Date of Award

3-2025

Degree Type

Dissertation

Degree Name

Master of Medicine (MMed)

First Advisor

Dr. Rose Ndumia

Second Advisor

Dr. Samuel Nguku

Department

Imaging and Diagnostic Radiology (East Africa)

Abstract

Background: Determination of axillary lymph node metastasis is a crucial part of breast cancer staging as it is the most important marker of overall recurrence and survival. Although axillary ultrasound (AUS) is the imaging reference standard, it has a wide range of sensitivity necessitating evaluation of other imaging modalities that may be used as adjuncts.18F-FDG PET-CT is recommended for use in metastatic and recurrent breast cancer with infrequent use in early disease due to its low spatial resolution for small axillary lymph nodes. The aim of this it study is to evaluate the diagnostic accuracy of axillary ultrasound compared to 18F-FDG PET-CT in identification of metastatic axillary lymph nodes in newly diagnosed breast cancer patients.

Materials and methods: This retrospective study analyzed AUS and 18F-FDG PET-CT performed for 147 newly diagnosed breast cancer patients between February 2019 and February 2024. Sensitivity, specificity, NPV, PPV and accuracy of both AUS and 18F-FDG PET-CT in identification of axillary nodal metastasis was calculated using histology as the reference standard. SUV-max of the primary tumor and axillary lymph node as well as morphologic characteristics of the lymph nodes on ultrasound were obtained. Palpability of the lymph node(s), histologic subtypes, receptor status and Ki-67 proliferation indices were abstracted from medical records. Descriptive analysis involved using frequency and percentages for categorical variables and mean (standard deviation) for continuous variables. Correlation between continuous variables was determined using the Spearmans correlation coefficient.

Results: Diagnostic accuracy, sensitivity, specificity, PPV and NPV were 83%, 91%, 45%, 89% and 50% for 18F-FDG PET-CT compared to 84%, 91%, 50%, 90% and 52% for AUS. Higher SUVmax values was associated with increased cortical thickness, short-axis diameter, round-shaped lymph nodes, absent fatty hilum, HER-2 positive tumors and basal-like molecular subtypes.

Conclusion: The diagnostic accuracy of 18F-FDG PET-CT was comparable to axillary ultrasound for newly diagnosed breast cancer patients in all stages of the disease. Suspicious sonographic features such as increased lymph node cortical thickness and short-axis diameter as well as roundshaped lymph nodes and absence of a fatty hilum correlated with higher SUV-max values. Higher SUV-max values were observed in more aggressive phenotypes such as HER-2 positive tumors and basal-like molecular subtype (TNBC).

First Page

1

Last Page

37

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