Multicatheter interstitial brachytherapy versus stereotactic radiotherapy with CyberKnife for accelerated partial breast irradiation: a comparative treatment planning study with respect to dosimetry of organs at risk.

BACKGROUND: The aim of the study was to dosimetrically compare multicatheter interstitial brachytherapy (MIBT) and stereotactic radiotherapy with CyberKnife (CK) for accelerated partial breast irradiation (APBI) especially concerning the dose of organs at risk (OAR-s). PATIENTS AND METHODS: Treatment plans of thirty-two MIBT and CK patients were compared. The OAR-s included ipsilateral non-target and contralateral breast, ipsilateral and contralateral lung, skin, ribs, and heart for left-sided cases. The fractionation was identical (4 x 6.25 Gy) in both treatment groups. The relative volumes (e.g. V100, V90) receiving a given relative dose (100%, 90%), and the relative doses (e.g. D0.1cm3, D1cm3) delivered to the most exposed small volumes (0.1 cm3, 1 cm3) were calculated from dose-volume histograms. All dose values were related to the prescribed dose (25 Gy). RESULTS: Regarding non-target breast CK performed slightly better than MIBT (V100: 0.7% vs. 1.6%, V50: 10.5% vs. 12.9%). The mean dose of the ipsilateral lung was the same for both techniques (4.9%), but doses irradiated to volume of 1 cm3 were lower with MIBT (36.1% vs. 45.4%). Protection of skin and rib was better with MIBT. There were no significant differences between the dose-volume parameters of the heart, but with MIBT, slightly larger volumes were irradiated by 5% dose (V5: 29.9% vs. 21.2%). Contralateral breast and lung received a somewhat higher dose with MIBT (D1cm3: 2.6% vs. 1.8% and 3.6% vs. 2.5%). CONCLUSIONS: The target volume can be properly irradiated by both techniques with similar dose distributions and high dose conformity. Regarding the dose to the non-target breast, heart, and contralateral organs the CK was superior, but the nearby organs (skin, ribs, ipsilateral lung) received less dose with MIBT. The observed dosimetric differences were small but significant in a few parameters at the examined patient number. More studies are needed to explore whether these dosimetric findings have clinical significance.

Radiotherapy for breast cancer induced long-term diminished accumulation of radiotracer on bone scan of the irradiated ribs.

Radiotherapy may result in long term effects and composition alterations in bones. Bone scintigraphy after radiotherapy may demonstrate decreased skeletal uptake; however, this is a transient effect with bone scan normalized after a few years. We describe a case of a 31-year-old female patient treated for left breast cancer with chemotherapy and radiotherapy, exhibiting reduced and diffuse diphosphonate uptake in the heavily irradiated sections of left ribs, even twelve years post-treatment. Similarly, quantitative computed tomography indicated altered bone composition. To our knowledge this is the first case describing such a long radiation side effect in breast cancer treatment.

Salvage Pulmonary Operations Following Stereotactic Body Radiotherapy for Small Primary and Metastatic Lung Tumors: Evaluation of the Operative Procedures.

Stereotactic body radiotherapy is an alternative treatment option for small-sized, primary lung cancers and pulmonary metastatic diseases. In the case of local relapse after stereotactic body radiotherapy, salvage pulmonary resection is considered cautiously. However, no study has described the difficulty of the salvage operations. This study aimed to assess the difficulty associated with salvage operative procedures. Eight patients who developed local relapse after stereotactic body radiotherapy and had undergone salvage pulmonary operations were enrolled in this study (stereotactic body radiotherapy group). Additionally, 439 patients who underwent video-assisted thoracoscopic lobectomy without previous stereotactic body radiotherapy were enrolled as the standard operative control group (non-stereotactic body radiotherapy group). In the stereotactic body radiotherapy group, 1 of the 8 patients had undergone lobectomy with composite resection of the third and fourth ribs. Of the 8 patients, 6 had undergone video-assisted thoracoscopic lobectomy and 1 had been inoperable because of rapid tumor progression. The operation time and the incision length of the utility port were apt to be longer in the stereotactic body radiotherapy group than in the non-stereotactic body radiotherapy group. On the contrary, the duration of drain placement and the length of hospital stay after the operation were not different. Thus, the salvage pulmonary operations were performed in the usual video-assisted thoracoscopic lobectomy approach, but slightly complicated than the standard video-assisted thoracoscopic lobectomy. Although to decide the indication of salvage operation might be difficult, it could be a feasible treatment option in local relapse after stereotactic body radiotherapy.

