Imaging description

In patients with metastases to the liver, treatment response to chemotherapy may result in a relative reduction of enhancement in the metastases such that they become more conspicuous and erroneously suggest disease progression (Figures 15.1–15.3). Such “pseudoprogression” has been primarily described in metastases from gastrointestinal stromal tumors treated with imatinib (Figure 15.4) [1], but can occur in other malignancies.

Importance

Misdiagnosis of treatment response as treatment failure may result in an unwarranted cessation or change of successful treatment.

Typical clinical scenario

Pseudoprogression can be seen in patients with hepatic metastases treated by chemotherapy in which treatment response is accompanied by a reduction in enhancement within the lesions. While the phenomenon is not well described and has been primarily reported in neuroradiology [2], my experience suggests it may be more frequent with contemporary chemotherapy regimens that incorporate novel anti-angiogenic and other biological agents that can affect tumor perfusion or cause tumor necrosis.

Differential diagnosis

When hepatic metastases become more conspicuous on treatment, the primary differential consideration is true disease progression. Correlation with disease evolution at other sites, with tumor markers or with PET imaging, may help in this distinction.