Clinical outcomes of stereotactic body radiotherapy for stage I non-small cell lung cancer using different doses depending on tumor size

Background

FDG-PET/CT imaging has an emerging role in staging and treatment planning of various tumor locations and a number of literature studies show that also the carcinoma of the anal canal may benefit from this diagnostic approach. We analyzed the potential impact of FDG-PET/CT in stage definition and target volume delineation of patients affected by carcinoma of the anal canal and candidates for curative radiotherapy.

Methods

Twenty seven patients with biopsy proven anal carcinoma were enrolled. Pathology was squamous cell carcinoma in 20 cases, cloacogenic carcinoma in 3, adenocarcinoma in 2, and basal cell carcinoma in 2. Simulation was performed by PET/CT imaging with patient in treatment position. Gross Tumor Volume (GTV) and Clinical Target Volume (CTV) were drawn on CT and on PET/CT fused images. PET-GTV and PET-CTV were respectively compared to CT-GTV and CT-CTV by Wilcoxon rank test for paired data.

Results

PET/CT fused images led to change the stage in 5/27 cases (18.5%): 3 cases from N0 to N2 and 2 from M0 to M1 leading to change the treatment intent from curative to palliative in a case. Based on PET/CT imaging, GTV and CTV contours changed in 15/27 (55.6%) and in 10/27 cases (37.0%) respectively. PET-GTV and PET-CTV resulted significantly smaller than CT-GTV (p = 1.2 × 10^-4) and CT-CTV (p = 2.9 × 10^-4). PET/CT-GTV and PET/CT-CTV, that were used for clinical purposes, were significantly greater than CT-GTV (p = 6 × 10^-5) and CT-CTV (p = 6 × 10^-5).

Conclusions

FDG-PET/CT has a potential relevant impact in staging and target volume delineation of the carcinoma of the anal canal. Clinical stage variation occurred in 18.5% of cases with change of treatment intent in 3.7%. The GTV and the CTV changed in shape and in size based on PET/CT imaging.     

Impact of CT and 18F-deoxyglucose positron emission tomography image fusion for conformal radiotherapy in esophageal carcinoma

PURPOSE: To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiotherapy planning for esophageal carcinoma patients. METHODS AND MATERIALS: Thirty-four esophageal carcinoma patients were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same treatment position. PET images were coregistered using five fiducial markers. Target delineation was initially performed on CT images, and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume. RESULTS: (18)F-fluorodeoxy-D-glucose-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative conformal radiotherapy. The gross tumor volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and increased in 7 patients (21%). The GTV reduction was > or =25% in 4 patients owing to a reduction in the length of the esophageal tumor. The GTV increase was > or =25% with FDG-PET in 2 patients owing to the detection of occult mediastinal lymph node involvement in 1 patient and an increased length of the esophageal tumor in 1 patient. Modifications of the GTV affected the planning treatment volume in 18 patients. Modifications of the delineation of the GTV and displacement of the isocenter of the planning treatment volume by FDG-PET also affected the percentage of total lung volume receiving >20 Gy in 25 patients (74%), with a dose reduction in 12 patients and dose increase in 13. CONCLUSION: In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of esophageal carcinoma. The affect on treatment outcome remains to be demonstrated.     

Impact of computed tomography (CT) and 18F-deoxyglucose positron emission tomography (FDG-PET) image fusion for conformal radiotherapy in esophageal carcinoma]

PURPOSE: To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiation therapy (CRT) planning for patients with esophageal carcinoma. PATIENTS AND METHODS: Thirty-four patients with esophageal carcinoma were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. PET-images were coregistered using five fiducial markers. Target delineation was initially performed on CT images and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative CRT. The Gross Tumor Volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and was increased in 7 patients (20.5%). The GTV reduction was >or=25% in 4 patients due to reduction of the length of the esophageal tumor. The GTV increase was >or=25% with FDG-PET in 2 patients due to the detection of occult mediastinal lymph node involvement in one patient and an increased length of the esophageal tumor in the other patient. Modifications of the GTV affected the planning treatment volume (PTV) in 18 patients. Modifications of delineation of GTV and displacement of the isocenter of PTV by FDG-PET also affected the percentage of total lung volume receiving more than 20 Gy (VL20) in 25 patients (74%), with a dose reduction in 12 patients and a dose increase in 13 patients. CONCLUSION: In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of patients with esophageal carcinoma related to modifications of GTV. The impact on treatment outcome remains to be demonstrated.     

