Breast Cancer

Screenshot for FDG PET CT of a 59-year-old female with newly diagnosed triple-negative, intermediate grade, invasive mammary/ductal carcinoma of right breast. PET CT images confirm right breast primary cancer of 1.4 cm with a moderate metabolic activity, but no evidence for local or distal metastasis. Imaging of the left breast is unremarkable. The imaging findings shall greatly help this patient’s treatment planning.

Globally, breast cancer is one of the most common cancers among women. In 2020, it accounted for about 2.3 million new cases and was the leading cause of cancer-related deaths among women1. The incidence of breast cancer varies across regions, with higher rates in developed countries compared to developing countries1 

In the United States, breast cancer is the most common cancer among women, excluding skin cancers. It is estimated that in 2021, there will be approximately 281,550 new cases of invasive breast cancer and 49,290 new cases of non-invasive breast cancer in the United States2. 

NCCN GUIDELINES FOR BREAST CANCER STAGING USING FDG PET/CT 

  • In Stage 1 and 2 Breast Cancer.  For stage 1 and 2 breast cancer, the routine use of PET/CT is not recommended according to the NCCN guidelines. Conventional imaging modalities such as mammography, ultrasound, and magnetic resonance imaging (MRI) are typically sufficient for initial staging8. 
  • Stage 3 Breast Cancer: For stage 3 breast cancer, which includes locally advanced breast cancer, the NCCN recommends using PET/CT as a tool for initial staging. PET/CT can provide valuable information about the extent of disease involvement, including the assessment of regional lymph nodes and potential distant metastases8. 
  • Stage 4 Breast Cancer: For stage 4 breast cancer, which indicates metastatic breast cancer, PET/CT is recommended to aid in the detection and evaluation of distant metastases. PET/CT can help identify the extent and location of metastatic disease, which can have implications for treatment planning and prognosis8. 

FDG-PET/CT is considered useful for the initial staging of breast cancer, regardless of the tumor’s molecular phenotype (such as triple-negative, luminal, or HER2+), as well as the tumor grade4. It is particularly beneficial for staging invasive ductal carcinoma; however, it can also provide valuable staging information for invasive lobular carcinomas4. 

SENSITIVITY AND SPECIFICITY OF PET/CT IN BREAST CANCER 
The sensitivity and specificity of PET/CT in breast cancer vary depending on various factors such as tumor subtype and stage. For detecting axillary lymph node metastases in newly diagnosed breast cancer, PET/CT has shown high sensitivity (approximately 80-90%)4. The specificity of PET/CT in breast cancer is reported to be approximately 80-90%, but it may be lower in certain scenarios, such as detecting small breast cancers4. 

Compared to other modalities, PET/CT provides additional functional information about glucose metabolism in tumors, which can be advantageous in detecting small metastases or hidden primary tumors. Additionally, PET/CT has demonstrated higher sensitivity than bone scintigraphy and CT for the detection of bone metastases in advanced breast cancer6. 

It’s important to note that individual patient factors, tumor characteristics, and clinical judgment may also influence the decision to use PET/CT in breast cancer staging. It is recommended to consult with a healthcare professional or specialist to determine the most appropriate staging.  

Sources: 

  1. World Health Organization. Breast Cancer: Key facts:  https://www.who.int/news-room/fact-sheets/detail/breast-cancer  
  2. American Cancer Society. Breast Cancer Facts & Figures 2021-2022. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/breast-cancer-facts-and-figures/breast-cancer-facts-and-figures-2021-2022.pdf  
  3. The value of 18F-FDG PET/CT imaging in breast cancer staging. https://pubmed.ncbi.nlm.nih.gov/28763628/  
  4. Breast cancer: initial workup and staging with FDG PET/CT https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8075837/  
  5. 18F-FDG PET/CT Imaging In Oncology: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3101722/ 
  6. A Prospective Study Comparing the Role of 18 FDG PET-CT with Contrast-Enhanced Computed Tomography and Tc99m Bone Scan for Staging Locally Advanced Breast Cancer: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8272774/ 
  7. NCCN Guidelines Version 4.2021. Breast Cancer: https://www.nccn.org/professionals/physician_gls/pdf/breast.pdf