Is PET/CT Better than CT for Monitoring Metastatic Breast Cancer Treatment?

Emerging research suggests the use of 2-deoxy-2-(18F)fluoro-D-glucose positron emission tomography/computed tomography (2-(18F)FDG-PET/CT) may provide a more accurate barometer of metastatic breast cancer treatment than conventional contrast-enhanced computed tomography (CECT).

For the prospective study, recently published in Scientific Reports, researchers compared the accuracy of CECT and 2-(18F)FDG-PET/CT for predicting progression-free survival (PFS) and disease-specific survival (DSS) in 87 patients (median age of 72) being treated for metastatic breast cancer. Baseline imaging revealed bone metastases in 74.7 percent of the patients and bone-only metastatic disease in 26.4 percent of the cohort, according to the study. The researchers noted a median follow-up period of 36.1 months.

For CECT, the study authors noted two-year PFS rates of 54.2 percent for treatment responders vs. 46 percent for non-responders whereas 2-(18F)FDG-PET/CT) was associated with a 59.1 percent PFS rate for treatment responders and a 14.3 percent PFS rate for non-responders at two years. The researchers found 83.3 and 77.8 percent DSS rates for responders and non-responders respectively on CECT in contrast to 84.6 percent and 61.9 percent DSS rates respectively for responders and non-responders with 2-(18F)FDG-PET/CT imaging.

The study authors emphasized that tumor treatment response on 2-(18F)FDG-PET/CT imaging was significantly associated with PFS (3.49 hazard ratio (HR)) and DSS (2.35 HR). There was no evidence of a significant association between CECT imaging of tumor response with PFS and DSS, according to the researchers.

“These findings indicate that 2-(18F)FDG-PET/CT provides an early and reliable indication of treatment efficacy compared with (CECT) since it correlates better with PFS and DSS,” wrote lead study author Marianne Vogsen, M.D., Ph.D., who is affiliated with the Departments of Oncology and Nuclear Medicine at Odense University Hospital in Odense, Denmark, and colleagues.

(Editor’s note: For related content, see “Could a Re-Emerging PET/CT Agent Enhance Detection of Bone Metastasis in Prostate and Breast Cancer Cases?”)

The study authors suggested that a nearly 75 percent incidence of bone metastases in the cohort may have been a factor in the study findings.

“Bone lesions are difficult to detect by (CECT) and may challenge its capacity to distinguish between tumor response and tumor progression in such lesions,” noted Vogsen and colleagues.

However, they maintained that the increased sensitivity afforded with 2-(18F)FDG-PET/CT may have a significant impact with treatment plan changes in high-risk patients.

“ … More sensitive imaging such as 2-(18F)FDG-PET/CT may have the potential to improve clinical decision-making , optimize the timing of treatment alterations, and avoid treating patients with ineffective toxic and expensive treatments,” explained Vogsen and colleagues.

In regard to study limitations, the researchers conceded that the single-center observational nature of their study limits broader extrapolation of the results and curtails assessment of quality of life and overall survival rate. While the authors initially utilized contrast-enhanced CT only for monitoring of treatment response, they noted that most of the cohort changed to 2-(18F)-FDG-PET/CT for treatment monitoring during the follow-up period of the study.