Evaluation of the dose variation for prostate heavy charged particle therapy using four-dimensional computed tomography.

We quantified dose variation effects due to respiratory-induced intrafractional motion in conventional carbon-ion prostate treatment by using four-dimensional computed tomography (4DCT). 4DCT scans of 20 patients were acquired under free-breathing conditions using a 256 multi-slice CT scanner. The clinical target volume (CTV) was defined as the prostate and the seminal vesicle. Two types of planning target volumes (PTVs) were defined to minimize excessive dose to the rectum. The first PTV (= PTV1) was calculated by adding a 3D uniform margin to the CTV. The second PTV (= PTV2) was cut in a straight line from the top surface of the rectum from PTV1. Compensating boli were designed for the respective PTVs at the peak-exhalation phase, and carbon-ion dose distributions for a single respiratory cycle were calculated using these boli. Dose conformation to prostate, CTV, PTV1 and PTV2 were unchanged for all respiratory phases. The dose for >95% volume irradiation (D95) was 97.7% for prostate, 92.5% for CTV, 74.1% for PTV1 and 96.1% for PTV2 averaged over all patients. The rectum volume at inhalation phase receiving ≤50% of the prescribed dose was smaller than the planning dose due to the abdominal thickness variation. The target dose is not affected by intrafractional respiration in carbon-ion prostate treatment. Small dose variations, however, were observed due to respiratory-induced abdominal thickness variation; therefore the geometrical changes should be considered for prostate particle therapy.

Imaging characteristics of metastatic chordoma.

PURPOSE: Our aim was to describe the incidence and sites of metastatic chordomas and show their characteristic computed tomography (CT) and magnetic resonance (MR) findings. MATERIALS AND METHODS: One hundred ninety-eight chordoma patients were registered in the institutional database and were followed up with CT and MR examinations for periods ranging from 1 to 158 months. Clinical features and CT and MR findings of metastatic chordomas were analyzed by two radiologists. RESULTS: We counted 86 metastatic sites in 49 of 198 patients. The incidence of metastasis was 24.7 %. Sites of metastases were bone, lung, liver, lymph node, muscle, skin, pleura, cerebellum, cardiac muscle, pericardium, and adrenal gland. Duration from the diagnosis to the first detection of metastasis ranged from 0 to 600 months, with an average of 45.0 months. Osteolytic lesions were most common bone metastases, but osteosclerotic metastasis was also encountered. Metastatic chordoma showed very high intensity on diffusion-weighted (DW) images in 29 of 31 patients. CONCLUSION: Metastases of chordoma are not rare and may occur several years after primary lesion presentation. The high intensity of DW images is characteristic and helpful for detecting metastatic chordoma.

Intrafractional respiratory motion for charged particle lung therapy with immobilization assessed by four-dimensional computed tomography.

The aim of this study was to quantify the magnitude of intrafractional lung tumor motion under free-breathing conditions with an immobilization device using four-dimensional computed tomography (4DCT). 4DCT data sets were acquired for 17 patients with lung tumors receiving carbon ion beam therapy. A single respiratory cycle was subdivided into 10 phases, and intrafractional tumor motion was calculated by identifying the gross tumor volume (GTV) center of mass (COM) in two scenarios; respiratory-ungated and -gated treatments, which were based on a whole respiratory cycle and a 30% duty cycle around peak exhalation, respectively. For the respiratory-ungated case, the mean (± standard deviation) GTV-COM displacements from the peak exhalation position over the 17 patients were 0.6 (± 0.8) / 0.9 (± 1.2) mm, 2.0 (± 1.4) / 0.4 (± 0.7) mm, and 0.2 (± 0.5) / 7.8 (± 6.9) mm in left/right, anterior/posterior and superior/inferior directions, respectively, while these were reduced for the respiratory-gated case to 0.3 (± 0.4) / 0.4 (± 0.6) mm (left/right), 0.8 (± 0.7) / 0.3 (± 0.5) mm (anterior/posterior), and 0.1 (± 0.2) / 2.8 (± 2.9) mm (superior/inferior). Quantitative analysis of tumor motion with immobilization is valuable not only for particle beam therapy but also for photon beam therapy.

