Critical Factors of Dose Distribution in Breast Cancer Tomotherapy With Metallic Port Breast Tissue Expander: Image Correction, Delivery Mode, and Volume Impact.

Objectives: Breast reconstruction helps patients enhance their body image after mastectomy. Metallic ports in tissue expanders lead to dose attenuation during radiotherapy. Tissue expander volume shifts the metallic port position, possibly causing various dose alterations. This study aimed to evaluate the impact of the MAGNA-SITETM tissue expander volume on tomotherapy. Methods: Boluses and MAGNA-SITETM were placed on a Rando phantom to simulate the tissue expander under the pectoralis major. Computed tomography simulation images were transformed through replacing the electron density of (a) metallic artifact region only (Image metallic port) and (b) metallic port and artifact regions (Image Homo). Planning was calculated using fixed-beam and helical-mode techniques. Radiation was delivered with different volumes of the tissue expander. Results: Integrated 997 dose points were calculated. Planning with Image metallic port provided a calculated dose significantly closer to a realistic dose. The percentage of doses achieving the prescribed dose was significantly higher in the helical mode. In layer 2, the 100-mL tissue expander had a significantly lower measurement dose than all other volumes. Volume 150 mL had the highest increase in the measured dose difference from the plan dose at layer 2. Volume 250 mL had the highest percentage of measurement doses passing the 5% dose difference from plan dose. The coldest dose areas were noted in layers 1 and 2, especially in the metallic port-direct image mode. The average dose reduction of the measured cold areas was 6.03 ± 1.94%. Conclusion: Dose distribution was affected by the volume of the metallic port tissue expander. Tomotherapy with proper image heterogeneity correction and helical mode can reduce the attenuation from the metallic port. A tissue expander volume of 150 to 250 mL is suitable. Patients with high risk at the chest wall should be evaluated carefully to avoid underdosing. Radiation oncologists should closely cooperate with plastic surgeons to optimize treatment for each patient.

Half-beam volumetric-modulated arc therapy in adjuvant radiotherapy for gynecological cancers.

PURPOSE: The purpose of this study is to introduce half-beam volumetric-modulated arc therapy (HVMAT), an innovative treatment planning technique from our work, for reducing dose to the organs at risk (OAR) during adjuvant radiotherapy for gynecological cancers. METHODS AND MATERIALS: Seventy-two treatment plans of 36 patients with gynecological cancers receiving adjuvant radiotherapy were assessed. Among them, 36 plans were designed using HVMAT and paired with the other 36 traditional volumetric-modulated arc therapy (VMAT) plans for each patient. The main uniqueness of the HVMAT designs was that it consisted of two opposite-shielded half-beam fields rotated inversely in two coplanar arcs, collocating with the specially-devised avoidance structures to enhance the control of the OAR doses. The dose distributions in HVMAT and VMAT were evaluated and compared using the random effects model. RESULTS: The ratios of OAR doses in HVMAT compared with VMAT showed a comprehensive OAR dose reduction when using HVMAT (V20Gy : bladder, 0.92; rectum, 0.95; V30Gy : bowel, 0.91; femoral heads, 0.66), except for the ilium (V30Gy : 1.12). The overall mean difference for each OAR across V40Gy , V30Gy , V20Gy , and bowel V15Gy was statistically significant (almost all p < 0.001). In addition, HVMAT promoted a better conformity index, homogeneity index, D2% , and V107% of the planning target volume (all p < 0.001). CONCLUSIONS: HVMAT is capable of generating deep double-concave dose distributions with the advantage of reducing dose to several OARs simultaneously. It is highly recommended for pelvic irradiation, especially for treating gynecological cancers in adjuvant radiotherapy.

Small bowel dose in subserosal tandem insertion during cervical cancer brachytherapy.

