Ethical issues related to the COVID-19 pandemic in patients with cancer: experience and organisations in a French comprehensive cancer centre.

BACKGROUND: The COVID-19 pandemic has aggressively reached the most vulnerable, not only the elderly but also patients with chronic conditions such as cancer. In this study, we present the outlines of ethical thinking and the measures implemented to try to respect our basic values of care, in the specific environment of an oncology hospital. METHODS: Our ethics committee created an ethical watch system based on 24/7 shifts to assist practitioners in their daily decisions. We discuss the challenges faced by patients with cancer during the pandemic, such as access to critical care and ethical dilemmas in the context of resource scarcity, as well as the issue of isolation of patients. We also debate the restrictions in access to oncology care in a health context strongly 'prioritised' against COVID-19. RESULTS: In all areas of an ethical dilemma, either for sorting out access to critical care or for the dramatic consequences of prolonged isolation of patients, our common thread was our attempt to protect, whenever possible, the principles of deontological ethics by strictly resisting utilitarian pressure. Respecting democratic health decision-making processes is a cornerstone of ethically relevant decisions, including in the context of a sanitary crisis. CONCLUSION: The role of an ethics committee related to real-life situations includes not only a reflexive perspective in respect of fundamental principles, but also the help to enlighten and resolve ethical dilemmas in complex clinical situations. This ethical watch team assists physicians in decision-making, promoting the supportive and palliative dimension of care with a holistic approach.

Venezia applicator with oblique needles improves clinical target volume coverage in distal parametrial tumor residue compared to parallel needles only.

PURPOSE: Residual distal parametrial involvement after radiochemotherapy is a true challenge for brachytherapists since the width and asymmetry of high-risk clinical target volume (HR-CTV) are difficult to cover properly with a standard implant. MATERIAL AND METHODS: Dosimetric plans of five patients treated with Venezia advanced gynecological applicator at our institution were reviewed. For each patient, we compared the original plan with a new plan where oblique needles were removed and re-optimized manually. Optimization process was halted when EQD210 D90 HR-CTV reached 90 Gy, when one hard constraint to organs at risk (OARs) was reached according to the EMBRACE II protocol, or when dose-rate of one of OARs exceeded 0.6 Gy/h. RESULTS: Tumors were large; median HR-CTV volume was 64 cc and median distance between tandem and outer contour of HR-CTV was 40 mm. For the five patients, HR-CTV EQD210 D90 was superior in the plan using oblique needles, with a median difference of 6.5 Gy (range, 1.7-8.5 Gy). Median D90 HR-CTV and intermediate-risk CTV (IR-CTV) were significantly increased with oblique needles: 85.9 Gy (range, 83.2-90.3 Gy) vs. 81.5 Gy (range, 77.4-84 Gy), and 68.7 Gy (range, 66.3-72.3 Gy) vs. 67 Gy (range, 64.3-69.1 Gy), p = 0.006 for both. There were no significant differences in the dose to OARs. Plans with only parallel needles had less favorable dose distribution, with cold spots on the outer parametria and higher vaginal activation to compensate parametrial coverage in its inferior part. CONCLUSIONS: VeneziaTM applicator permits reproducible application to increase CTV coverage in patients with distal parametrial tumor residue during brachytherapy, while maintaining acceptable dose to OARs.

EXPERIMENTAL EVALUATION OF DOSIMETRIC CHARACTERIZATION OF GAFCHROMIC EBT3 AND EBT-XD FILMS FOR CLINICAL CARBON ION BEAMS.

Radiochromic film is a very useful tool for 2D dosimetric measurements in radiotherapy because it is self-developing and has very high-spatial resolution. However, considerable care has to be taken in ion beam radiotherapy owing to the quenching effect of high-linear energy transfer (LET) radiation. In this study, the dose responses of GAFchromic EBT3 and EBT-XD films were experimentally investigated using the clinical carbon ion beam at the Heavy Ion Medical Accelerator in Chiba. Results showed that the relations between absorbed dose and net optical density could be expressed well using an equation proposed by Reinhardt (2015). The quenching effect was evaluated by determining their relative efficiencies for photon irradiation as a function of LET. A correction equation derived in this study allowed the absorbed dose to be determined in the small irradiation field used for carbon ion radiotherapy eye treatments. This study contributes to establishing an absolute dosimetry procedure for heavy ion beams using radiochromic film.

