[Influence of registration based on different reference markers on the displacement of the geometry consisted of all clips in the cavity for external-beam partial breast irradiation at moderate deep inspiration breath holding].

OBJECTIVE: To investigate the influence of registration based on different reference markers on the displacement of the geometry consisted of all clips in the cavity for external-beam partial breast irradiation at moderate deep inspiration breath holding assisted by active breathing control device. METHODS: Twenty-seven early stage breast cancer patients feasible for external beam partial breast irradiation (EB-PBI) were selected. The patients undertaken three-dimensional computed tomography (3DCT) simulation scan at moderate deep inspiration breath holding (mDIBH) assisted by active breathing control device, and two sets of mDIBH CT images were got and transferred to the Pinnacle 3 planning system. All of the silver clips were delineated and a geometry consisted of all clips were generated. On the account of automatic registration of mDIBH CT images, manual registration was carried out based separately on the topside clip in the cavity, the labeled skin at anterior surface of the cavity at central level and the metal mark on the body surface near the cavity, then the displacements of center of the geometry in left-right (LR), anterior-posterior (AP) and superior-inferior (SI) directions based separately on the three registrations were measured. RESULTS: The displacements of center of the geometry in LR, AP and SI directions based on registration of the clips, the labeled skin and the metal mark were (0.61 ± 0.62)mm vs. (1.11 ± 1.21)mm vs. (1.31 ± 1.55)mm, (0.63 ± 0.59)mm vs. (0.92 ± 0.93)mm vs. (1.19 ± 1.24)mm and (0.91 ± 0.96)mm vs. (2.13 ± 2.12)mm vs. (1.93 ± 1.55)mm, respectively. Compared the displacements of center of the geometry in the same direction between the three registrations, significant differences were found only in SI direction between clip registration and skin registration, clip registration and mark registration (t = 5.045, 7.210 and P = 0.025, 0.007) . Compared the displacements of center of the geometry between three dimensional directions for each reference registration, there was no significant difference (all P > 0.05). CONCLUSIONS: When EB-PBI is carried out in state of mDIBH, measurement of the intrafraction displacement based on registration of the clip in the cavity is a reasonable selection. Otherwise, excessive margin enlargement of PTV in SI direction will be generated if the regional skin or metal mark is selected as registration reference.

[Evaluation of dosimetric variance in forward intensity modulated radiotherapy of the breast based on 4D CT and 3D CT during free breathing].

OBJECTIVE: To explore the dosimetric variance in forward intensity modulated radiotherapy (IMRT) based on 4D CT and 3D CT after breast conserving surgery. METHODS: Seventeen patients after breast conserving surgery underwent 3D CT simulation scans followed by respiration-synchronized 4D CT simulation scans at free breathing state. The treatment plan constructed using the end inspiration (EI) scan was then copied and applied to the end expiration (EE), and 3D scans and dose distribution were calculated separately. Dose-volume histograms (DVHs) parameters for the CTV, PTV, ipsilateral lung and heart were evaluated and compared. RESULTS: The CTV volume difference was biggest between T0 and 3D CT, and the volume difference was 4.10 cm(3). Mean dose of PTV at EE was lower than that at EI (P = 0.019), but there were no statistically significant difference between 3D and EI, EE (all P > 0.05). The homogeneity index (HI) at EI, EE, 3D plans were 0.149, 0.159 and 0.164, respectively, and a significant difference was only between EI and EE (P = 0.039). The highest conformal index (CI) was at EI phase (P < 0.05), and there was no significant difference between EE and 3D (P = 0.758). The V(40) and V(50) of ipsilateral lung at EE phase were lower than that at EI (P < 0.05). There were no significant differences in all the indexes for heart (P > 0.05). CONCLUSIONS: The breast deformation during respiration may be disregarded in whole breast IMRT. PTV dose distribution is significantly changed between EI and EE phases, and the differentiation of the lung high dose area between EI and EE phases may be induced by thorax expansion. 3D treatment planning is sufficient for whole breast forward IMRT, but 4D CT scans assisted by respiratory gating ensures more precise delivery of radiation dose.