A cortical thickness and radiation dose mapping approach identifies early thinning of ribs after stereotactic body radiation therapy.

BACKGROUND AND PURPOSE: High rates of spontaneous rib fractures are associated with thoracic stereotactic body radiation therapy (SBRT). These fractures likely originate within the cortical bone and relate to the cortical thickness (Ct.Th). We report the development and application of a novel Ct.Th and radiation dose mapping technique to assess early site-specific changes of cortical bone in ribs. MATERIALS AND METHODS: Rib Ct.Th maps were constructed from pre-SBRT and 3month post-SBRT CT scans for 28 patients treated for peripheral lung lesions. The Ct.Th at approximately 50,000 homologous points within the entire rib cage was determined pre- and post-SBRT. Each rib was then divided into 30 homologous regions. The mean dose and thinning were determined per section. RESULTS: Regions of ribs that received ⩾10Gy exhibited significant thinning of cortical bone (p=0.001). The mean Ct.Th percent difference (95% CI) in regions receiving 10-20Gy, 20-30Gy, 30-40Gy, and ⩾40Gy were -7% (-4%,-11%), -14% (-18%,-11%), -15% (-19%,-11%), and -18% (-22%,-15%) respectively. Regions receiving >20Gy experienced significantly more thinning than regions receiving lower doses. CONCLUSIONS: Substantial early cortical bone thinning was observed post-SBRT in regions of ribs that received ⩾10Gy. The rapid thinning of ribs may predispose ribs to fracture after SBRT.

Rib fractures after reirradiation plus hyperthermia for recurrent breast cancer: Predictive factors.

BACKGROUND: Combining reirradiation (reRT) and hyperthermia (HT) has shown high therapeutic value for patients with locoregional recurrent breast cancer (LR). However, additional toxicity of reirradiation (e.g., rib fractures) may occur. The aim of this study is to determine the impact of potential risk factors on the occurrence of rib fractures. PATIENTS AND METHODS: From 1982-2005, 234 patients were treated with adjuvant reRT + HT after surgery for LR. ReRT consisted typically of 8 fractions of 4 Gy twice a week, or 12 fractions of 3 Gy four times a week. A total of 118 patients were irradiated with abutted photon and electron fields. In all, 60 patients were irradiated using either one or alternating combinations of abutted AP electron fields. Hyperthermia was given once or twice a week. RESULTS: The 5-year infield local control (LC) rate was 70 %. Rib fractures were detected in 16 of 234 patients (actuarial risk: 7 % at 5 years). All rib fractures occurred in patients treated with a combination of photon and abutted electron fields (p = 0.000); in 15 of 16 patients fractures were located in the abutment regions. The other significant predictive factors for rib fractures were a higher fraction dose (p = 0.040), large RT fields, and treatment before the year 2000. DISCUSSION AND CONCLUSION: ReRT + HT results in long-term LC. The majority of rib fractures were located in the photon/electron abutment area, emphasizing the disadvantage of field overlap. Large abutted photon/electron fields combined with 4 Gy fractions increase the number of rib fractures in this study group. However, as these factors were highly correlated no relative importance of the individual factors could be estimated. Increasing the number of HT sessions a week does not increase the risk of rib fractures.

Validation of automatic segmentation of ribs for NTCP modeling.