Four-dimensional lung treatment planning in layer-stacking carbon ion beam treatment: comparison of layer-stacking and conventional ungated/gated irradiation.

PURPOSE: We compared four-dimensional (4D) layer-stacking and conventional carbon ion beam distribution in the treatment of lung cancer between ungated and gated respiratory strategies using 4DCT data sets. METHODS AND MATERIALS: Twenty lung patients underwent 4DCT imaging under free-breathing conditions. Using planning target volumes (PTVs) at respective respiratory phases, two types of compensating bolus were designed, a full single respiratory cycle for the ungated strategy and an approximately 30% duty cycle for the exhalation-gated strategy. Beams were delivered to the PTVs for the ungated and gated strategies, PTV(ungated) and PTV(gated), respectively, which were calculated by combining the respective PTV(Tn)s by layer-stacking and conventional irradiation. Carbon ion beam dose distribution was calculated as a function of respiratory phase by applying a compensating bolus to 4DCT. Accumulated dose distributions were calculated by applying deformable registration. RESULTS: With the ungated strategy, accumulated dose distributions were satisfactorily provided to the PTV, with D95 values for layer-stacking and conventional irradiation of 94.0% and 96.2%, respectively. V20 for the lung and Dmax for the spinal cord were lower with layer-stacking than with conventional irradiation, whereas Dmax for the skin (14.1 GyE) was significantly lower (21.9 GyE). In addition, dose conformation to the GTV/PTV with layer-stacking irradiation was better with the gated than with the ungated strategy. CONCLUSIONS: Gated layer-stacking irradiation allows the delivery of a carbon ion beam to a moving target without significant degradation of dose conformity or the development of hot spots.

Comparison of efficacy and toxicity of short-course carbon ion radiotherapy for hepatocellular carcinoma depending on their proximity to the porta hepatis.

BACKGROUND AND PURPOSE: To compare the efficacy and toxicity of short-course carbon ion radiotherapy (C-ion RT) for patients with hepatocellular carcinoma (HCC) in terms of tumor location: adjacent to the porta hepatis or not. MATERIALS AND METHODS: The study consisted of 64 patients undergoing C-ion RT of 52.8 GyE in four fractions between April 2000 and March 2003. Of these patients, 18 had HCC located within 2 cm of the main portal vein (porta hepatis group) and 46 patients had HCC far from the porta hepatis (non-porta hepatis group). We compared local control, survival, and adverse events between the two groups. RESULTS: The 5-year overall survival and local control rates were 22.2% and 87.8% in the porta hepatis group and 34.8% and 95.7% in the non-porta hepatis group, respectively. There were no significant differences (P=0.252, P=0.306, respectively). Further, there were no significant differences in toxicities. Biliary stricture associated with C-ion RT did not occur. CONCLUSIONS: Excellent local control was obtained independent of tumor location. The short-course C-ion RT of 52.8 GyE in four fractions appears to be an effective and safe treatment modality in the porta hepatis group just as in the non-porta hepatis group.

Compensatory enlargement of the liver after treatment of hepatocellular carcinoma with carbon ion radiotherapy - relation to prognosis and liver function.

BACKGROUND AND PURPOSE: To examine whether liver volume changes affect prognosis and hepatic function in patients treated with carbon ion radiotherapy (CIRT) for hepatocellular carcinoma (HCC). MATERIAL AND METHODS: Between April 1995 and March 2003, among the cases treated with CIRT, 43 patients with HCC limited to the right hepatic lobe were considered eligible for the study. The left lateral segment was defined as the non-irradiated region. Liver volume was measured using contrast CT at 0, 3, 6, and 12 months after CIRT. We examined serum albumin, prothrombin activity, and total bilirubin level as hepatic functional reserve. RESULTS: After CIRT, the non-irradiated region showed significant enlargement, and enlarged volume of this region 3 months after CIRT 50 cm(3) was a prognostic factor. The 5-year overall survival rates were 48.9% in the larger enlargement group (enlarged volume of non-irradiated region 3 months after CIRT > or =50 cm(3)) and 29.4% in the smaller enlargement group (as above, <50 cm(3)). The larger enlargement group showed better hepatic functional reserve than the smaller enlargement group 12 months after CIRT. CONCLUSIONS: This study suggests that compensatory enlargement in the non-irradiated liver after CIRT contributes to the improvement of prognosis.

