Axial slices of CT (left) and fused PET/CT (right) scans before therapy (A) and after therapy (B) demonstrating large liver metastases. SUVmax decreased markedly (73 percent) after radioembolization, indicating therapy response, whereas tumor size as measured with CT did not change significantly. Source: J Nucl Med 2012;53(3):371-377

The change in standard uptake value (SUV)_max as assessed by 18F-FDG PET/CT before and three months after selective internal radiation therapy (SIRT) was identified as the only independent predictor of survival in patients with hepatic metastases of breast cancer, according to a study published in the February issue of the Journal of Nuclear Medicine.

Breast cancer is the most common malignancy affecting women in developed countries, wrote the study authors. Despite advances in adjuvant treatment, about 20 percent of patients with initially local disease will still develop metastases, frequently involving the liver. In most patients, curative surgical resection of liver metastases is not an option because of the presence of extrahepatic disease or multisegmental involvement of the liver.

90Y radioembolization (selective internal radiation therapy [SIRT]) has emerged as a valuable therapeutic option in unresectable, chemotherapy-refractory hepatic metastases from breast cancer. Thus, Alexander R. Haug, from the department of nuclear medicine from Ludwig-Maximilians-University of Munich in Germany, and colleagues sought to evaluate 18F-FDG PET/CT for predicting survival in these patients.

Haug and colleagues treated 58 consecutive patients with hepatic metastases from breast cancer with SIRT. Before therapy, all patients underwent MRI of the liver. They performed an 18F-FDG PET/CT at baseline and three months after SIRT to calculate percentage changes in maximum 18F-FDG standardized uptake value (SUV_max) relative to baseline. A decrease of more than 30 percent in the follow-up scan, compared with the baseline exam, indicated therapy response.

Also, treatment response at three months was assessed in 43 patients using contrast-enhanced MRI and CT on the basis of the Response Evaluation Criteria in Solid Tumors (RECIST). All patients were followed to complete survival data.

Overall, the median survival rate after SIRT was 47 weeks, according to the study authors. Response as assessed with SUV_max correlated significantly with survival after radioembolization, with responders having significantly longer survival (65 weeks) than nonresponders (43 weeks).

 In multivariate analysis the change in SUV_max was identified as the only independent predictor of survival (hazard ratio, 0.23). Furthermore, a high pre-therapeutic SUV_max (more than 20) was associated with a significantly shorter median survival than was a SUV_max of 20 or less (21 vs. 52 weeks). The presence of extrahepatic metastases (mean survival in both groups, 47 weeks), hormone receptor status (estrogen, P = 0.53; progesterone; Her-2/neu) and MRI/CT response did not predict survival.

“This study confirmed the effectiveness of SIRT in breast cancer patients with hepatic metastases,” Haug and colleagues wrote. “Response as assessed with the RECIST criteria and the pre-therapeutic tumor burden did not significantly predict survival in our study, though patients with progressive disease after SIRT and a high tumor burden tended to have a shorter survival. However, this finding simply underscores the controversies regarding the prognostic value of morphologic tumor response.”

The potential of 18F-FDG PET for predicting survival in patients with metastatic breast cancer undergoing treatments other than SIRT has been shown in several studies, they noted. In addition, 18F-FDG PET response also predicted overall survival in patients with metastasized breast cancer who started a new line of therapy. “Despite the fact that these women were heavily pretreated, further treatment options remain, which promise to improve their prognosis,” the researchers reported.