PET-CT在三维适形放射治疗晚期胰腺癌中的应用

目的:评价PET-CT在三维适形放射治疗晚期胰腺癌中靶区勾画的价值及放疗后评价疗效的意义。方法:对13例晚期胰腺癌患者,采用PET-CT检查并定位,分别勾画出大体肿瘤体积CT-GTV和PET-CT-GTV,并分别制定出三维适形放射治疗的GTV进行比较。放疗后3个月行PET-CT复查。结果:13例患者的PET-CT-GTV和CT-GTV均不同,其中5例患者PET-CT-GTV较CT-GTV平均减少10.9cm3(25.7%)。CT-GTV平均42.4 cm3,PET-CT-GTV平均为31.5cm3(P=0.0045);8例患者的PET-CT-GTV较CT-GTV增加45.3%(27.4 cm3),CT-GTV平均为60.4 cm3,PET-CT-GTV平均为87.8 cm3(P=0.0000)。治疗后3个月PET-CT复查示:7例胰腺病灶较前明显缩小,局部FDG代谢明显减低或消失。其余6例病灶略缩小,FDG不同程度减低。治疗后的SUVmax变化范围为1.6-6.0,SUVmean变化范围为1.4-2.2。结论:采用PET-CT融合图像能够更好地提高靶区确定的精度及不确定性,最大限度减少不同勾画者之间的差异性。治疗前后局部病灶代谢活性的不同程度改变,对评价放疗疗效具有一定的指导意义。     

Image fusion between 18FDG-PET and MRI/CT for radiotherapy planning of oropharyngeal and nasopharyngeal carcinomas

PURPOSE: Accurate diagnosis of tumor extent is important in three-dimensional conformal radiotherapy. This study reports the use of image fusion between (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG-PET) and magnetic resonance imaging/computed tomography (MRI/CT) for better targets delineation in radiotherapy planning of head-and-neck cancers. METHODS AND MATERIALS: The subjects consisted of 12 patients with oropharyngeal carcinoma and 9 patients with nasopharyngeal carcinoma (NPC) who were treated with radical radiotherapy between July 1999 and February 2001. Image fusion between 18FDG-PET and MRI/CT was performed using an automatic multimodality image registration algorithm, which used the brain as an internal reference for registration. Gross tumor volume (GTV) was determined based on clinical examination and 18FDG uptake on the fusion images. Clinical target volume (CTV) was determined following the usual pattern of lymph node spread for each disease entity along with the clinical presentation of each patient. RESULTS: Except for 3 cases with superficial tumors, all the other primary tumors were detected by 18FDG-PET. The GTV volumes for primary tumors were not changed by image fusion in 19 cases (89%), increased by 49% in one NPC, and decreased by 45% in another NPC. Normal tissue sparing was more easily performed based on clearer GTV and CTV determination on the fusion images. In particular, parotid sparing became possible in 15 patients (71%) whose upper neck areas near the parotid glands were tumor-free by 18FDG-PET. Within a mean follow-up period of 18 months, no recurrence occurred in the areas defined as CTV, which was treated prophylactically, except for 1 patient who experienced nodal recurrence in the CTV and simultaneous primary site recurrence. CONCLUSION: This preliminary study showed that image fusion between 18FDG-PET and MRI/CT was useful in GTV and CTV determination in conformal RT, thus sparing normal tissues.     

Comparison of five segmentation tools for 18F-fluoro-deoxy-glucose-positron emission tomography-based target volume definition in head and neck cancer

PURPOSE: Target-volume delineation for radiation treatment to the head and neck area traditionally is based on physical examination, computed tomography (CT), and magnetic resonance imaging. Additional molecular imaging with (18)F-fluoro-deoxy-glucose (FDG)-positron emission tomography (PET) may improve definition of the gross tumor volume (GTV). In this study, five methods for tumor delineation on FDG-PET are compared with CT-based delineation. METHODS AND MATERIALS: Seventy-eight patients with Stages II-IV squamous cell carcinoma of the head and neck area underwent coregistered CT and FDG-PET. The primary tumor was delineated on CT, and five PET-based GTVs were obtained: visual interpretation, applying an isocontour of a standardized uptake value of 2.5, using a fixed threshold of 40% and 50% of the maximum signal intensity, and applying an adaptive threshold based on the signal-to-background ratio. Absolute GTV volumes were compared, and overlap analyses were performed. RESULTS: The GTV method of applying an isocontour of a standardized uptake value of 2.5 failed to provide successful delineation in 45% of cases. For the other PET delineation methods, volume and shape of the GTV were influenced heavily by the choice of segmentation tool. On average, all threshold-based PET-GTVs were smaller than on CT. Nevertheless, PET frequently detected significant tumor extension outside the GTV delineated on CT (15-34% of PET volume). CONCLUSIONS: The choice of segmentation tool for target-volume definition of head and neck cancer based on FDG-PET images is not trivial because it influences both volume and shape of the resulting GTV. With adequate delineation, PET may add significantly to CT- and physical examination-based GTV definition.     

