A dosimetric analysis of intensity-modulated radiation therapy (IMRT) as an alternative to adjuvant high-dose-rate (HDR) brachytherapy in early endometrial cancer patients

P

Utitmblptsrobr

aM

Int. J. Radiation Oncology Biol. Phys., Vol. 65, No. 1, pp. 266–273, 2006Copyright © 2006 Elsevier Inc.

Printed in the USA. All rights reserved0360-3016/06/$–see front matter

doi:10.1016/j.ijrobp.2005.12.049

HYSICS CONTRIBUTION

A DOSIMETRIC ANALYSIS OF INTENSITY-MODULATED RADIATIONTHERAPY (IMRT) AS AN ALTERNATIVE TO ADJUVANT HIGH-DOSE-RATE

(HDR) BRACHYTHERAPY IN EARLY ENDOMETRIAL CANCER PATIENTS

BULENT AYDOGAN, PH.D.,*† ARNO J. MUNDT, M.D.,*† BRETT D. SMITH, M.SC.,†

LOREN K. MELL, M.D.,* STEVE WANG, PH.D.,* HAROLD SUTTON, M.D.,*†

AND JOHN C. ROESKE, PH.D.*†

*Department of Radiation and Cellular Oncology, The University of Chicago, Chicago, IL; †Department of Radiation Oncology,University of Illinois at Chicago, Chicago, IL

Purpose: To evaluate the role of intensity-modulated radiation treatment (IMRT) as an alternative to high-dose-rate (HDR) brachytherapy in the treatment of the vagina in postoperative early endometrial cancer patients aftersurgery.Methods and Materials: Planning computed tomography (CT) scans of 10 patients previously treated with HDRwere used in this study. In all cases, a dose of 700 cGy/fraction was prescribed at a distance of 0.5 cm from thecylinder surface. The same CT scans were then used in IMRT planning. In this paradigm, the vaginal cylinderrepresents a component of a hypothetical immobilization system that would be indexed to the linac treatmenttable.Results: Our study showed that IMRT provided relatively lower rectal doses than HDR when treatment wasprescribed at a distance of 0.5 cm away from the cylinder surface. Maximum rectal doses were lower with IMRTcompared with HDR (average: 89.0% vs. 142.6%, respectively, p < 0.05). Moreover, the mean rectal dose waslower in IMRT plans compared with HDR plans with treatment prescribed either to the surface (average: 14.8%vs. 21.4%, respectively, p < 0.05) or to 0.5 cm (average: 19.6% vs. 33.5%, respectively, p < 0.05). IMRT planshad planning target volume (PTV) coverage comparable with HDR (average PTV minimum for treatmentprescribed to 0.5 cm: 93.9% vs. 92.1%, p � 0.71, respectively) with less inhomogeneity (average PTV maximum:110.8% vs. 381.6%, p < 0.05).Conclusion: Our dosimetric analysis suggests that when used in conjunction with a suitable immobilizationsystem, IMRT may provide an alternative to HDR brachytherapy in women with early endometrial cancer afterhysterectomy. However, more studies are needed to evaluate the clinical merit of the IMRT in these patients.© 2006 Elsevier Inc.

Early endometrial cancer, High dose rate, Intensity-modulated radiotherapy, integral dose.

twfcdi7cac

eiti

F

INTRODUCTION

terine cancer is the most common gynecologic cancer inhe United States (1). Endometrial cancer, which originatesn the inner lining of the uterus, accounts for the majority ofhe uterine cancers (2). In the management of early endo-etrial cancer patients, total abdominal hysterectomy with

ilateral salpingo-oophorectomy with or without pelvicymph node sampling is the standard of care (3). Wholeelvic radiotherapy (WPRT) and brachytherapy are the in-egral components in the postoperative adjuvant therapy ofelected patients and in the management of inoperable orecurrent endometrial cancers. WPRT is used to treat theriginal tumor site and the regional lymph nodes, whereasrachytherapy is used to treat the vaginal cuff. Low-dose-ate brachytherapy was used extensively to treat these pa-

Reprint requests to: Bulent Aydogan, Ph.D., Department of Radi-tion and Cellular Oncology, The University of Chicago, 5758 S.

