Clinical significance of geographic miss when using conventional four field radiotherapy technique in treatment of locally advanced carcinoma cervix.

ABSTRACT

BACKGROUND: Although conventional four‑ field radiotherapy based on bony landmarks has been traditionally used, areas of geographical miss due to individual variation in pelvic anatomy have been identified with advanced imaging techniques. AIMS: The primary aim of this study is to evaluate the geographical miss in patientswhen using the conventional four‑field planningplanning and to find out the impact of 3‑D conformal CT based in patients with locally advanced carcinoma cervix. MATERIALS AND METHODS: In 50 patients, target volume delineation was done on planning computed tomography (CT) scans, according to guidelines by Taylor et al. Patients were treated with modified four field plan, except for the superior, where field border was kept at L4‑L5 interspace A dosimetric comparison was done between the conventional four‑field based on bony landmarks and the target volume delineated on computed tomography. The disease free survival, pelvic and para aortic nodal free survival, distant failures free survival were calculated using Kaplan Meir Product Limit Method. RESULTS: Patients were followed‑up for a median period of 11 months. The median V95 for conventional and modified extended four field plans were 89.4% and 91.3% respectively. Patients with V95 for modified extended pelvic fields less than 91.3% had a trend toward inferior disease free survival (mean DFS 9.8 vs. 13.9 months) though the difference was not statistically significant log rank test. CONCLUSIONS: Our preliminary data shows trend toward lower DFS in patients with inadequate target volume coverage. We recommend routine use of CT based planning for four field technique.