PET-CT在三维适形放射治疗晚期胰腺癌中的应用

目的：评价PET-CT在三维适形放射治疗晚期胰腺癌中靶区勾画的价值及放疗后评价疗效的意义。方法：对13例晚期胰腺癌患者,采用PET-CT检查并定位,分别勾画出大体肿瘤体积CT-GTV和PET-CT-GTV,并分别制定出三维适形放射治疗的GTV进行比较。放疗后3个月行PET-CT复查。结果：13例患者的PET-CT-GTV和CT-GTV均不同,其中5例患者PET-CT-GTV较CT-GTV平均减少10.9cm3（25.7%）。CT-GTV平均42.4 cm3,PET-CT-GTV平均为31.5cm3（P=0.0045）;8例患者的PET-CT-GTV较CT-GTV增加45.3%（27.4 cm3）,CT-GTV平均为60.4 cm3,PET-CT-GTV平均为87.8 cm3（P=0.0000）。治疗后3个月PET-CT复查示：7例胰腺病灶较前明显缩小,局部FDG代谢明显减低或消失。其余6例病灶略缩小,FDG不同程度减低。治疗后的SUVmax变化范围为1.6-6.0,SUVmean变化范围为1.4-2.2。结论：采用PET-CT融合图像能够更好地提高靶区确定的精度及不确定性,最大限度减少不同勾画者之间的差异性。治疗前后局部病灶代谢活性的不同程度改变,对评价放疗疗效具有一定的指导意义。     

The utility of multimodality imaging with CT and MRI in defining rectal tumour volumes for radiotherapy treatment planning: a pilot study

Aims: This study compares the volumetric and spatial relationships of gross tumour volume (GTV) derived from CT (CT-GTV) and GTV derived from MRI (MR-GTV) to determine the utility of multi-modality imaging for radiotherapy treatment planning in rectal cancer. Methods and Materials: Fifteen patients with T3 rectal cancer were accrued over 18 months. The male : female ratio was 2:1. The average age was 60.3 years (range 38–79). All patients underwent a diagnostic MRI and CT and MRI simulation. Data sets were co-registered. A site specialised diagnostic radiologist contoured all volumes in consultation with a radiation oncologist. CT-GTV was contoured while blinded to MR data sets. MR-GTV was contoured independently 2–4 weeks later whilst blinded to its respective CT-GTV data. Tumour volumes were analysed for three anatomical subregions (sigmoid, rectal and anal). Reference points on tumour volumes were used for spatial comparison and analysis. Results: The mean CT-GTV/MR-GTV ratio was 1.2 (range 0.5–2.9). The tumour volume ratios for the rectal subregion were well correlated. CT-GTV provided adequate spatial coverage of tumour in reference to MR-GTV with the average mean discrepancy of 0.12 (range −0.08–0.38) or a maximum discrepancy of <0.4 cm (1.54 standard deviation). CT-GTV coverage was inadequate for tumours with MRI evidence of anal and sigmoid invasion. Conclusions: Conventional simulation CT imaging provided a reasonable estimate of the GTV. Multi-modality imaging with staging MRI can assist target volume definition where there is involvement of the sigmoid and anorectal region and avoid geographic misses. The role of a simulation MRI may aid in this process but remains investigational.     