BACKGROUND AND PURPOSE: Determination of a dose-effect relation for rib fractures in a large patient group has been limited by the time consuming manual delineation of ribs. Automatic segmentation could facilitate such an analysis. We determine the accuracy of automatic rib segmentation in the context of normal tissue complication probability modeling (NTCP). MATERIALS AND METHODS: Forty-one patients with stage I/II non-small cell lung cancer treated with SBRT to 54 Gy in 3 fractions were selected. Using the 4DCT derived mid-ventilation planning CT, all ribs were manually contoured and automatically segmented. Accuracy of segmentation was assessed using volumetric, shape and dosimetric measures. Manual and automatic dosimetric parameters Dx and EUD were tested for equivalence using the Two One-Sided T-test (TOST), and assessed for agreement using Bland-Altman analysis. NTCP models based on manual and automatic segmentation were compared. RESULTS: Automatic segmentation was comparable with the manual delineation in radial direction, but larger near the costal cartilage and vertebrae. Manual and automatic Dx and EUD were significantly equivalent. The Bland-Altman analysis showed good agreement. The two NTCP models were very similar. CONCLUSIONS: Automatic rib segmentation was significantly equivalent to manual delineation and can be used for NTCP modeling in a large patient group.

Correlation between intensity modulated radiotherapy and bone marrow suppression in breast cancer.

OBJECTIVE: To study the correlation factors of bone marrow suppression in breast cancer radiotherapy and find out the method to guide the target area, dose limitation for breast cancer to reduce the risk of bone marrow suppression. PATIENTS AND METHODS: 72 cases of breast cancer patients were collected through retrospective, clinical control study. For patients with Grade 0-3, bone marrow suppression in the course of radiotherapy, the dose-volume parameters (V5, V10, V20, V30, V50, D20, D40, D60, D80, D100, Min, Max, Dmean) of the chest and rib of each patient were collected and analyzed from multiple points including tumor stage, age, lesion location, surgical approach, chemotherapy regimen and the number of cycles, bone dose-volume parameters. RESULTS: The relative parameters of the rib in the middle and severe bone marrow suppression group were significantly higher than those in the mild bone marrow depression group and the p values of V5, V10, V20, V30, Dmean, D40, D60, D80, D100 were less than 0.05. The difference of V50 in the two groups was statistically significant (p <0.05). For chemotherapy regimens containing doxorubicin, epirubicin, cyclophosphamide, the differences between bone marrow suppression group and non-bone marrow suppression were statistically significant (p =0.002). CONCLUSIONS: The dose-volume parameters of the rib radiation is one of the main factors causing the suppression of bone marrow in radiotherapy, and the volume of the 50Gy irradiation is also a contribution to the bone marrow. For patients accepted chemotherapy with doxorubicin, epirubicin, cyclophosphamide before radiotherapy, bone marrow suppression is more likely to occur during radiotherapy. After radical mastectomy or the volume of thoracic rib is increased because of the small breast, the occurrence of bone marrow suppression is increased. The effects of radiation on the bone marrow suppression were small, while its effect on the ribs was more evident, especially on the ribs V20 and Dmean and the difference was statically significant.

Comparative dosimetric findings using accelerated partial breast irradiation across five catheter subtypes.

PURPOSE: Accelerated partial breast irradiation (APBI) with balloon and strut adjusted volume implants (SAVI) show promising results with excellent tumor control and minimal toxicity. Knowing the factors that contribute to a high skin dose, rib dose, and D95 coverage may reduce toxicity, improve tumor control, and help properly predict patient outcomes following APBI. METHODS AND MATERIALS: A retrospective analysis of 594 patients treated with brachytherapy based APBI at a single institution from May 2008 to September 2014 was grouped by applicator subtype. Patients were treated to a total of 34 Gy (3.4 Gy x 10 fractions over 5 days delivered BID) targeting a planning target volume (PTV) 1.0 cm beyond the lumpectomy cavity using a high dose rate source. RESULTS: SAVI devices had the lowest statistically significant values of DmaxSkin (81.00 ± 29.83), highest values of D90 (101.50 ± 3.66), and D95 (96.09 ± 4.55). SAVI-mini devices had the lowest statistically significant values of DmaxRib (77.66 ± 32.92) and smallest V150 (18.01 ± 3.39). Multi-lumen balloons were able to obtain the smallest V200 (5.89 ± 2.21). Strut-based applicators were more likely to achieve a DmaxSkin and a DmaxRib less than or equal to 100 %. The effect of PTV on V150 showed a strong positive relationship (p < .001). PTV and DmaxSkin showed a weak negative relationship in multi-lumen applicators (p = .016) and SAVI-mini devices (p < .001). PTV and DmaxRib showed a weak negative relationship in multi-lumen applicators (p = .009), SAVI devices (p < .001), and SAVI-mini devices (p < .001). CONCLUSION: PTV volume is strongly correlated with V150 in all devices and V200 in strut based devices. Larger PTV volumes result in greater V150 and V200, which could help predict potential risks for hotspots and resulting toxicities in these devices. PTV volume is also weakly negatively correlated with max skin dose and max rib dose, meaning that as the PTV volumes increase one can expect slightly smaller max skin and rib doses. Strut based applicators are significantly more effective in keeping skin and rib dose constraints under 125 and 100 % when compared to any balloon based applicator.