266

ients until the high-dose-rate (HDR) brachytherapy methodas introduced. Currently, HDR brachytherapy is the pre-

erred modality, because of its technical advantages. Aylinder is placed in the vagina, and a 192Ir source is used toeliver vaginal cuff boost using HDR brachytherapy. At ournstitution, patients who have received WPRT are treated to00 cGy per fraction (3 fractions total) at the surface of theylinder. When brachytherapy is used as the sole therapyfter surgery, the same dose is delivered at a distance of 0.5m away from the cylinder surface.

High-dose-rate brachytherapy has several limitations. Forxample, because the tumor volume often extends deepernto vaginal mucosa, particularly in a patient with recurrentumors, it is impossible with HDR to treat deeper and/orrregularly shaped tumors without irradiating the surround-

ax: (312) 413-3068; E-mail: [email protected] Nov 10, 2005, and in revised form Dec 28, 2005.

ccepted for publication Dec 29, 2005.

itnclnrtr

mtipmprabuptsvb

Iecdtrufthb

pcit

P

ptrwtHWPttd

S

mmpmlbbR

T

ciuttrpIsAcd

T

bSmudti

ESuisacttppomdhtcwcdp

pd

267The role of IMRT in early endometrial cancer patients ● B. AYDOGAN et al.

ng organs at risk to a much higher dose than the prescrip-ion dose. It should be noted also that this treatment tech-ique necessitates a dedicated HDR brachytherapy unit andostly periodic source changes. Moreover, federal and stateaws on radioactive materials are very stringent. An alter-ative approach involves the use of intensity-modulatedadiotherapy (IMRT), which conforms the radiation dose tohe shape of the target in 3D, thereby sparing the organs atisk.

Intensity-modulated radiotherapy is a fairly new treat-ent planning and delivery modality that provides a means

o deliver higher than conventional doses of radiation, mak-ng dose escalation possible in high-risk patients and inatients with recurrent tumors without increasing the nor-al tissue complications. Moreover, IMRT can be used to

lan and deliver simultaneous integrated boost, therebyeducing the treatment time. IMRT is increasingly receivingttention in the management of gynecologic malignancies,ecause of its advantages. Most attention has focused on these of IMRT to deliver WPRT in these patients (4–7). Alsoroposed are the potential replacement of vaginal brachy-herapy with IMRT in cervical cancer patients (8, 9) andimultaneously integrated boost with IMRT for locally ad-anced gynecologic cancers that may not be amenable torachytherapy for anatomic or medical reasons (10).To date, no studies have been published to evaluate

MRT as an alternative to HDR brachytherapy in earlyndometrial cancer patients. In this paradigm, the vaginalylinder would be used as an immobilization device. Theevice we are developing will be indexed to the treatmentable such that the position of the vaginal cuff could beeproduced for each treatment. Similar to the HDR sched-le, an IMRT schedule of 3 fractions with 1 week betweenractions would be used to deliver the same dose prescrip-ion over the same time period as the HDR regimen. Ourypothesis is that IMRT will be able to produce similar oretter dose distributions compared to HDR planning.To test this hypothesis, we generated IMRT plans for 10

atients previously treated with HDR at our institution. Weompared planning target volume (PTV) coverage and crit-cal organ doses and evaluated the statistical significance ofhe results.

METHODS

atient populationTen women with early endometrial carcinoma who received

ostoperative WPRT were retrospectively selected. The endome-rial cancer patients had Stage IC–IIB disease. Stage IC patientseceived only intracavitary brachytherapy if lymph node dissectionas performed. Stage II patients received a combination of WPRT

o treat the original tumor site and the regional lymph nodes andDR brachytherapy to boost the vaginal cuff. The prescribedPRT dose in all patients was 45 Gy in 1.8 Gy daily fractions.

atients who received WPRT are treated to 700 cGy/fx (3 fractionsotal) at the surface of the cylinder. When brachytherapy is used ashe sole therapy after surgery, the same dose is delivered at a

imulationFollowing the American Brachytherapy Society (ABS) recom-endations, the largest diameter of cylinder that can be accom-odated was used (3). A computed tomography (CT) scan of each

atient in the treatment position was obtained using our depart-ental scanner (Picker PQ 500, Philips Medical Systems, Cleve-

and, OH) with radiopaque contrast material in the Foley catheteralloon and in the rectum to allow the bladder and rectal doses toe estimated as per International Committee on Radiation Unitseport 38 (ICRU 38) (11).

