Brachytherapy最新文献

Background: Palladium-103 (Pd-103) brachytherapy has been associated with excellent oncologic outcomes for favorable risk prostate cancer. Our purpose was to evaluate whether de-escalated dose Pd-103 was associated with a difference in biochemical failure (BF) compared with standard-dose Pd-103 for low-risk prostate cancer.

Materials and methods: Patients with low-risk prostate cancer (cT1b-T2b, Gleason 6, and prostate-specific antigen (PSA) ≤ 10 ng/mL) were randomized 1:1 to standard dose (125 Gy) versus de-escalated dose (110 Gy) Pd-103 brachytherapy. The primary endpoint was biochemical failure (BF), defined as PSA ≥ 0.4 ng/mL. Fine-Gray regression analysis was used to identify baseline factors associated with BF, with death as a competing risk. Grade 3 genitourinary (GU) and gastrointestinal (GI) toxicities were reported.

Results: This analysis included 316 patients, who were randomized between February 2006 and February 2014. At a median follow-up of 11.0 years, the 12-year cumulative incidences of BF for the standard and de-escalated dose arms were 1.3% and 2.7%, respectively (p = 0.40). On multivariate regression, body mass index (adjusted sub-distribution hazard ratio (sHR): 1.18; 95% confidence interval (CI) = 1.06-1.32; p = 0.003) and PSA (adjusted sHR: 1.76; 95% CI = 1.36-2.28; p < 0.001) were associated with BF. Cumulative incidences of Grade 3 GU toxicities at 12-years were 6.5% and 3.9% for standard and de-escalated arms, respectively (p = 0.34). There were no Grade 3 GI toxicities in either arm.

Conclusions: De-escalated dose Pd-103 (110 Gy) could be considered for patients with low-risk prostate cancer who opt for definitive treatment.

Background: The Xoft Axxent electronic brachytherapy (eBT) source is a miniature x-ray tube operating at 40-50 kVp. While a dosimetric formalism specific to eBT has been developed, this work focuses on determining TG-43 parameters using that framework.

Purpose: To evaluate the accuracy of the TOPAS Monte Carlo user code in simulating dosimetric parameters for Xoft eBT sources.

Methods: TOPAS was used to simulate electron transport through a cylindrical tungsten target to assess absorbed, backscattered, and transmitted electron fractions, along with bremsstrahlung production. Photon spectra were simulated on the surface of both bare and applicator-inserted sources (S7500 and S7600 models) using TOPAS and benchmarked against EGSnrc simulations. Dose to water was scored to derive radial dose function and polar anisotropy. Air kerma at 50 cm radial distance was used to calculate the dose rate conversion coefficient. Simulated results were compared against EGSnrc and available experimental data.

Results: TOPAS and EGSnrc simulations showed close agreement in electron absorption (max difference 0.47%), backscatter (0.63%), and transmission (0.21%). Average bremsstrahlung energy differed by only 0.09%. Spectral average energy differences between codes were 0.3% for the bare source and 1% for the applicator case. Radial dose functions agreed within 3% for both source types, and anisotropy functions also matched well. Slightly larger discrepancies were noted for the bare source than for the source in applicator.

Conclusion: TOPAS demonstrated strong agreement with EGSnrc and measured data, with marginally improved accuracy-potentially due to more realistic modeling of manufacturing-related spectral differences.

Background and purpose: Although dose planning aims in cervical cancer brachytherapy are well-defined, variability in clinical practices makes it difficult to draw generalizable conclusions on achievable dosimetry. This review and meta-regression aim to assess clinical practices in terms of their therapeutic dose window, that is, the balance between target and organs-at-risk (OAR) doses.

Materials and methods: A search of the literature was performed in Scopus, PubMed, and Web of Science databases. Peer-reviewed articles were included that described planning constraints and reported high-risk clinical target volume (CTV_HR) D_90% and OAR [Formula: see text] for intracavitary (IC) tandem and ring (T&R) / tandem and ovoid (T&O) / mold (M) applicators, possibly supplemented with interstitial (IS) needles (+N). To determine factors associated with target volume coverage (D_90%) and OAR sparing ( [Formula: see text] ), multivariate meta-regressions were performed.

