Measuring tumor cell proliferation with 18F-FLT PET during radiotherapy of esophageal squamous cell carcinoma: a pilot clinical study.
The primary aim of this study was to use serial (18)F-3'-deoxy-3'-fluorothymidine (FLT) PET/CT to measure tumor cell proliferation during radiotherapy of squamous cell carcinoma (SCC) of the esophagus.


METHODS
Twenty-one patients with inoperable locally advanced SCC of the esophagus underwent serial (18)F-FLT PET/CT during radiotherapy. Each patient received a pretreatment scan, followed by 1-3 scans after delivery of 2, 6, 10, 20, 30, 40, 50, or 60 Gy to the tumor.


RESULTS
Among the 19 patients who completed radiotherapy without interruption, parameters reflecting (18)F-FLT uptake in the tumor (i.e., maximum tumor standardized uptake value [SUVmax] and proliferation target volume) decreased steadily. All patients demonstrated an almost complete absence of proliferating esophageal tumor after 30 Gy and a complete absence after 40 Gy. In the 2 patients whose radiotherapy course was interrupted, (18)F-FLT uptake in the tumor was greater after the interruption than before the interruption. Marked early reduction of (18)F-FLT uptake in irradiated bone marrow was observed in all patients, even after only 2 Gy. All showed a complete absence of proliferating marrow in irradiated regions after 10 Gy. Both patients who underwent scans after completing the entire radiotherapy course showed no tumor uptake on (18)F-FLT PET/CT but high uptake on (18)F-FDG PET/CT. Pathologic examination of these regions revealed inflammatory infiltrates but no residual tumor.


CONCLUSIONS
(18)F-FLT uptake can be used to monitor the biologic response of esophageal SCC and normal tissue to radiotherapy. Increased uptake of (18)F-FLT after treatment interruptions may reflect accelerated repopulation. (18)F-FLT PET/CT may have an advantage over (18)F-FDG PET/CT in differentiating inflammation from tumor.
Yue
Jinbo
J
Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan, China.
Chen
Lusheng
L
Cabrera
Alvin R
AR
Sun
Xindong
X
Zhao
Shuqiang
S
Zheng
Fu
F
Han
Anqin
A
Zheng
Jinsong
J
Teng
Xuezhong
X
Ma
Li
L
Ma
Yidong
Y
Han
Dali
D
Zhao
Xianguang
X
Mu
Dianbin
D
Yu
Jinming
J
Li
Yuhui
Y
D000368:Aged; D000369:Aged, 80 and over; D001854:Bone Marrow Cells / Q000473:pathology / Q000528:radiation effects; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy*; D049109:Cell Proliferation; D003937:Diagnosis, Differential; D015224:Dideoxynucleosides; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007249:Inflammation / Q000175:diagnosis / Q000000981:diagnostic imaging; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D010865:Pilot Projects; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed
D015224:Dideoxynucleosides; D019788:Fluorodeoxyglucose F18; C002854:alovudine