Cervical cancer patients may sometimes experience subserosal tandem insertions during brachytherapy, which can lead to increased but unnoticed irradiations to the small bowel (SB). In this study, we aimed to quantify and further predict individual SB dose increase and to increase focus on the SB in subserosal tandem insertions. Images and dosimetry data of cervical cancer brachytherapy with subserosal insertion (SI) were reviewed. The percentage increases in the SB dose compared with intracavitary insertion (II) at 8 points of D(x)cc with 10 cc intervals were assessed. SI was classified into anterior and posterior SI according to the insertion site. The differences in minimum distance from the tandem tip to the SB on the axial view between these 2 insertions were tested using the Mann-Whitney test. The distance and D(x)cc were involved in the individual dose increase model by linear regression as prediction factors. A total of 27 insertions were evaluated, including 8 insertions with SI and 19 insertions with II. The median percentage increases in the normalized SB dose for all SI showed a logarithmic trend with a 55.4% increase at the hotspot. In contrast to posterior SI, anterior SI demonstrated a more significantly logarithmic trend, which featured highly increased doses at the hotspot (79.1% for the absolute SB dose and 137.8% for the normalized SB dose). The prediction models can predict the percentage dose increases in SI: Increased D(x)cc [%] = 31.370 - 7.865 ln(distance) - 3.949 ln(x) (absolute SB dose), and Increased D(x)cc [%] = 55.618 - 18.591 ln(distance) - 7.232 ln(x) (normalized SB dose). We developed prediction models for individual SB dose increase in SI in our study. SB hotspots in anterior SI require greater attention during cervical cancer brachytherapy. The models are new ones and are given for the first time.

Tangent-based volumetric modulated arc therapy for advanced left breast cancer.

PURPOSE: To introduce the benefits of tangent-based volumetric modulated arc therapy (TVMAT), an innovative radiotherapy planning technique, compared with traditional volumetric modulated arc therapy (VMAT) for advanced left breast cancer needing nodal irradiation. MATERIALS AND METHODS: Twenty-three patients with advanced left breast cancer who had received modified radical mastectomy (MRM) and needed adjuvant radiotherapy including nodal irradiation were assessed. Among 23 radiotherapy treatment plans, 17 plans were designed by using TVMAT technique and 6 plans were designed by using traditional VMAT. The main difference of TVMAT from VMAT was that the area of avoidance sector within specific degrees of angle that had no monitor unit (MU) delivery was used in the arc planning, including a total of 5 sectors in 5 partial arcs. The dosimetries of planning target volume (PTV), right breast, bilateral lungs, and heart between TVMAT and VMAT were compared. RESULTS: The conformity index (CI) and homogeneity index (HI) of PTV between two groups were statistically equivalent (CI: 0.98 ± 0.02 and 0.98 ± 0.03, P = 0.431; HI: 0.12 ± 0.03 and 0.11 ± 0.05, P = 0.177), which indicated that the treatment efficacy of the plans regarding TVMAT was compatible with VMAT. However, all neighboring organs at risk (OAR) showed a great percentage of reduction in mean doses (right breast: 53.1%, right lung: 37.7%, left lung: 8.8%, heart: 21.2%) and low dose parameters (V10: right breast: 72.3%, right lung: 86.1%, left lung: 12.5%, heart: 25.1%; V5: right breast: 56.5%, right lung: 28.3%, left lung: 12.7%, heart: 18.2%) by using TVMAT. CONCLUSION: TVMAT greatly decreases the radiation doses delivered to the OAR with maintained therapeutic efficacy. It is highly recommended for treating breast cancer, especially for difficult cases with left side disease needing nodal irradiation.

Dosimetric analysis of tangent-based volumetric modulated arc therapy with deep inspiration breath-hold technique for left breast cancer patients.