arget definitionFollowing the ICRU 38 (11) recommendations, a PTV and

ritical organs such as bladder and rectum were contoured onndividual axial CT slices in all patients. The PTV included thepper 4 cm of the vagina. For patients who underwent WPRT, thearget volume was obtained by subtracting the 0.1 cm wall fromhe cylinder to represent the cylinder surface. In women whoeceived only brachytherapy, the target was obtained via 3D ex-ansion of the cylinder volume by 0.5 cm. After both the HDR andMRT treatment plans were complete, the cylinder volume wasubtracted from the PTV to obtain the volume of the treated tissue.

structure was also created by subtracting the PTV plus theylinder volume from the whole body for calculating the integralose.

reatment planningHigh-dose-rate plans were produced using a commercial

rachytherapy planning system (BrachyVision, Varian Medicalystems, Palo Alto, CA) that employs an isotropic dose calculationodel as recommended by the ABS (3). This software allows the

ser to interactively modify the dose distribution to achieve aesired plan. The number of dwell positions was selected based onhe length of the target, and the dwell positions were 0.5 cm apartn all 10 patients.

Intensity-modulated radiotherapy plans were generated usingclipse/Helios inverse treatment planning system (Varian Medicalystems). Briefly, this system produces the optimal intensity mod-lation profiles using simple gradient optimization with line min-mization and calculates the dose distribution using convolutionuperposition. The prescription dose is defined by the user givenll dose–volume constraints of the PTV and normal tissues. Theseonstraints are monitored and may be changed interactively duringhe optimization process to obtain the best possible plan. To selecthe optimal number of fields and beam energy, plans for a testatient were generated using 4–11 equally spaced, coplanar 6 MVhoton beams. Dose constraints were set to minimize the volumef normal tissue receiving the prescription dose without compro-ising PTV coverage. Plans were compared in terms of isodose

istributions as well as normal tissue and PTV dose–volumeistograms (DVHs) (data not shown). This analysis demonstratedhat increasing the beam number was associated with better doseonformation to the PTV. However, no significant improvementas evident with the use of more than 9 beams. These results are

onsistent with planning studies showing that more than 7–9 fieldso not significantly improve dose conformation in IMRT treatmentlanning (5).Based on the above analysis, a 9-field, 6-MV, coplanar IMRT

lan was generated for each patient using an identical set ofose–volume constraints. Fields were equally spaced at 40° inter-

1hpg

D

artGr(p

Icptrslinsta

P

aTtIpid(I1MIp(da(

Pt

dasp

Hdp(Ip0aItaaI1t

I

car1ptd

twTactdtp

inpdIdepavdwlti

a

268 I. J. Radiation Oncology ● Biology ● Physics Volume 65, Number 1, 2006

60°, 200°, 240°, 280°, and 320°. All plans were normalized toave an equal or better PTV coverage when compared with HDRlans. DVHs were calculated for PTV, rectum, bladder, and inte-ral dose structure.

ata analysisMinimum, maximum, and average doses to the PTV, rectum,

nd bladder were compared. Integral doses were calculated sepa-ately for HDR and IMRT plans by multiplying the mean dose andotal irradiated body volume (target was excluded) and reported inray-liter (Gy-l). Data were analyzed using the paired t test and

eported as statistically significant if the p value was less than 0.05p � 0.05). The method of Holm–Sidak was used to adjustvalues for multiple hypothesis testing (12).

RESULTS

Representative isodose distributions of both HDR andMRT plans are shown in Fig. 1 at the mid level of theylinder. Figure 1a corresponds to the subsequent IMRTlan shown in Fig. 1b. Both plans provide good coverage ofhe target volume. However, the IMRT plan provides supe-ior dose uniformity through the target, as well as betterparing of the bladder and the rectum at the mid to high doseevels. A comparison of the DVHs for these plans is shownn Fig. 2. The HDR plans have a high degree of doseonuniformity compared to the IMRT plan. In particular, amall portion of the bladder and rectum receives greaterhan 100% of the prescription dose. With IMRT, the bladdernd the rectal doses are lower at all dose levels.

