Dosimetric and toxicity comparison between prone and supine position IMRT for endometrial cancer

PURPOSE: To determine the dosimetric and toxicity differences between prone and supine position intensity-modulate radiotherapy in endometrial cancer patients treated with adjuvant radiotherapy. METHODS: Forty-seven consecutive endometrial cancer patients treated with adjuvant RT were analyzed. Of these, 21 were treated in prone position and 26 in the supine position. Dose-volume histograms for normal tissue structures and targets were compared between the two groups. Acute and chronic toxicity were also compared between the cohorts. RESULTS: The percentage of volume receiving 10, 20, 30, 40, 45, and 50 Gy for small bowel was 89.5%, 69%, 33%, 12.2%, 5%, and 0% in the prone group and 87.5%, 62.7%, 26.4%, 8%, 4.3%, and 0% in the supine group, respectively. The difference was not statistically significant. The dose-volume histograms for bladder and rectum were also comparable, except for a slightly greater percentage of volume receiving 10 Gy (1.5%) and 20 Gy (5%) for the rectum in the prone group. Acute small bowel toxicities were Grade 1 in 7 patients and Grade 2 in 14 patients in the prone group vs. Grade 1 in 6 patients and Grade 2 in 19 patients in the supine group. Chronic toxicity was Grade 1 in 7 patients and Grade 3 in 1 patient in the prone group and Grade 1 in 5 patients in the supine group. CONCLUSION: These preliminary results suggest that no difference exists in the dose to the normal tissue and toxicity between prone and supine intensity-modulated radiotherapy for endometrial cancer. Longer follow-up and more outcome studies are needed to determine whether any differences exist between the two approaches.     

宫颈癌放疗仰、俯卧位固定下的摆位误差及剂量学差异探讨

目的:对比研究宫颈癌调强放疗中行仰卧位与俯卧位的两种固定方式时的摆位误差及剂量学差异。方法:随机选取64例宫颈癌患者分成两组,每组32例,分别选取仰卧位和俯卧位方式固定。两组患者均行首次摆位、摆位误差纠正及治疗期间的CBCT扫描,将CBCT扫描图像与治疗计划CT图像自动匹配配准,分别得到X轴（左右方向）、Y轴（头脚方向）、Z轴（腹背方向）的摆位误差数据;同时通过TPS计算两组病例靶区的D95、Dmean、CI、HI以及危及器官小肠、膀胱、直肠、结肠、股骨头、盆骨、脊髓、乙状结肠分别在等剂量线包含的体积百分比下的剂量值大小。结果:仰卧位患者与俯卧位患者在X、Y、Z轴方向平均误差分别为［（2.55±1.21） mm,（2.13±1.12） mm］、［（4.01±1.16） mm,（2.44±1.57） mm］、［（3.46±1.43） mm,（2.89±1.21） mm］。俯卧位固定组X、Y、Z轴方向平均误差均小于仰卧位固定组,且均具有统计学差异（P<0.05）;在靶区的D95、Dmean、CI、HI均不具有统计学差异（P>0.05）,除股骨头、盆骨、脊髓、乙状结肠外,俯卧位固定组的危及器官小肠、膀胱、直肠、结肠在等剂量线包含的体积百分比下的剂量值明显小于仰卧位固定组,且均具有统计学差异（P<0.05）。结论:在宫颈癌调强放疗中,与仰卧位固定相比,俯卧位固定可明显减少其摆位误差,以及在靶区受量归一一致的情况下,更好地保护了危及器官。     

宫颈癌体外自适应放疗

放疗已经成为宫颈癌的主要治疗手段之一,近年来在体外精确放疗技术治疗期间,器官运动、摆位误差、解剖学变化等因素可能导致实际接受剂量与初始计划不一致,从而造成靶区剂量不足及危及器官受照剂量过多。自适应放疗（ ART）可根据治疗过程中所得到的位置、体积、剂量等参数的反馈信息,利用图像引导及个体化建模等方法对后续治疗计划进行相应的优化和调整,从而在提高局部控制率的同时降低放疗不良反应的发生率。     

Use of MRI and spectroscopy in evaluation of external beam radiotherapy for prostate cancer

