Customized 3D-printed molds for high dose-rate brachytherapy in facial skin cancer: First clinical experience.

BACKGROUND AND OBJECTIVE: Radiotherapy of elderly, frail patients with facial skin cancer in proximity to critical organs is challenging. This is the first report on clinical experience with facial skin cancer treated by individualized 3D-printer-based mold high-dose-rate (HDR) brachytherapy (BT). PATIENTS AND METHODS: Fifteen patients not eligible for radical surgery or definitive external beam radiotherapy (EBRT) were treated with 3D-printer-based mold HDR-BT. Patient selection and treatment were in accordance with multidisciplinary tumor board recommendations. Clinical response, toxicity and cosmesis were analyzed. RESULTS: Median age was 77 years. Histology revealed squamous cell carcinoma in seven, basal cell carcinoma in five, melanoma in situ in one, Lentigo maligna in one, and melanoma in one patient, respectively. Median prescription dose was 39 Gy delivered in once-daily fractions of 3 Gy. After a median follow-up of 12.2 months, local recurrence was observed in one patient with melanoma in situ. Apart from one grade 4 cataract, no other > grade 2 late toxicity was documented. CONCLUSIONS: HDR-BT with 3D-printer-based molds for facial skin cancer is a well-tolerated and safe treatment option for elderly, frail patients not eligible for radical surgery or definitive EBRT due to functional inoperability or tumor location.

Image-guided high-dose-rate brachytherapy for rectal cancer: technical note and first clinical experience on an organ-preserving approach.

PURPOSE: As the population ages, the incidence of rectal cancer among elderly patients is rising. Due to the risk of perioperative morbidity and mortality, alternative nonoperative treatment options have been explored in elderly and frail patients who are clinically inoperable or refuse surgery. METHODS: Here we present technical considerations and first clinical experience after treating a cohort of six rectal cancer patients (T1­3, N0­1, M0; UICC stage I-IIIB) with definitive external-beam radiation therapy (EBRT) followed by image-guided, endorectal high-dose-rate brachytherapy (HDR-BT). Patients were treated with 10-13â€¯× 3 Gy EBRT followed by HDR-BT delivering 12-18 Gy in two or three fractions. Tumor response was evaluated using endoscopy and magnetic resonance imaging of the pelvis. RESULTS: Median age was 84 years. All patients completed EBRT and HDR-BT without any high-grade toxicity (> grade 2). One patient experienced rectal bleeding (grade 2) after 10 weeks. Four patients (67%) demonstrated clinical complete response (cCR) or near cCR, there was one partial response, and one residual tumor and hepatic metastasis 8 weeks after HDR-BT. The median follow-up time for all six patients is 42 weeks (range 8-60 weeks). Sustained cCR without evidence of local regrowth has been achieved in all four patients with initial (n)cCR to date. CONCLUSION: Primary EBRT combined with HDR-BT is feasible and well tolerated with promising response rates in elderly and frail rectal cancer patients. The concept could be an integral part of a highly individualized and selective nonoperative treatment offered to patients who are not suitable for or refuse surgery.

Effects of iodinated contrast agent on HU-based dose calculation and dose delivered in iridium-192 high-dose-rate brachytherapy.

PURPOSE: This study compares the effect of iodinated contrast agent on Hounsfield unit (HU)-based TG-186 dose calculation vs. delivered dose for high-dose-rate (HDR) iridium-192 brachytherapy using a phantom model. MATERIAL AND METHODS: A reservoir filled with a diluted contrast agent was placed inside a water phantom. A single steel needle applicator was centrally positioned inside the reservoir. Computed tomography (CT) datasets of five different contrast agent dilutions (25 to 300 mg/ml iodine concentration) were acquired, and dose calculations were performed with TG-186 ACE dose calculation formalism of Oncentra®Brachy (Elekta). The dose was measured with a PinPoint® ionization chamber (PTW) inside the contrast agent. ACE calculated and measured data were compared. RESULTS: For the different contrast agent dilutions, averaged Hounsfield units from 453 ±21 to 2623 ±221 were obtained. Electron densities derived from CT data were significantly higher than corresponding electron densities calculated from chemical compositions. Consequently, the measured dose was higher than corresponding HU-based calculated dose. Relative deviation ranged from 2.5% to 7% per 10 mm penetration depth, depending on contrast agent concentration. CONCLUSIONS: The application of HU-based TG-186 dose formalisms in the presence of high-Z contrast agent bulks overestimates electron densities. Consequently, HU-based dose calculations result in a higher delivered dose than expected from the treatment planning system.

Twenty years of experience of a tertiary cancer center in total body irradiation with focus on oncological outcome and secondary malignancies.