Long-Term Results of a Highly Performing Conformal Electron Therapy Technique for Chest Wall Irradiation After Mastectomy.

PURPOSE: To evaluate locoregional control and survival after mastectomy, as well as toxicity, in patients irradiated by a previously described postmastectomy highly conformal electron beam radiation therapy technique (PMERT). METHODS AND MATERIALS: We included all women irradiated by postmastectomy electron beam radiation therapy for nonmetastatic breast cancer between 2007 and 2011 in our department. Acute and late toxicities were retrospectively assessed using Common Terminology Criteria for Adverse Events version 3.0 criteria. RESULTS: Among the 796 women included, 10.1% were triple-negative, 18.8% HER2-positive, and 24.6% received neoadjuvant chemotherapy (CT). Multifocal lesions were observed in 51.3% of women, and 64.6% had at least 1 involved lymph node (LN). Internal mammary chain, supraclavicular, infraclavicular, and axillary LNs were treated in 85.6%, 88.3%, 77.9%, and 14.9% of cases, respectively. With a median follow-up of 64 months (range, 6-102 months), 5-year locoregional recurrence-free survival and overall survival were 90% (95% confidence interval 88.1%-92.4%) and 90.9% (95% confidence interval 88.9%-93%), respectively. Early skin toxicity was scored as grade 1 in 58.5% of patients, grade 2 in 35.9%, and grade 3 in 4.5%. Concomitant CT was associated with increased grade 3 toxicity (P<.001). At long-term follow-up, 29.8% of patients presented temporary or permanent hyperpigmentation or telangiectasia or fibrosis (grade 1: 23.6%; grade 2: 5.2%; grade 3: 1%), with higher rates among smokers (P=.06); 274 patients (34.4%) underwent breast reconstruction. Only 24 patients (3%) had early esophagitis of grade 1. Only 3 patients developed ischemic heart disease: all had been treated by anthracycline-based CT with or without trastuzumab, all had been irradiated to the left chest wall and LN, and all presented numerous cardiovascular risk factors (2-4 factors). CONCLUSIONS: This study demonstrated the good efficacy of this technique in terms of locoregional control and survival, and good short-term and long-term safety. Longer follow-up is required to analyze chronic cardiac events.

Whole breast radiotherapy in the lateral decubitus position: a dosimetric and clinical solution to decrease the doses to the organs at risk (OAR).

PURPOSE: To evaluate whole breast 3D-conformal radiotherapy (RT) delivered in the lateral decubitus position (isocentric lateral decubitus [ILD]) and to report the acute toxicity of a series of consecutive patients treated with ILD. MATERIALS AND METHODS: From January to December 2010, 56 consecutive patients with large breasts and early-stage breast cancer treated by breast conserving surgery underwent 3D-conformal whole breast RT in the lateral decubitus position. A dose of 50 Gy in 25 fractions via two opposed isocentric beams was prescribed to whole breast, with or without a 16 Gy photon tumor bed boost. Dosimetry of all patients was reviewed, and the acute toxicity of treatment, evaluated weekly using the NCI CTC v3.0 scale, was analyzed. RESULTS: Median age was 57 years (range: 33-71). 85% of patients had a breast circumference of at least 95 cm and 80% had at least a C cup size. Average breast volume was 991 cm(3) (range: 225-2791 cm(3)). Median dose to the breast was 50 Gy, while median dose to the tumor bed was 16 Gy. Grade 1, 2 and 3 dermatitis developed in 37.5%, 58.9% and 1.8% of patients, respectively. From a dosimetric point of view, doses to the ipsilateral lung were extremely low: average V(1Gy), V(2Gy) and V(5Gy) were 26.6%, 9.3% and 0.7%, respectively. Average mean lung dose was 0.96 Gy. For the 26 patients with left-sided tumors, heart doses were also extremely low: average V(1Gy), V(2Gy) and V(5Gy) were 58.8%, 14.2% and 0.7%, respectively. Average mean heart dose was 1.35 Gy. CONCLUSION: Whole breast radiotherapy in the lateral decubitus position for patients with large breasts and early-stage breast cancer provides an excellent dosimetric profile, with low doses to the heart and ipsilateral lung. It is also very well tolerated, with a good acute toxicity profile.

