Class solutions for conformal external beam prostate radiotherapy

PURPOSE: To determine a class solution coplanar plan from comparisons of three-field (3F), four-field (4F), and six-field (6F) plans in conformal non-intensity-modulated prostate radiotherapy. METHODS AND MATERIALS: Doses to two clinical target volumes, prostate only (PO) and prostate plus seminal vesicles (PSV) were evaluated in each of 10 patients using a variety of 3F, 4F, and 6F plans with a planning target volume margin of 10 mm. All plans were prescribed to 64 and 74 Gy. The class solution plan for each of 3F, 4F, and 6F was chosen from a variety of symmetrical and asymmetrical field arrangements that had been previously assessed. The class solution plans, 3F (0, 90, 270 degrees ), 4F (35, 90, 270, 325 degrees ), and 6F (50/lat/25) were compared with reference plans: 3F (0, 120, 240 degrees ), 4F (0, 90, 180, 270 degrees ), and 6F (55, 90, 125, 235, 270, 305 degrees ). Rectal volumes irradiated to greater than 50% (V(50)), 80% (V(80)), and 90% (V(90)) of the prescribed dose, normal tissue complication probabilities (NTCP) for rectum, bladder, and femoral heads (FH), and tumor control probabilities (TCP) were assessed. FH tolerance was set at 52 Gy to 10% volume. RESULTS: The field arrangement that gave the lowest irradiated rectal volume with acceptable bladder and FH doses was a 3F (0, 90, 270 degrees ) class solution plan. This plan gave a reduction in rectal V(80) of 1.2-12.4% for the PO group and 2.3-23.8% for the PSV group compared with the other plans. The reduction in rectal V(90) was 0.2-11.9% for the PO group and 1.5-23.3% for the PSV group using the 3F (0, 90, 270 degrees ) plan. This plan provided one of the lowest rectal NTCPs, but the difference was not significant when compared with the 4F class solution plan. When target volumes with 10-mm margins remain unchanged to 74 Gy, the irradiated rectal volumes for all plans were higher and rectal NTCPs can be trebled. CONCLUSION: The use of appropriate beam arrangements can provide a class solution plan using only 3 fields compared with 4 or 6 fields for the parameters considered. Both 3F (0, 90, 270 degrees ) and 4F (35, 90, 270, 325 degrees ) plans can be used as a class solution plan. Other practical issues that may influence the choice of class solution include delivery time with smaller number of fields, ease of verification, the use of 10-mm multileaf collimation vs. conformal blocks, and field shape fitting limitations when using dynamic wedges.     

Randomised pilot study of dose escalation using conformal radiotherapy in prostate cancer: long-term follow-up

Background:

Radical three-dimensional conformal radiotherapy (CFRT) with initial androgen suppression (AS) is a standard management for localised prostate cancer (PC). This pilot study evaluated the role of dose escalation and appropriate target volume margin. Here, we report long-term follow-up.

Methods:

Eligible patients had T1b-T3b N0 M0 PC. After neoadjuvant AS, they were randomised to CFRT, giving (a) 64 Gy with either a 1.0- or 1.5-cm margin and (b) ±10 Gy boost to the prostate alone.

Results:

One hundred and twenty-six men were randomised and treated. Median follow-up was 13.7 years. The median age was 66.6 years at randomisation. Median presenting prostate-specific antigen (PSA) was 14 ng ml⁻¹. Sixty-four out of 126 patients developed PSA failure. Forty-nine out of 126 patients restarted AS, 34 out of 126 developed metastases and 28 out of 126 developed castrate-resistant prostate cancer (CRPC). Fifty-one out of 126 patients died; 19 out of 51 died of PC. Median overall survival (OS) was 14.4 years. Although escalated dose results were favourable, no statistically significant differences were seen between the randomised groups; PSA control (hazard ratio (HR): 0.77 (95% confidence interval (CI): 0.47–1.26)), development of CRPC (HR: 0.81 (95% CI: 0.40–1.65)), PC-specific survival (HR: 0.59 (95% CI:0.23–1.49)) and OS (HR: 0.81 (95% CI: 0.47–1.40)). There was no evidence of a difference in PSA control according to margin size (HR: 1.01 (95% CI: 0.61–1.66)).

Interpretation:

Long-term follow-up of this small pilot study is compatible with a benefit from dose escalation, but confirmation from larger trials is required. There was no obvious detriment using the smaller radiotherapy margin.     