[Comparison of three methods to delineate internal gross target volume of the primary hepatocarcinoma based on four-dimensional CT simulation images].

OBJECTIVE: To compare the position and magnitude of internal target gross volume (IGTV) of primary hepatocarcinoma delineated by three methods based on four-dimensional computed tomography (4D-CT) and to investigate the relevant factors affecting the position and magnitude. METHODS: Twenty patients with primary hepatocarcinoma after transcatheter arterial chemoembolization (TACE) underwent big bore 4D-CT simulation scan of the thorax and abdomen using a real-time position management (RPM) system for simultaneous record of the respiratory signals. The CT images with respiratory signal data were reconstructed and sorted into 10 phase groups in a respiratory cycle, with 0% phase corresponding to end-inhale and 50% corresponding to end-exhale. The maximum intensity projection (MIP) image was generated. IGTVs of the tumor were delineated using the following three methods: (1) The gross tumor volume (GTV) on each of the ten respiratory phases of the 4D-CT image set was delineated and fused ten GTV to produce IGTV10; (2) The GTVs delineated separately based on 0% and 50% phase were fused to produce IGTV(IN+EX); (3) The visible tumor on the MIP image was delineated to produce IGTV(MIP). Twenty patients were divided into groups A and B based on the location of the target center,and were divided into groups C and D based on the tumor maximum diameter. The patients were divided into groups E and F based on the three-dimensional (3D) motion vector of the target center. The position of the target center, the volume of target, the degree of inclusion (DI) and the matching index (MI) were compared reciprocally between IGTV10, IGTV(IN+EX) and IGTV(MIP), and the influence of the tumor position and 3D motion vector on the related parameters were compared based on the grouping. RESULTS: The average differences between the position of the center of IGTVs on direction of X, Y and Z axes were less than 1.5 mm, and the difference was statistically not significant. The volume of IGTV10 was larger than that of IGTV(IN+EX), but the difference was not significant (t = 0.354, P = 0.725). The volume of IGTV10 was larger than that of IGTV(MIP) but the difference was not significant (t = -0.392, P = 0.697). The ratio of IGTV(IN+EX) to IGTV10 was 0.75 +/- 0.15 and the ratio of IGTV(MIP) to IGTV10 was 0.78 +/- 0.14. The DI of IGTV(IN+EX) in IGTV10 was (74.85 +/- 15.09)% and that of IGTV(MIP) in IGTV10 was (68.87 +/- 13.69)%. The MI between IGTV10 and IGTV(IN+EX), IGTV10 and IGTV(MIP) were 0.75 +/- 0.15 and 0.67 +/- 0.13, respectively. The median of ratio of IGTV(IN+EX)/ IGTV10 was 0.57 in group A versus 0.87 in group B, statistically with a significant difference between the groups A and B (Z = -3.300,P = 0.001). The median of ratio of IGTV(MIP)/IGTV10 was 0.51 in the group A and 0.72 in group B, with a significant difference between the groups A and B (Z = -3.413, P = 0.001). The median of ratio of IGTV(IN+EX)/IGTV10 was 0.79 in group C versus 0.74 in group D, with a difference not significant (Z = -0.920, P = 0.358). The median of ratio of IGTV(MIP)/IGTV10 was 0.85 in group C versus 0.80 in group D, with a non-significant difference (Z = -0.568, P = 0.570). The median of ratio of IGTV(IN+EX)/IGTV10 was 0.87 in group E versus 0.68 in group F, with a significant difference between the two groups (Z = -2.897, P = 0.004). The median of ratio of IGTV(MIP)/IGTV10 was 0.85 in the group E versus 0.81 in the group F, with a non-significant difference (Z = -0.568, P = 0.570). CONCLUSIONS: The center displacement of the IGTVs delineated separately by the three techniques based on 4D-CT images is not obvious. IGTV(IN+EX) and IGTV(MIP) can not replace IGTV10, however, IGTV(IN+EX) is more close to IGTV10 comparing with IGTV(MIP). The ratio of IGTV10 and IGTV(MIP) is correlated to the 3D motion vector of the tumor. When the tumor is situated in the upper part of the liver and with a 3D motion vector less than 9 mm, IGTV10 should be the best IGTV.

