Conventional four-field pelvic radiotherapy technique without computed tomography-treatment planning in cancer of the cervix: potential geographic miss and its impact on pelvic control.
OBJECTIVE
To evaluate the impact of inadequate margins on pelvic control using the conventional four-field pelvic portals without computed tomography (CT)-treatment planning.


METHODS
Between 1986 and 1991, 34 patients with invasive cancer of the cervix were eligible for outcome study of conventional four-field radiation therapy (10 Stage I, 16 Stage II, 8 Stage III). The eligibility for this study includes four-field pelvic technique, definitive radiation therapy, and diagnostic CT scan of the pelvis. For this study, an inadequate margin is arbitrarily defined as < or = 1.0 cm of normal tissue around the CT-defined tumor volume.


RESULTS
All 34 patients had adequate margins for anterio-posterior/posterio-anterior portals. However, 19 patients had an inadequate margin at the posterior border (S2-S3 interspace) and/or custom-shaped rectal block for lateral pelvic portals. Two patients had inadequate margins at the anterior border (level of symphysis pubis) due to an enlarged uterus. With a median follow-up of 36 months, pelvic control for adequate margins and inadequate margins was 100% and 71% for Stage IB disease and 88% and 50% for Stage IIB disease, respectively. However, pelvic control for Stage IIIB disease was 50% for both groups. There was no difference in total dose to point A or point B between the two groups.


CONCLUSIONS
Our preliminary data show higher local failure in patients with an inadequate margin. For four-field pelvic radiation therapy, we strongly recommend CT-treatment planning. Otherwise, anterio-posterior/posterio-anterior pelvic therapy is the most reliable treatment for cancer of the uterine cervix.
Kim
R Y
RY
Department of Radiation Oncology, University of Alabama Medical Center, Birmingham 35233.
McGinnis
L S
LS
Spencer
S A
SA
Meredith
R F
RF
Jennelle
R L
RL
Salter
M M
MM
D005260:Female; D006801:Humans; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted; D014057:Tomography, X-Ray Computed; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000532:radiotherapy*