Detection of bone metastases using diffusion weighted magnetic resonance imaging: comparison with (11)C-methionine PET and bone scintigraphy.

PURPOSE: We evaluated the ability of diffusion-weighted imaging (DWI) to detect bone metastasis by comparing the results obtained using this modality with those obtained using (11)C-methionine (MET) positron emission tomography (PET) and bone scintigraphy. MATERIALS AND METHODS: This retrospective study involved 29 patients with bone metastasis. DWI was obtained using a single-shot echo planar imaging (EPI) sequence with fat suppression using a short inversion time inversion recovery sequence. The detection capabilities of DWI for bone metastases were compared with those of whole body MET PET (in 19 patients) and 99mTc-methylene diphosphonate bone scintigraphy (in 15 patients). RESULTS: Among the 19 patients who were diagnosed using DWI and PET, the PET identified 39 bone metastases, while the DWI identified 60 metastases out of 69 metastases revealed with conventional magnetic resonance imaging (MRI). Among the 15 patients who were diagnosed using DWI and bone scintigraphy, the bone scintigraphy identified 18 bone metastases, while the DWI identified 72 metastases out of 78 metastases revealed with conventional MRI. The overall bone metastasis detection rates were 56.5% for PET, 23.1% for bone scintigraphy and 92.3% for DWI. CONCLUSION: DWI is a very sensitive method for detecting bone metastasis and is superior to MET PET and bone scintigraphy in terms of its detection capabilities.

Comparison of respiratory-gated and respiratory-ungated planning in scattered carbon ion beam treatment of the pancreas using four-dimensional computed tomography.

PURPOSE: We compared respiratory-gated and respiratory-ungated treatment strategies using four-dimensional (4D) scattered carbon ion beam distribution in pancreatic 4D computed tomography (CT) datasets. METHODS AND MATERIALS: Seven inpatients with pancreatic tumors underwent 4DCT scanning under free-breathing conditions using a rapidly rotating cone-beam CT, which was integrated with a 256-slice detector, in cine mode. Two types of bolus for gated and ungated treatment were designed to cover the planning target volume (PTV) using 4DCT datasets in a 30% duty cycle around exhalation and a single respiratory cycle, respectively. Carbon ion beam distribution for each strategy was calculated as a function of respiratory phase by applying the compensating bolus to 4DCT at the respective phases. Smearing was not applied to the bolus, but consideration was given to drill diameter. The accumulated dose distributions were calculated by applying deformable registration and calculating the dose-volume histogram. RESULTS: Doses to normal tissues in gated treatment were minimized mainly on the inferior aspect, which thereby minimized excessive doses to normal tissues. Over 95% of the dose, however, was delivered to the clinical target volume at all phases for both treatment strategies. Maximum doses to the duodenum and pancreas averaged across all patients were 43.1/43.1 GyE (ungated/gated) and 43.2/43.2 GyE (ungated/gated), respectively. CONCLUSIONS: Although gated treatment minimized excessive dosing to normal tissue, the difference between treatment strategies was small. Respiratory gating may not always be required in pancreatic treatment as long as dose distribution is assessed. Any application of our results to clinical use should be undertaken only after discussion with oncologists, particularly with regard to radiotherapy combined with chemotherapy.

Changes in tumor volume of sacral chordoma after carbon ion radiotherapy.

