18F-FDG positron emission tomography staging and restaging in rectal cancer treated with preoperative chemoradiation.
OBJECTIVE
To assess the information supplied by FDG-PET in patients with locally advanced rectal cancer both in the initial staging and in the evaluation of tumor changes induced by preoperative chemoradiation (restaging).


METHODS
Twenty-five consecutive patients with rectal cancer were included, with tumor stages (c)T(2-4)N(x)M(0), during the period 1997-1999. We prospectively performed two FDG-PET scans in all patients to assess disease stage (1) at initial diagnosis and (2) presurgically, 4 to 5 weeks after protracted chemoradiation. Protracted chemoradiation was carried out during 5-6 weeks with 45-50 Gy, plus concurrent oral tegafur 1200 mg/day or 5-fluorouracil 500-1000 mg/m(2) administered as a 24-h continuous i.v. infusion on Days 1-4 and 21-25 of the radiotherapy treatment. Tumors were staged with CT in 95% of patients, whereas endorectal ultrasound was used in 90% of patients. Maximum standardized uptake value (SUVmax) was used as the quantitative parameter to estimate the tumor:tissue metabolic ratio.


RESULTS
Preoperative chemoradiation significantly decreased the SUVMAX: 5.9 (mean SUVmax at initial staging) vs. 2.4 (mean SUVmax after chemoradiation) with p < 0.001. Unknown liver metastases were detected by FDG-PET in 2 patients, in 1 of them with the initial staging FDG-PET scan, and with the restaging FDG-PET scan in the other. After an average follow-up of 39 months, the value of SUVmax > or =6 allowed us to discriminate for survival at 3 years: 92% vs. 60% (p = 0.04). T downstaging (total 62%) was significantly correlated with SUVmax changes: 1.9 vs. 3.3 (p = 0.03). The degree of rectal cancer response to chemoradiation, established as mic vs. mac categories, was not associated with SUVmax differences (mean values of 2.0 vs. 2.7).


CONCLUSIONS
Preliminary results observed suggest the potential utility of FDG-PET as a complementary diagnostic procedure in the initial clinical evaluation (8% of unsuspected liver metastases) as well as in the assessment of chemoradiation response (any T downstaged event) of locally advanced rectal cancer. Initial SUVmax might be of prognostic value related to long-term patient outcome.
Calvo
Felipe A
FA
Department of Oncology, Hospital General Universitario Gregorio Marañón, C/Dr. Esquerdo 46, Madrid 28007, Spain.
Domper
Marta
M
Matute
Raúl
R
Martínez-Lázaro
Raúl
R
Arranz
José A
JA
Desco
Manuel
M
Alvarez
Emilio
E
Carreras
José Luis
JL
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D003131:Combined Modality Therapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D008297:Male; D009367:Neoplasm Staging / Q000379:methods; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy / Q000628:therapy*; D005641:Tegafur / Q000008:administration & dosage; D014055:Tomography, Emission-Computed
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D005641:Tegafur; D005472:Fluorouracil