Pretreatment second look PET/CT catches cancer metastases: Study

In half of the patients, the researchers discovered new lymph node metastases.

Switzerland: A second PET/CT scan is needed before radiotherapy treatment when there are delays of more than 4 weeks after initial PET/CT staging in patients with advanced head and neck squamous cell cancer, finds a recent study. This is expected to directly influence oncologic outcomes as it led to changes in treatment planning in more than half of the cases.

The study is published in the journal Clinical and Translational Radiation Oncology. 

18F-FDG PET/CT is regularly used for staging in patients diagnosed with locoregionally advanced head and neck squamous cell carcinoma (LAHNSCC). In cases of delays in radiotherapy (RT) planning CT more than 4 weeks following initial scan or clinically suspected progress, PET/CT is repeated for restaging and as an RT planning reference. 

Olgun Elicin, University of Bern, Bern, Switzerland, and colleagues aimed to determine the impact of second-look PET/CT on stage migration, treatment change, and RT planning.

In the study, consequent treatment changes were categorized as minor and major. Minor changes were identified as PET/CT-based modifications of RT plans, e.g., the addition of anatomical compartments, changes in high- and low-risk dose levels or both. Major changes included changes from curative to palliative treatment intent and alterations of interdisciplinary treatment plans, such as the addition of induction chemotherapy, switch to primary surgery, no treatment and/or the necessity of additional diagnostic work-up resulting in the postponement or cancellation of treatment. 

32 newly diagnosed LAHNSCC patients who were treated between 2014 and 2018 underwent second-look PET/CT (median interval 42.5 days). 

Elicin and colleagues concluded, a second look PET/CT due to a delay of more than four weeks to RT in LAHNSCC or in case of clinical suspicion of tumor progression led to tumor upstaging in 13% of patients and changes in treatment planning in more than half of patients, which is expected to directly influence oncologic outcome.

Reference:

The study titled, "Impact of pretreatment second look 18FDG-PET/CT on stage and treatment changes in head and neck cancer," is published in the journal Clinical and Translational Radiation Oncology.

DOI: https://www.ctro.science/article/S2405-6308(21)00075-6/fulltext