plan, MLC errors have been introduced to modify the slits in position or width (shifts from 0.1 to 0.5 mm on one or both banks). Then errors have been defined on the EPID to investigate detection system deviations (signal sensitivity and position variations). Finally, 110 DICOM-RT images have been generated and analyzed by each software system. All software systems have shown good performances to quantify the position errors, even though the leaf pair identifications can be wrong in some cases regarding the analysis method considered. The slit width measurement (not calculated by all software systems) has shown good sensitivity, but some quantification difficulties have been highlighted regardless of the analysis method used. Linked to the expected accuracy of the PF test, the imager variations have demonstrated considerable influence in the results. Differences in the results and the analysis methods have been pointed out for each software system. The results can be helpful to optimize the settings of each analysis software system depending on expectations and treatment modalities of each institution.

Cardiac implantable electronic device dysfunctions in patients undergoing radiotherapy: A prospective cohort study.

BACKGROUND: Increasing numbers of patients with cardiac implantable electronic devices (CIEDs) are undergoing radiotherapy (RT) for cancer. The aim of the study was to prospectively evaluate the incidence, characteristics, and associated factors of CIED dysfunctions related to RT. METHODS: Between April 2013 and March 2020, all patients with a CIED who underwent ≥1 RT session were enrolled. Patients were monitored according to a systematic protocol, including device interrogation before the first and after each RT session. The primary endpoint was CIED dysfunction, defined as oversensing, total or partial deprogramming, and/or unrecoverable reset. RESULTS: We included a total of 92 CIED RT courses: 77 (83.7%) in patients with a pacemaker and 15 (16.3%) in those with an implantable cardioverter-defibrillator. Overall, 13 dysfunctions (14.1%) were observed during 92 courses (1509 sessions), giving an incidence of 0.9 per 100 sessions. These included nine deprogramming (three total resets to back-up pacing mode and six partial deprogramming that were all successfully reprogrammed), three transient oversensing, and one unrecoverable oversensing requiring CIED and leads replacement. There were no adverse clinical events related to device dysfunction. In multivariable analysis, neutron-producing irradiation (odds ratio [OR], 5.59; 95% confidence interval [CI], 1.09-28.65; p = .039) and cumulative tumor dose (OR, 1.05; 95% CI, 1.01-1.10; p = .007) remained significantly associated with CIED dysfunction. CONCLUSION: In this prospective study, transient or permanent subclinical CIED dysfunction occurred in 14.1% of RT courses. Our findings emphasize the importance of high-energy beams and neutron-producing irradiation in risk assessment.

Impact of rectal distension on prostate CBCT-based positioning assessed with 6 degrees-of-freedom couch.

INTRODUCTION: Prostate requires a daily correction of its 3-dimensional position in relation with rectal distension. In this study, we sought to determine whether rectal distension with respect to the rectal behavior might have an impact on prostate translations and/or rotations during prostate image guided radiation therapy using a 6 degrees-of-freedom (DOF) couch. METHODS AND MATERIALS: We reviewed the data from 39 patients with localized prostate cancer treated with protracted external radiation therapy using a 6 DOF couch. Before each fraction, a kilovoltage cone beam computed tomography (kV-CBCT) scan was performed. The automatic fusion algorithm was set to fuse on soft tissue and allowed correction for translations in 3 dimensions and rotations in the longitudinal axis ("roll") and lateral axis ("pitch"). After contouring the rectum on each kV-CBCT, we determined the cross-sectional area (CSA) and relative CSA (CSArel) by dividing with the CSA of planning CT. The standard deviation of CSArel per patient was used to classify the patients in 2 groups: patients with a stable rectum and patients with an unstable rectum. The CSArel was compared between these 2 groups with a linear mixed model with group as fixed effect and patient as random effect. RESULTS: A total of 616 kV-CBCT were analyzed, and 2 subgroups of patients could be defined a posteriori: 19 patients had a stable rectum, mean CSArel (1.06 ± 0.08); the other 20 patients had an unstable rectum, mean CSArel (1.43 ± 0.08). The average pitch in the group with a stable rectum was 0.36° (±0.21) versus 0.40° (±0.20) (P = .898). The pitch was not correlated with the CSArel (P = -.065, r = 0.119). The average roll in the group with a stable rectum was 0.27° (±0.16) versus 0.05° (±0.16) (P = .137). The roll was not correlated with the CSA (P = .094, r = 0.068). The average CSArel was higher (P = .0013) and more variable (P = .035) in the unstable group. CONCLUSION: Rectal distension had no impact on the pitch or on the roll, which suggest that a 6 DOF couch has little interest in daily practice for prostate image guided radiation therapy.

Absolute volume of the rectum and AUC from rectal DVH between 25Gy and 50Gy predict acute gastrointestinal toxicity with IG-IMRT in prostate cancer.