PURPOSE: To characterize the metabolic response in the prostate, the time to resolution of disease, and the correlation between magnetic resonance imaging (MRI) with spectroscopy (MRSI) results, biopsy findings, and serum prostate-specific antigen (PSA) level after external beam radiotherapy. METHODS AND MATERIALS: A total of 55 patients underwent MRSI before and/or at varying times after external beam radiotherapy. The percentage of the cancerous, healthy, and atrophic voxels was calculated, and the time to resolution of disease was determined and compared with the PSA nadir. RESULTS: Of the 55 patients, 70% had negative MRSI and 30% had positive MRSI findings. A strong correlation was found between negative MRSI and negative biopsy findings (n = 11) and between positive MRSI and positive biopsy findings (n = 7). A weak correlation was observed between the PSA level and the MRSI and biopsy findings. The mean time to disease resolution was 40.3 months and the mean time to PSA nadir was 50 months. With time, an increase in atrophy and a decline in cancerous metabolism was found. CONCLUSION: When used in conjunction with PSA measurement and biopsy, the results of this study suggest that MRSI contributes to a greater level of confidence in determining the outcome and may be a useful adjunct for assessing local control before PSA failure when striving to distinguish the benign "blip" from local recurrence.     

前列腺癌的外照射放疗进展

外照射放疗作为前列腺癌的主要治疗手段之一,随着放疗技术的进步、靶区认识的统一,已进入精确放疗时代.高剂量放疗的准确实施,使前列腺癌的疗效显著提高.而影像引导的放射治疗、质子放疗和低分割放疗则是疗效进一步提高的研究方向.     

Internal organ motion in prostate cancer patients treated in prone and supine treatment position.

BACKGROUND AND PURPOSE: To compare supine and prone treatment positions for prostate cancer patients with respect to internal prostate motion and the required treatment planning margins. MATERIALS AND METHODS: Fifteen patients were treated in supine and fifteen in prone position. For each patient, a planning computed tomography (CT) scan was used for treatment planning. Three repeat CT scans were made in weeks 2, 4, and 6 of the radiotherapy treatment. Only for the planning CT scan, laxation was used to minimise the rectal content. For all patients, the clinical target volume (CTV) consisted of prostate and seminal vesicles. Variations in the position of the CTV relative to the bony anatomy in the four CT scans of each patient were assessed using 3D chamfer matching. The overall variations were separated into variations in the mean CTV position per patient (i.e. the systematic component) and the average 'day-to-day' variation (i.e. the random component). Required planning margins to account for the systematic and random variations in internal organ position and patient set-up were estimated retrospectively using coverage probability matrices. RESULTS: The observed overall variation in the internal CTV position was larger for the patients treated in supine position. For the supine and prone treatment positions, the random components of the variation along the anterior-posterior axis (i.e. towards the rectum) were 2.4 and 1.5 mm (I standard deviation (1 SD)), respectively; the random rotations around the left-right axis were 3.0 and 2.9 degrees (1 SD). The systematic components of these motions (1 SD) were larger: 2.6 and 3.3 mm, and 3.7 and 5.6 degrees, respectively. The set-up variations were similar for both treatment positions. Despite the smaller overall variations in CTV position for the patients in prone position, the required planning margin is equal for both groups (about 1 cm except for 0.5 cm in lateral direction) due to the larger impact of the systematic variations. However, significant time trends cause a systematic ventral-superior shift of the CTV in supine position only. CONCLUSIONS: For internal prostate movement, it is important to distinguish systematic from random variations. Compared to patients in supine position, patients in prone position had smaller random but somewhat larger systematic variations in the most important coordinates of the internal CTV position. The estimated planning margins to account for the geometrical uncertainties were therefore similar for the two treatment positions.     

Radiation dose to laterally transposed ovaries during external beam radiotherapy for cervical cancer

The purpose of this study was to estimate the radiation dose to laterally transposed ovaries from external beam radiotherapy for cervical cancer. Dose measurements were performed in a modified humanoid phantom using a 6 MV photon beam. The dependence of the ovarian dose upon the field size, the distance from the primary irradiation field and the presence of wedges or gonadal shielding was determined. For a tumor dose of 45 Gy, ovarian dose was 0.88-8.51 Gy depending on the field size employed and the location of the transposed ovary in respect to the treatment field. Positioning of 7 cm thick shielding reduced the dose to ovary by less than 19%. The use of wedges increased the ovarian dose by a factor up to 1.5. Accurate radiographic localization of the ovaries allows the use of the presented dosimetric results to obtain a reasonable prediction of the ovarian dose.     

