High-dose-rate brachytherapy delivered in two fractions as monotherapy for low-risk prostate cancer.

PURPOSE: High-dose-rate (HDR) brachytherapy has been accepted as an effective and safe method to treat prostate cancer. The aim of this study was to describe acute toxicity following HDR brachytherapy to the prostate, and to examine the association between dosimetric parameters and urinary toxicity in low-risk prostate cancer patients. MATERIAL AND METHODS: Patients with low-risk prostate cancer were given HDR brachytherapy as monotherapy in two 12.5 Gy fractions. Planning objectives for the planning target volume (PTV) were V100% ≥ 90% and V150% ≤ 35%. Planning objectives for organs at risk were V75% ≤ 1 cc for the bladder, rectum and perineum, and V125% ≤ 1 cc for the urethra. Toxicity was assessed three months after treatment using the Common Terminology Criteria for Adverse Events. RESULTS: Seventy-three patients were included in the analysis. Thirty-three patients (45%) reported having any type of toxicity in the three months following HDR brachytherapy. Most toxicity cases (26%) were grade 1 urinary toxicity. Mean coverage index was 0.89 and mean V100 was 88.85. Doses administered to the urethra were associated with urinary toxicity. Patients who received more than 111.3% of the prescribed dose in 1 cc of the urethra were four times more likely to have urinary toxicity compared to patients receiving less than 111.3% (OR = 4.71, 95% CI: 1.43-15.6; p = 0.011). CONCLUSIONS: High-dose-rate brachytherapy administered as monotherapy for prostate cancer proved to be a safe alternative treatment for patients with low-risk prostate cancer. Urinary toxicity was associated with the dose administered to 1 cc and 0.1 cc of the urethra and was remarkably inferior to the reported toxicity in similar studies.

Fusión de imágenes y protección de hipocampo para el tratamiento de metástasis cerebrales con radioterapia / Image fusion and hippocampus protection in radiotherapy treatment of brain metastases

Las imágenes de simulación obtenidas mediante TAC son actualmente el estándar para uso en los sistemas de planificación de haces externos empleados en los tratamientos de radioterapia. Sin embargo, una de las limitaciones es su bajo contraste y poca especificidad para la identificación y caracterización de lesiones tumorales y algunas estructuras a nivel de sistema nervioso central. Los nuevos algoritmos implementados en los sistemas de planificación de radioterapia permiten realizar la fusión de imágenes de RM con TAC de simulación, definir y proteger estructuras como el hipocampo, buscando administrar dosis bajas en esta zona, lograr mayores dosis a los volúmenes tumorales y disminuir los efectos secundarios derivados de tratamientos holoencefálicos con radioterapia. En este artículo se presentan las imágenes correspondientes a esta técnica de tratamiento.

CT simulation images are the current standard in external beam radiotherapy planning systems. However, the limitations of images obtained from CT scanning include their low contrast and low specificity in the identification and characterization of tumor lesions and some central nervous system structures. The new algorithms implemented in radiotherapy planning systems allow image fusion to be performed using MRI images and CT simulation images. It also allows structures like the hippocampus to be defined and protected, by administering lower Radiosurgery; doses to this area and higher doses to the tumor volume, thus decreasing side effects arising from whole brain radiotherapy treatment. Images corresponding to this treatment technique are presented in this article.

Displacements of fiducial markers in patients with prostate cancer treated with image guided radiotherapy: A single-institution descriptive study.

