Kinetic analysis of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) in head and neck cancer patients before and early after initiation of chemoradiation therapy

Abstract

The purpose of this study was to investigate the kinetic behavior of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) before and early after initiation of chemoradiation therapy in patients with squamous cell head and neck cancer.

Methods: A total of 8 patients with head and neck cancer underwent (18)F-FLT PET scans (7 patients at baseline and after 5 d [10 Gy] of radiation therapy given with concomitant chemotherapy and 1 patient only at baseline). Dynamic PET images were obtained with concurrent arterial or venous blood sampling. Kinetic parameters including the flux constant of (18)F-FLT based on compartmental analysis (K-FLT), the Patlak influx constant (K-Patlak), and standardized uptake value (SUV) were calculated for the primary tumor and (18)F-FLT-avid cervical lymph nodes for all scans.

Results: Mean pretreatment values of uptake for the primary tumor and cervical nodes were 0.075 +/- 0.006 min(-1), 0.042 +/- 0.004 min(-1), and 3.4 +/- 0.5 (mean +/- SD) for K-FLT, K-Patlak, and SUV, respectively. After 10 Gy of radiation therapy, these values were 0.040 +/- 0.01 min(-1), 0.018 +/- 0.016 min(-1), and 1.8 +/- 1.1 for K-FLT, K-Patlak, and SUV, respectively. For all lesions seen on pretherapy and midtherapy scans, the correlation was 0.90 between K-FLT and K-Patlak, 0.91 between K-FLT and SUV, and 0.99 between K-Patlak and SUV.

Conclusion: The initial (18)F-FLT uptake and change early after treatment in squamous head and neck tumors can be adequately characterized with SUV obtained at 45-60 min, which demonstrates excellent correlation with influx parameters obtained from compartmental and Patlak analyses.

Figures

FIGURE 1

Standard 18F-FLT plasma curves presented as value normalized by administered dose (Bq/mL/MBq). Solid line represents measured curve, and dashed line is metabolite-corrected curve. Individual patient data and table of plotted values are available in supplemental material.

FIGURE 2

Pretherapy (left) and midtherapy (right) 18F-FLT PET images of patient with right tonsillar neoplasm (arrowhead), with bilateral cervical nodal metastases (solid arrows). Note interval decrease in 18F-FLT uptake in tumor and marked reduction in cervical bone marrow activity (dashed arrow).

FIGURE 3

Comparison of SUV60 with K-FLT derived from 4-parameter fits in 4 patients with arterial blood sampling (A) and with K-Patlak in all patients (B), including pretherapy and midtherapy scans. B includes values determined in patients without arterial sampling through use of scaled standard input function.

FIGURE 4

Comparison of change in SUV60 between pretherapy and midtherapy scans with change in K-FLT in patients with arterial blood sampling (A) and comparison of SUV and K-Patlak in all patients (B). B includes values determined in patients without arterial sampling through use of scaled standard input function.

FIGURE 5

18F-FLT uptake in primary tumor at different time points expressed as percentage of the concentration at 60 min after administration at pretherapy (A) and midtherapy (B) scans. Heavy solid line represents mean value at each time point. At 45 min, uptake is within ±10% of 60-min concentration in all patients for both pretherapy and midtherapy scans.

FIGURE 6

Correlation between K-Patlak and SUV at particular time point vs. midpoint time (min) of imaging interval for pretherapy (solid curve) and midtherapy (dashed curve) scans.