Radiation-induced skin ulcer and rib fractures following percutaneous coronary intervention (PCI): A case of right back skin ulcer and adjacent rib fractures after single PCI.

We experienced a 75-year-old male patient with a refractory and severely painful skin ulcer on the right back. He had suffered from ischemic heart disease and undergone percutaneous coronary intervention 5 months prior to the consultation with us. The characteristic clinical appearance, location of the lesion and his past medical history led us to the diagnosis of radiation-induced skin ulcer. Magnetic resonance imaging, computed tomography as well as bone scintigraphy showed fractures of the right back rib adjacent to the ulcer, which was thought to be attributable to bone damage due to X-ray radiation and/or persistent secondary inflammation of the chronic ulcer. In the published work, there are no other reports of bone fractures associated with radiation dermatitis after coronary interventional radiology.

Spatio-temporal quantitative thermography of pre-focal interactions between high intensity focused ultrasound and the rib cage.

OBJECTIVE: The aim of this paper is to quantitatively investigate the thermal effects generated by the pre-focal interactions of a HIFU beam with a rib cage, in the context of minimally invasive transcostal therapy of liver malignancies. MATERIALS AND METHODS: HIFU sonications were produced by a phased-array MR-compatible transducer on Turkey muscle placed on a sheep thoracic cage specimen. The thoracic wall was positioned in the pre-focal zone 3.5 to 6.5 cm below the focus. Thermal monitoring was simultaneously performed using fluoroptic sensors inserted into the medullar cavity of the ribs and high resolution MR-thermometry (voxel: 1 × 1 × 5 mm3, four multi-planar slices). RESULTS: MR-thermometry data indicated nearly isotropic distribution of the thermal energy at the ribs' surface. The temperature elevation at the focus was comparable with the pericostal temperature elevation around unprotected ribs, while being systematically inferior, by more than a factor of four on average, to the intra-medullar values. The spatial profiles of the pericostal and intra-medullar thermal build-up measurements could be smoothly connected using a Gaussian function. The dynamics of the post-sonication thermal relaxation as determined by fluoroptic measurements was demonstrated to be theoretically coherent with the experimental observations. CONCLUSION: The experimental findings motivate further efforts for the transfer towards clinical routine of effective rib-sparing strategies for hepatic HIFU.

Laser radiation effect on chondrocytes and intercellular matrix of costal and articular cartilage impregnated with magnetite nanoparticles.

BACKGROUND AND OBJECTIVE: Magnetic nanoparticles with the ability to absorb laser radiation are the perspective agents for the early diagnostics and laser therapy of degenerative cartilage. The effect of starch stabilized magnetite nanoparticles (SSNPs) on the cartilage structure components has never been studied before. The aim of the work is to establish the Erbium:glass laser effect on costal and articular cartilage impregnated with SSNPs. MATERIALS AND METHODS: Porcine articular and costal cartilage disks (2.0 mm in diameter and 1.5-2 mm in thickness) were impregnated with SSNPs and irradiated using a 1.56 µm laser in therapeutic laser setting. The one sample group underwent the second irradiation after the SSNPs impregnation. The samples were analyzed by the means of histology, histochemistry and transmission electron microscopy (TEM) to reveal the alterations of cells, glycosaminoglycans and collagen network. RESULTS: The irradiated cartilage demonstrates the higher content of cell alterations than the intact one due to the heat and mechanical affection in the course of laser irradiation. However the alterations are localized at the areas near the irradiated surfaces and not dramatic. The impregnation of SSNPs does not cause any additional cell alterations. For both costal and articular cartilage the matrix alterations of irradiated samples are not critical: there is the slight decrease in acid proteoglycan content at the irradiated areas while the collagen network is not altered. Distribution and localization of impregnated SSNPs is described: agglomerates of 150-230 nm are observed located at the borders between matrix and cell lacunas of articular cartilage; SSNPs of 15-45 nm are found in the collagen network of costal cartilage. CONCLUSIONS: It was shown that SSNPs do not appreciably affect the structural components of both articular and costal cartilage and can be safely used for the laser diagnostics and therapy. The area of structural alterations is diffuse and local as the result of the mechanical and heat effect of laser impact. SSNPs reveal the areas of the structural alterations of cartilage matrix and give information about the size of the pores and defects.