Dose escalation with 3D-CRT in prostate cancer: French study of dose escalation with conformal 3D radiotherapy in prostate cancer-preliminary results

PURPOSE: To evaluate the feasibility of dose escalation in a multi-institutional study in prostate cancer patients. METHODS AND MATERIALS: Between October 1995 and October 1998, 164 patients with localized adenocarcinoma of the prostate were treated with 3-dimensional conformal radiotherapy at one of five French institutions. The dose of radiation was escalated from 66 to 80 Gy (ICRU point). The maximum dose to the rectal wall was limited to 75 Gy. RESULTS: Results were compared in two groups, one (group 1) receiving the standard dose (n = 46 patients; 66 to 70 Gy) and the other (group 2) receiving the escalated dose (n = 118 patients; 74 to 80 Gy). There was no difference in the characteristics of patients between the two groups. The mean follow-up time was 32 months in group 1 and 17.5 months in group 2. No statistical difference between the two groups was observed in the incidence of late gastrointestinal and urinary toxicities. The probability of achieving a posttreatment prostate-specific antigen nadir of 相似文献   

A comparison of multileaf collimator with conformal blocks for the boost phase of dose-escalated conformal prostate radiotherapy.

A multileaf collimator (MLC) is compared with conformal blocks for delivering the boost phase of dose-escalated conformal prostate radiotherapy. When using conformal blocks, the volume of rectum irradiated to 90% (V90) is lower (1.4+/-1.3%, 1 SD) for a three-field plan with gantry angles 0 degree, 90 degrees, 270 degrees than for a six-field plan with gantry angles 50 degrees, 90 degrees, 130 degrees, 230 degrees, 270 degrees, 310 degrees (2.1 +/- 1.3%, P = 0.002). However, when using an MLC in which the leaves and wedge are oriented at right angles, V90 is higher (4.7 +/- 3.0%) for a three-field plan than for a six-field plan (2.7 +/- 1.6%, P=0.05). The larger increase in V90 for the three-field plan when changing from conformal blocks to MLC is mainly due to the limitation imposed upon the MLC orientation by the use of wedges.     

HDR prostate monotherapy: dosimetric effects of implant deformation due to posture change between TRUS- and CT-imaging.

HDR monotherapy for prostate cancer consists of four fractions. The first fraction is delivered with online TRUS-based treatment planning. For the last three fractions the treatment plan is based on a CT-scan acquired in between fractions 1 and 2. The patient position (high lithotomy, rectal US probe) during TRUS-guided catheter implantation and first fraction differs from the patient position in the CT-scan and the remaining three fractions (lowered legs, no TRUS probe). This study describes the effect of posture changes on dose distributions when a plan designed for the TRUS anatomy is applied to the CT-scan anatomy. The aim is to quantify dosimetrical errors that would result from skipping the use of a planning CT-scan, and rely for all fractions on the TRUS plan. Such a procedure would substantially reduce the involved workload, and would increase patient comfort. For three prostate cancer patients, images were acquired during TRUS-guided catheter implantation. Furthermore, a CT-scan (no US probe in rectum, different position of legs) was acquired and matched with the TRUS set. On both TRUS and CT, prostate, urethra and rectum were delineated and all catheters were traced. For each patient, an optimized treatment plan was designed using TRUS images and contours. Catheters with obtained dwell positions of the TRUS plan were transferred individually to the catheter positions in the CT. Changes in dose distribution due to relocation of catheters were evaluated using DVHs. For all patients the dose distributions changed significantly due to rearrangement of the catheters, having most impact on the urethra (maximum observed change: 32% volume receiving > or = 120% of the prescribed dose) and a reduction of PTV coverage (6-28%). Implant deformation when changing from TRUS patient set-up to CT set-up affected negatively the quality of optimized treatment plans. Inclusion of more patients in this study was planned, but because of the observed strong negative effects it is already concluded that the TRUS plan cannot be used for the last three fractions with a deviating patient set-up.     

