Phase I trial of accurate new method of preoperatively identifying clear-cell RCC

Divgi CR et al. (2007) Preoperative characterisation of clear-cell renal carcinoma using iodine-124-labelled antibody chimeric G250 (124I-cG250) and PET in patients with renal masses: a phase I trial. Lancet Oncol 8: 304–310

Divgi et al. have carried out a prospective, open-label pilot study—the first of its kind—to determine whether iodine-124-labelled antibody chimeric G250 (¹²⁴I-cG250) and PET can accurately distinguish clear-cell renal cell carcinoma (RCC) from other renal masses. The ability to preoperatively identify tumor type in patients with renal masses would greatly assist patient management. G250 is a monoclonal antibody that binds specifically to clear-cell RCC and, when labeled with a radioactive isotope, can be visualized with PET.

A total of 26 patients with renal masses underwent resection by laparotomy. An intravenous infusion of ¹²⁴I-cG250 was administered 1 week before surgery, and all patients underwent abdominal ¹²⁴I-PET imaging in the 3 hours before surgery, the results of which were made known to the surgeon. Postoperatively, histopathology findings were compared with the ¹²⁴I-PET imaging results.

As a means of identifying clear-cell RCC, ¹²⁴I-cG250 PET had a sensitivity of 94% (95% CI 70–100%), a negative predictive value of 90% (55–100%), a specificity of 100% (66–100%), and a positive predictive accuracy of 100% (78–100%). One patient who received inactive antibody was excluded from the analysis. All nine cases of non-clear-cell RCC were correctly identified, as were 15 of the16 cases of clear-cell RCC.

On the basis of these findings, the authors propose that ¹²⁴I-cG250 PET imaging should be used as an alternative to renal biopsy to characterize incidentally discovered renal masses. A prospective trial is planned.