rescription point is at the cylinder surfaceMinimum, maximum, and mean doses to PTV, bladder,

nd rectum for each of the 10 patients are shown in Table 1.he averages of the mean bladder doses (as a percentage of

he prescription dose) were 20.9% and 19.3% for HDR andMRT plans, respectively (p � 0.55). In only 6 out of the 10lans, IMRT produced lower maximum bladder doses, andn 1 patient, both plans produced the same mean bladderose. IMRT provided a lower mean bladder dose than HDRaverage: IMRT � 74.1% vs. HDR � 66.2%, p � 0.05).MRT plans resulted also in lower mean rectal doses for all0 patients (14.8%) than HDR plans (21.4%) (p � 0.05).oreover, the maximum rectal doses also were lower in all

MRT plans compared to the HDR plans (84.6% vs. 72.8%,� 0.05). The minimum dose to PTV was nearly identical

IMRT � 95.3% vs. HDR � 95.2%, p � 0.68). The doseistribution was more homogenous with IMRT. The aver-ges of the maximum PTV doses were 108.7% and 241.7%p � 0.05) for the IMRT and HDR plans, respectively.

rescription point is at a distance of 0.5 cm away fromhe cylinder surface

Minimum, maximum, and mean doses to the PTV, blad-er, and rectum for all 10 patients are shown in Table 2. Theverage mean bladder doses (as a percentage of the pre-cription dose) were 32.5% and 25.9% for HDR and IMRT

DR produced lower mean bladder doses. Maximum blad-er doses were lower for IMRT plans compared with HDRlans, but the difference was not statistically significantaverage: IMRT � 83.1% vs. HDR � 120%, p � 0.07).MRT plans resulted in lower mean rectal doses for all 10atients (averages: IMRT � 20.7% vs. HDR � 34.6%, p �.05). Moreover, the maximum rectal doses were lower inll IMRT plans compared with the HDR plans (averages:MRT � 89% vs. HDR � 142.6%, p � 0.05). On average,he minimum dose to PTV was higher using IMRT (aver-ges: IMRT � 93.9% vs. HDR � 92.1%, p � 0.71). Inddition, the dose distribution was more homogenous withMRT planning. The average maximum target dose was10.8% and 381.6% for the IMRT and HDR plans, respec-ively (p � 0.05).

ntegral doseThe average integral doses for the 10 patients were very

omparable with HDR (8.6 Gy-l) and IMRT (9.3 Gy-l),lthough they are statistically significant. The integral dosesanged from 6.7 Gy-l to 11.9 Gy-l for HDR and from 6.9 to2.4 Gy-l for IMRT plans (p � 0.05). In only 1 out of 10atients, the integral dose was less with IMRT (10.5 Gy-l)han it was with HDR (10.7 Gy-l). The average integralose, in this study, was only 7.2% higher with IMRT.

DISCUSSION

The feasibility of IMRT as an alternative to HDR brachy-herapy in women with early endometrial cancer treatedith radiation therapy after hysterectomy is investigated.hese patients typically receive a combination of WPRTnd brachytherapy (treatment generally prescribed at theylinder surface). When brachytherapy is used as the solereatment modality, treatment is, in general, prescribed at aistance of 0.5 cm from the cylinder surface. We conductedhis study by comparing the IMRT and the HDR planserformed separately based on these prescription points.When treating the surface of the cylinder, IMRT resulted

n very similar dose distributions compared with HDR plan-ing. However, the IMRT dose distribution was, as ex-ected, more homogenous. Maximum and mean targetoses were within 10% of the prescription doses. UnlikeMRT planning, in HDR planning the maximum targetoses ranged between 197% and 354%. In the treatment ofndometrial cancer, the bladder and the rectum are therimary organs of concern. When the IMRT and HDR plansre compared, the maximum and mean bladder doses areery comparable. However, the maximum and mean rectaloses were considerably lower with IMRT than they wereith HDR. The mean rectal dose was, on average, 45%

ower with IMRT. In a comparison of the two treatmentechniques, HDR plans resulted in approximately 18% lessntegral dose than IMRT.