Three-dimensional conformal external beam radiotherapy versus the combination of external radiotherapy with high-dose rate brachytherapy in localized carcinoma of the prostate: comparison of acute toxicity

AIMS AND BACKGROUND: Radiotherapy represents one of the basic therapeutic methods in treatment of localized carcinoma of the prostate. Optimal irradiation dose is the cornerstone of a successful treatment. Along with local control of the disease and overall survival of the patient, possible acute and long-term side effects need to be monitored very closely. METHODS: A non-randomized prospective study comparing the acute genitourinary and gastrointestinal toxicity in patients irradiated for localized carcinoma of the prostate. Fifty-seven patients were treated with three-dimensional conformal external beam radiotherapy alone, and in the second treatment arm a combination of external beam radiotherapy and high-dose rate brachytherapy was employed in 40 patients. RESULTS: Three-dimensional conformal external beam radiotherapy. Acute G1 genitourinary toxicity was recorded in 35.1% of patients, G2 in 22.8%, and G2-3 in one patient (1.7%). Acute gastrointestinal toxicity was experienced by 54.4% of patients, G1 in 28.1%, G2 in 17.5%, and G3 in 8.8%. Three-dimensional conformal external beam radiotherapy + brachytherapy. Acute G1 genitourinary toxicity was recorded in 37.5% and grade 2 in 15% of the patients. Only G1 acute gastrointestinal toxicity was recorded in 40% of the patients. CONCLUSIONS: Acute G1 genitourinary toxicity was experienced by a similar percentage of patients in both treatment arms. Acute G2 genitourinary toxicity was more frequent in the three-dimensional conformal radiotherapy arm. Higher acute genitourinary toxicity, G3 or G4, was recorded only in one patient per treatment arm. Acute gastrointestinal toxicity was more frequent in the three-dimensional conformal radiotherapy arm. Higher acute gastrointestinal toxicity, G2 and G3, was only observed in the three-dimensional conformal radiotherapy arm. The acute toxicity observed was of a low grade. The combination of external beam radiotherapy with brachytherapy resulted in a lower incidence of gastrointestinal toxicity than external beam radiotherapy alone.     

Health-related quality of life after permanent I-125 brachytherapy and conformal external beam radiotherapy for prostate cancer - a matched-pair comparison

Background and purpose

The aim of the study was to compare quality of life after permanent I-125 brachytherapy (BT) and external beam radiotherapy (EBRT) for prostate cancer.

Materials and methods

A group of 104 patients (52 in each group) have been surveyed prospectively before EBRT/BT (time A), at the last day of EBRT (70.2-72.0 Gy) or one month after BT (time B), and a median time of 16 months after EBRT/BT (time C) using a validated questionnaire (Expanded Prostate Cancer Index Composite). Pairs were matched according to the following criteria: age ±5years, prostate volume ±10 cc, use of antiandrogens, and erectile function.

Results

Urinary function/bother scores decreased significantly more after BT both at time B and time C. Bowel function/bother scores tended to be higher after BT, with a lower percentage of patients with painful bowel movements (BT: 12%/27%/15%; EBRT: 19%/52%/35% at time A/B/C; p < 0.05 for differences at times B/C) and rectal bleeding (BT: 12%/12%/12%; EBRT: 8%/14%/17%). No difference concerning erectile dysfunction was found (67% vs. 61% with preserved erections firm enough for intercourse after BT vs. EBRT at time C).

Conclusions

BT was associated with higher urinary, but lower rectal toxicity. The risk of treatment-associated erectile dysfunction did not differ between these methods.     

Phase III pilot study of dose escalation using conformal radiotherapy in prostate cancer: PSA control and side effects

