ICHNO-ECHNO 2022 - Abstract Book

S6

ICHNO-ECHNO 2022

Materials and Methods Patients with HPV-positive, node positive OPSCC HNSCC treated with radical radiotherapy (RT) between January 2013 and July 2019 were identified from the PET-CT database. PET-CT responses were classified as CR, incomplete (ICR) or equivocal (EQR), as defined by the PET-Neck study, by 2 radionucleotide radiologist. Patient demographics and clinical outcomes were obtained from electronic patient records. Results 310 patients were identified, patient and tumour characteristics are detailed in Table 1 . The median time from end of radiotherapy to PET scan was 93 days (IQR 87-101). Median follow-up was 46.7 (IQR, 34.9-63.0) months. 61.3% (190/310) achieved a CR, 24.5% (76/310) EQR, 14.2% (44/310) ICR nodal response. Within the EQR group, 5.3% (4/76) had an IND, 2 (50%) were pathologically positive. Median time from end of RT to IND was 4.8 (4.2-5.8) months. 9 (of 76, 11.8%) patients had a delayed ND, median time 9.3 (7.1 – 28.9) months post RT. 5 of 9 (55.6%) were pathologically positive. 63/76 in the EQR group did not have a ND at any timepoint and 61/63 are alive and disease free. Overall, of the 76 patients with an EQR on 12-week PET-CT, 66 (86.8%) had no residual disease during follow up (either no subsequent relapse or pathologically negative ND). Median survival of the EQR and CR groups were not reached with no statistically significant differences in overall survival (OS) between the groups, p=1.0, Figure 1 . Median survival of ICR was not reached. However, OS for ICR group was significantly worse than that of CR, and EQR, p<0.001 and p=0.001 respectively, Figure 1.