Results: Out of 1590 articles, 34 met the full inclusion criteria. In most studies, the CTV_HRD_90% aimed at ≥84-86 Gy EQD2_{α/β = 10Gy}, and constraints for the OARs were 80-90 Gy, 65-75 Gy and 70-75 Gy EQD2_{α/β = 3Gy} for the bladder, rectum and sigmoid [Formula: see text] , respectively. Studies using IC/IS applicators were associated with a ∼4 Gy increase in CTV_HRD_90% compared to IC only, with no effect on OAR dose. T&R studies achieved improvements of 3.2 Gy and 2.8-3.4 Gy at typical planning aims in comparison with T&O applicators in target and OAR doses. In 100% (15/15) of patient groups treated with T&R + N both CTV_HR and OAR objectives were met for the population average. For T&R, T&O, and T&O + N groups, this was the case in 89% (8/9), 43% (6/14), and 50% (4/8), respectively.

Conclusion: Studies using interstitial needles with T&R applicators in MR-guided brachytherapy for cervical cancer seem to be associated with a favorable therapeutic target dose/OAR sparing ratio.

Purpose: To report clinical outcomes of cervical cancer patients treated with single implant and multiple fractions of high-dose-rate brachytherapy (HDR BT).

Materials and methods: Patients treated with (chemo)radiation followed by single implant with all fractionated HDR BT delivered within 24-36 hours were included. Treatment protocol recommended >70 Gy equivalent doses in 2 Gy (EQD2_10Gy) at point A for intracavitary BT (ICBT) and >85 Gy EQD2_10Gy for those receiving interstitial-intracavitary BT (IC-ISBT). Local control, locoregional control and disease-free survival was estimated along with late gastrointestinal (GI) and genitourinary (GU) toxicity.

Results: From 2020-2022, 116 patients were treated with single implant multiple fractions HDR-BT. The median dose to Point A, HRCTV D90, B2cc, R2cc and S2cc was 75.1 (72.4-77.8), 80.2 (76-84), 85.2 (83.1-90.1), 69.1 (65.0-73.9) and 67.9 (61-75.3) Gy for those treated with ICBT. The median dose to high risk clinical target volume D90, Bladder 2cc, Rectum 2cc and Sigmoid 2cc was 83.2 (78.2-88.4), 87.4 (84.2-91), 69.6 (64.1-75) and 68.1 (59.5-77.1) Gy in those with IC-ISBT respectively. The median follow-up was 36 months (2-60 months). The 5-year local control, loco-regional control, disease free survival and overall survival was 89%, 84%, 70.8% and 81.6% respectively. Grade ≥3 GI and GU toxicity were 11.3% and 1.7% respectively. The incidence Grade ≥3 GI was higher in those who received 8-9 Gy in three fractions than 5-7.5 Gy in 3-4 fractions.

Conclusion: The abbreviated HDR BT schedule of single implant 3-4 fractions for LACC patients is radiobiological iso-effective for tumor control. There seems to be a fraction size dependence of abbreviated fractionation schedule for severe GI toxicity.

Purpose: Reirradiation for para-aortic lymph node (PALN) recurrence is technically challenging due to prior radiation exposure and the anatomical proximity of critical organs such as the small intestine and kidneys, making external beam radiation therapy (EBRT) difficult or unfeasible. High-dose-rate interstitial brachytherapy (HDR-IBT) offers a highly localized treatment alternative; however, it requires precise applicator placement to ensure safety and efficacy.