When treatment is prescribed at a distance of 0.5 cmway from the cylinder surface, the volume of the bladder

ootosdc

ttpdep

269The role of IMRT in early endometrial cancer patients ● B. AYDOGAN et al.

n the patient anatomy. Using HDR increased the volumef surrounding critical organs that receives higher thanhe prescription dose. Particularly, parts of the criticalrgans toward the end of the vaginal cylinder were ob-erved to receive higher radiation doses. This is mainlyue to increased dwell time to compensate minimal dose

Fig. 1. (a) High-dose-rate (HDR) and (b) intensity-mopatient at the mid level of the cylinder. Dose prescriptionTarget volume is shown in red, bladder in light blue, anddose (blue) and the maximum dose (red).

ontribution from the other dwell positions at the tip of T

he cylinder. IMRT, on the other hand, was able to keephe maximum critical organ dose at about the level of therescription dose. In particular, the rectal and bladderoses were lower at the mid to high dose levels. Forxample, the average maximum bladder dose for the 10atients studied in this work was 67% more with HDR.

radiotherapy (IMRT) dose distributions for the sames at a distance of 0.5 cm away from the cylinder surface.in brown. Dose scaled between 10% of the prescription

dulatedpoint irectum

here was only modest difference in the mean bladder

dmwh

pdiH

270 I. J. Radiation Oncology ● Biology ● Physics Volume 65, Number 1, 2006

oses between IMRT (32.5%) and HDR (25.5%). Theean rectal dose, however, was 70% higher, on average,ith HDR. The average maximum rectal dose was alsoigher with HDR (74%).

Fig. 2. Dose–volume histograms for (a) High-dose-rate (Hsame patient. Dose prescription point is at a distance obladder, green; rectum, brown.

In contrast to what is expected, integral doses were com- t

arable between IMRT and HDR plans when treating at aistance of 0.5 cm from the cylinder surface. IMRT resultsn larger volumes that are irradiated to low doses. WithDR, on the other hand, small volumes are irradiated to mid

nd (b) intensity-modulated radiotherapy (IMRT) for them away from the cylinder surface. Colors: target, red;

DR) af 0.5 c

o high doses and large volumes to very low doses. It is still

clr

Irwtsi

cJpsiirdaf

stccbtb

etblcbfvtonf

1234567891MS

1234567891MS

271The role of IMRT in early endometrial cancer patients ● B. AYDOGAN et al.

ontroversial and not well understood whether “a lot to aittle” or a “little to a lot” is better in terms of reducing theisk of a secondary malignancy (13).

Whole-body dose may be a concern when treating withMRT, though there are only limited data to estimate theisk. Hall and Wu estimated that the secondary cancer riskould increase from 1% for conventional radiation therapy

o 1.75% for IMRT (14). However, to our knowledge, notudies have characterized the excess cancer risk with IMRTn comparison with brachytherapy.

Most of our knowledge on radiation-induced canceromes from survivors of the atomic bomb attack onapan, radiation accidents, and individuals medically ex-osed to radiation. One of the conclusions from thetudies that investigated the second malignancies inducedn patients by radiation therapy was that sarcomas arenduced in heavily irradiated tissues in or close to theadiation fields (14, 15). Brenner et al. reported that mostramatic increases in the second cancers after radiother-py for prostate cancer were for the bladder and rectum

Table 1. Percent minimum, maximum, and mean (a) high-dose-and rectum for individual patients and mean and standard deviat

cylin

(a) % high

Patient

Planning target volume

Min Max Mean Min

96 198 129 1098 267 123 799 243 120 8

100 267 123 990 230 128 492 207 132 590 354 120 1296 200 124 494 254 148 5

0 96 197 132 6ean 95.1 241.7 127.9 7

D 3.5 16.5 11.9 2.7

(b) % intensity-mod

Patient

Planning target volume

Min Max Mean Mi

196 112 108 998 109 106 296 105 103 3

101 120 113 590 110 104 293 110 106 293 102 107 296 106 103 194 106 103 2

0 96 107 103 1ean 95.3 108.7 105.6 2.9

D 3.2 4.9 3.2 2.4

or 10 or more years after diagnosis (15). In a separate o

tudy, Boice et al. reported that bladder is the organ withhe highest second cancer risk factor after radiotherapy inervical cancer patients (16). Based on these studies, onean argue that IMRT may provide significant advantages,ecause it reduces the rectal and bladder doses at the mido high dose levels in women who receive vaginalrachytherapy only.Tumor volume in endometrial cancer patients often