PET/CT对非小细胞肺癌临床分期及精确放疗计划的影响

目的 观察PET／CT对非小细胞肺癌（NSCLC）临床分期和靶区勾画的作用,探讨PET／CT对其精确放疗计划的影响。方法 对拟行根治性放疗或手术治疗的58例确诊的NSCLC患者进行PET／CT检查。参照1997年WHO肺癌分期标准,判定PET／CT对NSCLC临床分期的影响,再分别以CT图像、PET／CT融合图像勾画大体靶区（GTV）,以相同参数制定三维适形放疗（3D-CRT）计划。选择GTV体积（V GTV）、受照量≥20Gy的肺占全肺体积的比例（V20）、平均全肺受照剂量（MLD）、肿瘤控制概率（TCP）、正常组织并发症概率（NTCP）、脊髓受照剂量（Ds）等指标进行统计学对比研究,评价两个计划的优劣,分析PET／CT对NSCLC精确放疗计划的影响。结果 PET／CT使21例（36．2％）的临床分期发生改变,其中分期升高者14例,下降者7例,使16例（27．6％）的治疗计划因而发生改变,32例手术患者中,术后病理结果与PET／CT分期一致者29例,假阴性1例,假阳性2例;PET／CT分期的敏感性为96．9％,准确性为90．6％。由PET／CT与由CT制定的放疗计划的VGTV、V20和MLD之间的差异均有统计学意义（P均〈0．01）,前者小于后者,而Ds、TCP、NTCP（左肺、右肺、皮肤、脊髓）的差异无统计学意义（P〉0．05）。结论 PET／CT对NSCLCS临床分期与术后病理分期的符合率高。应用PET／CT勾画靶区,在伴有肺不张和阻塞性肺炎时可明显减小GTV,可更好地保护周围正常肺组织;PET／CT检测纵隔淋巴结敏感性较CT高,可避免靶区遗漏。PET／CT可明显减小V20和MLD,从而有效地减少放射性肺炎的发生。PET／CT可在保证Ds、TCP和NTCP符合临床要求的前提下,更精确地确定NSCLC放疗靶区和制定放疗计划。     

Impact of computed tomography (CT) and 18F-deoxyglucose-coincidence detection emission tomography (FDG-CDET) image fusion for optimisation of conformal radiotherapy in non-small-cell lung cancers]

To report a retrospective study concerning the impact of fused 18F-fluorodeoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on three-dimensional conformal radiation therapy (3D-CRT) planning for patients with non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: One hundred and one patients consecutively treated for stages I-III NSCLC were studied. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. Images were coregistered using five fiducial markers. Target volume delineation was initially performed on the CT images and the corresponding FDG-PET data were subsequently used as an overlay to the CT data to define target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 8 patients making them ineligible for curative CRT (one patient presented some positive uptakes corresponding to concomitant pulmonary tuberculosis). Another patient was ineligible for curative treatment because fused CT/PET images demonstrated excessively extensive intrathoracic disease. The gross tumor volume (GTV) was decreased by CT/PET image fusion in 21 patients (23%) and was increased in 24 patients (26%). The GTV reduction was > or = 25% in 7 patients because CT/PET image fusion reduced pulmonary GTV in 6 patients (3 patients with atelectasis) and mediastinal nodal GTV in 1 patient. The GTV increase was > or = 25% in 14 patients due to an increase of the pulmonary GTV in 11 patients (4 patients with atelectasis) and detection of occult mediastinal lymph node involvement in 3 patients. Among 81 patients receiving a total dose > or = 60 Gy at ICRU point, after CT/PET image fusion, the percentage of total lung volume receiving more than 20 Gy (VL20) increased in 15 cases and decreased in 22 cases. The percentage of total heart volume receiving more than 36 Gy increased in 8 patients and decreased in 14 patients. The spinal cord volume receiving at least 45 Gy (2 patients) decreased. After multivariate analysis, one single independent factor made significant effect of FDG/PET on the modification of the size of the GTV: tumor with atelectasis (P = 0.0001). Conclusion. - Our study confirms that integrated hybrid PET/CT in the treatment position and coregistered images have an impact on treatment planning and management of patients with NSCLC. FDG images using dedicated PET scanners with modern image fusion techniques and respiration-gated acquisition protocols could improve CT/PET image coregistration. However, prospective studies with histological correlation are necessary and the impact on treatment outcome remains to be demonstrated.     