Particle therapy for clinically diagnosed stage I lung cancer: comparison with pathologically proven non-small cell lung cancer.

BACKGROUND: The purpose of the present study was to present the treatment outcomes of particle therapy for indeterminate pulmonary nodules (IPNs) diagnosed as stage I non-small cell lung cancer, including a comparative analysis involving pathologically proven lung cancer (PPLC). MATERIAL AND METHODS: A total of 54 patients (57 lesions) who underwent particle therapy for IPNs were enrolled in this study. Median patient age was 76 (range 52-87) years. T-classification was: T1a, 30; T1b, 16; and T2a, 11. Particle therapy using protons or carbon ions was delivered at total doses of 52.8-80 Gy equivalent in 4-26 fractions. The PPLC cohort included 111 patients. RESULTS: The median follow-up time was 41 (range 7-90) months. For all IPN patients, the three-year overall survival, progression-free survival, local control and distant progression-free survival rates were 90%, 72%, 94% and 79%, respectively. Grade 2 toxicities were radiation pneumonitis (19%), dermatitis (9%), rib fracture (2%), chest wall pain (2%) and neuropathy (2%). No ≥grade 3 toxicities were observed. In univariate analysis, the IPN group showed significantly better survival relative to the PPLC group. However, after adjustment for baseline imbalances between these two groups in multivariate analysis, pathological confirmation did not correlate with survival. CONCLUSIONS: Particle therapy for IPNs provided favorable outcomes with minimal toxicities, which may be comparable to those for PPLC patients. Further studies are needed to clarify the optimal management of IPN patients.

Dosimetric experience with 2 commercially available multilumen balloon-based brachytherapy to deliver accelerated partial-breast irradiation.

The purpose of this work was to report dosimetric experience with 2 kinds of multilumen balloon (MLB), 5-lumen Contura MLB (C-MLB) and 4-lumen MammoSite MLB (MS-MLB), to deliver accelerated partial-breast irradiation, and compare the ability to achieve target coverage and control skin and rib doses between 2 groups of patients treated with C-MLB and MS-MLB brachytherapy. C-MLB has 5 lumens, the 4 equal-spaced peripheral lumens are 5 mm away from the central lumen. MS-MLB has 4 lumens, the 3 equal-spaced peripheral lumens are 3 mm away from the central lumen. In total, 43 patients were treated, 23 with C-MLB, and 20 with MS-MLB. For C-MLB group, 8 patients were treated with a skin spacing < 7 mm and 12 patients with rib spacing < 7 mm. For MS-MLB group, 2 patients were treated with a skin spacing < 7 mm and 5 patients with rib spacing < 7 mm. The dosimetric goals were (1) ≥ 95% of the prescription dose (PD) covering ≥ 95% of the target volume (V(95%) ≥ 95%), (2) maximum skin dose ≤ 125% of the PD, (3) maximum rib dose ≤ 145% of the PD (if possible), and (4) the V(150%) ≤ 50 cm(3) and V(200%) ≤ 10 cm(3). All dosimetric criteria were met concurrently in 82.6% of C-MLB patients, in 80.0% of MS-MLB patients, and in 81.4% of all 43 patients. For each dosimetric parameter, t-test of these 2 groups showed p > 0.05. Although the geometric design of C-MLB is different from that of MS-MLB, both applicators have the ability to shape the dose distribution and to provide good target coverage, while limiting the dose to skin and rib. No significant difference was observed between the 2 patient groups in terms of target dose coverage and dose to organs at risk.