AIM: To describe daily displacements when using fiducial markers as surrogates for the target volume in patients with prostate cancer treated with IGRT. BACKGROUND: The higher grade of conformity achieved with the use of modern radiation technologies in prostate cancer can increase the risk of geographical miss; therefore, an associated protocol of IGRT is recommended. MATERIALS AND METHODS: A single-institution, retrospective, consecutive study was designed. 128 prostate cancer patients treated with daily on-line IGRT based on 2D kV orthogonal images were included. Daily displacement of the fiducial markers was considered as the difference between the position of the patient when using skin tattoos and the position after being relocated using fiducial markers. Measures of central tendency and dispersion were used to describe fiducial displacements. RESULTS: The implant itself took a mean time of 15 min. We did not detect any complications derived from the implant. 4296 sets of orthogonal images were identified, 128 sets of images corresponding to treatment initiation were excluded; 91 (2.1%) sets of images were excluded from the analysis after having identified that these images contained extreme outlier values. If IGRT had not been performed 25%, 10% or 5% of the treatments would have had displacements superior to 4, 7 or 9 mm respectively in any axis. CONCLUSIONS: Image guidance is required when using highly conformal techniques; otherwise, at least 10% of daily treatments could have significant displacements. IGRT based on fiducial markers, with 2D kV orthogonal images is a convenient and fast method for performing image guidance.

IMRT, RapidArc® and conformal radiotherapy in the treatment of tumours of the anal canal.

PURPOSE: To compare dosimetric results of the use of RapidArc® with simultaneous integrated boost, sliding window intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost, and conformal radiotherapy with sequential boost in the management of anal canal cancer. METHODS: Two patients with squamous cell cancer of the anal canal with compromised inguinal nodes were included. The simulation was performed in the supine position with a customized Vac-Lok™ immobilizer. Treatment volumes and organs at risk were defined in accordance with international recommendations. Dosimetric comparisons were made in the target volume by means of tumour conformity, coverage, and homogeneity indexes; in healthy organs, integral doses were compared. RESULTS: A similar planning target volume coverage was achieved with the three techniques. The two IMRT techniques demonstrated benefits in doses received by healthy organs compared to the conformal radiotherapy. RapidArc® showed reduction in the execution time and monitor units required for treatment compared with sliding window IMRT. CONCLUSIONS: The IMRT showed coverage and tumour conformity indexes similar to those of conformal radiotherapy with better dosimetric results in the organs at risk, which should translate into a better toxicity profile. RapidArc® demonstrated benefits over the sliding window IMRT, which makes treatment more comfortable for the patient with less uncertainty about intrafraction motion and a reduced potential for radiation-induced tumours.

Intensity modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) in a patient with left breast cancer and pectus excavatum.

INTRODUCTION: Pectus excavatum is a frequent anomaly. It represents a challenge for adjuvant radiotherapy in the conservative treatment of breast cancer. Primary objective of this study is to compare dosimetric outcomes, normal tissue complication probability (NTCP), and integral dose using four radiation techniques. Secondary objective is to describe acute toxicity and setup errors. METHODS AND MATERIALS: A 57-year-old female patient with an inner quadrant, left breast, ductal carcinoma in situ, was identified. Whole breast was prescribed with 50 Gy in 25 fractions. Boost planning target volume (PTV) was prescribed with 60 Gy in 30 fractions for sequential boost (SB) plans or 57.5 Gy in 25 fractions in the simultaneous integrated boost (SIB) plan. All plans were normalized to deliver 47.5 Gy to 95 % of the breast PTV. Daily image-guided radiotherapy (IGRT) was performed. Setup deviations were described. RESULTS: Constraints were not accomplished for heart when using intensity modulated radiotherapy (IMRT) + SB or conformal radiotherapy with three photon fields and SB. Left lung constraint was not achieved by any of the techniques in comparison. IMRT + SIB and conformal photons and electrons + SB plan were closer to the objective. Integral doses were lower with IMRT for heart and ipsilateral lung; however, it were higher for contralateral breast and lung. Coverage and tumoral conformity indexes were similar for all techniques in comparison. Greater inhomogeneity was observed with the photons and electrons + SB. IMRT + SIB treatment was administered daily with grade I skin toxicity. The highest setup error was observed in Y direction. CONCLUSION: Planning target volume coverage was similar with the four techniques. Homogeneity was superior with both IMRT plans. A good balance between dose constraints for organs at risk, PTV coverage, homogeneity, and NTCP was observed with IMRT + SIB. The documented daily setup error justifies the use of online IGRT.