Impact of computed tomography and F-deoxyglucose coincidence detection emission tomography image fusion for optimization of conformal radiotherapy in non–small-cell lung cancer

PURPOSE: To report a retrospective study concerning the impact of fused 18F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and CT images on three-dimensional conformal radiotherapy planning for patients with non-small-cell lung cancer. METHODS AND MATERIALS: A total of 101 patients consecutively treated for Stage I-III non-small-cell lung cancer were studied. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same treatment position. Images were coregistered using five fiducial markers. Target volume delineation was initially performed on the CT images, and the corresponding FDG-PET data were subsequently used as an overlay to the CT data to define the target volume. RESULTS: 18F-fluoro-deoxy-D-glucose-PET identified previously undetected distant metastatic disease in 8 patients, making them ineligible for curative conformal radiotherapy (1 patient presented with some positive uptake corresponding to concomitant pulmonary tuberculosis). Another patient was ineligible for curative treatment because the fused PET-CT images demonstrated excessively extensive intrathoracic disease. The gross tumor volume (GTV) was decreased by CT-PET image fusion in 21 patients (23%) and was increased in 24 patients (26%). The GTV reduction was > or = 25% in 7 patients because CT-PET image fusion reduced the pulmonary GTV in 6 patients (3 patients with atelectasis) and the mediastinal nodal GTV in 1 patient. The GTV increase was > or = 25% in 14 patients owing to an increase in the pulmonary GTV in 11 patients (4 patients with atelectasis) and detection of occult mediastinal lymph node involvement in 3 patients. Of 81 patients receiving a total dose of > or = 60 Gy at the International Commission on Radiation Units and Measurements point, after CT-PET image fusion, the percentage of total lung volume receiving >20 Gy increased in 15 cases and decreased in 22. The percentage of total heart volume receiving >36 Gy increased in 8 patients and decreased in 14. The spinal cord volume receiving at least 45 Gy (2 patients) decreased. Multivariate analysis showed that tumor with atelectasis was the single independent factor that resulted in a significant effect on the modification of the size of the GTV by FDG-PET: tumor with atelectasis (with vs. without atelectasis, p = 0.0001). CONCLUSION: The results of our study have confirmed that integrated hybrid PET/CT in the treatment position and coregistered images have an impact on treatment planning and management of non-small-cell lung cancer. However, FDG images using dedicated PET scanners and respiration-gated acquisition protocols could improve the PET-CT image coregistration. Furthermore, the impact on treatment outcome remains to be demonstrated.     

Target Volume Definition in Rectal Cancer: What Is the Best Imaging Modality?

All patients with rectal cancer should undergo an accurate preoperative staging, including local staging for tumour extension and reliable staging for synchronous distant metastases. Imaging is of utmost importance as a basis for selecting the optimal treatment strategies and as an aid for precise target delineation. Anatomical imaging such as computed tomography (CT) and magnetic resonance imaging (MRI) have been the most commonly used pretreatment staging modalities, whereas endorectal ultrasonography may be useful for staging of smaller tumours (T2 or lower). MRI is the most accurate imaging technique for staging of T3 and T4 tumours. The role of fluorodeoxyglucose positron emission tomography (PET)/CT is under investigation, and diffusion-weighted MRI seems promising for prediction of pathological complete response. For target delineation, planning CT, preferably contrast-enhanced, is the most used imaging technique. For locally advanced tumours, coregistration with MRI or PET/CT may prove to be useful. In this article, the literature published on target delineation in rectal cancer radiotherapy is evaluated, with focus on the best imaging modality for volume definition and radiotherapy planning.     

The Application of Positron Emission Tomography/Computed Tomography in Radiation Treatment Planning: Effect on Gross Target Volume Definition and Treatment Management

AimsTo analyse the effect of the use of molecular imaging on gross target volume (GTV) definition and treatment management.Materials and methodsFifty patients with various solid tumours who underwent positron emission tomography (PET)/computed tomography (CT) simulation for radiotherapy planning from 2006 to 2008 were enrolled in this study. First, F-18 fluorodeoxyglucose (FDG)-PET and CT scans of the treatment site in the treatment position and then a whole body scan were carried out with a dedicated PET/CT scanner and fused thereafter. FDG-avid primary tumour and lymph nodes were included into the GTV. A multidisciplinary team defined the target volume, and contouring was carried out by a radiation oncologist using visual methods. To compare the PET/CT-based volumes with CT-based volumes, contours were drawn on CT-only data with the help of site-specific radiologists who were blind to the PET/CT results after a median time of 7 months.ResultsIn general, our PET/CT volumes were larger than our CT-based volumes. This difference was significant in patients with head and neck cancers. Major changes (≥25%) in GTV delineation were observed in 44% of patients. In 16% of cases, PET/CT detected incidental second primaries and metastatic disease, changing the treatment strategy from curative to palliative.ConclusionsIntegrating functional imaging with FDG-PET/CT into the radiotherapy planning process resulted in major changes in a significant proportion of our patients. An interdisciplinary approach between imaging and radiation oncology departments is essential in defining the target volumes.     