BACKGROUND: Tangent-based intensity modulated radiation therapy (TIMRT) is a common adjuvant radiotherapy strategy for breast cancer patients. This study compared the dosimetric characteristics of tangent-based volumetric modulated arc therapy (TVMAT) and TIMRT for left breast cancer patients during deep inspiration breath-hold (DIBH) and free breathing (FB) techniques. METHODS: Fourteen patients with left breast cancer after breast-conserving surgery were included. The first arc started at 331.8-353.6 degrees and stopped at 281.8-315.0 degrees. The third arc started at 123.2-149.1 degrees and stopped at 88.0-96.0 degrees. The second and fourth arcs were reverse arcs of first and third arcs. DIBH-TIMRT inversing plans were generated using opposing tangential fields. Wilcoxon signed rank test and Spearman correlation were used to examine the significance of dose difference. RESULTS: Compared with FB-TVMAT, the mean heart dose of DIBH-TVMAT plans was reduced from 7.9 Gy to 3.2 Gy (p < 0.001). The average left lung volume receiving 30 Gy or more (V30Gy) was reduced from 12.9 to 5.7% (p < 0.001). DIBH-TVAMT plans resulted in a lower mean dose to the contralateral breast and lung (2 Gy and 0.7 Gy vs 3.4 Gy and 1.5 Gy, respectively) as compared to FB-TVMAT plans. Compared with DIBH-TIMRT, the average left lung V30Gy of DIBH-TVMAT plans was reduced from 8.5 to 5.7% (p = 0.031). As for low-dose areas, exposure of the left lung, right breast, heart and right lung volume with 10 Gy or more was not significantly different between the IMRT- and VMAT-plans. CONCLUSIONS: DIBH-TVMAT for left breast cancer treatment retains treatment plan quality similar to the DIBH-IMRT technique without compromising dose restrictions to the heart, right breast and right lung. DIBH-TVMAT increased left lung protection but still had higher V5Gy to right breast and substantially higher V5Gy to heart. For left breast cancer patients receiving treatment with the DIBH technique, DIBH-TVMAT provides better treatment quality and is a safe and feasible treatment strategy.

Quantitative analysis of respiration-induced motion of each liver segment with helical computed tomography and 4-dimensional computed tomography.

BACKGROUND: To analyze the respiratory-induced motion of each liver segment using helical computed tomography (helical CT) and 4-dimensional computed tomography (4DCT), and to establish the individual segment expansion margin of internal target volume (ITV) to facilitate target delineation of tumors in different liver segments. METHODS: Twenty patients who received radiotherapy with CT-simulation scanning of the whole liver in both helical CT and 10-phase-gated 4DCT were investigated, including 2 patients with esophagus cancer, 4 with lung cancer, 10 with breast cancer, 2 with liver cancer, 1 with thymoma, and 1 with gastric diffuse large B-cell lymphoma (DLBCL). For each patient, 9 representative points were drawn on the helical CT images of liver segments 1, 2, 3, 4a, 4b, 5, 6, 7, and 8, respectively, and adaptively deformed to 2 phases of the 4DCT images at the end of inspiration (phase 0 CT) and expiration (phase 50 CT) in the treatment planning system. Using the amplitude of each point between phase 0 CT and phase 50 CT, we established quantitative data for the respiration-induced motion of each liver segment in 3-dimensional directions. Moreover, using the amplitude between the original helical CT and both 4DCT images, we rendered the individual segment expansion margin of ITV for hepatic target delineation to cover more than 95% of each tumor. RESULTS: The average amplitude (mean ± standard deviation) was 0.6 ± 3.0 mm in the left-right (LR) direction, 2.3 ± 2.4 mm in the anterior-posterior (AP) direction, and 5.7 ± 3.4 mm in the superior-inferior (SI) direction, respectively. All of the segments moved posteriorly and superiorly during expiration. Segment 7 had the largest amplitude in the SI direction, at 8.6 ± 3.4 mm. Otherwise, the segments over the lateral side, including segments 2, 3, 6, and 7, had greater excursion in the SI direction compared to the medial segments. To cover more than 95% of each tumor, the required expansion margin of ITV in the LR, AP, and SI directions were at least 2.5 mm, 2.5 mm, and 5.0 mm on average, respectively, with variations between different segments. CONCLUSIONS: The greatest excursion occurred in liver segment 7, followed by the segments over the lateral side in the SI direction. The individual segment expansion margin of ITV is required to delineate targets for each segment and direction.

3M Cavilon No-Sting Barrier Film or topical corticosteroid (mometasone furoate) for protection against radiation dermatitis: A clinical trial.