[Displacement of the silver clips in surgical cavity based on four-dimensional CT images for patients undertaking external-beam partial breast irradiation after breast-conserving surgery].

OBJECTIVE: To explore the displacement of the selected clips and the center of the geometry consisted of all the clips in the surgical cavity measured on the basis of four-dimensional computed tomography (4D-CT) simulation images. METHODS: Fourteen breast cancer patients after breast-conserving surgery were recruited for external beam partial-breast irradiation (EB-PBI), and received large aperture CT simulation. The 4D-CT image data sets were collected when the patient was in the free breathing state. Using the Varian Eclipse treatment planning system, the selected four clips in the cavity were separately delineated on the CT images from 10 phases of the breath cycle, and all of the clips in the cavity were marked to obtain the geometry. Then the displacement of the four selected clips and the center of the geometry in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were measured. The differences of the displacement were compared. RESULTS: The displacements in the AP and SI directions were always greater than the displacement in LR direction for the same selected clip. The difference of the displacements in the same direction of the different selected clips was not statistically significant (P>0.05). The displacements of the geometry center consisted of all of the clips in the LR, AP, SI directions were (1.34±0.39) mm, (2.01±1.02) mm and (1.89±1.03) mm, respectively, and the difference of the displacements between LR and AP, LR and SI were all statistically significant (P<0.05). In the same directions (LR, AP and SI), the displacement of geometry center was always greater than the displacement of the selected clips, and the difference except SI direction was all statistically significant (P<0.05). In the SI direction, the association between the displacement of geometry center and the upper clip, geometry center and the lower clip was statistically significant (P<0.05). CONCLUSION: When the target for EB-PBI is defined on the basis of 4D-CT simulation images, the displacement of the selected clips at the border of the surgical cavity is not qualified to substitute the displacement of the target defined basing on all of the clips in the surgical cavity.

Demethylation of miR-34a upregulates expression of membrane palmitoylated proteins and promotes the apoptosis of liver cancer cells.

BACKGROUND: Liver cancer is a common cancer and the main cause of cancer-related deaths worldwide. Liver cancer is the sixth most common cancer in the world. Although miR-34a and palmitoyl membrane palmitoylated protein (MPP2) are reportedly involved in various cell processes, their precise roles in liver cancer are still unclear. AIM: To investigate the expression of micro RNA 34a (miR-34a), methylation of the miR-34a promoter and the expression of MPP2 in liver cancer cells and their related mechanisms. METHODS: Together, 78 cases of liver cancer tissues and 78 cases of adjacent tissues were collected. The methylation degree of miR-34a promoter in liver cancer/ paracancerous tissue and liver cancer cells/normal liver cells, and the expression levels of miR-34a and MPP2 in the above samples were detected. Demethylation of liver cancer cells or transfection of liver cancer cells with miR-34a mimetic was performed. The MPP2 overexpression vector was used to transfect liver cancer cells, and the changes in proliferation, invasion, apoptosis, migration, and other biological functions of liver cancer cells after the above interventions were observed. Double luciferase reporter genes were used to detect the targeting relationship between miR-34a and MPP2. RESULTS: Clinical samples showed that the expression levels of miR-34a and MPP2 in liver cancer tissues were lower than those in the normal tissues. The methylation degree of miR-34a promoter region in liver cancer cells was higher than that in normal liver cells. After miR-34a demethylation/mimetic transfection/MPP2 overexpression, the apoptosis of liver cancer cells was increased; the proliferation, invasion and migration capabilities were decreased; the expression levels of caspase 3, caspase 9, E-cadherin, and B-cell lymphoma 2 (Bcl-2)-associated X protein were increased; and the expression levels of Bcl-2, N-cadherin, and ß-catenin were decreased. Double luciferase reporter genes confirmed that MPP2 is targeted by miR-34a. Rescue experiments showed that small interfering MPP2 could counteract the promoting effect of miR-34a demethylation on apoptosis and the inhibitory effect on cell proliferation, invasion, and migration. CONCLUSION: miR-34a demethylation upregulates the expression level of MPP2 in liver cancer cells and promotes the apoptosis of liver cancer cells. miR-34a demethylation is a potential method for liver cancer treatment.

