The finding of a better liver outcome with initial chemotherapy "makes sense," session comoderator Dr. Marylise Boutros, of McGill University in Montreal, said in an interview. "That’s something that we would expect, that you can treat the largest burden of the disease, which is the metastasis – it’s a systemic disease – with chemotherapy up-front."
"But it’s definitely a smaller study, and this needs to be looked at in a larger subset and in a prospective fashion," she added.
Giving some background to the research, Dr. Slesser noted that "the mainstay of surgical treatment for these patients with limited metastatic disease is a sequential resection. Patients tend to have an up-front primary tumor resection, followed by adjuvant chemotherapy, followed by hepatic resection if feasible. On the other hand, patients who have extensive metastatic disease tend to have neoadjuvant chemotherapy prior to a surgical intervention."
He and his coinvestigators studied patients with isolated synchronous colorectal liver metastases who were referred to the Royal Marsden Hospital for treatment between 2005 and 2010 and had imaging done at baseline, 3 months, and 6 months.
The mean age of the cohort was 64 years, and the ratio of men to women was about 2:1. In terms of treatment, 51% of the patients underwent primary tumor resection, while the other 49% received neoadjuvant chemotherapy.
Dr. Marylise Boutros
In univariate analysis, the factor most strongly associated with progression of liver metastases – defined as an increase in their cumulative diameter of at least 20% – at 3 months was a primary tumor resection, according to Dr. Slesser.
In a multivariate analysis, relative to their counterparts in the neoadjuvant chemotherapy group, patients undergoing primary tumor resection had dramatically elevated odds of progression of liver metastases (odds ratio, 9.0; P = .001).
Additionally, metastatic burden showed an upward trend between baseline and 6 months in the group undergoing primary tumor resection (from 40 to 51 mm; P = .19), whereas it decreased significantly in the neoadjuvant chemotherapy group (from 96 to 52 mm; P = .001).
Overall, 93% of patients having a primary tumor resection went on to receive adjuvant chemotherapy, according to Dr. Slesser.
Comparing baseline to 3 months versus 3 months to 6 months, liver metastases began regressing in the primary tumor resection group, with the growth rate changing from 4.0 to –3.0 mm/month (P less than .001), reflecting the effect of the adjuvant chemotherapy, he said. Liver metastases in the neoadjuvant chemotherapy group continued to regress, albeit also at a slower pace, with the growth rate changing from –5.6 to –4.0 mm/month (P = .003).
Dr. Slesser disclosed no relevant conflicts of interest.