MEASUREMENT OF RESPONSE TO TREATMENT IN COLORECTAL LIVER METASTASES

Assessment of tumour response to chemotherapy is important when assess ing efficacy of treatment and comparing differing therapeutic regimens . Percentage hepatic replacement (PHR) is commonly used to assess resp onse to treatment of colorectal hepatic metastases. PHR is dependent n ot only on tumour volume, but also on hepatic parenchymal volume. The effect of tumour growth on hepatic parencymal volume is unclear but is of importance owing to its effect on PHR. We assessed tumour and hepa tic parenchymal weights in an animal tumour model using dissection, an d tumour and hepatic parenchymal volumes in patients with colorectal h epatic metastases using CT scanning, in order to establish how hepatic parenchyma varied with change in metastasis size. There was no signif icant correlation between tumour and liver parenchyma in either the an imal model (r=-0.03, P>0.05) or the patient study (r=0.3, P<0.05). Thi s suggests that hepatic parenchymal volume was preserved in the presen ce of increasing tumour volume. In a further study of computerised tom ographic (CT) scans before and after treatment in patients whose tumou rs either responded to chemotherapy or continued to grow, change in PH R (median proportion of PHR change=0.40) significantly (P=0.04) undere stimated the change in tumour volume (median proportion of tumour volu me change=0.56), particularly at higher (>400 ml) volumes. There was g ood correlation between change in tumour volume and WHO criteria in as signing patients to tumour growth, stable disease or tumour response c ategories. This study suggests that, in clinical trials comparing colo rectal liver metastasis treatments, metastasis volume and not PHR shou ld be used to assess extent of disease and the effect of treatment.