OBJECTIVE: We evaluated changes in tumor volume in cases of sacral chordoma after carbon ion radiotherapy. METHODS: Thirty-four patients with sacral chordoma underwent carbon ion radiotherapy between June 1996 and June 2003. We assessed 23 patients without previous surgery using T2-weighted magnetic resonance imaging. The tumor volume was calculated semiautomatically. RESULTS: Two cases showed local recurrence. The median interval of this examination was 46 months. At the end of the treatment, the tumor showed an enlargement larger than 10% of its volume in 13 of the 23 cases, no change in 4 cases, and regression in 6 cases. At the last examination, 20 cases showed a reduction in tumor volume, and the median ratio, determined as the tumor volume at the last examination divided by that before the treatment, was 0.36. CONCLUSIONS: An increase in tumor volume at the end of the treatment does not indicate the ineffectiveness of carbon ion radiotherapy.

Dosimetric variation due to CT inter-slice spacing in four-dimensional carbon beam lung therapy.

When CT data with thick slice thickness are used in treatment planning, geometrical uncertainty may induce dosimetric errors. We evaluated carbon ion dose variations due to different CT slice thicknesses using a four-dimensional (4D) carbon ion beam dose calculation, and compared results between ungated and gated respiratory strategies. Seven lung patients were scanned in 4D mode with a 0.5 mm slice thickness using a 256-multi-slice CT scanner. CT images were averaged with various numbers of images to simulate reconstructed images with various slice thicknesses (0.5-5.0 mm). Two scenarios were studied (respiratory-ungated and -gated strategies). Range compensators were designed for each of the CT volumes with coarse inter-slice spacing to cover the internal target volume (ITV), as defined from 4DCT. Carbon ion dose distribution was computed for each resulting ITV on the 0.5 mm slice 4DCT data. The accumulated dose distribution was then calculated using deformable registration for 4D dose assessment. The magnitude of over- and under-dosage was found to be larger with the use of range compensators designed with a coarser inter-slice spacing than those obtained with a 0.5 mm slice thickness. Although no under-dosage was observed within the clinical target volume (CTV) region, D95 remained at over 97% of the prescribed dose for the ungated strategy and 95% for the gated strategy for all slice thicknesses. An inter-slice spacing of less than 3 mm may be able to minimize dose variation between the ungated and gated strategies. Although volumes with increased inter-slice spacing may reduce geometrical accuracy at a certain respiratory phase, this does not significantly affect delivery of the accumulated dose to the target during the treatment course.

Impact of intrafractional bowel gas movement on carbon ion beam dose distribution in pancreatic radiotherapy.

PURPOSE: To assess carbon ion beam dose variation due to bowel gas movement in pancreatic radiotherapy. METHODS AND MATERIALS: Ten pancreatic cancer inpatients were subject to diagnostic contrast-enhanced dynamic helical CT examination under breath-holding conditions, which included multiple-phase dynamic CT with arterial, venous, and delayed phases. The arterial-venous phase and arterial-delayed phase intervals were 35 and 145 s, respectively. A compensating bolus was designed to cover the target obtained at the arterial phase. Carbon ion dose distribution was calculated by applying the bolus to the CT data sets at the other two phases. RESULTS: Dose conformation to the clinical target volume was degraded by beam overshoot/undershoot due to bowel gas movement. The D95 for clinical target volume was degraded from 98.2% (range, 98.0-99.1%) of the prescribed dose to 94.7% (range, 88.0-99.0%) at 145 s. Excessive dosing to normal tissues varied among tissues and was, for example, 12.2 GyE/13.1 GyE (0 s/145 s) for the cord and 38.8 GyE/39.8 GyE (0 s/145 s) for the duodenum. The magnitude of beam overshoot/undershoot was particularly exacerbated from the anterior and left directions. CONCLUSIONS: Bowel gas movement causes dosimetric variation to the target during treatment for radiotherapy. The effect of bowel gas movement varies with beam angle, with greatest influence on the anterior-posterior and left-right beams.