Helical tomotherapy for inoperable breast cancer: a new promising tool.

BACKGROUND: We investigated the feasibility of helical tomotherapy (HT) for inoperable large breast tumors, after failing to achieve adequate treatment planning with conformal radiation techniques. MATERIAL AND METHODS: Five consecutive patients with locally advanced breast cancer (LABC) were treated by preoperative HT. All patients received up-front chemotherapy before HT. Irradiated volumes included breast and nodal areas (45-50 Gy) in 4 patients. One patient received a simultaneous integrated boost (55 Gy) to gross tumor volume (GTV) without lymph node irradiation. Acute toxicity was assessed with Common Toxicity Criteria for Adverse Events v.4. Patients were evaluated for surgery at the end of treatment. RESULTS: Patients were staged IIB to IIIC (according to the AJCC staging system 2010). HT was associated in 4 patients with concomitant chemotherapy (5-fluorouracil and vinorelbine). Two patients were scored with grade 3 skin toxicity (had not completed HT) and one with grade 3 febrile neutropenia. One patient stopped HT with grade 2 skin toxicity. All patients were able to undergo mastectomy at a median interval of 43 days (31-52) from HT. Pathological partial response was seen in all patients. CONCLUSIONS: HT is feasible with acceptable toxicity profiles, potentially increased by chemotherapy. These preliminary results prompt us to consider a phase II study.

Implant breast reconstruction followed by radiotherapy: can helical tomotherapy become a standard irradiation treatment?

To evaluate the benefits and limitations of helical tomotherapy (HT) for loco-regional irradiation of patients after a mastectomy and immediate implant-based reconstruction. Ten breast cancer patients with retropectoral implants were randomly selected for this comparative study. Planning target volumes (PTVs) 1 (the volume between the skin and the implant, plus margin) and 2 (supraclavicular, infraclavicular, and internal mammary nodes, plus margin) were 50 Gy in 25 fractions using a standard technique and HT. The extracted dosimetric data were compared using a 2-tailed Wilcoxon matched-pair signed-rank test. Doses for PTV1 and PTV2 were significantly higher with HT (V95 of 98.91 and 97.91%, respectively) compared with the standard technique (77.46 and 72.91%, respectively). Similarly, the indexes of homogeneity were significantly greater with HT (p = 0.002). HT reduced ipsilateral lung volume that received ≥20 Gy (16.7 vs. 35%), and bilateral lungs (p = 0.01) and neighboring organs received doses that remained well below tolerance levels. The heart volume, which received 25 Gy, was negligible with both techniques. HT can achieve full target coverage while decreasing high doses to the heart and ipsilateral lung. However, the low doses to normal tissue volumes need to be reduced in future studies.

Simplified field-in-field technique for a large-scale implementation in breast radiation treatment.