BACKGROUND: To determine whether dose/volume specific endpoints (DVSE) or Area under the rectal DVH curve (rAUC) better predict acute gastrointestinal (GI) toxicity in prostate cancer patients treated with IMRT in the era of daily image guidance (IG-IMRT). METHODS: A set of DVSE was recorded from V25 to V75 (increments of 5Gy) (both in % and in cc) for 180 men. The rAUC was calculated for doses ranging between 25Gy and 50Gy (rAUC25-50). Univariate and multivariate logistic regressions were performed to determine the relationship between DVSE or rAUC25-50 and the appearance of any acute GI toxicity. RESULTS: The rates of acute grade 1 (G1), G2 and G3 GI toxicities were 53.3 %, 10.6 % and 1.1 %, respectively. No G4+ toxicity was observed. Rectal V25 to V75 expressed in % were not predictive of G ≥ 1 GI toxicity (p ≥ 0.12) whereas rectal V25 to V50 expressed in cc did correlate with GI toxicity G ≥ 1 (p ≤ 0.04). rAUC25-50 expressed in cc. Gy correlated significantly with the occurrence of any acute GI toxicity G ≥ 1 (p = 0.027). CONCLUSIONS: The absolute volume of the rectum between 25Gy and 50Gy and rAUC25-50 could significantly predict any acute rectal toxicity in prostate cancer patients treated with daily IG-IMRT.

Focal or whole-gland salvage prostate brachytherapy with iodine seeds with or without a rectal spacer for postradiotherapy local failure: How best to spare the rectum?

PURPOSE: Salvage prostate permanent implant (sPPI) for postradiation local failure provides high rates of biochemical control. The cumulative dose delivered to the prostate and the rectum is still unknown. METHODS AND MATERIALS: We reviewed the postimplant CT-based dosimetry of 18 selected patients who underwent sPPI with (125)I seeds for isolated biopsy-proven local failure several years after external beam radiation therapy. Ten patients had whole-prostate sPPI, and 8 patients had multiparametric MRI-based focal sPPI. In 8 patients, hyaluronic acid (HA) gel was injected into the prostate-rectum space. RESULTS: The median cumulative biological effective dose after EBRT + sPPI for the prostate and the rectum was higher in patients treated with whole-gland sPPI than in patients treated with focal sPPI (313.5 Gy2 vs. 174.4 Gy2; p = 0.06 and 258.1 Gy3 vs. 172.6 Gy3; p < 0.01, respectively). The median D0.1cc for the rectum was significantly lower in patients who had HA gel: 63.3 Gy (29.0-78.3) vs. 83.9 Gy (34.9-180.0) (p = 0.04). CONCLUSIONS: Cumulative prostate and rectum biological effective doses were lower with focal sPPI. D0.1cc delivered to the rectum was significantly lower with HA gel, while there was no difference between focal or whole-gland plans.

Multiparametric MRI and post implant CT-based dosimetry after prostate brachytherapy with iodine seeds: The higher the dose to the dominant index lesion, the lower the PSA bounce.

PURPOSE: To determine whether post-implant MRI-based dosimetry of the Dominant Intra-prostatic Lesion (DIL) could best predict the occurrence of PSA bounce after prostate brachytherapy. METHODS AND MATERIALS: We selected 66 patients with a low risk prostate cancer treated with (125)I prostate brachytherapy as monotherapy. Post-implant dosimetry based on day 30 CT-scan and multiparametric MRI co-registration was generated: planned D90, D95, V100, V150 values were calculated for each DIL. Bounce was defined as a PSA elevation ⩾ 0.2 ng/mL from the previous baseline value followed by a decrease to or below the prior nadir with no additional treatment. RESULTS: After a median follow-up of 35.5 months (range 13.2-72.5), a PSA bounce occurred in 24 (36.4%) patients. The mean planned D90 of the DIL was significantly lower in bouncers: 196 ± 61 Gy vs. 234 ± 62 Gy, p = 0.018. The mean planned V150 of the DIL was 56 ± 32% for bouncers while it was 75 ± 30% for non-bouncers, p = 0.026. CONCLUSION: A lower planned D90 or V150 in the DIL were predictive of PSA bounce after prostate brachytherapy. PSA bounce could be caused by delayed cell death related to sublethal damage accumulation in the tumor.

Mapping of failures after radiochemotherapy in patients with non-metastatic esophageal cancer: A posteriori analysis of the dose distribution in the sites of loco-regional relapse.

BACKGROUND AND PURPOSE: We aimed to evaluate the patterns of loco-regional failure (LRF) after exclusive chemoradiotherapy (eCRT) for esophageal cancer with respect to planned dose and/or the incidental (unplanned) dose outside target volumes. MATERIALS AND METHODS: Co-image registration of CT or (18)F-FDG PET-CT at the time of failure (tf) and at the time of CRT (t0) was performed in 34 patients with LRF. Dosimetric parameters with regard to local failure (LF), nodal failure (NF) and involved nodal stations (NS) were derived. RESULTS: Twenty-two patients (64.7%) had LF, the majority of which (95.5%) were located at the epicenter of the GTV of the primary tumor. The mean doses recalculated to the NS at tf were more likely to be lower than the planned dose delivered to the PTV at t0: Dmean=33.9 ± 20.8 Gy vs 52.2 ± 8.5 Gy (p=0.0009), D95%=27.5 ± 21 Gy vs 46.1 ± 4.8 Gy (p=0.004). Among the 12 patients with NF outside the elective nodal irradiation (ENI) volume, Dmean of NS outside the ENI was significantly lower (19.4 ± 21.4 Gy) than the Dmean of NS with failure within the ENI (45.1 ± 6.1 Gy, p=0.01). CONCLUSION: Loco-regional failure after exclusive chemoradiotherapy for esophageal cancer may be due to an inadequately low dose.