Four-dimensional measurement of intrafractional respiratory motion of pancreatic tumors using a 256 multi-slice CT scanner.

PURPOSE: To quantify pancreas and pancreatic tumor movement due to respiratory motion using volumetric cine CT images. MATERIALS AND METHODS: Six patients with pancreatic tumors were scanned in cine mode with a 256 multi-slice CT scanner under free breathing conditions. Gross tumor volume (GTV) and pancreas were manually contoured on the CT data set by a radiation oncologist. Intrafractional respiratory movement of the GTV and pancreas was calculated, and the results were compared between the respiratory ungated and gated phases, which is a 30% duty cycle around exhalation. RESULTS: Respiratory-induced organ motion was observed mainly in the anterior abdominal side than the posterior side. Average GTV displacement (ungated/gated phases) was 0.7 mm/0.2mm in both the left and right directions, and 2.5mm/0.9 mm in the anterior, 0.1 mm/0mm in the posterior, and 8.9 mm/2.6mm in the inferior directions. Average pancreas center of mass displacement relative to that at peak exhalation was mainly in the inferior direction, at 9.6mm in the ungated phase and 2.3mm in the gated phase. CONCLUSIONS: By allowing accurate determination of the margin, quantitative analysis of tumor and pancreas displacement provides useful information in treatment planning in all radiation approaches for pancreatic tumors.

Prediction of early response to radiotherapy of uterine carcinoma with dynamic contrast-enhanced MR imaging using pixel analysis of MR perfusion imaging.

PURPOSE: To assess the predictability of the response to radiotherapy of uterine carcinoma, this study retrospectively analyzed dynamic contrast-enhanced magnetic resonance images (DCE-MRI) taken before radiotherapy. MATERIALS AND METHODS: Forty-two patients with uterine carcinoma were studied, of whom 22 had adenocarcinoma and 20 had squamous cell carcinoma (SCC). In DCE-MRI analysis, two parameters, SIe and R(down), were measured. SIe is a median value for the degree of signal intensity change in all selected pixels in the tumor at 1-2 min after contrast agent injection. R(down) is the ratio of the number of down-sloped pixels to that of all selected pixels 3-7 min after injection. The tumor volume reduction rate (TVRR) was measured by MRI-based volumetry in pre- and post-radiotherapy transverse T2-weighted images. RESULTS: Overall, TVRR was significantly correlated to both SIe (r=0.37, P=.015) and R(down) (r=0.73, P<.0001). In the separate patient groups, SIe but not R(down) was significantly different between the adenocarcinoma and SCC patients (t=3.64, P<.001). TVRR was not correlated to SIe in any group. TVRR was significantly correlated to R(down) in adenocarcinoma patients (r=0.78, P<.001) but not in SCC patients. CONCLUSION: SIe may reflect differences in histological characteristics. R(down) may be useful for predicting the response to radiotherapy of uterine carcinoma.

Carbon ion radiotherapy for elderly patients 80 years and older with stage I non-small cell lung cancer.

Surgical resection is the standard treatment for stage I non-small cell lung cancer (NSCLC). However, elderly patients with NSCLC often suffer from other conditions, such as chronic obstructive pulmonary disease (COPD) or cardiovascular disease, and are not suitable candidates for surgery. Different modalities to treat stage I NSCLC have been developed, such as stereotactic radiotherapy (SRT), proton beam radiotherapy and carbon ion radiotherapy (CIRT). Between April 1999 and November 2003, we treated 129 patients with stage I NSCLC using CIRT. In this study, we focused on 28 patients aged 80 years and older who underwent CIRT, and analyzed the effectiveness of CIRT in treating their lung cancer and the impact on their activity of daily life (ADL). The 5-year local control rate for these patients was 95.8%, and the 5-year overall survival rate was 30.7%, but there were no patients who started home oxygen therapy or had decreased ADL. Our data demonstrate that CIRT was effective in treating elderly patients with stage I NSCLC.

