Practical Radiation Oncology最新文献

Purpose: Adjuvant radiation therapy (RT) to a cutaneous target has been associated with elevated risk of surgical complications such as graft, flap, or skin substitute reconstruction failure. We sought to better quantify the risk of surgical site complications after hypofractionated adjuvant RT delivered in the modern era to patients undergoing surgical reconstruction for their primary site cutaneous melanoma.

Methods and materials: We reviewed clinical data on all patients treated for cutaneous melanoma at our center between 2008 and 2021 with primary tumor resection and reconstruction (graft, flap, or skin substitute), followed by 5 × 6 Gy RT. Details on post-treatment complications were assessed.

Results: A total of 193 patients with melanoma undergoing surgical reconstruction followed by hypofractionated RT were identified. Most patients carried at least 1 risk factor for wound healing complications (70% with cardiovascular disease, 64% overweight, and 23% with diabetes). Most tumors were located in the head and neck (89%). Patients initiated RT a median of 7 weeks (IQR, 5-9 weeks) from surgical reconstruction. Skin grafts were used in 62% of reconstructions, and flaps used in 44%. Electron-based RT was used for the majority of patients (n = 166, 86%). Ten patients (5%) required surgical revision after reconstruction, with half occurring after RT. The primary reconstruction for all 5 patients requiring surgical revision after RT was graft reconstruction of the scalp, with a wide range of times from reconstruction to RT (5-11 weeks) and a wide range of times from RT to surgical revision (2-28 months).

Conclusions: The risk of surgical revision after adjuvant hypofractionated RT to a surgical reconstruction involving a graft, flap, or skin substitute is low. Half of graft failures occurred before adjuvant RT and half after, which suggests that adjuvant RT only marginally increases the risk of postreconstruction complications if adequate time for healing is given.

Purpose: Stereotactic body radiation therapy (SBRT) is increasingly used for spinal metastases. Contouring for SBRT typically follows the International Spine Radiosurgery Consortium (ISRC) guidelines, leading to large planning target volumes (PTV). We compared minimal-volume contouring, which yields a more focused PTV, with conventional contouring and developed predictive models for adverse outcomes.

Methods and materials: We analyzed all patients treated for spinal metastases at our center over the past decade. After exploratory and correlation analyses, we compared the contouring methods for adverse outcomes and PTV and spinal cord dose distributions. Logit and support vector machine (SVM) models were used for outcome prediction.

Results: Among 121 patients (235 lesions), 147 lesions received minimal-volume contouring, 67 followed ISRC recommendations, and 21 were unassigned. The median prescription dose was 20 Gy (15-22 Gy) for single-session, and 24 Gy (19.5-30 Gy) for hypofractionated treatments. The median PTV was 11.1 cm³ (0.2-173.7 cm³). Complications correlated significantly with pre-SBRT Karnofsky status (Cramer V = 0.277). Local control rates were comparable (80.5% vs 78.4%), but complication rates were lower with minimal contouring (15.1% vs 27.8%). Minimal contouring resulted in significantly higher median PTV biologically effective dose (BED) (75.9 Gy vs 57.5 Gy) and lower maximum spinal cord BED (72.7 Gy vs 81.9 Gy, both P < .001). Logit models identified mean PTV (P = .001) and vertebral dose (P < .001) as significant predictors of vertebral fractures but showed limited accuracy (49.3% for local recurrence, 73.3% for fractures). SVM classifiers outperformed logit models, achieving higher accuracy (89.9% for recurrence, 92.0% for fractures) and improved positive predictive values (83.7% and 86.7%, respectively).

Conclusions: Minimal-volume target delineation based on thin-layer magnetic resonance imaging and prostate-specific membrane antigen/fluorodeoxyglucose-positron emission tomography-computed tomography/magnetic resonance imaging may be as effective as contouring according to the ISRC guidelines, if those imaging modalities are available. Further studies are warranted to assess minimal and expanded volumes. SVM models show promising potential for predicting patient outcomes, warranting further exploration.

Purpose: Recurrence in glioblastoma (GBM) is common, and the success of salvage strategies, including re-resection and reirradiation, is limited. Brachytherapy with Cs-131 collagen tiles enables intraoperative focal dose intensification with rapid dose fall-off and limited normal brain radiation exposure. We report the outcomes of Cs-131 collagen tile implantation at the time of resection for recurrent GBM.

Methods and materials: We reviewed 15 adults with previously irradiated, recurrent isocitrate dehydrogenase (IDH) wild-type GBM who underwent maximal safe resection followed by intraoperative Cs-131 collagen tile implantation at a single institution. Candidates had surgically accessible, primarily enhancing recurrences ≥6 months after prior external beam radiation therapy, and were anticipated to have a gross total resection. The prescription dose was 60 Gy at a depth of 5 mm. We assessed overall survival, progression-free survival, toxicity, and patterns of failure (local ≤0.5 cm from the cavity, marginal 0.5-1 cm, and distant >1 cm) after implantation.