Comparison of CT- and FDG-PET-defined gross tumor volume in intensity-modulated radiotherapy for head-and-neck cancer

PURPOSE: To compare the gross tumor volume (GTV) identified on CT to that obtained from fluorodeoxyglucose (FDG) positron emission tomography (PET) and determine the differences in volume and dose coverage of the PET-GTV when the CT-GTV is used for radiotherapy planning. METHODS AND MATERIALS: A total of 40 patients with intact squamous cell carcinoma arising in the head-and-neck region underwent intensity-modulated radiotherapy (IMRT) at one department. All patients underwent CT simulation for treatment planning followed by PET-CT in the treatment position. CT simulation images were fused to the CT component of the PET-CT images. The GTV using the CT simulation images was contoured (CT-GTV), as was the GTV based on the PET scan (PET-GTV). The IMRT plans were obtained using the CT-GTV. RESULTS: The PET-GTV was smaller, the same size, and larger than the CT-GTV in 30 (75%), 3 (8%), and 7 (18%) cases respectively. The median PET-GTV and CT-GTV volume was 20.3 cm(3) (range, 0.2-294) and 37.2 cm(3) (range, 2-456), respectively. The volume of PET-GTV receiving at least 95% of the prescribed dose was 100% in 20 (50%), 95-99% in 10 (25%), 90-94% in 3 (8%), 85-89% in 1 (3%), 80-84% in 2 (5%), 75-79% in 1 (3%), and <75% in 3 (8%) cases. The minimal dose received by 95% of the PET-GTV was >/=100% in 19 (48%), 95-99% in 11 (28%), 90-94% in 5 (13%), 85-89% in 2 (5%), and <75% in 3 (8%) cases. CONCLUSION: The PET-GTV was larger than the CT-GTV in 18% of cases. In approximately 25% of patients with intact head-and-neck cancer treated using IMRT, the volume of PET-GTV receiving at least 95% of the prescribed dose and minimal dose received by 95% of the PET-GTV were less than optimal.     

Radiation treatment planning with an integrated positron emission and computer tomography (PET/CT): a feasibility study

PURPOSE: To investigate the usefulness of hardware coregistered PET/CT images for target volume definition. METHODS AND MATERIALS: Thirty-nine patients presenting with various solid tumors were investigated. CT and a FDG-PET were obtained in treatment position in an integrated PET/CT scanner, and coregistered images were used for treatment planning. First, volume delineation was performed on the CT data. In a second step, the corresponding PET data were used as an overlay to the CT data to define the target volume. Delineation was done independently by two investigators. RESULTS: Coregistered PET/CT showed good fusion accuracy. The GTV increased by 25% or more because of PET in 17% of cases with head-and-neck (2/12) and lung cancer (1/6), and in 33% (7/21) in cancer of the pelvis. The GTV was reduced > or =25% in 33% of patients with head-and-neck cancer (4/12), in 67% with lung cancer (4/6), and 19% with cancer of the pelvis (4/21). Overall, in 56% (22/39) of cases, GTV delineation was changed significantly if information from metabolic imaging was used in the planning process. The modification of the GTV translated into altered PTV changes exceeding >20% in 46% (18/39) of cases. With PET, volume delineation variability between two independent oncologists decreased from a mean volume difference of 25.7 cm(3) to 9.2 cm(3) associated with a reduction of the standard deviation from 38.3 cm(3) to 13.3 cm(3) (p = 0.02). In 16% of cases, PET/CT revealed distant metastasies, changing the treatment strategy from curative to palliative. CONCLUSION: Integrated PET/CT for treatment planning for three-dimensional conformal radiation therapy improves the standardization of volume delineation compared with that of CT alone. PET/CT has the potential for reducing the risk for geographic misses, to minimize the dose of ionizing radiation applied to non-target organs, and to change the current practice to three-dimensional conformal radiation therapy planning by taking into account the metabolic and biologic features of cancer. The impact on treatment outcome remains to be demonstrated.     

