Contrast enhanced dynamic MRI of cervical carcinoma during radiotherapy: early prediction of tumour regression rate

This prospective study investigated the relationship between changes in the MRI dynamic enhancement of cervical carcinoma early during radiotherapy, a nd tumour regression rate throughout radiotherapy. A total of 36 MRI examin ations was performed in seven patients with cervical carcinoma, including a T-2 weighted sequence weekly during radiotherapy and also a multislice dyn amic Gd-DTPA enhanced sequence before and after the first 2 weeks of radiot herapy. Tumour enhancement was determined on dynamic images using a region of interest and signal-to-noise ratio method. Serial tumour volumes over ti me on T-2 weighted images were estimated using the Cavalieri method of mode rn design-based stereology to obtain tumour regression rate. It was found t hat peak and mean enhancement prior to radiotherapy ranged from 3.0 to 13.3 , and from 1.9 to 12.2, respectively. After 2 weeks of radiotherapy, peak a nd mean enhancement ranged from 7.5 to 13.0, and from 6.3 to 10.6, respecti vely. The change in peak and mean tumour enhancement between dynamic scans ranged, respectively, from -2.0 to 8.4 and from -4.5 to 8.5. Tumour volume decreased exponentially with time (p<0.01). Tumour regression rates ranged from 2.0% to 15.2% per day, and correlated positively with changes of both peak and mean tumour enhancement (p<0.01). It is concluded that MRI dynamic enhancement during the first 2 weeks of radiotherapy may provide early pre diction of tumour regression rate, and therefore be of value in designing t reatment schedules for cervical carcinoma.