Methods and materials: We report a case of PALN recurrence located between the aorta and inferior vena cava (IVC) in a patient previously treated with multiple courses of EBRT. Due to the lesion's high-risk location and prior irradiation, further EBRT was not a viable option. In collaboration with interventional radiologists, a novel posterior paravertebral approach was adopted. Under fluoroscopic and computed tomography (CT) guidance, a 17 G percutaneous transhepatic cholangiography (PTC) needle was inserted from the patient's back. The guidewire was advanced through the psoas muscle and intentionally redirected caudally at an angle of nearly 90 degrees to avoid major vascular structures. Following tract dilation using a ureteral balloon and dilator system, a flexible brachytherapy applicator was inserted and fixed in place. The patient received six fractions of 5 Gy (total dose: 30 Gy), with the applicator maintained in situ throughout the treatment period.

Results: The treatment was completed without any adverse events. CT imaging at 4 months post-treatment showed tumor shrinkage and reduced contrast enhancement. No radiation-related toxicities were observed during or after treatment. Local control has been maintained for over 4 years.

Conclusions: This case demonstrates the feasibility and safety of fractionated HDR-IBT for reirradiation of deeply located PALN recurrence in a previously irradiated field. While single-fraction HDR-IBT can be performed via a direct posterior approach, fractionated treatment requires stable applicator placement over several days. To mitigate the risk of vascular injury due to applicator displacement, precise angulation of the insertion trajectory was critical. This report highlights how interdisciplinary collaboration enabled accurate, vessel-sparing needle placement, providing a minimally invasive and effective treatment option for patients with PALN recurrence who are not candidates for further EBRT.

Purpose: Patients are increasingly using artificial intelligence (AI) chatbots for health information. Evaluating their reliability for specialized topics, such as brachytherapy, is crucial for guiding their safe use. We assessed a readily accessible AI chatbot's suitability for answering frequently asked questions (FAQ) related to brachytherapy.

Methods: We compared responses from an AI chatbot (ChatGPT 4o-mini) against gold standard (GS) authoritative sources for 10 brachytherapy frequently asked questions. Four blinded board-certified brachytherapy experts evaluated 80 response pairs using metrics, including accuracy, clinical appropriateness, readability, and tone. Five simulated patient personas with varying literacy levels were used to assess helpfulness, readability, and emotional tone. The objective readability metrics were also calculated.

Results: Experts rated the AI chatbot higher for accuracy (75% highly/mostly accurate vs. 50% for GS) and appropriateness (77% vs 55%), although inaccuracies were noted in both sources in a blinded review. Simulated patients preferred GS responses (62% vs. 34%), particularly lower-literacy personas, citing better perceived readability (92% easy/very easy vs. 44% for AI) and a more reassuring tone (42% vs. 24% for AI). Objective analysis confirmed that both sources significantly exceeded the recommended reading levels (e.g., >12th grade Flesch-Kincaid), with AI responses being substantially longer. Performance varied considerably across individual questions for both AI and GS sources.

Conclusions: In this blinded cross-sectional evaluation, a publicly available AI chatbot provided accurate responses to brachytherapy-related FAQs. However, further development and validation focused on accessibility, trustworthiness, and user-centered design are required before these tools can be safely and effectively integrated into patient-care workflows.

Purpose: COMS established iodine-125 (¹²⁵I) brachytherapy as standard of care for medium-sized choroidal melanomas. However, there remains a gap in the literature regarding reduced dosing for medium-sized choroidal melanomas and standard dosing for small-sized choroidal melanomas. We explored the impact of reduced dose ¹²⁵I brachytherapy on local tumor control and ocular adverse events (AEs).

Methods: Patients diagnosed 2005-2019 with choroidal melanoma <5 mm thick and managed with ¹²⁵I brachytherapy dose of 65 Gy to depth of 5 mm were included. Dose metrics were calculated using Monte Carlo-based dosimetry. Kaplan-Meier method was used to estimate overall survival and radiation-related AEs. Distant metastasis and local recurrence were reported using cumulative incidence with death as a competing risk. Univariate and multivariate associations were analyzed using Cox proportional hazards regression.