We wanted to evaluate a simplified "field-in-field" technique (SFF) that was implemented in our department of Radiation Oncology for breast treatment. This study evaluated 15 consecutive patients treated with a simplified field in field technique after breast-conserving surgery for early-stage breast cancer. Radiotherapy consisted of whole-breast irradiation to the total dose of 50 Gy in 25 fractions, and a boost of 16 Gy in 8 fractions to the tumor bed. We compared dosimetric outcomes of SFF to state-of-the-art electronic surface compensation (ESC) with dynamic leaves. An analysis of early skin toxicity of a population of 15 patients was performed. The median volume receiving at least 95% of the prescribed dose was 763 mL (range, 347-1472) for SFF vs. 779 mL (range, 349-1494) for ESC. The median residual 107% isodose was 0.1 mL (range, 0-63) for SFF and 1.9 mL (range, 0-57) for ESC. Monitor units were on average 25% higher in ESC plans compared with SFF. No patient treated with SFF had acute side effects superior to grade 1-NCI scale. SFF created homogenous 3D dose distributions equivalent to electronic surface compensation with dynamic leaves. It allowed the integration of a forward planned concomitant tumor bed boost as an additional multileaf collimator subfield of the tangential fields. Compared with electronic surface compensation with dynamic leaves, shorter treatment times allowed better radiation protection to the patient. Low-grade acute toxicity evaluated weekly during treatment and 2 months after treatment completion justified the pursuit of this technique for all breast patients in our department.

Use of deformable image fusion to allow better definition of tumor bed boost volume after oncoplastic breast surgery.

Although the use of boost irradiation is recommended, the standard technique and definition of the boost volume after oncoplastic surgery have not been clearly established. This multidisciplinary study based on image registration was designed to propose practical solutions for the definition of tumor bed boost in this setting.

Practical use of Gafchromic(®) EBT films in electron beams for in-phantom dose distribution measurements and monitor units verification.

PURPOSE: The possibility of using the Gafchromic(®) EBT films parallel to incident electron beams was assessed in order to facilitate quality assurance tests for electron dose calculation algorithms. MATERIALS AND METHODS: Calibration curves were made for electron energies of 6, 9 and 12MeV. A set-up was suggested for EBT film irradiation parallel to the beam, and the dose measurements were compared to Ionization Chamber (IC) measurements in standard and small electrons beams. A more complex Quality Assurance (QA) set-up was performed with the cylindrical CARPET(®) phantom in order to test our Treatment Planning System (TPS) (Eclipse, Varian Medical Systems, Palo Alto, California) for the clinical situation of a chest wall electron beam therapy. Two dimensional dose distribution and gamma index results were compared to the calculated distribution given by the TPS. RESULTS: The reproducibility was found to be better than 1.5%. We found that applying strong pressure and aligning carefully the film edge with the phantom surface, as recommended for radiographic films, did not completely eliminate the air gap effect. Adding an ultrasound transmission gel and 2 complementary EBT films on the surface gave satisfactory results. The absolute dose for the reference 10×10cm(2) field was always within 1% of IC measurements and for smaller elongated fields (5×10, 4×10 and 3×10cm(2)) the mean difference was -1.4% for the three energies. The mean difference with the IC measurements in R(100), R(90) and R(50) was 0.9mm for all fields and for the three energies. The mean difference in the width of the 90% and the 50% isodoses at R(100) was 0.6mm. With the CARPET(®) phantom set-up very good agreement was found in the 2D dose distribution; 99% of the points satisfied the γ<1 criteria (3%-3mm). CONCLUSION: EBT films parallel to the beam axis could be used for absolute measurements of 2D dose distribution if ultrasound gel and overlying perpendicular films are added on the phantom surface.

Improving the definition of tumor bed boost with the use of surgical clips and image registration in breast cancer patients.