Results: Patients (median age, 63 years; range, 39-76) had good performance status (median Karnofsky Performance Status score, 90; range, 70-100) and prior chemoradiation (most to 60 Gy/30 fractions). Tiles (median, 6.5/patient; range, 3-13) were implanted at first recurrence in 12 of 15 patients (80%) and at second recurrence in 3 (20%), at a median of 15 months after external beam radiation therapy (range, 8.9-47). At 13 months median follow-up (range, 1.4-21), the median overall survival after Cs-131 implantation was not reached (NR) (95% CI, 6.7-NR months); the median time to progression after Cs-131 implantation was 9 months (95% CI, 6.0-NR); and the cumulative incidence of first progression (local or distant) after Cs-131 implantation was 53.3% over the follow-up period. The first failures were local (n = 2), marginal (n = 2), distant (n = 3), and combined local and distant (n = 1). One patient developed symptomatic grade 3 radionecrosis, which improved with bevacizumab. No patients required reoperation for Cs-131 toxicity.

Conclusions: Intraoperative Cs-131 tile brachytherapy for recurrent GBM is feasible and well tolerated. Distant failures remain common. Integrating effective systemic therapy and careful patient selection may optimize outcomes.

Purpose: The digitally reconstructed radiograph (DRR) has traditionally been used for geometric radiation therapy (RT) treatment verification, with no reported dosimetric applications to date. This study aimed to introduce a methodology for the first time, allowing us to derive a dose distribution within an RT treatment plan using the DRR image.

Methods and materials: Initially, the correlation between the pixel values of the DRR image and the depth of the water phantom was established. Subsequently, the relationship between depth and absorbed dose was derived. By combining these 2 equations, the connection between the pixel values of the DRR and the absorbed dose was established. This approach was then used to calculate the dose distribution for homogeneous and RANDO phantoms. To verify the accuracy of this technique, the results were compared with the dose distribution from the treatment planning system.

Results: The comparison of point doses at the isocenter of the RANDO phantom indicated differences of 1% and 2.4% for energies of 6 and 15 MV, respectively. A region-based dose distribution comparison using gamma analysis (3%-3 mm criteria) resulted in agreements of 98% and 95% for energies of 6 and 15 MV, respectively.

Conclusions: DRR dosimetry is an innovative method that employs DRR images to calculate dose distribution in RT planning, enhancing their traditional geometric use. It operates independently of a treatment planning system, making it a cost-effective solution that can run on personal computers. This approach acts as a supplementary tool, ensuring dosimetric verification and quality control in RT treatments.

Purpose: Total skin irradiation (TSI) techniques vary widely in dosimetric performance, yet no standardized metric exists to evaluate their overall quality. Current guidelines address parameters such as dose homogeneity, depth-dose fall-off, and x-ray contamination, but lack a comprehensive quantitative tool. This study introduces and validates the Total Skin Irradiation Quality Index (TSI-QI), a novel composite metric for assessing TSI techniques based on these 3 critical parameters.

Methods and materials: Radiographic films were placed in transverse sections of an anthropomorphic phantom and irradiated using full-treatment TSI to generate entrance-to-exit dose profiles (EEDP). From these profiles, 3 key metrics were derived: dose uniformity within the target, dose fall-off beyond the target, and internal x-ray contamination. Each factor was normalized against established clinical thresholds and combined to calculate the TSI-QI using the formula TSI-QI = H^f + D^f + X^f, where H^f represents homogeneity, D^f denotes dose fall-off, and X^f indicates x-ray contamination. The index's efficacy was evaluated on 2 widely adopted techniques: Stanford total skin electron irradiation (TSEI) and total skin helical irradiation (TSHI).

Results: TSEI yielded a TSI-QI score of 0.554, within the acceptable quality range, whereas TSHI scored 1.893, exceeding the threshold. Thresholds were defined according to AAPM Report No. 23 and European Organization for Research and Treatment of Cancer recommendations (EORTC). Detailed analysis showed that TSEI provided superior homogeneity, sharper fall-off, and lower x-ray contamination compared with TSHI.

Conclusions: These dosimetric parameters are directly related to clinical safety and toxicity, because dose fall-off and photon contamination reflect healthy tissue protection, whereas homogeneity ensures effective skin tumor coverage. The TSI-QI, thus, offers a reliable tool for evaluating and comparing TSI techniques, supporting institutional quality assurance and cross-center standardization while helping identify protocols unsuitable for safe clinical implementation.