Impact of integrated PET/CT on variability of target volume delineation in rectal cancer

Several studies have demonstrated substantial variability among individual radiation oncologists in defining target volumes using computed tomography (CT). The objective of this study was to determine the impact of combined positron emission tomography and computed tomography (PET/CT) on inter-observer variability of target volume delineation in rectal cancer. We also compared the relative concordance of two PET imaging tracers, 18F-fluorodeoxyglucose (FDG) and 18F-fluorodeoxythymidine (FLT), against conventional computed tomography (CT). Six consecutive patients with locally advanced rectal cancer were enrolled onto an institutional protocol involving preoperative chemoradiotherapy and correlative studies including FDG- and FLT-PET scans acquired in the treatment position. Using these image data sets, four radiation oncologists independently delineated primary and nodal gross tumor volumes (GTVp and GTVn) for a hypothetical boost treatment. Contours were first defined based on CT alone with observers blinded to the PET images, then based on combined PET/CT. An inter-observer similarity index (SI), ranging from a value of 0 for complete disagreement to 1 for complete agreement of contoured voxels, was calculated for each set of volumes. For primary gross tumor volume (GTVp), the difference in estimated SI between CT and FDG was modest (CT SI = 0.77 vs. FDG SI = 0.81), but statistically significant (p = 0.013). The SI difference between CT and FLT for GTVp was also slight (FLT SI = 0.80) and marginally non-significant (p < 0.082). For nodal gross tumor volume, (GTVn), SI was significantly lower for CT based volumes with an estimated SI of 0.22 compared to an estimated SI of 0.70 for FDG-PET/CT (p < 0.0001) and an estimated SI of 0.70 for FLT-PET/CT (p < 0.0001). Boost target volumes in rectal cancer based on combined PET/CT results in lower inter-observer variability compared with CT alone, particularly for nodal disease. The use of FDG and FLT did not appear to be different from this perspective.     

FDG PET对非小细胞肺癌合并肺不张三维适形放疗时靶区确定的临床意义

目的 探讨^18F-脱氧葡萄糖（FDG）PET对合并肺不张的非小细胞肺癌（NSCLC）行三维适形放疗时病变靶区确定的临床意义。方法 对14例经病理组织学证实为NSCLC且其影像学检查伴有不同程度肺不张者，先后行胸部增强明扫描及胸部或全身FDGP盯肿瘤显像。根据扫描及显像结果勾画原发病灶范围，分别称为CT-GTV和PET-GTV，并由CMS治疗计划系统给出GTV体积的具体数值加以比较。结果 全部患者的CT-GTV与PET-GTV均有不同程度差别，其中1例患者PET-GTV较CT-GTV增加16．9％（22cm^3），CT-GTV为130cm3，PET-G11V为152cm^3；13例患者PET-GTV较CT-GTV平均减少20．4％（27．2cm^3），CT-GTV平均为133cm^3（90-180cm^3），PET-GTV平均为106cm^3（60—153cm^3）（P=0．000）。GTV的减少主要原因是PET显像除外了因肿瘤原因造成的肺不张，从而引起靶区范围的缩小，进而避免对周围正常组织（主要是正常或不张的肺组织、脊髓及心血管）的不必要照射，最大限度地保护了正常组织。结论 FDG PET在确定肺不张与局部病变相互关系方面具有一定临床价值，并由此提高了靶区定位的精确性。     