[Comparison of overlap ratios of the target volume in different respiratory states with active breathing control for external-beam partial breast irradiation].

OBJECTIVE: To explore the overlap ratio of the target volume in different respiratory statuses of active breath control (ABC) and their differences during external-beam partial breast irradiation (EB-PBI), and from the perspective of target volume overlap to determine the influence of the ABC-assisted breathing condition on intra-fractional target movement of EB-PBI. METHODS: The patients, who received breast-conserving surgery with silver clips marked at the margins of the cavity and were suitable for EB-PBI, were immobilized on the breast bracket to undertake CT simulation assisted by ABC device, six sets of CT simulation images including two sets of image in state of moderate deep inspiration breathing control (mDIBH), two sets of images in state of free breath (FB) and two sets of images in state of deep expiration breathing control (DEBH) were obtained. The six sets of images were transferred to Pinnacle(3) treatment planning system (TPS), then automatic fusion and registration between two sets of mDIBH images, two sets of FB images, two sets of DEBH images and mDIBH image and DEBH image were achieved separately. Thereafter, the overlap ratios of GTV with GTV, CTV with CTV, PTV with PTV were calculated by the Pinnacle(3) TPS. The differences between the overlap ratios of the three kinds of targets in the same registered image and the difference between the overlap ratios of the same kind of target in the different registered images were statistically analyzed using statistical package of SPSS 11.5. RESULTS: Based on mDIBH/mDIBH registration, the overlap ratios of GTV/GTV, CTV/CTV and PTV/PTV were (83.54 ± 11.41)%, (93.00 ± 6.49)%, and (95.26 ± 4.90)%, respectively, and the differences of the overlap ratios between GTV/GTV and CTV/CTV, GTV/GTV and PTV/PTV were all statistically significant (P < 0.05), but statistically not significant between CTV/CTV and PTV/PTV (P > 0.05). Based on FB/FB registration, the overlap ratios of GTV/GTV, CTV/CTV and PTV/PTV were (72.55 ± 29.10)%, (89.36 ± 9.53)% and (92.47 ± 7.25)%, respectively, and the differences of the overlap ratios between GTV/GTV and CTV/CTV, CTV/CTV and PTV/PTV were all not statistically significant (P > 0.05), but statistically significant between GTV/GTV and PTV/PTV (P < 0.05). Based on DEBH/DEBH registration, the overlap ratios of GTV/GTV, CTV/CTV and PTV/PTV were (79.48 ± 22.31)%, (92.83 ± 6.77)% and (95.05 ± 4.81)%, respectively, and the differences of the overlap ratios between GTV/GTV and CTV/CTV (P = 0.000), CTV/CTV and PTV/PTV (P = 0.037), GTV/GTV and PTV/PTV (P = 0.000) were statistically all significant (P = 0.000). The differences of the overlap ratios of GTV/GTV, CTV/CTV, and PTV/PTV (P = 0.000) between mDIBH/mDIBH and DEBH/DEBH, mDIBH/mDIBH and FB/FB, FB/FB and DEBH/DEBH were all statistically significant (P = 0.000), and not statistically significant between mDIBH/mDIBH and mDIBH/DEBH, FB/FB and mDIBH/DEBH. CONCLUSIONS: During the delivering of EB-PBI assisted by ABC, the intra-fractional overlap ratios of the target volume between the same breathing state is increasing in the order of GTV/GTV → CTV/CTV → PTV/PTV. The difference of the overlap ratios of the target volumes between mDIBH and mDIBH, FB and FB, DEBH and DEBH is not significant, and the overlap ratios of PTV/PTV in the three breathing statuses of mDIBH, FB and DEBH reaches a higher level. Therefore, from the perspective of target volume overlap, if the setup error is corrected online before delivering, the necessity of breathing control during delivering of EB-PBI is worthy discussing.