Radical radiotherapy is a standard form of management of localised prostate cancer. Conformal treatment planning spares adjacent normal tissues reducing treatment-related side effects and may permit safe dose escalation. We have tested the effects on tumour control and side effects of escalating radiotherapy dose and investigated the appropriate target volume margin. After an initial 3-6 month period of androgen suppression, 126 men were randomised and treated with radiotherapy using a 2 by 2 factorial trial design. The initial radiotherapy tumour target volume included the prostate and base of seminal vesicles (SV) or complete SV depending on SV involvement risk. Treatments were randomised to deliver a dose of 64 Gy with either a 1.0 or 1.5 cm margin around the tumour volume (1.0 and 1.5 cm margin groups) and also to treat either with or without a 10 Gy boost to the prostate alone with no additional margin (64 and 74 Gy groups). Tumour control was monitored by prostate-specific antigen (PSA) testing and clinical examination with additional tests as appropriate. Acute and late side effects of treatment were measured using the Radiation Treatment and Oncology Groups (RTOG) and LENT SOM systems. The results showed that freedom from PSA failure was higher in the 74 Gy group compared to the 64 Gy group, but this did not reach conventional levels of statistical significance with 5-year actuarial control rates of 71% (95% CI 58-81%) in the 74 Gy group vs 59% (95% CI 45-70%) in the 64 Gy group. There were 23 failures in the 74 Gy group and 33 in the 64 Gy group (Hazard ratio 0.64, 95% CI 0.38-1.10, P=0.10). No difference in disease control was seen between the 1.0 and 1.5 cm margin groups (5-year actuarial control rates 67%, 95% CI 53-77% vs 63%, 95% CI 50-74%) with 28 events in each group (Hazard ratio 0.97, 95% CI 0.50-1.86, P=0.94). Acute side effects were generally mild and 18 weeks after treatment, only four and five of the 126 men had persistent > or =Grade 1 bowel or bladder side effects, respectively. Statistically significant increases in acute bladder side effects were seen after treatment in the men receiving 74 Gy (P=0.006), and increases in both acute bowel side effects during treatment (P=0.05) and acute bladder sequelae (P=0.002) were recorded for men in the 1.5 cm margin group. While statistically significant, these differences were of short duration and of doubtful clinical importance. Late bowel side effects (RTOG> or =2) were seen more commonly in the 74 Gy and 1.5 cm margin groups (P=0.02 and P=0.05, respectively) in the first 2 years after randomisation. Similar results were found using the LENT SOM assessments. No significant differences in late bladder side effects were seen between the randomised groups using the RTOG scoring system. Using the LENT SOM instrument, a higher proportion of men treated in the 74 Gy group had Grade > or =3 urinary frequency at 6 and 12 months. Compared to baseline scores, bladder symptoms improved after 6 months or more follow-up in all groups. Sexual function deteriorated after treatment with the number of men reporting some sexual dysfunction (Grade> or =1) increasing from 38% at baseline to 66% at 6 months and 1 year and 81% by year 5. However, no consistent differences were seen between the randomised groups. In conclusion, dose escalation from 64 to 74 Gy using conformal radiotherapy may improve long-term PSA control, but a treatment margin of 1.5 cm is unnecessary and is associated with increased acute bowel and bladder reactions and more late rectal side effects. Data from this randomised pilot study informed the Data Monitoring Committee of the Medical Research Council RT 01 Trial and the two studies will be combined in subsequent meta-analysis.     

中心型NSCLC常规分割适形放疗与同期加量适形放疗剂量学比较

目的:比较局部晚期中心型非小细胞肺癌同期加量适形放疗和常规分割适形放疗计划的剂量分布。方法:收集经病理确诊的局部晚期非小细胞肺癌患者10例,每例患者均设计2个放疗计划。1)常规分割适形放疗计划(conven-tional fractionation radiotherapy,CFR):计划靶体积(planning target volume,PTV)照射剂量60Gy/30次;2)同期加量适形放疗计划(SIB-CR):PTV处方剂量50.4Gy/28次,临床靶体积(clinic target volume,CTV)处方剂量64.4Gy/28次。比较2种放疗计划的靶区剂量及肺、食管、脊髓和心脏等危及器官受量。结果:SIB-CR组较CFR组的大体肿瘤体积(gross tumor volume,GTV)D90、GTV D95分别增加了(1.777 0±0.200 5)Gy(P=0.005)、(1.757 0±0.135 9)Gy(P=0.008),差异均有统计学意义。SIB-CR组肺平均剂量、V5、V8、V10、V13、V20、V30、V40、V50和V55均小于CFR组,其中肺平均剂量、V8、V10、V13、V20、V30、V40和V50差异均有统计学意义,P<0.05。SIB-CR组脊髓最大剂量、平均剂量、V40及正常组织并发症概率(normal tissue complication probability,NTCP)均小于CFR组,其中脊髓最大剂量比较差异有统计学意义,P=0.022。SIB-CR组的食管最大剂量、平均剂量、食管V45、食管全周受照45Gy长度(LETT45)均小于CFR组,其中平均剂量、V45差异有统计学意义,P值分别为0.002和0.003。SIB-CR组的心脏最大剂量、平均剂量、V40均小于CFR组,差异无统计学意义,P>0.05。结论:SIB-CR较CFR能获得更高的肿瘤剂量,且能降低肺、脊髓、食管和心脏等危及器官受量,但还有待于进一步的临床研究。     

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

Background and purpose

To evaluate the dosimetry of helical tomotherapy (HT) and three-dimensional conformal radiotherapy (3D-CRT) in breast cancer patients undergoing whole breast radiation with simultaneous integrated boost (SIB) of the tumor bed.

