Value of [18F]FDG PET/CT in the work-up to neoadjuvant systemic therapy in breast cancer
L.E.W. Raaijmakers, MD1; J. Tol, MD, PhD2; P.C. Barneveld, MD3; M. Bessems, MD, PhD, MBA1
1Department of Surgery, 2Internal Medicine and 3Radiology and Nuclear Medicine, Jeroen Bosch Hospital, ‘s-Hertogenbosch
Introduction
Breast cancer is the most common type of cancer among women worldwide. Neoadjuvant systemic therapy (NST) is increasingly applied in its treatment due to the ability to evaluate response of therapy to guide postoperative treatment decisions (1,2) and its benefit of allowing less extensive surgery. Initial staging of breast cancer is a precondition for determining treatment strategy and accurate response evaluation. Staging is carried out according to the TNM staging system of the American Joint Committee on Cancer (3).
Ultrasonography (US) and magnetic resonance imaging (MRI) of the breast and axilla are commonly performed for assessing the primary tumour extent and spread to regional lymph nodes. In locally advanced breast cancer, screening for distant metastasis is recommended because the probability of metastasis is substantially increased (4,5). For this purpose, 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography ([18F]FDG PET/CT) is the first choice as it has been proven to be more accurate in detecting distant metastases than a conventional multimodality imaging algorithm including chest X-ray, abdominal US and bone scintigraphy (6,7). Additionally, it provides information about regional lymph nodes, including those extraaxillary, which may be missed when imaging with US and MRI exclusively. However, of the diagnostic modalities US, MRI, and [18F]FDG PET/CT, none can be considered most reliable for determination of the N status (7-9). Consequently, a combination of US, MRI, and [18F]FDG PET/CT is often executed in initial staging. Several studies have pointed out the utility of [18F]FDG PET/CT in stage ≥IIB, as it leads to significant restaging and alteration of treatment (10-13). Still, its contribution in stage I-IIA breast cancer remains debatable (14-16). The high sensitivity of an [18F]FDG PET/CT harbours the potential for detecting incidental findings. Only 1.2-2.0% of incidental findings are clinically relevant (pre)malignant lesions, of which the gastrointestinal tract, lungs, and thyroid are the most common sites (17,18). Such unexpected findings might result in additional investigations, treatment delays, and unwarranted patient concerns.
This study investigates the impact of performing an [18F]FDG PET/CT in stage I-II breast cancer patients eligible for NST with respect to change of initial staging, treatment plan and the occurrence of incidental findings.
The utility of 18F-fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) in the initial staging of stage I-IIA breast cancer remains unclear. No firm recommendations on its applicability in these low stages can be drawn from previous research. This single-institution retrospective cohort study was designed to assess the addition of [18F]FDG PET/CT to ultrasonography (US) and magnetic resonance imaging (MRI) in the initial staging of breast cancer patients in work-up to neoadjuvant systemic therapy (NST). Data of 304 patients newly diagnosed with breast cancer between 2018 and 2021 who underwent US, MRI, and [18F]FDG PET/CT for initial staging of breast cancer were evaluated. Our aim was to assess the impact of preoperative [18F]FDG PET/CT on staging, alteration of treatment strategy, incidental findings, and delay in starting NST. Alteration of initial staging occurred in 16.1%, and alteration of breast cancer treatment plan in 19.3% of cases. Multicentricity (OR 3.2; 3.0) and a cN+ status (OR 3.9; 3.2) were significant risk factors for alteration. A total of 99 incidental findings occurred, resulting in 157 additional investigations by which 4.0% of findings were proven malignant. The performance of an [18F]FDG PET/CT did not lead to a significant delay in starting NST. [18F]FDG PET/CT is of added value alongside US and MRI in the initial staging of advanced and low stage multicentric, cT3-4, or cN+ breast cancer. In all other breast cancer cases, it may be worth contemplating omitting [18F]FDG PET/CT.