病例为基础的局部晚期NSCLC靶区勾画共识与争议

目的 分析局部晚期NSCLC靶区勾画中的专家共识与争议。方法 调查国内12家单位对NSCLC靶区勾画相关15个问题意见。由复旦大学附属肿瘤医院选择1份局部晚期NSCLC病例,将定位CT图像和病史资料发送至12家单位,各单位自行组织讨论并委派1位医师在第六届肿瘤精准放化疗暨肺癌多学科高峰论坛上主讲对该病例靶区勾画情况及理论认识,参会专家共同讨论。结果 12家单位全部填写问卷并按时发回。肺癌靶区勾画标准肺窗的窗宽/窗位为800~1600/-600~-750 HU,纵隔窗为350~400/20~40 HU。呼吸动度的测量:经验外扩2~5 mm、模拟定位机测定、四维CT测定、模拟定位机+四维CT测定。GTV外扩CTV距离:原发灶鳞癌5~6 mm、腺癌5~8 mm;纵隔淋巴结转移灶6家单位采用5 mm,6家单位采用同原发病灶一致距离。摆位误差:10家单位5 mm、1家单位3 mm、1家单位4~6 mm。双肺V₂₀限定:10家单位<30%、1家单位<35%、1家单位<28%。局部晚期NSCLC同步放化疗放疗剂量:9家单位60 Gy分30次、1家单位62.7 Gy分33次、1家单位50~60 Gy分25~30次、1家单位60~70 Gy分25~30次。肺内原发病灶靶区勾画:3家GTV→IGTV→PTV、8家GTV→CTV→ITV→PTV、1家GTV→CTV→PTV或GTV→IGTV→CTV→PTV;纵隔淋巴结转移灶靶区勾画:3家GTV→IGTV→PTV、8家GTV→CTV→ITV→PTV、1家GTV→CTV→PTV。放疗过程中10%~100%患者需要改野,38~50 Gy时改野合适。关于PET-CT定位及靶区勾画SUV值尚无统一标准,7家单位已开展MRI定位,10家单位已开展了SBRT治疗早期NSCLC。早期NSCLC (T_1-2N₀M₀)的SBRT靶区勾画:5家单位GTV→IGTV→PTV、3家单位IGTV→PTV、2家单位GTV→CTV→ITV→PTV。周围型早期NSCLC分割6.0~12.5 Gy/次,3~12次;中央型早期NSCLC分割4.6~10.0 Gy/次,5~10次。靶区勾画讨论结果:肺癌靶区勾画目前应采用4DCT或模拟机测定呼吸动度;勾画肺癌靶区时CT肺窗的窗宽/窗位为1600/-600 HU,纵隔窗为400/20 HU;争议主要是纵隔转移淋巴结CTV_nd为累及野照射还是选择性淋巴结预防照射。结论 对局部晚期NSCLC靶区勾画的CT的窗宽、窗位,呼吸运动和摆位误差测量、原发灶靶区勾画方法、同步放化疗放疗剂量及改野时机均已基本达成共识。主要争议和尚未达成共识的是PET-CT定位勾画靶区时显示病灶的最佳SUV值、SBRT治疗早期NSCLC最佳剂量分割模式、CTV_nd的勾画。     

Marges dans le cancer pulmonaire : volume cible interne/volume cible anatomoclinique

The aim of this study was to carry out a review of margins that should be used for the delineation of target volumes in lung cancer, with a focus on margins from gross tumour volume (GTV) to clinical target volume (CTV) and internal target volume (ITV) delineation. Our review was based on a PubMed literature search with, as a cornerstone, the 2010 European Organisation for Research and Treatment of Cancer (EORTC) recommandations by De Ruysscher et al. The keywords used for the search were: radiotherapy, lung cancer, clinical target volume, internal target volume. The relevant information was categorized under the following headings: gross tumour volume definition (GTV), CTV–GTV margin (first tumoural CTV then nodal CTV definition), in field versus elective nodal irradiation, metabolic imaging role through the input of the PET scanner for tumour target volume and limitations of PET-CT imaging for nodal target volume definition, postoperative radiotherapy target volume definition, delineation of target volumes after induction chemotherapy; then the internal target volume is specified as well as tumoural mobility for lung cancer and respiratory gating techniques. Finally, a chapter is dedicated to planning target volume definition and another to small cell lung cancer. For each heading, the most relevant and recent clinical trials and publications are mentioned.     

Clinical validation of FDG-PET/CT in the radiation treatment planning for patients with oesophageal cancer

BackgroundThe aim of this prospective study was to determine the proportion of locoregional recurrences (LRRs) that could have been prevented if radiotherapy treatment planning for oesophageal cancer was based on PET/CT instead of CT.Materials and methodsNinety oesophageal cancer patients, eligible for high dose (neo-adjuvant) (chemo)radiotherapy, were included. All patients underwent a planning FDG-PET/CT-scan. Radiotherapy target volumes (TVs) were delineated on CT and patients were treated according to the CT-based treatment plans. The PET images remained blinded. After treatment, TVs were adjusted based on PET/CT, when appropriate. Follow up included CT-thorax/abdomen every 6 months. If LRR was suspected, a PET/CT was conducted and the site of recurrence was compared to the original TVs. If the LRR was located outside the CT-based clinical TV (CTV) and inside the PET/CT-based CTV, we considered this LRR possibly preventable.ResultsBased on PET/CT, the gross tumour volume (GTV) was larger in 23% and smaller in 27% of the cases. In 32 patients (36%), >5% of the PET/CT-based GTV would be missed if the treatment planning was based on CT. The median follow up was 29 months. LRRs were seen in 10 patients (11%). There were 3 in-field recurrences, 4 regional recurrences outside both CT-based and PET/CT-based CTV and 3 recurrences at the anastomosis without changes in TV by PET/CT; none of these recurrences were considered preventable by PET/CT.ConclusionNo LRR was found after CT-based radiotherapy that could have been prevented by PET/CT. The value of PET/CT for radiotherapy seems limited.