[Influence of active breathing control on the dose distribution in the target of forward whole-breast intensity-modulated radiotherapy after breast conserving surgery].

OBJECTIVE: To explore the influence of intrafraction and interfraction target displacement on the dose distribution in the target of forward whole-breast intensity-modulated radiotherapy (IMRT) assisted by active breathing control (ABC). METHODS: Each of the selected patient who had received breast conserving surgery was immobilized and received the primary CT simulation assisted by ABC device to get five sets of CT images in three different breathing status, including free breathing (FB) (one set), moderate deep inspiration breathing hold (mDIBH)(two sets) and deep expiration breathing hold (DEBH) (2 sets). After 10 to 15 fractions of radiation, the repeated CT simulation was completed and the same five sets of CT images were obtained at FB, mDIBH, and DEBH, respectively. In the Pinnacle3 treatment planning system, the forward IMRT planning was completed on the first set of mDIBH CT images from the primary CT simulation, and the planning was separately copied by the special system order to the second set of CT images from the primary CT simulation and to the first set of CT images from the repeated CT simulation, keeping the primary angle, direction, size and shape of the MLC field and prescribed dose un-changed. the volumes covered by selected high dose area in the selected segment were compared. RESULTS: In the planning based on the first set of mDIBH CT images from the primary CT simulation, the volume irradiated by equal and more than 103% of prescribed dose in the segment was (1.16 +/- 0.39) cm3, and the volumes were (3.88 +/- 1.07) cm3 and (51.66 +/- 8.68) cm3 in the plannings copied from the first set of mDIBH CT images from the primary CT simulation respectively to the second set of CT images from the primary CT simulation and first set of CT images from the repeat CT simulation, the difference of the volume in the two plannings based on the two set mDIBH CT image from the primary CT simulation was not statistically significant (t = -1.672, P = 0.103). The difference of the volume in the two plannings based on the two sets of mDIBH CT images respectively from the primary and repeat CT simulations had a significant difference (t = -5.728, P < 0.01). CONCLUSION: If the same threshold of mDIBH is maintained during IMRT after breast conserving surgery, the influence of the intrafraction target displacement on the dose distribution is not significant. However, if set-up error is not adjusted, the interfraction change of position of the segment given to cover the high dose area in the IMRT planning will be significant, resulting in a significant change of dose distribution in the breast.

[Relationship of dose-volume histogram parameters and computed tomography grading of radiation-induced lung injury in patients with non-small cell lung cancer treated by three-dimensional conformal radiotherapy].

OBJECTIVE: To explore the relationship of dose-volume histogram (DVH) parameters and computed tomography grading of radiation-induced lung injury in patients with non-small cell lung cancer (NSCLC) treated by three-dimensional conformal radiotherapy (3D-CRT). METHODS: One hundred sixty-nine patients with stage I approximately III NSCLC, treated by 3D-CRT and followed by CT scan for more than six months after 3D-CRT, were divided into grade 0 to grade 4 based on the appearance of radiation-induced lung injury on CT image defined jointly by radiotherapist and radiologist. The patients were divided into CT positive group (grade 2 to grade 4) and CT negative group (grade 0 to grade 1), then the treatment planning shown to the patients were reviewed to compare and analyze the relationship of CT grading of radiation-induced lung injury and the DVH parameter selected. RESULTS: Regardless of whole lung or tumor-bearing lung, there was a statistically significant difference in normal tissue complication probability (NTCP) between the patients grouped with different CT grading of radiation-induced lung injury, and the mean of NTCP increased along with upgrade of CT grading. There was a statistically significant difference of mean lung dose (MLD) regardless of whole lung or tumor-bearing lung between the patients grouped with different CT grading of radiation-induced lung injury, and MLD increased along with upgrade of CT grading. There was a statistically significant difference of the volume received equal or more than 20 Gy (V(20)), 30 Gy (V(30)), 40 Gy (V(40)) of whole lung and tumor-bearing lung between the patients grouped with different CT grading of radiation-induced lung injury, and V(20), V(30), V(40) increased along with upgrade of CT grading. There were not statistically significant differences of the DVH parameters of the contralateral lung in the patients of different groups based on the CT grading. On statistical analysis, the DVH parameters of whole lung and tumor-bearing lung closely correlated with CT grading of radiation-induced injury of the tumor-bearing lung, and there was a relatively strongest relationship between NTCP and CT grading of the tumor-bearing lung (eta = 0.522). CONCLUSION: DVH parameters such NTCP, MLD, V(20), V(30), and V(40) are statistically correlated closely with CT grading of radiation-induced lung injury after radiotherapy for the patients with NSCLC treated by 3D-CRT. Therefore the parameters can be selected as the reference for evaluation after 3D-CRT for patients with NSCLC.