PURPOSE: To evaluate the accuracy of a boost technique. METHODS AND MATERIALS: Twenty-two patients underwent tumorectomy with placement of two or more clips in the surgical cavity before breast remodeling. Preoperative and postoperative computed tomography scans, with match-point registration, were performed on all patients. The relationship between the location of the gross tumor volume (GTV), defined on the preoperative scan, and clip clinical target volume (CTV) (clips with a 5-mm margin on the postoperative scan) was then studied, by use of commercial volume analysis software. RESULTS: Of the patients, 4 had two clips, 2 had three clips, 8 had four clips, and 8 had five clips. The median GTV was 1.06 mL (range, 0.2-5.3 mL); clip CTV ranged from 2.4 to 21.5 mL. Volumetric analysis showed that in 7 cases (32%), there was no intersection between the GTV and the clip CTV, with the following distribution: 4 patients with two clips, 1 patient with three clips, 1 patient with four clips, and 1 patient with five clips. The common contoured volume was defined as the percent ratio between the intersection of the GTV and clip CTV and the GTV. It was found to be significantly increased if three or more clips were used vs. only two clips (common contoured volume, 35.45% vs. 0.73%; p = 0.028). Finally, the GTV and clip CTV volume relationship can be presented as follows: 12.5% to 33% overlap in 8 patients (36.4%), 50% to 75% in 5 patients (22.7%), and greater than 90% in 2 patients (9%). CONCLUSIONS: The use of three or more clips during tumorectomy increases the accuracy of tumor bed delineation.

Simultaneous integrated boost in breast conserving treatment of breast cancer: a dosimetric comparison of helical tomotherapy and three-dimensional conformal radiotherapy.

BACKGROUND AND PURPOSE: To evaluate the dosimetry of helical tomotherapy (HT) and three-dimensional conformal radiotherapy (3D-CRT) in breast cancer patients undergoing whole breast radiation with simultaneous integrated boost (SIB) of the tumor bed. MATERIAL AND METHODS: Thirteen patients with breast cancer treated by lumpectomy and requiring whole breast radiotherapy with tumor bed boost were planned using both HT and 3D-CRT using the field-in-field technique. The whole breast and tumor bed were prescribed 50.68 Gy and 64.4 Gy, respectively, in 28 fractions. Dosimetries for both techniques were compared. RESULTS: Coverage of the whole breast was adequate with both techniques (V(95%)=96.22% vs. 96.25%, with HT and 3D-CRT, respectively; p=0.64). Adequate tumor bed coverage was also achieved, although it was significantly lower with HT (V(95%)=97.18% vs. 99.72%; p<0.001). Overdose of the breast volume outside the tumor bed was significantly lower with HT (V(54.23 Gy)=12.47% vs. 30.83%; p<0.001). Ipsilateral lung V(20 Gy) (6.34% vs. 10.17%; p<0.001), V(5 Gy) (16.54% vs. 18.53%; p<0.05) and mean dose (4.05 Gy vs. 6.36 Gy; p<0.001) were significantly lower with HT. In patients with left-sided tumors, heart V(30 Gy) (0.03% vs. 1.14%; p<0.05) and mean dose (1.35 Gy vs. 2.22 Gy; p<0.01) were significantly lower with HT, but not V(5 Gy). Contralateral breast V(5 Gy) (0.27% vs. 0.00%; p<0.01) and maximum dose were significantly increased with HT. CONCLUSIONS: In breast cancer treated with SIB, both HT and 3D-CRT provided adequate target volume coverage and low heart doses. Tumor bed coverage was slightly lower with HT, but HT avoided unnecessary breast overdosage while improving ipsilateral lung dosimetry.

How to boost the breast tumor bed? A multidisciplinary approach in eight steps.

PURPOSE: To describe a new procedure for breast radiotherapy that will improve tumor bed localization and radiotherapy treatment using a multidisciplinary approach. PATIENTS AND METHODS: This pilot study was conducted by departments of radiation oncology, surgery, and radiology. A new procedure has been implemented, summarized as eight steps: from pre-surgery contrast CT to surgery, tumor bed planning target volume (PTV) determination, and finally breast and tumor bed irradiation. RESULTS: Twenty patients presenting with T1N0M0 tumors were enrolled in the study. All patients underwent lumpectomy with the placement of surgical clips in the tumor bed region. During surgery, 1 to 5 clips were placed in the lumpectomy cavity before the plastic procedure. All patients underwent pre- and postoperative CT scans in the treatment position. The two sets of images were registered with a match-point registration. All volumes were contoured and the results evaluated. The PTV included the clips region, the gross tumor volume, and the surgical scar, with an overall margin of 5-10 mm in all directions, corresponding to localization and setup uncertainties. For each patient the boost PTV was discussed and compared with our standard forward-planned PTV. CONCLUSIONS: We demonstrate the feasibility of a tumor bed localization and treatment procedure that seems adaptable to routine practice. Our study shows the advantages of a multidisciplinary approach for tumor bed localization and treatment. The use of more than 1 clip associated with pre- to postoperative CT image registration allows better definition of the PTV boost volume.