Dose-volume effects for normal tissues in external radiotherapy: Pelvis

A great deal of quantitative information regarding the dose-volume relationships of pelvic organs at risk has been collected and analysed over the last 10 years. The need to improve our knowledge in the modelling of late and acute toxicity has become increasingly important, due to the rapidly increasing use of inverse-planned intensity-modulated radiotherapy (IMRT) and the consequent need of a quantitative assessment of dose-volume or biological-based cost functions. This comprehensive review concerns most organs at risk involved in planning optimisation for prostate and other types of pelvic cancer. The rectum is the most investigated organ: the largest studies on dose-volume modelling of rectal toxicity show quite consistent results, suggesting that sufficiently reliable dose-volume/EUD-based constraints can be safely applied in most clinical situations. Quantitative data on bladder, bowel, sexual organs and pelvic bone marrow are more lacking but are rapidly emerging; however, for these organs, further investigation on large groups of patients is necessary.     

Dose-volume histogram analysis as predictor of radiation pneumonitis in primary lung cancer patients treated with radiotherapy

PURPOSE: To determine the relationship between various parameters derived from lung dose-volume histogram analysis and the risk of symptomatic radiation pneumonitis (RP) in patients undergoing radical radiotherapy for primary lung cancer. METHODS AND MATERIALS: The records of 156 patients with lung cancer who had been treated with radical radiotherapy (>/=45 Gy) and for whom dose-volume histogram data were available were reviewed. The incidence of symptomatic RP was correlated with a variety of parameters derived from the dose-volume histogram data, including the volume of lung receiving 10 Gy (V(10)) through 50 Gy (V(50)) and the mean lung dose (MLD). RESULTS: The rate of RP at 6 months was 15% (95% confidence interval 9-22%). On univariate analysis, only V(30) (p = 0.036) and MLD (p = 0.043) were statistically significantly related to RP. V(30) correlated highly positively with MLD (r = 0.96, p < 0.001). CONCLUSION: V(30) and MLD can be used to predict the risk of RP in lung cancer patients undergoing radical radiotherapy.     

Dose-volume histogram and dose-surface histogram analysis for skin reactions to carbon ion radiotherapy for bone and soft tissue sarcoma

Background and purpose

To evaluate the usefulness of the dose-volume histogram (DVH) and dose-surface histogram (DSH) as clinically relevant and available parameters that helped to identify bone and soft tissue sarcoma patients at risk of developing late skin reactions, including ulceration, when treated with carbon ion radiotherapy.

Materials and methods

Thirty-five patients with bone and soft tissue sarcoma treated with carbon ion beams were studied. The clinical skin reactions were evaluated. Some pretreatment variables were compared with the grade of late skin reactions.

Results

Average DVH and DSH were established in accordance with the grading of the skin reactions. Prescribed dose, the difference in depths between the skin surface and the proximal extent of the tumor, and some DVH/DSH parameters were correlated with late skin reaction (≧grade 3) according to univariate analysis. Furthermore, the area irradiated with over 60 GyE (S₆₀ > 20 cm²) on DSH was the most important factor by multivariate analysis.

Conclusions

The area irradiated with over 60 GyE (S₆₀ > 20 cm²) on DSH was found to be a parameter for use as a predictor of late skin reactions.     

A simple technique for craniospinal radiotherapy in the supine position.

PURPOSE: Craniospinal irradiation poses technical difficulties that may be addressed with the use of the newer technologies that have become available over the past decade. The use of CT simulation allows improved target localisation and beam geometry definition while significantly reducing the treatment simulation time. We have developed a CT-based technique for whole CNS irradiation in the supine position that uses fixed field parameters, asymmetric jaws for field matching and drastically reduces simulation and treatment times. METHODS: The patient is CT scanned and treated in the supine position. The clinical target volume and relevant critical structures are outlined on a planning CT scan. Half beam blocked lateral fields with a collimator rotation are used to match the beam divergence from the superior border of the spinal field at the C2 vertebral body. The shielding for the cranial fields is generated automatically, and the dose distribution is calculated using a 3D treatment planning system. Fixed field parameters are used for the planning and treatment. The position of the isocenter of the spine field is always a fixed longitudinal distance from the isocenter of the brain fields. If multiple posterior fields are required, the isocenter of the second spine field is always a fixed longitudinal distance from that of the first and the gap between the fields is determined using virtual simulation and feathered during treatment using the asymmetric jaws of the linear accelerator. All treatment portals are filmed daily during the first week of treatment, and after each junction change thereafter. RESULTS AND CONCLUSION: The supine position provides numerous advantages. Patients are more comfortable, the treatment position is more reproducible, and access to the airway is possible, if necessary, for patient sedation. The use of CT simulation decreases the simulation time, allows for increased planning accuracy, and enables the use of multimodality image registration, and 3D treatment planning. The use of asymmetric jaws allows for junction feathering without changing the patient setup or using a couch angle.     