BACKGROUND/PURPOSE: Evidence on the prevention of radiation dermatitis is lacking. The aim of this study was to investigate the effect of 3M Cavilon No Sting Barrier Film and topical corticosteroids on irradiated skin. METHODS: Thirty-nine postoperative breast cancer patients were randomized into three groups for intraindividual comparison (skin to be irradiated was divided into 2 parts): (1) 3M No Sting Barrier Film versus no treatment; (2) corticosteroid versus no treatment; and (3) corticosteroid versus 3M No Sting Barrier Film. The primary end points monitored were the time to first occurrence of grade 1 pruritus, pain score of 3 and grade 2 radiation dermatitis. The secondary end points studied were the incidence of grade 3 radiation dermatitis and total pain scores. Data analysis was done using the SPSS software version 10. RESULTS: Skin given the 3M barrier film experienced a later occurrence of pruritus compared to both corticosteroids and untreated, although this was statistically insignificant. Corticosteroids delayed the time to occurrence of grade 2 dermatitis compared to both untreated skin and 3M barrier film, (mean day of onset = corticosteroid: 52 vs. untreated: 43, p = 0.092; corticosteroid: 53.4 vs. 3M barrier film: 44.5, p = 0.002, t test). Skin given corticosteroids had the lowest incidence of grade 3 dermatitis among all three conditions, although the differences were statistically insignificant. No statistically significant differences were noted in total pain scores. CONCLUSION: The 3M barrier film may be helpful against dermatitis associated pruritus. Corticosteroids may delay the time of onset of severe skin reactions and also reduce the incidence of severe radiation dermatitis.

Impact of magnetic resonance imaging versus CT on nasopharyngeal carcinoma: primary tumor target delineation for radiotherapy.

BACKGROUND: Our aim was to assess the capacity of CT versus MRI for delineating to the primary tumor extent of nasopharyngeal carcinoma (NPC) in treated patients. METHODS: From December 1997 to April 2000, 258 patients with NPC were enrolled. We focused on the primary tumor extension and the discrepancy between CT and MRI. The delineation of tumor invasion was crucial for determination of the gross tumor volume (GTV) before radiation therapy. RESULTS: A total of 104 patients (40.3%) had intracranial infiltration detected by MRI, whereas CT showed negative findings (p = 6.879 x 10(-11)). Once the pterygopalatine fossa was involved, the chance of intracranial invasion was increased (96.1%). The detectable percentage of pterygopalatine fossa involvement accompanying intracranial invasion was higher with MRI than with CT (96.1% vs 56.9%). CONCLUSIONS: More detailed information about T and N classification of NPC was provided by MRI than by CT, which led to better target delineation for radiotherapy.

Dysphagia in patients with nasopharyngeal cancer after radiation therapy: a videofluoroscopic swallowing study.

This study evaluated swallowing status and the factors influencing swallowing in patients with nasopharyngeal carcinoma (NPC) after radiation therapy. During the period from July 1995 to June 1999, this cross-sectional study used videofluoroscopic swallowing study (VFSS) to evaluate 184 NPC patients who had completed radiation therapy [113 cases had completed radiation therapy < or = 12 months prior to evaluation (acute group) and 71 cases had completed radiation therapy > 12 months prior to evaluation (chronic group)]. The numbers of patients with tumors in each of the four stages were as follows: 24 in stage I, 45 in stage II, 41 in stage III, and 74 in stage IV. Swallowing abnormalities of the acute and chronic groups were correlated with multiple variables, including gender, age, the stage of the tumor, use of either neoadjuvant chemotherapy or radiosensitizer, and radiation modality. The analytical results indicated that the chronic group had a significantly higher proportion of swallowing abnormalities. Radiation modality, chemotherapy, and tumor staging were not significantly associated with swallowing dysfunction. Trend analysis revealed a progressive deterioration of most parameters of swallowing function in this group of patients. These findings indicate that swallowing function continues to deteriorate over time, even many years after radiation therapy in patients with NPC. Our results indicate that the time elapsed since radiation therapy correlates with the severity of dysphagia in NPC patients.