Water-equivalent pathlength reproducibility due to respiratory pattern variation in charged-particle pancreatic radiotherapy.

We evaluated the water-equivalent length (WEL) reproducibility due to variation in the external respiratory marker position when using a 4DCT scan in respiratory-gated charged-particle treatment. Two sets of pancreatic 4DCT data from two patients were acquired under free breathing conditions with 256-slice CT. The 4DCT data included two exhalation phases and the respiratory patterns in each patient differed, one being regular and the other irregular. The WEL calculation region is defined in the first respiratory cycle by two planes, one at the patient entrance surface and the other behind the target in the anterior-posterior (AP) and posterior-anterior (PA) directions. In the regular respiratory pattern, the WEL variation within the target region was less than 1.7 mm between the first and second exhalations in both AP and PA calculation directions. However, in the irregular breathing pattern, the respiratory amplitude at the second exhalation was 20% lower than that at the first exhalation; therefore, WEL variations from 8.1 to -9.1 mm and from 3.1 to -3.4 mm were observed within the target region in the AP and PA calculation directions, respectively. The WEL variation in the PA direction was smaller than that in the AP direction because the abdominal thickness is affected more in the AP direction. Respiratory pattern variation even affects WEL values in the respiratory-gated phase. This variation should be considered in treatment planning, and necessary improvements in respiratory reproducibility should be made.

Magnitude of residual internal anatomy motion on heavy charged particle dose distribution in respiratory gated lung therapy.

PURPOSE: To assess the variation in carbon beam dose distribution due to residual motion in lung cancer patients undergoing respiratory-gated radiotherapy. METHODS AND MATERIALS: A total of 11 lung cancer patients underwent four-dimensional computed tomography with a 256-multislice computed tomography scanner under free-breathing conditions. A compensating bolus was designed to cover the treatment beam for all planning target volumes during a 30% duty cycle centered on exhalation (gating window). This bolus was applied to the four-dimensional computed tomography data for one respiratory cycle, and then the carbon beam dose distribution was calculated. RESULTS: A water equivalent pathlength variation of <5 mm was observed in the gating window, but this increased to 95% volume irradiation is dependent on the respiratory phase but not the gating window. However, the dose for >95% volume irradiation correlated well with the tumor displacement distance. More than 90% of the dose for >95% volume irradiation could be delivered in the gating window with <4-mm tumor displacement resulting from exhalation. CONCLUSION: The results of our study have shown that even when the treatment beam delivery occurs outside the gating window, the prescribed dose to the target is not affected in patients with a tumor displacement of <4 mm. Thus, respiratory gating is not required in radiotherapy for patients with <4-mm tumor displacement in a respiratory cycle.

ADC value and diffusion tensor imaging of prostate cancer: changes in carbon-ion radiotherapy.

PURPOSE: To assess the apparent diffusion coefficient (ADC) value and diffusion tensor image (DTI) including fractional anisotropy (FA) of the noncancerous prostate and prostate cancer before and after carbon-ion radiotherapy (CIRT). MATERIALS AND METHODS: Nine patients with biopsy-proven prostate cancer underwent 1.5T magnetic resonance (MR) examinations. One patient with benign prostatic hypertrophy and one healthy volunteer were also examined as references. The changes in ADC values and DTI of the entire prostate calculated from b-values of 0 and 700 (s/mm(2)) were estimated between before and after CIRT. RESULTS: ADC values of prostate cancer significantly increased after CIRT by paired t-test (P < 0.01) but those of noncancerous inner gland (IG) and peripheral zone (PZ) showed no significant change. By analysis of variance, significant differences in ADC values were observed among prostate cancer and noncancerous IG and PZ before CIRT (P < 0.05). After CIRT, those significant differences had disappeared. FAs showed no significant differences in any comparisons. DTI showed changes in the direction of the main axis of the tensor in prostate cancer after CIRT. CONCLUSION: There were changes in ADC and DTI in prostate cancer after CIRT. They may be useful for monitoring prostatic structural changes under radiotherapy.