Chest wall and rib irradiation and toxicities of early-stage lung cancer patients treated with CyberKnife stereotactic body radiotherapy.

AIM: The aim of the study is to evaluate the chest wall and rib toxicities in primary lung cancer patients treated with CyberKnife-based stereotactic body radiotherapy. MATERIALS & METHODS: In this study, data were collected from the 118 patients, of which 25 patients who had longer follow-up (mean: 21.9 months) were considered. Studied parameters were maximum point dose, doses to 1-100 cm(3) of chest wall and 1-10 cm(3) of ribs. RESULTS: Three patients developed chest wall pain (grade I). 25 studied patients, on average, received 27.7 Gy to 30 cm(3) of chest wall and 50.4 Gy to 1 cm(3) of rib. Nine patients had more than 30 Gy dose to 30 cm(3) of chest wall. No rib bone fracture was found. CONCLUSION: No correlations of chest wall pain and volume of irradiation were found.

Dosimetric evaluation of multilumen intracavitary balloon applicator rotation in high-dose-rate brachytherapy for breast cancer.

The objective of this work is to evaluate dosimetric impact of multilumen balloon applicator rotation in high-dose-rate (HDR) brachytherapy for breast cancer. Highly asymmetrical dose distribution was generated for patients A and B, depending upon applicator proximity to skin and rib. Both skin and rib spacing was ≤ 0.7 cm for A; only rib spacing was ≤ 0.7 cm for B. Thirty-five rotation scenarios were simulated for each patient by rotating outer lumens every 10° over ± 180° range with respect to central lumen using mathematically calculated rotational matrix. Thirty-five rotated plans were compared with three plans: 1) original multidwell multilumen (MDML) plan, 2) multidwell single-lumen (MDSL) plan, and 3) single-dwell single-lumen (SDSL) plan. For plan comparison, planning target volume for evaluation (PTV_EVAL) coverage (dose to 95% and 90% volume of PTV_EVAL) (D95 and D90), skin and rib maximal dose (Dmax), and normal breast tissue volume receiving 150% (V150) and 200% (V200) of prescribed dose (PD) were evaluated. Dose variation due to device rotation ranged from -5.6% to 0.8% (A) and -6.5% to 0.2% (B) for PTV_EVAL D95; -5.2% to 0.4% (A) and -4.1% to 0.7% (B) for PTV_EVAL D90; -2.0 to 18.4% (A) and -7.8 to 17.5% (B) for skin Dmax; -11.1 to 22.8% (A) and -4.7 to 55.1% (B) of PD for rib Dmax, respectively. Normal breast tissue V150 and V200 variation was < 1.0 cc, except for -0.1 to 2.5cc (B) of V200. Furthermore, 30° device rotation increased rib Dmax over 145% of PD: 152.9% (A) by clockwise 30° rotation and 152.5% (B) by counterclockwise 30° rotation. For a highly asymmetric dose distribution, device rotation can outweigh the potential benefit of improved dose shaping capability afforded by multilumen and make dosimetric data worse than single-lumen plans unless it is properly corrected.

Monte Carlo calculations of lung dose in ORNL phantom for boron neutron capture therapy.

Monte Carlo simulations were performed to evaluate dose for possible treatment of cancers by boron neutron capture therapy (BNCT). The computational model of male Oak Ridge National Laboratory (ORNL) phantom was used to simulate tumours in the lung. Calculations have been performed by means of the MCNP5/X code. In this simulation, two opposite neutron beams were considered, in order to obtain uniform neutron flux distribution inside the lung. The obtained results indicate that the lung cancer could be treated by BNCT under the assumptions of calculations.

Effects of ionizing radiation and preservation on biomechanical properties of human costal cartilage.