Results: 143 patients met inclusion criteria with median follow-up of 7 years. Five-year Kaplan-Meier estimates of ocular AEs were 59.6% radiation maculopathy, 42.0% cystoid macular edema, 55.2% nonproliferative radiation retinopathy, 10.8% proliferative radiation retinopathy, and 35.6% radiation papillopathy. Five-year cumulative incidence of local recurrence was 0%, 5-year cumulative incidence of distant metastasis was 6.1%, and 5-year Kaplan-Meier estimate of overall survival was 96.5%.

Conclusion: Reduced dose ¹²⁵I brachytherapy is feasible with excellent local tumor control.

Purpose: Androgen deprivation therapy (ADT) for prostate cancer typically reduces prostate volume. This study investigated how the timing of ADT relative to low-dose-rate (LDR) brachytherapy influences the resulting dosimetric outcomes.

Methods: Using deformable image registration and principal component analysis on pre- and post-ADT magnetic resonance images of 34 patients, we developed a statistical model of ADT-induced prostate deformation. We applied this model to 30 low-dose-rate (LDR) brachytherapy plans (prescription dose: 145 Gy) to simulate seed displacement and dose distribution changes from prostate shrinkage. Prostate deformation over time post-ADT was categorized into early, linear, and late response phases. Dosimetric outcomes were analyzed across scenarios with varying prostate volume reduction magnitudes and different intervals between ADT initiation and brachytherapy.

Results: When ADT was initiated concurrently with brachytherapy, the model predicted substantial dose escalation if prostate shrinkage occurred early (prostate D90 ∼206 Gy; urethral V200 ∼47.7%) compared to late shrinkage response (D90 ∼183 Gy; V200 ∼7.1%). In contrast, separating the treatments in time greatly mitigated this effect. For example, assuming early response, performing brachytherapy 3 months before ADT yielded a prostate D90 of ∼183.0 Gy (urethral V200 ∼7.7%), while delaying brachytherapy to 3 months after ADT yielded a D90 of ∼177.8 Gy (V200 ∼1.2%).

Conclusions: Dosimetric analysis showed that greater prostate volume reduction, early ADT response, and concurrent ADT all corresponded to substantially increased doses to the prostate and urethra. Clinically, these findings underscore the importance of carefully planning the timing of ADT relative to brachytherapy to optimize target coverage and minimize unintended dose escalation to normal tissues.

Purpose: The purpose of this work, a first-in-human randomized clinical trial, was to compare gMCO, a GPU-based multi criteria optimization (MCO) algorithm, to reference plans in terms of planning time and plan quality for prostate HDR brachytherapy.

Methods and materials: The brachytherapy procedure was as follows: (1) Patient installation, (2) Catheter implantation under transrectal ultrasound (US) guidance, (3) 3D US scan, (4) Contouring/catheter reconstruction on Oncentra Prostate (Elekta, Veenendaal, Netherlands), (5) Planning, (6) Treatment. Planning (step 5) was performed, after randomization, using either IPSA (Oncentra Prostate, Veenendaal, Netherlands) or gMCO. The planning times on IPSA or gMCO were recorded. Patients previously had a planning MR in order to identify whether a gross tumor volume (GTV, PIRADS 3 and above) was visible and, if present, the GTV was boosted to a minimum of 19 Gy of the prescription dose. Fifty-five patients were accrued and distributed randomly between both treatment arms. Dosimetric indices (Prostate V100, V150, V200, GTV D90, Urethra D10, Rectum and Bladder V75 and D1cc) of gMCO and Inverse-Planning Simulated Annealing algorithm (IPSA) plans were compared to determine if plan quality and planning times were statistically different.

Results: Results show that the optimization time is reduced by half when using gMCO as compared to IPSA, going from 10-5.2 minutes. Although no statistically significant difference is present between gMCO and IPSA plans when comparing pairs of individual dosimetric indices, gMCO plans exhibit a higher pass rate (higher by a factor ranging from 1.3 to 1.6), as compared to IPSA, when considering a basket of dosimetric indices simultaneously.

Conclusion: The use of gMCO halves the planning time for prostate HDR brachytherapy as compared to IPSA, without decreasing plan quality. The overall gain in efficiency related to the planning process has led to the use of gMCO for all of our HDR prostate cases.