Development and performance evaluation of the second model 256-detector row CT.

Since our initial development of the 256-detector row CT scanner (256-row CT) for four-dimensional (4D) imaging of moving organs in 2003, the results of physical performance and those in animal and human studies have suggested that this scanner may be useful in the examination of moving organs such as the heart and lungs. We have now developed a second model of the 256-row CT with improved specifications, with a scan time of 0.5 s/rotation at the highest speed and real-time reconstruction and display of dynamic 3D images (4D images). Here, we investigated the image characteristics of the new model, including spatial resolution, noise, and low-contrast detectability, as well as the dose profile and its integral in stationary phantoms. One volunteer and one patient with lung cancer were scanned, and their images were evaluated. The results show that all characteristics have been improved compared with those of the first model, with a remarkable improvement in the low-contrast detectability and slice sensitivity profile. In a contrast study, coronary arteries were clearly visualized in the normal heart without electrocardiographic gating. Movement and deformation of the tumor in the patient with lung cancer was captured in a study of a single breath cycle. The second model 256-row CT with improved characteristics may be beneficial in imaging of moving organs such as the heart and lungs, and may enable cerebral perfusion studies of the whole brain.

Design of a compensating bolus by use of exhalation CT data for covering residual motion in respiratory-gated charged-particle lung therapy: four-dimensional carbon beam dose calculation.

We developed an algorithm which we used to design a compensating bolus by using respiratory-gated CT data for respiratory-gated carbon beam lung therapy and evaluated it by calculating dose distributions as a function of time. Four-dimensional CT (4DCT) images were obtained for seven lung cancer patients under free breathing conditions. The internal target volume (ITV) was calculated by maximum intensity projection processing which use of three types of gross tumor volumes (GTVs): at peak exhalation and with a 5 mm shift of the GTV to both superior and inferior sides. Then a compensating bolus was designed which use of the ITV and applied to 4DCT data at the gating window (around exhalation phase). The carbon beam distribution was calculated by a pencil-beam algorithm as a function of time. The compensating bolus provides a sufficient prescribed dose to the target in the gating window and minimizes any excessive dose to the normal tissues. The metric of dosimetric assessment metrics of D95 in all patients is greater than 96% of the prescribed dose in the gating window. Our results will be beneficial for improving the accuracy of charged-particle radiotherapy for hospitals where 4DCT cannot be used.

Carbon ion radiotherapy for stage I non-small cell lung cancer using a regimen of four fractions during 1 week.

BACKGROUND: A phase I/II study was first conducted for the treatment of stage I non-small cell lung cancer (NSCLC) from 1994 to 1999 to determine the optimal dose. On the basis on the results, a phase II study using a regimen of four fractions during 1 week was performed. The purpose of the present study was to determine the local control and 5-year survival rates. METHODS: From December 2000 to November 2003, 79 patients with 80 primary lesions were treated. Using a fixed dose of 52.8 GyE for stage IA NSCLC and 60.0 GyE for stage IB NSCLC in four fractions during 1 week, the primary tumors were irradiated with carbon beams alone. The average age of the patients was 74.8 years. Sixty-two (78.5%) of these patients were medically inoperable. Local control and survival were determined using the Kaplan-Meier method. The data were statistically processed using the log-rank test. RESULTS: All patients were observed for a minimum of 3 years or until death, with a median follow-up time of 38.6 months, ranging from 2.5 to 72.2 months. The local control rate for all patients was 90% (T1: 98%, T2: 80%). The patients' 5-year lung cancer-specific survival rate was 68% (IA: 87%, IB: 42%). The overall survival was 45% (IA: 62%, IB: 25%). Half of the deaths were attributable to intercurrent diseases. No toxic reactions in the lung greater than grade 3 were detected. CONCLUSION: Carbon ion beam radiotherapy with a regimen of four fractions during 1 week has been proven as a valid alternative to surgery for stage I NSCLC and to offer particular benefits, especially for elderly and inoperable patients.