Analysis of the rate of non-target disease progression in patients with stable or responding target disease by the Response Evaluation Criteria in Solid Tumors (RECIST)

Abstract

6603 Background: RECIST suggests progression of non-target disease is rare in patients with stable or responding target disease. We reviewed outcomes by RECIST to determine the rate of non-target (NT) progressive disease (PD). Methods: Outcomes of RECIST-based blinded independent central review (BICR) of 962 breast and colon cancer patients were used to identify 514 patients that had a progression event in order to determine the incidence of NT-PD. The radiographs of the 55 patients that had NT-PD were further reviewed by the authors (KB, RF) to confirm the NT-PD was “unequivocal.” To be considered unequivocal, there had to be a definite, substantial increase in the size of one or more metastatic NT lesions that was clearly not related to differences in imaging technique. To confirm the subjective nature of the “unequivocal progression,” the lesion(s) upon which PD was assessed was measured and a 20% increase in the lesion(s) since nadir was required. Results: Of the patients with PD, 11% (55/514) progressed only on worsening of NT disease. In 82% (45/55) of cases where the NT-PD was unequivocal, either the target disease was increasing but had not met the quantitative requirement for progression or the increase in NT disease would have resulted in target progression had the NT site(s) of disease been included with the baseline target lesions. Of the remaining 18% (10/55) where the two criteria described above did not apply, and an additional evaluation was performed, the next evaluation confirmed PD. Conclusions: Progression on the basis of NT disease can be reliably assessed if the target disease has started to increase from the nadir or if the increase in NT disease is significant enough to have resulted in target disease progression if classified as such. If one of the above criteria is not met, it is recommended that treatment continue until progression can be confirmed at the next evaluation. No significant financial relationships to disclose.