Timing of Response Assessment PET CT in OPSCC Post Treatment and Salvage Neck Dissection Rates
Fiona Williams,
United Kingdom
PD-0399
Abstract
Timing of Response Assessment PET CT in OPSCC Post Treatment and Salvage Neck Dissection Rates
Authors: Fiona Williams1, Nicholas Morley2, David Smith3, Carl Passsant4, Stuart Quine5, Sandeep Berry5, Mouli Doddi3, David Owens5, Andrew Harris6, Thomas Rackley1, Richard Webster1, Elin Evans1, Mererid Evans1, Nachi Palaniappan1
1Velindre Cancer Centre, Clinical Oncology, Cardiff, United Kingdom; 2Velindre Cancer Centre, Radiology, Cardiff, United Kingdom; 3Royal Glamorgan Hospital, ENT Surgery, Cardiff, United Kingdom; 4Royal Gwent Hospital, ENT Surgery, Newport, United Kingdom; 5University Hospital of Wales, ENT Surgery, Cardiff, United Kingdom; 6Royal Gwent Hospital, ENT Surgery, Cardiff, United Kingdom
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Purpose or Objective
Response assessment PET CT scans post curative chemoradiotherapy (CRT) or radiotherapy (RT) for oropharyngeal SCC (OPSCC) are routinely performed, 12 weeks after completion of treatment. Patients who are found to have nodal equivocal response (EQR) and incomplete response (ICR) undergo further investigations and are assessed for salvage treatment.
Studies have shown delaying the PET CT or repeating the scan 4 weeks later, improves nodal complete response (CR) rates. We analysed the rates of salvage neck dissection for patients who had a response assessment PET CT scan less than (<) 16 weeks (Group A) versus (vs) greater than or equal to (≥) 16 weeks (Group B) post treatment.
Material and Methods
Patients who had PET CT scans following curative treatment for OPSCC from 2016 to 2022 in South East Wales were identified using the PET CT request database. 260 patients fulfilled the criteria. Demographics, treatment details, PET CT outcomes, rates of salvage neck dissection and patient outcomes (overall survival, disease free survival, nodal, primary and distant recurrence rate and second primary) were analysed and compared between groups. Last follow up date was 30/09/2022.
PET CT response for nodes were categorised as CR, EQR and ICR. The study population was grouped into Group A and B based on the timing of the PET CT. We then analysed the number of patients who underwent salvage neck dissections in each group.
Results
Of the 260 patients, 204 were male, 217 were p16 positive and 200 had concurrent CRT. There were 169/260 (65%) patients in Group A and 91/260 (35%) patients in Group B. The median time to PET CT was 13.5 weeks vs 17.5 weeks in Group A and B respectively.
The nodal CR rates were 134/169 (79%) vs 77/91 (85%); nodal EQR/ ICR rates were 35/169 (21%) vs 14/91 (15%) in Group A and B respectively. Of the EQR/ICR cohort, 9/35 (26%) vs 8/14 (57%) patients underwent nodal biopsies in Group A and B respectively. None of the biopsies were positive in Group A and one biopsy was positive in Group B.
Twenty-three patients underwent a salvage neck dissection, of these 17 (74%) patients who were in Group A, 9/17 (53%) had residual disease and of the 6 (26%) patients who were in Group B, 3/6 (50%) had residual disease in the neck nodes.
The overall survival, disease free survival, nodal, primary and distant recurrence rate and second primary rates are 139/169 (82%) vs 78/91 (86%); 123/169 (73%) vs 72/91 (79%); 8/169 (5%) vs 0/91 (0%); 14/169 (9%) vs 4/91 (4%); 16/169 (9%) vs 9/91 (10%); 12/160 (7%) vs 6/91 (7%) in Group A and B respectively.
Conclusion
Of the patients who underwent salvage neck dissections, a higher proportion were in the group who had a PET CT performed <16 weeks post treatment. The disease outcomes in both groups were similar. More work needs to be done to assess whether delaying PET CT scans could reduce surgical morbidity in the future.