Changes in tumour volume and motion during radiotherapy for thoracic oesophageal cancer.

BACKGROUND AND PURPOSE: Variations of target volume and position were important factors in correction of radiotherapy planning. The purpose was to investigate the changes in volume and motion of oesophageal cancer during radiotherapy using four-dimensional computed tomography (4D-CT). METHODS AND MATERIALS: In total, 109 enhanced 4D-CT data sets were acquired for 38 patients throughout treatment. Gross tumour volumes (GTVs) were outlined on each data set. Variations in volume, motion, and position were calculated for GTV and internal GTV (IGTV) during treatment. RESULTS: GTV (25%, P<0.01) and IGTV (27%, P<0.01) had decreased significantly when measured at the twentieth fraction. Larger intrafractional GTV centre shifts (P<0.01) were observed in the superior-inferior direction (median value of 3.1mm) compared with the right-left and anterior-posterior directions (1.6mm and 1.4mm, respectively). The interfractional shift of the IGTV centre was not significant during radiotherapy. The overlap ratios of the targets decreased for both GTV and IGTV during treatment. CONCLUSIONS: Variations in GTV and IGTV centre shifts were not significant throughout treatment. However, tumour volume decreased significantly by the twentieth fraction. Finally, changes in oesophageal tumour volume and motion may decrease the overlap ratio for GTV and IGTV during radiotherapy.

Phase I/II study of induction chemotherapy plus concurrent chemotherapy and SMART-IMRT-based radiotherapy in locoregionally-advanced nasopharyngeal cancer.

This study aimed to evaluate the efficacy, toxicity and tolerability of simultaneous modulated accelerated radiation therapy (SMART)-intensity modulated radiotherapy (IMRT) plus cisplatin and 5-fluorouracil (5-FU) chemotherapy for patients with advanced nasopharyngeal cancer (NPC). Forty-five patients with stage II-IV NPC, determined by the American Joint Committee on Cancer system, were treated with prescribed doses of 72 Gy total to the gross tumor volume, 60 Gy to the clinical target volume and metastatic nodal station, and 54 Gy to the clinically-negative neck region. Before radiotherapy, two cycles of cisplatin (30 mg/m(2)/day on days 1-3) plus 5-FU (400 mg/m(2)/day on days 1-5) were delivered every three weeks for two cycles. Patients received two cycles of cisplatin (30 mg/m(2) day on days 1-3) every three weeks during radiotherapy. In addition, two cycles of cisplatin and 5-FU were given after radiation. All patients completed the prescribed radiotherapy and all scheduled cycles of chemotherapy. Thirty of the 45 patients (66.6%) had a complete response at the end of treatment. Grade 3 mucositis occurred in 4/45 patients (8.8%) and grade 3 dermatitis occurred in 5/45 (11.1%) during radiotherapy. Grade 3 neutropenia occurred in 6/45 (13.3%) during concurrent chemotherapy. There was no treatment-related mortality. After a median follow-up time of 51 months, only three patients' treatments had failed. Local and distant failure rates were 1.5 and 3.0%, respectively. SMART-IMRT plus cisplatin and 5-FU chemotherapy showed promising activity with manageable toxicity. It is a feasible regimen and improves locoregional disease control.

Evaluation of dosimetric variance in whole breast forward-planned intensity-modulated radiotherapy based on 4DCT and 3DCT.

