The role of stable disease in objective response assessment and its impact on survival in advanced colorectal cancer: is "stable disease" a homogenous response category?

ABSTRACT

Stable disease is a category which is not included in the evaluation of the overall treatment response rate. In many studies with a response rate below 20%, chemotherapy almost doubles the survival of patients. In the most chemotherapy trials with advanced colorectal cancer patients, about 30-50% had stable disease. Despite belonging to the same category of therapy response, some patients with stable disease have achieved symptom improvement, but some have not. The aim of the study was to investigate whether the stabilization of the disease with clinical benefit is associated with benefit in survival. A total of 99 patients with advanced colorectal cancer were treated with carboplatin (80 mg/m2, day 1-7), 5-FU (750 mg/m2, day 1-5), leucovorin (100 mg/m2, day 1-5) every 4 weeks. After 4 courses, in the case of stable disease (SD), the patients were stratified according to clinical benefit achievement in Group A--patients with clinical benefit who continued with chemotherapy until 8 cycles or until disease progression; group B--patients without clinical benefit in whom chemotherapy was stopped after 4 cycles. Clinical benefit was a composite of assessment of pain, ECOG performance status, weight and temperature. Clinical benefit required a sustained improvement in at least one parameter without worsening in any other. Of 97 evaluable patients 48 achieved stable disease. Of 22 pts. with SD clinical benefit performance status improvement was recorded in 17, pain relief in 14, improvement in body weight in 14 and temperature disappearance in 8 pts. Of 26 pts. with SD without clinical benefit, 7 were asymptomatic from beginning of the chemotherapy. No difference was detected in the survival between responders and SD clinical benefit pts. (p = 0.24), but there was significant difference between responders and SD pts. without clinical benefit (p = 0.0004). SD clinical benefit pts. had significant difference in survival in comparison to pts. with progressive disease (p = 5.1 x 10(-6)). The results of our study indicate that under category "stable disease" there are two different subpopulations of patients with quite different symptom response to chemotherapy, different time to progression and possible different survival.