Material and methods

Thirteen patients with breast cancer treated by lumpectomy and requiring whole breast radiotherapy with tumor bed boost were planned using both HT and 3D-CRT using the field-in-field technique. The whole breast and tumor bed were prescribed 50.68 Gy and 64.4 Gy, respectively, in 28 fractions. Dosimetries for both techniques were compared.

Results

Coverage of the whole breast was adequate with both techniques (V_95% = 96.22% vs. 96.25%, with HT and 3D-CRT, respectively; p = 0.64). Adequate tumor bed coverage was also achieved, although it was significantly lower with HT (V_95% = 97.18% vs. 99.72%; p < 0.001). Overdose of the breast volume outside the tumor bed was significantly lower with HT (V_54.23Gy = 12.47% vs. 30.83%; p < 0.001). Ipsilateral lung V_20Gy (6.34% vs. 10.17%; p < 0.001), V_5Gy (16.54% vs. 18.53%; p < 0.05) and mean dose (4.05 Gy vs. 6.36 Gy; p < 0.001) were significantly lower with HT. In patients with left-sided tumors, heart V_30Gy (0.03% vs. 1.14%; p < 0.05) and mean dose (1.35 Gy vs. 2.22 Gy; p < 0.01) were significantly lower with HT, but not V_5Gy. Contralateral breast V_5Gy (0.27% vs. 0.00%; p < 0.01) and maximum dose were significantly increased with HT.

Conclusions

In breast cancer treated with SIB, both HT and 3D-CRT provided adequate target volume coverage and low heart doses. Tumor bed coverage was slightly lower with HT, but HT avoided unnecessary breast overdosage while improving ipsilateral lung dosimetry.     

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.     

Long-term results of conformal radiotherapy for prostate cancer: impact of dose escalation on biochemical tumor control and distant metastases-free survival outcomes

PURPOSE: To report prostate-specific antigen (PSA) relapse-free survival and distant metastases-free survival (DMFS) outcomes for patients with clinically localized prostate cancer treated with high-dose conformal radiotherapy. METHODS AND MATERIALS: Between 1988 and 2004, a total of 2,047 patients with clinically localized prostate cancer were treated with three-dimensional conformal radiotherapy or intensity-modulated radiotherapy. Prescribed dose levels ranged from 66-86.4 Gy. Median follow-up was 6.6 years (range, 3-18 years). RESULTS: Although no differences were noted among low-risk patients for the various dose groups, significant improvements were observed with higher doses for patients with intermediate- and high-risk features. In patients with intermediate-risk features, multivariate analysis showed that radiation dose was an important predictor for improved PSA relapse-free survival (p < 0.0001) and improved DMFS (p = 0.04). In patients with high-risk features, multivariate analysis showed that the following variables predict for improved PSA relapse-free survival: dose (p < 0.0001); age (p = 0.0005), and neoadjuvant-concurrent androgen deprivation therapy (ADT; p = 0.01). In this risk group, only higher radiation dose was an important predictor for improved DMFS (p = 0.04). CONCLUSIONS: High radiation dose levels were associated with improved biochemical tumor control and decreased risk of distant metastases. For high-risk patients, despite the delivery of high radiation dose levels, the use of ADT conferred an additional benefit for improved tumor control outcomes. We observed a benefit for ADT in high-risk patients who received higher doses.     

192Ir or 125I prostate brachytherapy as a boost to external beam radiotherapy in locally advanced prostatic cancer: a dosimetric point of view.

