Monitoring primary breast cancer throughout chemotherapy using FDG-PET.

Area of Science:

• Oncology
• Nuclear Medicine
• Radiochemistry

Background:

• Anthracycline-based chemotherapy is a standard treatment for large or locally advanced breast cancers (LABC).
• Accurate prediction of pathologic chemotherapy response is crucial for tailoring treatment strategies and improving patient outcomes.
• 2-deoxy-2-[(18)F]-fluoro-D-glucose positron emission tomography (FDG-PET) is a functional imaging technique that can assess metabolic activity in tumors.

Purpose of the Study:

• To compare different methods for defining tumor volume using FDG-PET imaging.
• To determine the optimal imaging time point during neoadjuvant chemotherapy for predicting pathologic treatment response in LABC.
• To evaluate the efficacy of FDG-PET in differentiating between high and low responders to chemotherapy.

Main Methods:

• FDG-PET scans were acquired at multiple time points during neoadjuvant chemotherapy: before cycles 1 and 2, midpoint, and endpoint.
• Tumor uptake was quantified using mean and maximum standardized uptake values (SUV) and coefficient of variation.
• Receiver-operator characteristic (ROC) analysis was employed to assess the predictive accuracy of different quantification methods and time points.

Main Results:

• Tumor-to-background ratio (TBR) > 5 was necessary for differentiating response categories.
• No significant advantage was found for specific quantification methods or imaging time points in general.
• Mean SUV at the midpoint of therapy provided the best discrimination, correctly identifying 100% of high responders and 77% of low responders (ROC area = 0.93).

Conclusions:

• FDG-PET is effective in predicting pathologic response for most primary breast tumors during neoadjuvant chemotherapy.
• The technique's effectiveness is limited in tumors with low contrast on pre-therapy PET scans.
• Midpoint FDG-PET imaging using mean SUV shows promise for early prediction of chemotherapy response in LABC.