xtends deeper in the vaginal mucosa, especially in pa-ients with recurrent tumors. Because the volume of theladder and the rectum irradiated at the mid to high doseevel is linearly proportional to the prescription pointhosen, a compromise is made in the HDR brachytherapyy prescribing the treatment at a distance of 0.5 cm awayrom the cylinder surface in patients who will receiveaginal brachytherapy only. With HDR brachytherapy,reating deeper in the vaginal wall might increase the riskf acute and chronic toxicities due to the large volumes oformal tissue irradiated. IMRT, with its ability to con-orm the high-dose region to the shape of the target,

d (b) intensity-modulated radiotherapy doses to target, bladder,D) for the 10 patients when the treatment was prescribed at theface

rate dose

Bladder Rectum

Max Mean Min Max Mean

120 31 6 92 2456 19 4 76 1668 24 5 88 25

106 29 7 89 2774 16 4 120 2591 20 3 69 1559 22 3 55 1121 8 8 69 2580 23 6 91 2366 17 5 97 2374.1 20.9 5.1 84.6 21.48.8 4.7 2.4 9.7 4.8

radiotherapy dose

Bladder Rectum

Max Mean Min Max Mean

97 40 1 88 1959 19 1 67 966 29 1 85 1992 34 1 83 2262 10 1 97 1888 24 1 73 1442 6 1 15 229 6 2 66 1883 21 2 82 1444 4 1 72 1366.2 19.3 1.2 72.8 14.823.2 12.6 0.4 22.7 5.9

rate anion (Sder sur

-dose-

ulated

n

ffers a modality to reduce radiation-related sequelae and

ptpt

Iaiiiu

sdipp

wissrtPIiitSatidtwt

1234567891MS

1234567891MS

272 I. J. Radiation Oncology ● Biology ● Physics Volume 65, Number 1, 2006

otentially allow for the delivery of higher than conven-ional doses. One immediate application of the techniqueresented in this study may be the treatment of recurrentumors.

It is important to note that the clinical evaluation of theMRT technique presented in this study is a must beforeny conclusion is made or the technique is implementedn the clinic. The construction and evaluation of themmobilization device before the clinical evaluation is anntegral part of the proposed IMRT technique, and it isnder way.

CONCLUSION

The dosimetric analysis of IMRT presented in thistudy showed that IMRT provides reduced critical organoses, especially in patients where the prescription points 0.5 cm away from the cylinder surface. With the resultresented in this study, one can conclude that IMRT may

Table 2. Percent minimum, maximum, and mean (a) high-dose-bladder, and rectum for individual patients and mean and standar

prescribed at a distance of

(a) % h

Patient

Planning target volume

Min Max Mean Min

92 337 146 1688 488 147 1192 366 139 1293 388 140 1596 318 139 695 407 142 991 283 133 1995 394 150 692 475 159 9

0 87 360 155 10ean 92.1 381.6 145 11.3

D 2.9 64.4 8.0 4.3

(b) %

Patient

Planning target volume

Min Max Mean Min

92 105 103 1690 109 106 296 112 107 1094 120 113 598 112 108 496 111 108 394 110 108 395 112 108 294 110 107 6

0 90 107 103 1ean 93.9 110.8 107.1 5.2

D 2.0 4.0 2.8 4.6

rovide an alternative to HDR brachytherapy in women c

ith early endometrial cancer after hysterectomy when its used in conjunction with a suitable immobilizationystem. Moreover, when brachytherapy is used as theole radiation therapy after surgery, use of IMRT couldeduce the volume of critical organs irradiated at the mido high dose levels while keeping the integral dose to theTV comparable with that for HDR brachytherapy.MRT may offer a significant advantage over HDR alson conforming the prescription dose of radiation to therregularly shaped targets while sparing the bladder andhe rectum, especially in patients with recurrent tumors.uch an approach may reduce normal-tissue toxicity andllow for dose escalation. However, the clinical evalua-ion of this method, including the immobilization device,s crucial before any conclusion about its efficacy israwn or any clinical use is initiated. The accuracy of thearget delineation and delivery may be further improvedith the use of image-guided radiation therapy. In addi-

ion, IMRT may present a feasible option for cancer

d (b) intensity-modulated radiotherapy (IMRT) doses to target,ation (SD) for the 10-patient population when the treatment wasfrom the cylinder surface