A randomized trial of supine vs. prone positioning in patients undergoing escalated dose conformal radiotherapy for prostate cancer.

BACKGROUND AND PURPOSE: The optimal treatment position for patients receiving radical radiation therapy for prostate cancer has been a source of controversy. To resolve this issue, we conducted a randomized trial to evaluate the effects of supine and prone positioning on organ motion, positioning errors, and dose to critical organs during escalated dose conformal irradiation for localized prostate cancer and patient and therapist satisfaction with setup technique. PATIENTS AND METHODS: Twenty eight patients were randomized to commence treatment immobilized in the supine or prone position and were subsequently changed to the alternate positioning for the latter half of their treatment. Patients underwent CT simulation and conformal radiotherapy planning and treatment in both positions. The clinical target volume encompassed the prostate gland. Alternate day lateral port films were compared to corresponding simulator radiographs to measure the isocentre positioning errors (IPE). Prostate motion (PM) and total positioning error (TPE) were measured from the same films by the displacements of three implanted fiducial markers. Dose volume histograms (DVHs) for the two treatment positions were compared at the 95, 80 and 50% dose (D%) levels. The patients and radiation therapists completed weekly questionnaires regarding patient comfort and ease of setup. RESULTS: Seven patients, who started in the supine position, subsequently refused prone position and received their whole treatment supine. Small bowel in the treatment volume, not present in the supine position, prevented one patient from being treated prone. PM in anterior posterior direction was statistically significantly less in the supine position (P<0.05). There was no significant difference in superior inferior PM for the two treatment positions. No statistically significant difference between supine and prone positioning was observed in isocentre positioning error (IPE) or total positioning error (TPE) due to a policy of daily pre-treatment correction. However, more pre-treatment corrections were required for patients in the prone position. The DVH analysis demonstrated larger volumes of the bladder wall, rectal wall and small bowel within the D95, D80 and D50% when comparing the planning target volumes (PTVs) actually treated for prone positioning. When the prone PTV was expanded to account for the greater PM encountered in that position, a statistically significant difference (P<0.007) was observed in favour of the supine position at all dose levels. In the prone position, four patients had small bowel within the 60 Gray (Gy) isodose and in the supine position, no patients had small bowel in the 60 or 38Gy volumes. Supine position was significantly more comfortable for the patients and setup was significantly easier for the radiation therapists. The median patient comfort score was 0.79 (Standard deviation (SD) 0.03) supine and 0.45 (SD 0.05) prone (P<0.001) The therapist convenience of setup was 0.80 (SD 0.016) supine and 0.54 (SD 0.025) prone (P<0.005). No statistically significant difference was seen for the other parameters studied. CONCLUSIONS: We demonstrated significantly less PM in the supine treatment position. There was no difference for either treatment position in IPE or TPE, however, more pre-treatment corrections were required in the prone position. Prone position required a larger PTV with resulting increased dose to critical organs. There were statistically significant improvements at all dose levels for small bowel, rectal wall and bladder wall doses in the supine position once corrections were made for differences in organ motion. Linear analogue scores of patient comfort and radiation therapist convenience demonstrated statistically significant improvement in favour of the supine position. Supine positioning has been adopted as the standard for conformal prostatic irradiation at our centre.     

Ultrasound image fusion for external beam radiotherapy for prostate cancer

: To determine whether real-time ultrasound imaging and targeting system for the treatment of prostate cancer was feasible. The initial phase of this project included a study to develop and determined (a) software for the fusion of ultrasound images to standard x-rays obtained during simulation, and (b) the potential reduction in field size with real time imaging.

: During 13 patient simulations a transrectal ultrasound image was obtained. Orthogonal x-ray films were acquired with the rectal probe in place. Both the x-ray and ultrasound images were digitized and a fusion image was created of the prostate position in relation to the probe, bladder, and rectum. The two-dimensional area of the rectum, bladder, and prostate was determined in the lateral projection. Potential conformal blocks were designed for the lateral portals in a four-field treatment technique.

: The transrectal ultrasound probe enabled real-time prostrate imaging. The lateral field size can be reduced to 6.08 × 5.68 cm² ± 0.62 × 0.48 cm² from the standard 8 × 8 cm² field. The posterior rectal wall was physically displaced out of the lateral field. The area of the rectum included in the lateral field in 1.75 cm² ± 0.85 cm².