Postmastectomy electron beam chest wall irradiation in women with breast cancer: a clinical step toward conformal electron therapy.

PURPOSE: Electron beam radiotherapy of the chest wall with or without lymph node irradiation has been used at the Institut Curie for >20 years. The purpose of this report was to show the latest improvements of our technique developed to avoid hot spots and improve the homogeneity. METHODS AND MATERIALS: The study was split into two parts. A new electron irradiation technique was designed and compared with the standard one (dosimetric study). The dose distributions were calculated using our treatment planning software ISIS (Technologie Diffusion). The dose calculation was performed using the same calculation parameters for the new and standard techniques. Next, the early skin toxicity of our new technique was evaluated prospectively in the first 25 patients using Radiation Therapy Oncology Group criteria (clinical study). RESULTS: The maximal dose found on the five slices was 53.4 +/- 1.1 Gy for the new technique and 59.1 +/- 2.3 Gy for the standard technique. The hot spots of the standard technique plans were situated at the overlap between the internal mammary chain and chest wall fields. The use of one unique field that included both chest wall and internal mammary chain volumes solved the problem of junction. To date, 25 patients have been treated with the new technique. Of these patients, 12% developed Grade 0, 48% Grade 1, 32% Grade 2, and 8% Grade 3 toxicity. CONCLUSIONS: This report describes an improvement in the standard postmastectomy electron beam technique of the chest wall. This new technique provides improved target homogeneity and conformality compared with the standard technique. This treatment was well tolerated, with a low rate of early toxicity events.

CT-scan based localization of the internal mammary chain and supra clavicular nodes for breast cancer radiation therapy planning.

BACKGROUND AND PURPOSE: To evaluate the influence of the position and the exact localizations of supra clavicular nodes (SCN) and internal mammary chain (IMC) and their variability among patients in order to improve treatment planning in breast cancer (BC) patients. PATIENTS AND METHODS: A total of 46 CT scans of the chest were examined. All patients were female treated with breast conserving surgery and radiotherapy. The study was divided into two phases. The first consisted of measurements on 20 diagnostic CT scans, performed in the supine position with both arms over the head. All patients received contrast. This first phase was performed as a training program for radiologist and radiation oncologist to prepare for the second phase of the study: 26 CT scans in treatment position on angled board without injection. For this second group, patients had one arm raised above the head (treated side) and the other kept by the side (contralateral side). Measurements were performed on both sides to evaluate the influence of the arm position. The depths of IM- and SC vessels were measured at five points: (1) the origin of the internal mammary artery, (2) the sterno-clavicular articulation, (3-5) the first, second and third rib interspaces (RI). Measurements of the depth and of the distance between the internal mammary vessels and the middle axis of the sternum were obtained using electronic calipers on a PACS workstation. RESULTS: There were important individual variations of the depth of SCN, as follows: 20-84 mm (diagnostic) and 19-64 (treatment position). No differences in the depth of the IMC were found between treated and contralateral side at the region of the I, II, and III rib interspaces. The lateral margin of the IMC was never more than 40 mm from the middle axis of the sternum (I, II, III rib interspaces). There was no difference in the lateral limits of IMC (the distance between the IM vessels and the middle axis of the sternum) between the two sides: treated and contralateral. CONCLUSIONS: This study shows the importance of the patients' individual anatomy, their position and the large variability in the depth of SCN. It is important to visualize these regions to permit individual dosimetric optimization.

[A French survey on breast radiotherapy techniques for simulation and treatment]. / Enquête sur les techniques de préparation et de traitement utilisées pour la radiothérapie du sein en France.