se-rate

Bladder Rectum

Max Mean Min Max Mean

214 49 10 164 3885 28 6 115 25

100 35 7 131 37165 45 11 134 41107 23 7 233 39148 32 6 130 25

92 35 4 84 1635 13 12 111 39

137 37 11 151 38117 28 8 173 37120 32.5 8.2 142.6 33.549.2 10.4 2.7 41.1 8.4

dose

Bladder Rectum

Max Mean Min Max Mean

104 49 2 111 2855 17 1 61 897 37 1 106 2592 31 1 83 2099 29 1 111 31

109 33 1 105 2284 15 1 38 340 11 2 91 20

105 34 3 109 2846 3 1 75 1183.1 25.9 1.4 89 19.625.9 14.8 0.7 24.4 9.5

rate and devi0.5 cm

igh-do

IMRT

enters without HDR capabilities.

273The role of IMRT in early endometrial cancer patients ● B. AYDOGAN et al.

REFERENCES

1

1

1

1

1

1

1

1. Jemal A, Tiwari RC, Murray T, et al. Cancer statistics, 2004.CA Cancer J Clin 2004;54:8–29.

2. Creasman WT, Odicino F, Maisonneuve P, et al. Carcinomaof the corpus uteri. Int J Gynecol Obstet 2003;83:79–118.

3. Nag S, Erickson B, Parikh S, et al. The American Brachy-therapy Society recommendations for high-dose-rate brachy-therapy for carcinoma of the endometrium. Int J Radiat OncolBiol Phys 2000;48:779–790.

4. Mundt AJ, Lujan AE, Rotmensch J, et al. Intensity-modulatedwhole pelvic radiotherapy in women with gynecologic malig-nancies. Int J Radiat Oncol Biol Phys 2002;52:1330–1337.

5. Roeske JC, Lujan A, Rotmensch J, et al. Intensity-modulatedwhole pelvic radiation therapy in patients with gynecologicmalignancies. Int J Radiat Oncol Biol Phys 2000;48:1613–1621.

6. Ahamad A, Jhingran A. New radiation techniques in gyneco-logical cancer. Int J Gynecol Cancer 2004;14:569–579.

7. Portelance L, Chao KS, Grigsby PW, et al. Intensity-modu-lated radiation therapy (IMRT) reduces small bowel, rectum,and bladder doses in patients with cervical cancer receivingpelvic and para-aortic irradiation. Int J Radiat Oncol Biol Phys2001;51:261–266.

8. Wahab SH, Malyapa RS, Mutic S, et al. A treatment planningstudy comparing HDR and AGIMRT for cervical cancer. MedPhys 2004;31:734–743.

9. Roeske JC, Lujan A, Rotmensch J, et al. A feasibility study of

receive intracavitary brachytherapy. In: Enderle JD, editor.22nd Annual International Conference of the IEEEEngineering in Medicine and Biology Society. Los Alamitos,CA: EEE Publications; 2000. p. 463–465.

0. Guerrero M, Li XA, Ma L, et al. Simultaneous integratedintensity-modulated radiotherapy boost for locally advancedgynecological cancer: Radiobiological and dosimetric consid-erations. Int J Radiat Oncol Biol Phys 2005;62:933–939.

1. International Commission on Radiation Units and Measure-ments, ICRU Report 38. Dose and volume specification forreporting intracavitary therapy in gynecology. ICRU, Be-thesda, MD (1985).

2. Glantz SA. Primer of biostatistics. 5th ed. Columbus, OH:McGraw-Hill; 2001.

3. Zaider M, Amols HI. A little to a lot or a lot to a little: IsNTCP always minimized in multiport therapy? Int J RadiatOncol Biol Phys 1998;41:945–950.

4. Hall EJ, Wuu CS. Radiation-induced second cancers: Theimpact of 3D-CRT and IMRT. Int J Radiat Oncol Biol Phys2003;56:83–88.

5. Brenner DJ, Curtis RE, Hall EJ, et al. Second malignancies inprostate carcinoma patients after radiotherapy compared withsurgery. Cancer 2000;88:398–406.

6. Boice JD, Jr., Engholm G, Kleinerman RA, et al. Radiationdose and second cancer risk in patients treated for cancer of