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1606. Relation Between the FDG Uptake and the EGFR / Alk Mutation Status in Patients with Adenocarcinoma of Lung: Indian Perspective
Authors * Denotes Presenting Author
  1. Govindarajan Mallarajapatna *; Apollo Hospitals; Mirror Health Pvt Ltd
Objective:
To correlate Max SUV of the primary tumor on F18 FDG PET CT scan in patients of adenocarcinoma of lung with EGFR / Alk mutation status - a single center experience and Indian perspective. This study aims to assess the relation, if any, between the level of metabolic activity of the primary lung tumors on F18 FDG PET CT scan in patients diagnosed with adenocarcinoma of lung and the status of EGFR mutation / ALK rearrangement in the tumor.

Materials and Methods:
The F18 FDG PET CT scans performed as initial pre-treatment staging investigation in patients diagnosed with adenocarcinoma lung were retrospectively assessed. Only the cases where histopathology (adenocarcinoma) and EGFR / Alk mutation status were available were included for calculations. The primary tumor was identified on CT scan images (obtained as part of the PET CT study) and the Maximum Substrate Uptake Value (Max SUV) of this lesion was documented using PET CT fused image on a dedicated workstation. Presence or absence of mutation in the tumor of each patient was documented. Additionally, metastatic disease when present was documented with respect to lymphadenopathy, sites of distant metastases etc.

Results:
PET CT scans of 70 patients were evaluated. Forty-nine (49/70) patients had EGFR / Alk mutation positivity with 47 being metastatic, 1 being non-metastatic but inoperable and 1 being early stage (operated after PET CT scan). Twenty one (21/70) patients were negative for the mutation status and 2 of them were non-metastatic. Max SUV range among the positive and negative mutation status patients were 2.1 to 27 and 4.5 to 18 respectively. The mean and median values of Max SUV between the mutation positive and negative groups were nearly the same (11 vs 10.9 and 11 vs 11 respectively) though with a higher standard deviation in the mutation positive group (5.7 vs 3.6 respectively).

Conclusion:
Most patients had metastatic disease. The Max SUV range in the mutation positive group was wider (2.1 to 27) as compared the negative group (4.5 to 18). The highest Max SUV was seen in the mutation positive group. Mean and median values were not significantly different between the two groups. There was significant overlap of the SUV values between the two groups. Max SUV of the primary tumor on F18 FDG PET CT scan was not accurate in predicting the EGFR / Alk mutation status in the tumor in this study. Even though F18 FDG uptake in the EGFR / Alk mutation positive tumor cells is expected to be lower due to possible reversal of the Warburg effect, the available literature data is conflicting. However, our retrospective study contradicts this hypothesis and the F18 FDG PET CT scan seems to be an unreliable tool for predicting EGFR/Alk mutation status although large scale randomized trials may be required to confirm these findings. Limitation of our study is the retrospective nature with relatively small sample size.