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ABSTRACT: To generate a reproducible step-wise guideline for the delineation of the lumbosacral plexus (LSP) on axial computed tomography (CT) planning images and to provide a preliminary dosimetric analysis on 15 representative patients with rectal or anal cancers treated with an intensity-modulated radiotherapy (IMRT) technique.
A standardized method for contouring the LSP on axial CT images was devised. The LSP was referenced to identifiable anatomic structures from the L4-5 interspace to the level of the sciatic nerve. It was then contoured retrospectively on 15 patients treated with IMRT for rectal or anal cancer. No dose limitations were placed on this organ at risk during initial treatment planning. Dosimetric parameters were evaluated. The incidence of radiation-induced lumbosacral plexopathy (RILSP) was calculated.
Total prescribed dose to 95% of the planned target volume ranged from 50.4 to 59.4 Gy (median 54 Gy). The mean (± standard deviation [SD]) LSP volume for the 15 patients was 100 ± 22 cm(3) (range, 71-138 cm(3)). The mean maximal dose to the LSP was 52.6 ± 3.9 Gy (range, 44.5-58.6 Gy). The mean irradiated volumes of the LSP were V40Gy = 58% ± 19%, V50Gy = 22% ± 23%, and V55Gy = 0.5% ± 0.9%. One patient (7%) was found to have developed RILSP at 13 months after treatment.
The true incidence of RILSP in the literature is likely underreported and is not a toxicity commonly assessed by radiation oncologists. In our analysis the LSP commonly received doses approaching the prescribed target dose, and 1 patient developed RILSP. Identification of the LSP during IMRT planning may reduce RILSP. We have provided a reproducible method for delineation of the LSP on CT images and a preliminary dosimetric analysis for potential future dose constraints.
International journal of radiation oncology, biology, physics 02/2012; 84(2):376-82. · 4.59 Impact Factor
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ABSTRACT: Intensity-modulated radiotherapy (IMRT) treatment plans generated by segmental multileaf collimator (SMLC) and helical tomotherapy (HT) techniques for patients with nasopharyngeal carcinoma were compared using standardized criteria proposed by Radiation Therapy Oncology Group (RTOG) protocol 0225. The goal was to deliver a prescribed dose of 70 Gy to at least 95% of the planning target volume (PTV) encompassing gross tumor, and 59.4 Gy and 50.4 Gy, respectively, to areas at high and low risk for microscopic disease, over 33 treatments while respecting constraints to organs at risk (OAR). HT-IMRT significantly reduced dose to the contralateral parotid gland and improved dose homogeneity to the PTVs. Mean doses to the inner and middle ears were also reduced by 18% and 24%, respectively, on the ipsilateral side, and 24%, and 35%, respectively, on the contralateral side using HT-IMRT compared to SMLC-IMRT. Additionally, HT-IMRT reduced mean doses to brainstem (p = 0.02), larynx (p = 0.03), and oral cavity (p = 0.03). These findings suggest that HT-IMRT may be of improve the therapeutic ratio in the radiotherapeutic treatment of nasopharyngeal carcinoma.
Technology in cancer research & treatment 06/2010; 9(3):291-8. · 2.02 Impact Factor
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ABSTRACT: The aim of this study was to determine the incidence of esophageal toxicity after radiation therapy for head and neck cancer.
The records of 211 patients treated by radiation therapy for head and neck cancer were reviewed to identify those with dysphagia lasting more than 90 days after therapy. Late toxicity criteria established by the Radiation Therapy Oncology Group were used to score the symptoms.
The incidence of grade 3+ esophageal toxicity at 3 and 6 months was 30% and 19%, respectively. The rate of gastrotomy-tube dependence at 3 and 6 months was 20% and 11%, respectively. Hypopharyngeal and unknown primary site (p = .01, for both), T4 disease (p = .01), and the use of concurrent chemotherapy (p = .001) were associated with grade 3+ esophageal toxicity and stricture formation.
A significant proportion of patients exhibit symptoms of esophageal toxicity after radiation therapy for head and neck cancer. Therefore, preventive strategies need further investigation.
Head & Neck 07/2009; 32(2):178-83. · 2.40 Impact Factor
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ABSTRACT: To report a single-institutional experience with the use of helical tomotherapy (HT)-based intensity-modulated radiotherapy (IMRT) for head and neck cancer.
Seventy-seven consecutive patients were treated with HT for squamous cell carcinoma of the head and neck to a median dose of 66 Gy (range, 60 to 72 Gy). Megavoltage CT scans were obtained as part of an image-guided registration protocol for patient alignment before each treatment. Concurrent chemotherapy was administered to 48 patients (62%).
The 2-year estimates of overall survival, local-regional control, and disease-free survival were 82%, 77%, and 71%, respectively. Spatial evaluation of local-regional failures revealed that 16 of the 18 patients who progressed in the primary site or neck failed in the high-dose planning target volume (PTV).
HT appears to achieve clinical outcomes comparable to contemporary series reporting on IMRT for head and neck cancer.
Head & Neck 05/2009; 31(12):1571-8. · 2.40 Impact Factor
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ABSTRACT: The growing use of IMRT with volumetric kilovoltage cone-beam computed tomography (kV-CBCT) for IGRT has increased concerns over the additional (typically unaccounted) radiation dose associated with the procedures. Published data quantify the in-field dose of IGRT and the peripheral dose from IMRT. This study adds to the data on dose outside the target area by measuring peripheral CBCT dose and comparing it with out-of-field IMRT dose.
Measurements of the CBCT peripheral dose were made in an anthropomorphic phantom with TLDs and were compared to peripheral dose measurements for prostate IMRT, determined with MOSFET detectors.
Doses above 1cGy (per scan) were found outside the CBCT imaged volume, with 0.2cGy at 25 cm from the central axis. IMRT peripheral dose was 1cGy at 20 cm and 0.4cGy at 25 cm (per fraction).
An appreciable dose can be found beyond the edge of the IGRT field; of similar order of magnitude as peripheral dose from IMRT (mGy), and approximately half the dose delivered to the same point from the IMRT treatment (0.2cGy c.f. 0.4cGy 25 cm from the isocenter). This shows that peripheral dose, as well as the in-field dose from CBCT, needs to be taken into account when considering long term care of radiation oncology patients.
Radiotherapy and Oncology 09/2008; 89(3):304-10. · 5.58 Impact Factor
