FDG-PET/CT PATTERNS AND PREVALENCE OF PERITONEAL SPREAD IN OVARIAN CANCER Srour SF 1, Bar-Shalom R 2 Srour SF 1, Bar-Shalom R 2 1 Department of Diagnostic Imaging 1 Department of Diagnostic Imaging 2 Institute of Nuclear Medicine Rambam Health Care Campus Rambam Health Care Campus Haifa, Israel Haifa, Israel

Background Ovarian cancer (O.C) is the second most common, and the most common cause for cancer-related death among gynecological tumors It is responsible for more than half of gynecological mortality Most cases revealed at a late stage The most common secondary spread is to peritoneum and retroperitoneal L.N. Peritoneal spread (p.s) changes the stage of tumor and affects treatment strategy and prognosis

Imaging Methods Conventional imaging methods (US, CT, MRI) are limited for detecting peritoneal spread CT sensitivity for p.s.: 17-54%, depends on size, place, morphology, ascitic fluid, diminished abd. fat volume, and bowel distention with contrast size, place, morphology, ascitic fluid, diminished abd. fat volume, and bowel distention with contrast PET/CT imaging for peritoneal spread is not well established, but recent studies are encouraging PET/CT patterns of p.s. are variable and not clearly recognized

Purpose To describe and characterize the incidence and patterns of peritoneal spread of ovarian cancer as demonstrated by PET/CT examination

Methods Retrospective evaluation of 150 o.c patients who underwent FDG-PET/CT. Period: 8/2001 – 3/2007 Parameters collected: Normal study vs. P.S. only vs. other secondary spread Focal vs. Diffuse P.S Monofocal vs. Multifocal P.S Anatomical site of spread SUV (Standardized Uptake Value) CT size

Methods Analysis of: Analysis of: Relative incidence of each P.S. pattern SUV average CT average size Relation-ship between size on CT and SUV Present different examples of P.S patterns as seen on PET/CT.

Results Exam indication 82 (55%) – Relapse 45 (30%) – Restaging 23 (15%) – Evaluation after treatment  average age = 60 yrs (range: 27-81)

Incidence of P.S. Patterns Peritoneal spread was found in 45/150 (30%) 71/150 (47%) other secondary spread was found: Retroperit. L.N, liver, lungs…(not P.S) 34/150 (23%) were normal studies 34/150 (23%) were normal studies

Peritoneal Spread Three P.S. patterns were found: Monofocal, Multifocal, and Diffuse 24 / 45 (53%) were with P.S. only 8/24 (33%) – Monofocal P.S 9/24 (38%) – Multifocal P.S 7/24 (29%) – Diffuse P.S 21 / 45 (47%) were with P.S. and other secondary spread 7/21 (33%) - Monofocal P.S 13/21 (62%) - Multifocal P.S 1/21 (5%) - Diffuse P.S

Peritoneal Spread P.S. Patterns Number % of total P.S Focal P.S Monofocal p.s 1533 Multifocal ps 2249 Total focal spread 3782 Diffuse P.S 818 Total P.S 45100

Anatomical Distribution of P.S SiteMonofocal N (%) Multifocal Diffuse pelvis 7 (47) 16 (73) 6 (75) Mesentry & ant. abd. 5 (33) 7 (32) 7 (88) Liver surface 0 (0) 7 (32) 6 (75) Lt paracolic 0 (0) 4 (18) 6 (75) Rt paracolic 0 (0) 2 (9) 7 (88) Inf. Abd. 3 (20) 0 (0) 5 (63) total 15 (100) 22 (100) 8 (100)

Most Monofocal spread was to pelvis, mesentry and ant. abd. Most multifocal spread was to pelvis, mesentry and ant. abd.and liver surface Diffuse spread was to all the anatomical sites in the same incidence because of its widespread nature.

SUV for P.S. Patterns No significant difference was found in the SUV between the two focal spread patterns [p=0.636]: Monofocal: suv=8.3 (range ) Multifocal: suv=8.8 (range ) In Diffuse pattern, because of its widespread nature we couldn’t accurately evaluate the SUV for this category but it seemed to be less than the focal spread.

CT size for P.S. Patterns Average size on CT in the monofocal spread was: 1.7cm (range:0.9-3cm) Average size on CT in the Multifocal spread was: 2cm (range: cm) We found significant relationship between SUV of peritoneal spread and average size on CT in the focal spread patterns [p= ]: Big size on CT was related to high SUV Big size on CT was related to high SUV

Examples of P.S. in Ovarian Cancer mono-focal spread to pelvis

Mono-focal spread to anterior abdomen All the other focal absorption are physiologic in bowel loops

Multi-focal spread to pelvis

Multi-focal spread to liver surface

Spread to ant. Abd. as part of diffuse spread with ascites

Diffuse spread with ascites

Diffuse spread on liver surface Common in diffuse and multi-focal spread. Difficult for diagnosis by CT scan only.

Conclusion Peritoneal spread in ovarian cancer is common (30% in our study) As FDG-PET/CT is being an important tool for assessing these patients, familiarity with the variable peritoneal spread patterns on PET/CT is important for accurate assessment of disease status of ovarian cancer patients