Ultrasound localization of the ovaries for radiation-induced ovarian ablation

The case notes and simulator films were reviewed from 70 sequential patients who received pelvic irradiation to induce an early menopause as part of their treatment for breast cancer at the Staffordshire Oncology Centre. These patients underwent ultrasound localization of the ovaries immediately prior to simulation. Altogether, 128 ovaries were plotted on a diagrammatic representation of a gynaecoid pelvis to represent their position in both craniocaudal and lateral dimensions in relation to the true bony pelvis. The craniocaudal ovarian position varied from 2.5 cm above the lower aspect of the sacroiliac joint to 2.0 cm above the symphysis pubis. Three (4.6%) right sided ovaries were within 1 cm medial to the right lateral side wall, with none lying lateral to the wall. Seventeen (26%) left sided ovaries were lying within 1 cm of the left pelvic side wall, with four of these lying outside. The limits of the pelvic fields used were from the top of the sacroiliac joint to the bottom of the symphysis pubis. Sixty-one (88%) upper borders were on or above the lower sacroiliac joint. Twenty-six (38%) and 49 (71%) fields were outside the right and left pelvic side walls respectively. This would suggest that field sizes were larger than standard; however, 87% were smaller than 150 cm(2) (assuming a 10x15-cm field as standard). Only one patient failed to respond to treatment. This was thought to be due to underdosing rather than a geographical miss. This patient was successfully retreated. The authors advocate the use of ultrasound localization prior to planning an irradiation menopause, to ensure that the ovaries are encompassed in the pelvic field, thus preventing a geographical miss and reducing field sizes.