PURPOSE: Total body irradiation (TBI) is a common part of the myelo- and immuno-ablative conditioning regimen prior to an allogeneic hematopoietic stem cell transplantation (allo-HSCT). Due to concerns regarding acute and long-term complications, there is currently a decline in otherwise successfully established TBI-based conditioning regimens. Here we present an analysis of patient and treatment data with focus on survival and long-term toxicity. METHODS: Patients with hematologic diseases who received TBI as part of their conditioning regimen prior to allo-HSCT at Frankfurt University Hospital between 1997 and 2015 were identified and retrospectively analyzed. RESULTS: In all, 285 patients with a median age of 45 years were identified. Median radiotherapy dose applied was 10.5 Gy. Overall survival at 1, 2, 5, and 10 years was 72.6, 64.6, 54.4, and 51.6%, respectively. Median follow-up of patients alive was 102 months. The cumulative incidence of secondary malignancies was 12.3% (n = 35), with hematologic malignancies and skin cancer predominating. A TBI dose ≥ 8 Gy resulted in significantly improved event-free (p = 0.030) and overall survival (p = 0.025), whereas a total dose ≤ 8 Gy and acute myeloid leukemia (AML) diagnosis were associated with significantly increased rates of secondary malignancies (p = 0.003, p = 0.048) in univariate analysis. No significant correlation was observed between impaired renal or pulmonary function and TBI dose. CONCLUSION: TBI remains an effective and well-established treatment, associated with distinct late-toxicity. However, in the present study we cannot confirm a dose-response relationship in intermediate dose ranges. Survival, occurrence of secondary malignancies, and late toxicities appear to be subject to substantial confounding in this context.

Individualized mould-based high-dose-rate brachytherapy for perinasal skin tumors: technique evaluation from a dosimetric point of view.

PURPOSE: Dosimetric treatment planning evaluations concerning patient-adapted moulds for iridium-192 high-dose-rate brachytherapy are presented in this report. MATERIAL AND METHODS: Six patients with perinasal skin tumors were treated with individual moulds made of biocompatible epithetic materials with embedded plastic applicators. Treatment plans were optimized with regard to clinical requirements, and dose was calculated using standard water-based TG-43 formalism. In addition, retrospective material-dependent collapsed cone calculations according to TG-186 protocol were evaluated to quantify the limitations of TG-43 protocol for this superficial brachytherapy technique. RESULTS: The dose-volume parameters D90, V100, and V150 of the planning target volumes (PTVs) for TG-43 dose calculations yielded 92.2% to 102.5%, 75.1% to 93.1%, and 7.4% to 41.7% of the prescribed dose, respectively. The max- imum overall dose to the ipsilateral eyeball as the most affected organ at risk (OAR) varied between 8.9 and 36.4 Gy. TG-186 calculations with Hounsfield unit-based density allocation resulted in down by -6.4%, -16.7%, and -30.0% lower average D90, V100, and V150 of the PTVs, with respect to the TG-43 data. The corresponding calculated OAR doses were also lower. The model-based TG-186 dose calculations have considered reduced backscattering due to environmental air as well as the dose-to-medium influenced by the mould materials and tissue composition. The median PTV dose was robust within 0.5% for simulated variations of mould material densities in the range of 1.0 g/cm3 to 1.26 g/cm3 up to 7 mm total mould thickness. CONCLUSIONS: HDR contact BT with individual moulds is a safe modality for routine treatment of perinasal skin tumors. The technique provides good target coverage and OARs' protection, while being robust against small variances in mould material density. Model-based dose calculations (TG-186) should complement TG-43 dose calculations for verification purpose and quality improvement.

HDR brachytherapy with individual epithetic molds for facial skin cancer: techniques and first clinical experience.

BACKGROUND: Facial skin cancer lesions in close proximity to critical organs require further development of radiotherapeutic techniques for highly conformal treatment, especially when treating elderly frail patients. We report on our treatment technique and first clinical experience for patients with perinasal/periorbital skin cancer treated with individualized epithetic mold high-dose-rate brachytherapy (BRT). METHODS: From January 2019, patients with complex shaped or unfavorably located skin cancer not eligible for surgery or external beam radiotherapy (RT) were screened for mold-based BRT. Six patients were identified. Toxicity and clinical response were documented during therapy and posttreatment follow-up. RESULTS: Median patient age was 80 years (74-92 years). Median prescription dose was 42 Gy (range, 33-44 Gy) delivered in once-daily fractions of 3 or 4 Gy. Two patients had treatment interruptions caused by acute conjunctivitis grade 2 and a nontreatment-related cardiac event, respectively. At a median follow-up of 335 days (96-628 days), no ≥ grade 2 late toxicity was documented with all patients showing complete clinical response. CONCLUSIONS: High-dose-rate BRT with individualized epithetic molds for perinasal/periorbital skin cancer is a well-tolerated and safe treatment option for patients not eligible for primary surgery or definitive external beam RT because of comorbidities or tumor location.