A dosimetric planning study comparing intensity-modulated radiotherapy with four-field conformal pelvic radiotherapy for the definitive treatment of cervical carcinoma.

AIMS

To compare the dose to organs at risk (OAR) between a conventional four-field whole pelvis radiotherapy (4F-WPRT) plan and an initial single intensity-modulated WPRT (IM-WPRT) plan for definitive treatment of cervical cancer. The magnitude of potential dose sparing of OAR is unknown when planning target volumes are defined to include potential organ motion and microscopic disease extent.

MATERIALS AND METHODS

Planning computed tomography scans of 50 consecutive, previously treated patients were re-planned using 4F-WPRT and IM-WPRT. Margins compatible with the literature on organ motion were used to create the planning target volume. Dose-volume histograms for target and OAR were compared for each patient with paired t-tests and waterfall plots.

RESULTS

The mean target volume covered by 95% (V47.8) was 99.7% for 4F-WPRT and 98.8% for IM-WPRT (P>0.05, ns). Intensity-modulated radiotherapy (IMRT) was associated with a significant reduction in the dose to OAR at the V50, V45, V40 and V30 level. There was a >20% difference in V50 in most patients: 84% (bladder), 58% (small bowel), 54% (sigmoid) and 84% (rectum).

CONCLUSIONS

A single, initial IMRT plan with appropriate margins encompassing initial gross and potential microscopic pelvic disease leads to a reduction in the dose to OAR without compromising target coverage. This offers a potential 'class solution' for definitive treatment of patients with cervical cancer. Clinical outcome data are still needed to verify this planning study.