PURPOSE: This work aims at comparing the dosimetric possibilities of 125I or 192Ir prostate brachytherapy (Bt) as a boost to external beam radiotherapy in the treatment of locally advanced adenocarcinoma. METHODS AND MATERIALS: From 1/1997 to 12/2002, 260 patients were treated. Until 12/2001 a low dose rate (LDR) treatment with 192Ir wires was used, later replaced by a high dose rate (HDR) delivered with an 192Ir stepping source technology. For the present work, we selected 40 patients including the last 20 treated, respectively, by LDR and HDR. The planning CT Scans of all these 40 patients were transferred into the 3D Prowess system for 125I permanent implants design according to the Seattle method. The reference data for dosimetric comparisons were the V100 and the prescribed dose for 192Ir as well as the dose delivered with 125I techniques to the 192Ir V100. We compared V100-150 data as well as doses to the organs at risks (OR) and cold spots (CS). RESULTS: The V100 is 85.3+/-8% for 192Ir LDR and 96+/-2% for HDR techniques (P < 0.0001). In comparison with 125I, the 192Ir LDR mode induces higher hyperdosage volumes inside the CTV but also more CS, while maximal doses to urethra and rectum are, respectively, 17 and 39% less with 125I (P < 0.0001). In comparison with the 192Ir HDR mode, 125I Bt induces higher hyperdosage volumes and slightly more CS deliberately planned around the bladder neck. If delivered doses to urethra are identical, those to the 20% anterior part of the rectum are 33% less with 125I (P < 0,0001). The 125I Bt technique was only possible in 24 out of the 40 patients studied due to pelvic bone arch interference. CONCLUSIONS: At the present time, there is no evident dosimetric superiority of one Bt method when all the criteria are taken into account. However, improving Bt techniques to implant any prostatic size could found the superiority of the 125I or permanent implants. 125I indeed allows large hyperdosage volumes inside the CTV in comparison with 192Ir HDR techniques while lowering doses to OR and minimizing CS.     

Intensity-modulated radiotherapy in nasopharyngeal carcinoma: dosimetric advantage over conventional plans and feasibility of dose escalation

PURPOSE: To compare intensity-modulated radiotherapy (IMRT) with two-dimensional RT (2D-RT) and three-dimensional conformal radiotherapy (3D-CRT) treatment plans in different stages of nasopharyngeal carcinoma and to explore the feasibility of dose escalation in locally advanced disease. MATERIALS AND METHODS: Three patients with different stages (T1N0M0, T2bN2M0 with retrostyloid extension, and T4N2M0) were selected, and 2D-RT, 3D-CRT, and IMRT treatment plans (66 Gy) were made for each of them and compared with respect to target coverage, normal tissue sparing, and tumor control probability/normal tissue complication probability values. In the Stage T2b and T4 patients, the IMRT 66-Gy plan was combined with a 3D-CRT 14-Gy boost plan using a 3-mm micromultileaf collimator, and the dose-volume histograms of the summed plans were compared with their corresponding 66-Gy 2D-RT plans. RESULTS: In the dosimetric comparison of 2D-RT, 3D-CRT, and IMRT treatment plans, the T1N0M0 patient had better sparing of the parotid glands and temporomandibular joints with IMRT (dose to 50% parotid volume, 57 Gy, 50 Gy, and 31 Gy, respectively). In the T2bN2M0 patient, the dose to 95% volume of the planning target volume improved from 57.5 Gy in 2D-RT to 64.8 Gy in 3D-CRT and 68 Gy in IMRT. In the T4N2M0 patient, improvement in both target coverage and brainstem/temporal lobe sparing was seen with IMRT planning. In the dose-escalation study for locally advanced disease, IMRT 66 Gy plus 14 Gy 3D-CRT boost achieved an improvement in the therapeutic ratio by delivering a higher dose to the target while keeping the normal organs below the maximal tolerance dose. CONCLUSIONS: IMRT is useful in treating all stages of nonmetastatic nasopharyngeal carcinoma because of its dosimetric advantages. In early-stage disease, it provides better parotid gland sparing. In locally advanced disease, IMRT offers better tumor coverage and normal organ sparing and allows room for dose escalation.     

A comparison of CT- and ultrasound-based imaging to localize the prostate for external beam radiotherapy

PURPOSE: This study assesses the accuracy of NOMOS B-mode acquisition and targeting system (BAT) compared with computed tomography (CT) in localizing the prostate. METHODS AND MATERIALS: Twenty-six patients were CT scanned, and the prostate was localized by 3 observers using the BAT system. The BAT couch shift measurements were compared with the CT localization. Six of the patients had gold markers present in the prostate, and the prostate movement determined by BAT was compared with the movement determined by the gold markers. RESULTS: Using the BAT system, the 3 observers determined the prostate position to be a mean of 1-5 mm over all directions with respect to the CT. The proportion of readings with a difference >3 mm between the observers was in the range of 25% to 44%. The prostate movement based on gold markers was an average of 3-5 mm different from that measured by BAT. The literature assessing the accuracy and reproducibility on BAT is summarized and compared with our findings. CONCLUSIONS: We have found that there are systematic differences between the BAT-defined prostate position compared with that estimated on CT using gold grain marker seeds.