Breast radiotherapy is still in progress. The target volumes - whole breast and lymph nodes - are usually located by clinical palpation and the use of bony landmarks. However computed tomography has allowed a better definition of the deep edge of the volumes and the calculation of 3D dose distributions. A survey of 194 centers has started in June 2005 in France. The questionnaire that was sent included questions about general techniques in breast radiotherapy. Preliminary results on 50 centers showed that patient anatomical data were in the vast majority acquired by a simulator-CT or a CT (for 92%). In the 50 departments, beam placement is done either directly at the simulator (20 centers), or on the TPS (16 centers). Virtual simulation software is used in 8 centers. In about 20% (11) radiotherapy departments, 3D target volumes are contoured and the beams adapted to their shapes.

Accurate setup of paraspinal patients using a noninvasive patient immobilization cradle and portal imaging.

Because of the proximity of the spinal cord, effective radiotherapy of paraspinal tumors to high doses requires highly conformal dose distributions, accurate patient setup, setup verification, and patient immobilization. An immobilization cradle has been designed to facilitate the rapid setup and radiation treatment of patients with paraspinal disease. For all treatments, patients were set up to within 2.5 mm of the design using an amorphous silicon portal imager. Setup reproducibility of the target using the cradle and associated clinical procedures was assessed by measuring the setup error prior to any correction. From 350 anterior/posterior images, and 303 lateral images, the standard deviations, as determined by the imaging procedure, were 1.3 m, 1.6 m, and 2.1 in the ant/post, right/left, and superior/inferior directions. Immobilization was assessed by measuring patient shifts between localization images taken before and after treatment. From 67 ant/post image pairs and 49 lateral image pairs, the standard deviations were found to be less than 1 mm in all directions. Careful patient positioning and immobilization has enabled us to develop a successful clinical program of high dose, conformal radiotherapy of paraspinal disease using a conventional Linac equipped with dynamic multileaf collimation and an amorphous silicon portal imager.

CT image-guided intensity-modulated therapy for paraspinal tumors using stereotactic immobilization.

PURPOSE: To design and implement a noninvasive stereotactic immobilization technique with daily CT image-guided positioning to treat patients with paraspinal lesions accurately and to quantify the systematic and random patient setup errors occurring with this method. METHODS AND MATERIALS: A stereotactic body frame (SBF) was developed for "rigid" immobilization of paraspinal patients. The inherent accuracy of this system for stereotactic CT-guided treatment was evaluated with phantom studies. Seven patients with thoracic and lumbar spine lesions were immobilized with the SBF and positioned for 33 treatment fractions using daily CT scans. For all 7 patients, the daily setup errors, as assessed from the daily CT scans, were corrected at each treatment fraction. A retrospective analysis was also performed to assess what the impact on patient treatment would have been without the CT-based corrections (i.e., if patient setup had been performed only with the SBF). RESULTS: The average magnitude of systematic and random errors from uncorrected patient setups using the SBF was approximately 2 mm and 1.5 mm (1 SD), respectively. For fixed phantom targets, the system accuracy for the SBF localization and treatment was shown to be within 1 mm (1 SD) in any direction. Dose-volume histograms incorporating these uncertainties for an intensity-modulated radiotherapy plan for lumbar spine lesions were generated, and the effects on the dose-volume histograms were studied. CONCLUSION: We demonstrated a very accurate and precise method of patient immobilization and treatment delivery based on a noninvasive SBF and daily image guidance for paraspinal lesions. The SBF provides excellent immobilization for paraspinal targets, with setup accuracy better than 2 mm (1 SD). However, for highly conformal paraspinal treatments, uncorrected systematic and random errors of 2 mm in magnitude can result in a significantly greater (>100%) dose to the spinal cord than planned, even though the planned target coverage may not change substantially. With daily CT guidance using the SBF, we showed that the maximal spinal cord dose is ensured to be within 10-15% of the planned value.