: The prostate position can be determined with certainty on a regular basis with transrectal ultrasonography. The amount of normal tissue in the high dose volume can be reduced. This approach may reduce acute and chronic morbidity and allow further dose escalation.     

Dose-volume impact in high-dose-rate Iridium-192 brachytherapy as a boost to external beam radiotherapy for localized prostate cancer--a phase II study.

BACKGROUND AND PURPOSE: Evaluation of dose-volume-time-related factors in 64 patients treated with high-dose-rate brachytherapy (HDR-BT) as a boost to external beam radiotherapy (EBRT) for localized prostate cancer. PATIENTS AND METHODS: Clinical parameters were correlated with morbidity scores of the EPIC (Expanded Prostate Cancer Index) questionnaire. Median time after radiotherapy (HDR-BT up to 18 Gy in two fractions and EBRT up to a median dose of 50.4 Gy) was 1.5 and 3 years (first and second questionnaire). RESULTS: A significant impact of a urethra D1 exceeding 15 Gy in at least one HDR fraction concerning urinary morbidity and a rectum D1 exceeding 6 Gy to the rectal mucosa in the first and second HDR fraction concerning the rectal bleeding rate was found. A higher number of needles was associated with lower urinary and bowel scores after 1.5 years. A prostate length >4.8 cm and a longer duration of EBRT (independently of the dose) predisposed for lower urinary and bowel scores. In contrast to a urethra D1 > 15 Gy as an independent factor, a rectum D1 > 6 Gy per HDR fraction correlated with a higher number of needles and an increased prostate length. CONCLUSIONS: To minimize morbidity in HDR-BT for prostate cancer, a maximum dose to the urethra of 15 Gy and a maximum dose to the rectal mucosa of 6 Gy is advisable. Treatment- and patient-related factors have a major impact on toxicity.     

Target volume shape variation during irradiation of rectal cancer patients in supine position: Comparison with prone position

Purpose

To quantify the inter-fraction shape variation of the mesorectum for rectal cancer patients treated with 5 × 5 Gy in supine position and compare it to variation in prone position.

Methods and materials

For 28 patients a planning CT (pCT) and five daily cone-beam-CT (CBCT) scans were acquired in supine position. The mesorectal part of the CTV (MesoRect) was delineated on all scans. The shape variation was quantified by the distance between the pCT- and the CBCT delineations and stored in surface maps after online setup correction. Data were analyzed for male and female patients separately and compared to prone data.

Results

A large range of systematic, 1-8 mm (1SD), and random, 1-5 mm, shape variation was found, comparable to prone patients. Random-shape variation was comparable for male and female patients, while systematic variation was 3 mm larger for female patients.

Conclusions

Shape variation of the MesoRect is substantial, heterogeneous and different between male and female patients. Differences between supine and prone orientation, however, are small. Clinical margins should be differentiated in position along the cranio-caudal axis, in anterior-posterior direction and for gender. Margins should also be increased, even when online setup correction is used. Due to the small margin differences between prone and supine treatments, the setup choice should be determined on dose to the organs at risk.     

Interfractional variation in position of the uterus during radical radiotherapy for cervical cancer.

BACKGROUND AND PURPOSE: This study was conducted to investigate the positional change of the uterus during radiotherapy which can degrade the accuracy of three-dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT). PATIENTS AND METHODS: Sixty-six patients received radical radiotherapy for cervical cancer in Samsung Medical Center. For each patient, two MRI scans were taken; one was before beginning radiotherapy and the other was in the third or fourth week of radiotherapy. In T2-weighted MRI images, the positional change of the uterus was quantified by measuring six parameters; the distance from the external uterine opening to the isthmus of the uterus (Dcx), the distance from the isthmus of the uterus to the uterine fundus (Dco), the perpendicular distance of the uterine body to the uterine corpus (Dco-per), the angle between the vertical line and the cervical canal in sagittal images (Acx), the uterine corpus angle from the vertical line in sagittal plan (Aco), the angle between the uterine corpus from an arbitrary bony landmark and a vertical mid line in axial images (Aco-axi) RESULTS: Mean value of change in Dcx+Dco of tumor size during treatment was 8.0 mm in small tumors and 17.9 mm in large tumors. Among 44 anteflexed uterus patients, 5 changed into a retroflexed position. 12 patients (18%) had a greater than 30 degrees variation in any angle. For patients under 60 years, the difference in Acx was statistically significant. CONCLUSIONS: Positional changes of the uterus during radiotherapy should be considered in the treatment planning of 3DCRT or IMRT, particularly in patients under 60 years or those with tumor size greater than 4 cm in diameter.