By Dr. Khurram Shehzad
Abstract:
Objectives/Purpose:
Locally advanced Nasopharyngeal
carcinoma (LA-NPC) is the most common presentation of NPC
in Saudi Arabia and many countries including East Asia and
North Africa. There is a great need for prognostic factors in
LA-NPC due to limited value of TMN staging system. This
study aimed to evaluate the prognostic value of 18F-FDG PET
scans following chemotherapy of locally advanced NPC.
Materials/Methods: Using a cohort of 107 LA-NPC patients
recruited for a clinical trial with a different aim, patients had
PET scan two weeks after the completion of the two cycle of
induction chemotherapy, and before definitive radiotherapy.
The PET scan was measured by the maximum Standardized
update volume (SUVmax), Metabolic Tumor Volume MTV, or
total lesion glycolysis (TLG). Correlation was assessed using
Cox proportional hazard regression analysis for continuous
and ordinal variables and significance of separation in
Kaplan-Meier survival curves were measured using log-rank
test.
Results:
There was no significant correlation between PET
scan of the primary tumor after chemotherapy whether
measured by SUVmax, MTV or TLG. However, there was
significant correlation between PET scan of the involved
lymph nodes after chemotherapy measured as TLG and
relapse-free survival (RFS, p=0.008), metastasis-free survival (MFS, p=0.010) but not with overall survival (OS, p=0.08).
Similarly, PET-CT metrics measured by SUVmax in the
involved lymph nodes after definitive chemoradiotherapy
correlated significantly with RFS (p<0.001) but not with MFS
(p=0.07) or OS (p=0.33). A Clinician Assessed PET Response
(CA PET), which was considered the response to be
“complete” if SUVmax was < 4, “Partial” if SUVmax was >4
and a “progressed tumor” if SUV surpassed SUV at diagnosis
and if there is new lesions) was also assessed. Indeed, CA PET
highly correlated with DFS (p<0.001), MFS (p<0.001) and OS
(p<0.001),
Conclusions:
Our findings support the use of PET-CT after
chemotherapy as a valuable early prognostic marker for risk
stratification in locally advanced NPC, potentially guiding
therapeutic decisions and improving personalized treatment
strategies. Our clinician assessed PET response which consider
PET scan after before and after therapy outperformed interval
specific PET measurements. More work is still warranted to
optimize the use PET in diagnosis and therapy monitoring of
LA-NPC.