PET in Colorectal Cancer

Indications for FDG PET

• Rising marker, (-) CT/MRI• Nonspecific findings on CT/MRI, recurrence or post treatment changes?• Known metastases; evaluate extent or disease or identify other sites of recurrence• Evaluate response to chemotherapy

LV

12/09/9304/23/9608/22/96

PET-FDG SCAN IN RECTAL CA

191642

Coronal

MSKCC AL361200

Case 1Case 1Case 1

Comparison of PET and CT

N=40 pts. (93 biopsies)

WCT=0.73+/-.06*

WPET=0.97/-.02*

*P<.001

Biopsy Correlated Finding SUV in Colon Cancer

0.00

0.20

0.40

0.60

0.80

1.00

0 1 2 3 4 5 6 7 8 9

PET-FDG SUV

Fra

cti

on

of

PE

T F

ind

ing

s

FPF

TPF

PET in Colorectal Cancer

0

0.1

0.20.3

0.4

0.5

0.6

0.70.8

0.9

1

0.00 0.20 0.40 0.60 0.80 1.00

Prevalence of Disease

Pos

t-tes

t Dis

ease

pro

babi

lity

T+/D+

T-/D+

Change: post vs pre

Diagnostic Imaging in Oncology• Detection

• Differential Diagnosis

• Tumor biology relevant to therapy

• Staging

• Recurrence

• Response

PET in Colorectal Cancer• PET accuracy between 88 - 92% > CT (75%)• Among pt.s with suspected recurrence, SUV > 3.5

has a 90% probability of tumor, and a 10% prob of being a benign lesion

• Most common reasons for missing lesions is size (< 1 cm in diameter), location (peritoneum), and artifact (lesion near high count area)

• PET >> CT for Rx response in rectal Ca