Absolute increase in tumour size can improve the metric evaluating disease progression in metastatic colorectal cancer

Abstract

Background The assessment of response to therapy in advanced solid cancer diseases is predicated on the Response Evaluation Criteria In Solid Tumours for the evaluation of disease state by the relative changes in lesion size. The underlying assumption is that a larger relative increase in lesion size implicates less efficacious therapy, worse prognosis and shorter survival. Methods We analyzed retrospective data of metastatic colorectal cancer patients from three clinical datasets, stratified into three cohorts by the treatment protocol. We evaluated the first relative and absolute increase in target lesion size for their association with overall survival. Results About fifty four percent of the patient population increased in target lesion size during the first-line treatment. A multivariate analysis showed that patients with larger relative increase in lesion size had slightly longer survival in all three cohorts (\(HR = 0.85, HR=0.95 ,HR = 0.75\) for Cohorts 1–3, respectively); p-values showed no significance. In contrast, patients with larger absolute increase in total lesion size had significantly shorter survival (\(HR = 1.1 \left(p=0.05\right), HR=1.2 \left(p=0.04\right), HR = 1.25(p=0.02)\) for Cohorts 1–3, respectively). We also found a negative correlation between the SLD at nadir and relative increase. Conclusions The different impact of the absolute and the relative increase in SLD at relapse reflects the different growth patterns of small and big tumours. Further validation of our results is required. We believe that the first absolute increase in total lesion size may become a useful metric, upon which a more precise categorization of survival-related disease progression can be based.