Intensity Modulated Radiation Therapy (IMRT) May Reduce Small Bowel, Rectum, and Bladder Complications in Patients with Cervical Cancer Treated to the Pelvis and Paraaortic Area

John Han-Chih Chang, MD
OncoLink Assistant Editor
Last Modified: November 3, 1999

Presenter: Lorraine Portelance
Affiliation: Mallinckrodt Institute of Radiology, St Louis, MO

Background:
Combined modality therapy (chemotherapy plus radiation therapy) has made a major impact on treatment of cervix cancer from bulky Stage I disease up to Stage IV. With the improvement of local control and survival with the use of combined modality, normal tissue toxicity has also been affected. The rate of severe (grade 3 or greater) gastrointestinal and genitourinary side effects from the combination of these two modalities has been reported to be over 30%.

Materials and Methods:

Ten cervical cancer patients who underwent CT simulation were retrospectively evaluated
The targets defined were the para-aortic, common iliac, external iliac, internal iliac lymph nodes along with the cervix and uterus.
The authors compared treatment plans utilized in a prior national protocol (2 - 4 field arrangement) versus 4, 7 and 9 field plans created with inverse treatment planning of IMRT.
All plans were created to optimize the dose to the above stated targets and reduce the dose to small bowel, rectum and bladder.

Results:

The amount of small bowel receiving the prescribed dose was only 11 - 15% with the various IMRT techniques, while the conventional treatment plans yielded 35%.
The fraction of rectum receiving the prescribed dose was nearly 10 times higher for the 2 field conventional method versus IMRT (84% versus 3 - 9% favoring IMRT). The four field plan did reduce the fraction to just under 50%.
Twenty-seven (27%) to 32% percent of the bladder volume would have received the prescribed dose versus 93% for the standard 2 field arrangement and 60.5% for the 4 field arrangement.
The dose volume histograms were compared and all were able to deliver a minimum of 42 Gy of a prescribed 45 Gy to the target indicated above.
NO clinical treatment data were reported.

Clinical/Scientific Implications:

Conformal RT with intensity modulation is feasible and can adequately deliver prescribed dose with reduction in the amount of normal tissue receiving maximum dose.
Prospective clinical data are required to establish the true utility of this modality of RT.

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