COMPARATIVE STUDY
JOURNAL ARTICLE

Intensity-modulated radiation therapy after hysterectomy: comparison with conventional treatment and sensitivity of the normal-tissue-sparing effect to margin size

Anesa Ahamad, Warren D'Souza, Mohammad Salehpour, Revathy Iyer, Susan L Tucker, Anuja Jhingran, Patricia J Eifel
International Journal of Radiation Oncology, Biology, Physics 2005 July 15, 62 (4): 1117-24
15990017

PURPOSE: To determine the influence of target-volume expansion on the reduction in small-bowel dose achieved with use of intensity-modulated radiation therapy (IMRT) vs. standard conformal treatment of the pelvis after hysterectomy, and to investigate the influence of patient body habitus on the normal-tissue sparing achieved with use of IMRT.

METHODS AND MATERIALS: A clinical target volume (CTV) was contoured on each of 10 planning computed tomography scans of patients who had been treated for cervical or endometrial cancer after a hysterectomy. Treatment planning was based on vaginal CTVs and regional nodal CTVs. To account for internal motion, margins were added to form an initial planning target volume (PTVA) as follows: 0.0 mm were added to the regional nodal CTV; 10 mm were added anteriorly to the vaginal CTV; and 5 mm were added to the vaginal CTV in all other directions. Two further PTVs (PTVB and PTVC) were produced by a 5-mm expansion of PTVA to give PTVB and a further 5-mm expansion to give PTVC. Treatment plans for all 3 PTVs were produced by use of 2 conformal fields (2FC), 4 conformal fields (4FC), or IMRT to deliver 45 Gy to more than 97% of the PTV. The primary goal of IMRT was to spare small bowel. The change in sparing that accompanied the increase in margin size was assessed by comparison of dose-volume histograms that resulted from PTVA, PTVB, and PTVC. Measured patient dimensions were correlated with bowel sparing.

RESULTS: Significantly less small bowel was irradiated by IMRT than by 2FC (p < 0.0001) or 4FC (p < 0.0001) for doses greater than 25 Gy. Significantly less rectum was irradiated by IMRT than by 2FC (p < 0.0001) or 4FC (p < 0.0001). Significantly less bladder was irradiated by IMRT than by 2FC (p < 0.0001). However, the magnitude of the sparing achieved by use of IMRT decreased as margins increased. In particular, the volume of small bowel spared by IMRT vs. 2FC or 4FC decreased as margin size increased (p = 0.0002 and p = 0.008 for 2FC and 4FC, respectively). The amount of normal-tissue sparing achieved by use of IMRT vs. 4FC was inversely correlated with patient body mass index.

CONCLUSION: Because the small-bowel sparing achieved with use of IMRT is markedly reduced by relatively small expansions of the target volume, accurate target delineation, highly reproducible patient immobilization, and a clear understanding of internal-organ motion are needed to achieve optimal advantage in the use of IMRT over conventional methods of posthysterectomy pelvic radiation therapy.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read
15990017
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"