This study was performed to explore and compare the dosimetric variance caused by respiratory movement in the breast during forward-planned IMRT after breast-conserving surgery. A total of 17 enrolled patients underwent the 3DCT simulation scans followed by 4DCT simulation scans during free breathing. The treatment planning constructed using the 3DCT images was copied and applied to the end expiration (EE) and end inspiration (EI) scans and the dose distributions were calculated separately. CTV volume variance amplitude was very small (11.93 ± 28.64 cm(3)), and the percentage change of CTV volumes receiving 50 Gy and 55 Gy between different scans were all less than 0.8%. There was no statistically significant difference between EI and EE scans (Z =-0.26, P = 0.795). However, significant differences were found when comparing the Dmean at 3DCT planning with the EI and EE planning (P = 0.010 and 0.019, respectively). The homogeneity index at EI, EE and 3D plannings were 0.139, 0.141 and 0.127, respectively, and significant differences existed between 3D and EI, and between 3D and EE (P = 0.001 and 0.006, respectively). The conformal index (CI) increased significantly in 3D treatment planning (0.74 ± 0.07) compared with the EI and EE phase plannings (P = 0.005 and 0.005, respectively). The V30, V40, V50 and Dmean of the ipsilateral lung for EE phase planning were significantly lower than for EI (P = 0.001-0.042). There were no significant differences in all the DVH parameters for the heart among these plannings (P = 0.128-0.866). The breast deformation during respiration can be disregarded in whole breast IMRT. 3D treatment planning is sufficient for whole breast forward-planned IMRT on the basis of our DVH analysis, but 4D treatment planning, breath-hold, or respiratory gate may ensure precise delivery of radiation dose.

Detection of interfraction displacement and volume variance during radiotherapy of primary thoracic esophageal cancer based on repeated four-dimensional CT scans.

BACKGROUND: To investigate the interfraction displacement and volume variation of primary thoracic esophagus carcinoma with enhanced four-dimensional computed tomography (4DCT) scanning during fractionated radiotherapy. METHODS: 4DCT data sets were acquired at the time of treatment simulation and every ten fraction for each of 32 patients throughout treatment. Scans were registered to baseline (simulation) 4DCT scans by using bony landmarks. The gross tumor volumes (GTVs) were delineated on each data set. Coordinates of the GTV centroids were acquired on each respiration phase. Distance between center of the GTV contour on the simulation scan and the centers on subsequent scans were used to assess interfraction displacement between fractions. Volumes were constructed using three approaches: The GTV delineated from the maximum intensity projection (MIP) was defined IGTVMIP, all 10 GTVs were combined to form IGTV10, GTVmean was the average of all 10 phases of each GTV. RESULTS: Interfraction displacement in left-right (LR), anterior-posterior (AP), superior-inferior (SI) directions and 3D vector were 0.13 ± 0.09 cm, 0.16 ± 0.12 cm, 0.34 ± 0.26 cm and 0.43 ± 0.24 cm, respectively between the tenth fraction and simulation 4DCT scan. 0.14 ± 0.09 cm, 0.19 ± 0.16 cm, 0.45 ± 0.43 cm and 0.56 ± 0.40 cm in LR, AP, SI and 3D vector respectively between the twentieth fraction and simulation 4DCT scan. Displacement in SI direction was larger than LR and AP directions during treatment. For distal esophageal cancer, increased interfraction displacements were observed in SI direction and 3D vector (P = 0.002 and P = 0.001, respectively) during radiotherapy. The volume of GTVmean, IGTVMIP, and IGTV10 decreased significantly at the twentieth fraction for middle (median: 34.01%, 33.09% and 28.71%, respectively) and distal (median: 22.76%, 25.27% and 23.96%, respectively) esophageal cancer, but for the upper third, no significant variation were observed during radiotherapy. CONCLUSIONS: Interfractional displacements in SI direction were larger than LR and AP directions. For distal location, significant changes were observed in SI direction and 3D vector during radiotherapy. For middle and distal locations, the best time to reset position should be selected at the twentieth fraction when the primary tumor target volume changed significantly, and it was preferable to guide target correction and planning modification.