Tissue banks around the world store human cartilage obtained from cadaveric donors for use in diverse reconstructive surgical procedures. To ensure this tissue is sterile at the time of distribution, tissues may be sterilized by ionizing radiation. In this work, we evaluate the physical changes in deep frozen costal cartilage (-70 °C) or costal cartilage preserved in high concentrations of glycerol (>98 %) followed by a terminal sterilization process using ionizing radiation, at 3 different doses (15, 25 and 50 kGy). Tension and compression tests were carried out to determine the mechanical changes related both to the different preservation methods and irradiation doses. For both methods of preservation, tension strength was increased by about 24 %, when cartilage tissue was irradiated with 15 kGy. Deep frozen samples, when irradiated with 25 or 50 kGy, had a decrease in their mechanical performance, albeit to a lesser extent than when tissues were preserved in high concentration of glycerol and equally irradiated. In conclusion, processing in high concentration of glycerol did not increase tissue protection against radiation damage; while cartilage preserved in high concentrations of glycerol withstands radiation up to 25 kGy, deep frozen human costal cartilage may be sterilized with a doses up to 50 kGy without significant mechanical impact.

The effect of rib and lung heterogeneities on the computed dose to lung in Ir-192 high-dose-rate breast brachytherapy: Monte Carlo versus a treatment planning system.

AIMS: This study investigates to what extent the dose received by lungs from a commercially available treatment planning system, Ir-192 high-dose-rate (HDR), in breast brachytherapy, is accurate, with the emphasis on tissue heterogeneities, and taking into account the presence of ribs, in dose delivery to the lung. MATERIALS AND METHODS: A computed tomography (CT) scan of a breast was acquired and transferred to the 3-D treatment planning system and was also used to construct a patient-equivalent phantom. An implant involving 13 plastic catheters and 383 programmed source dwell positions were simulated, using the Monte Carlo N-Particle eXtended (MCNPX) code. The Monte Carlo calculations were compared with the corresponding commercial treatment planning system (TPS) in the form of percentage isodose and cumulative dose-volume histogram (DVH) in the breast, lungs, and ribs. RESULTS: The comparison of the Monte Carlo results and the TPS calculations showed that a percentage of isodose greater than 75% in the breast, which was located rather close to the implant or away from the breast curvature surface and lung boundary, were in good agreement. TPS calculations overestimated the dose to the lung for lower isodose contours that were lying near the breast surface and the boundary of breast and lung and were relatively away from the implant. CONCLUSIONS: Taking into account the ribs and entering the actual data for breasts, ribs, and lungs, revealed an average overestimation of the dose by a factor of 8% in the lung for TPS calculations. Therefore, the accuracy of the TPS results may be limited to regions near the implants where the treatment is planned, and is a more conservative approach for regions at boundaries with curvatures or tissues with a different material than that in the breast.

Pathological vertebral fracture after stereotactic body radiation therapy for lung metastases. Case report and literature review.

BACKGROUND: Stereotactic body radiation therapy (SBRT) is a radiation technique used in patients with oligometastatic lung disease. Lung and chest wall toxicities have been described in the patients but pathological vertebral fracture is an adverse effect no reported in patients treated with SBRT for lung metastases. CASE PRESENTATION: A 68-year-old woman with the diagnosis of a recurrence of a single lung metastatic nodule of urothelial carcinoma after third line of chemotherapy. The patient received a hypo-fractionated course of SBRT.A 3D-conformal multifield technique was used with six coplanar and one non-coplanar statics beams. A total dose of 48 Gy in three fractions over six days was prescribed to the 95% of the CTV. Ten months after the SBRT procedure, a CT scan showed complete response of the metastatic disease without signs of radiation pneumonitis. However, rib and vertebral bone toxicities were observed with the fracture-collapse of the 7th and 8th vertebral bodies and a fracture of the 7th and 8th left ribs. We report a unique case of pathological vertebral fracture appearing ten months after SBRT for an asymptomatic growing lung metastases of urothelial carcinoma. CONCLUSION: Though SBRT allows for minimization of normal tissue exposure to high radiation doses SBRT tolerance for vertebral bone tissue has been poorly evaluated in patients with lung tumors. Oncologists should be alert to the potential risk of fatal bone toxicity caused by this novel treatment. We recommend BMD testing in all woman over 65 years old with clinical risk factors that could contribute to low BMD. If low BMD is demonstrated, we should carefully restrict the maximum radiation dose in the vertebral body in order to avoid intermediate or low radiation dose to the whole vertebral body.