The clinical role of PET scanning in a consecutive series of GIST patients

1. The clinical role of PET scanning in a consecutive series of GIST patients Frits van Coevorden & Lester van Ravenswade Department of Surgery Netherlands Cancer Institute - Antoni van Leeuwenhoek ziekenhuis Amsterdam The Netherlands

2. The metabolic activity in GastroIntestinal Stromal Tumors has become of interest in this era of targeted therapy • Positron Emission Tomography is the imaging modality to assess metabolic activity in tumors

3. The metabolic activity in GastroIntestinal Stromal Tumors has become of interest in this new Imatinib era • Positron Emission Tomography is the imaging modality to assess metabolic activity in tumors • PET imaging may reveal the metastatic character of tumors • Comparing PET activity before and after the start of TKI’s may provide useful information in assessing the response to drug treatment

4. In a consecutive series of 98 evaluable patients seen in the Netherlands Cancer Institute between 2000 – 2007 our GIST database was reviewed with focus on the use of PET scanning • The indication for PET imaging was classified as: • Diagnostic to evaluate the primary tumor • Diagnostic to evaluate metastatic disease

5. In a consecutive series of 98 evaluable patients seen in the Netherlands Cancer Institute between 2000 – 2007 our GIST database was reviewed with focus on the use of PET scanning • The indication for PET imaging was classified as: • Diagnostic to evaluate a primary tumor • Diagnostic to evaluate metastatic disease • Diagnostic tool to prove or exclude recurrent or residual disease after previous surgery • Response assessment of drug treatment

6. Methods • We reviewed all files and PET -CT studies • Classified PET imaging as: • diagnostic only • diagnostic and used for response evaluation

7. Methods • We reviewed all files and PET -CT studies • Classified PET imaging as: • diagnostic only • diagnostic and used for response evaluation • Correlated the outcome to the associated CT scan • Classified the comparison results as: • Conformal or Discrepant

8. Methods • We reviewed all files and PET -CT studies • Classified PET imaging as: • diagnostic only • diagnostic and used for response evaluation • Correlated the outcome to the associated CT scan • Classified the comparison results as: • Conformal or Discrepant • Correlated the results to the clinical course of the patient with follow up

9. Results (1) • the data here presented are an update of those in abstract 934 • 98 evaluable patients • 45 patients had one or more PET scans • 4 scans as tool to search for residual or possible recurrent disease after surgery: • All were negative, as was the clinical and CT correlate • In 41 patients PET was supposed to show activity

10. Results (2) • PET was false negative in 9 /45 patients (20 %) • 3 in active primary or local recurrent disease • 6 in metastatic hepatic or peritoneal disease

11. Results (2) • PET was false negative in 9 /45 patients (20 %) • 3 in active primary or local recurrent disease • 45 yr female 6 cm bilobar endogastric Gist

12. Results (2) • PET was false negative in 9 /45 patients (20%) • 3 in active primary or local recurrent disease • 51 yr male 10 cm small curvature gastric Gist 50% vital after 1 yr Imatinib

13. Results (3) • PET was false negative in 9 /45 patients (20 %) • PET was true negative in 4 patients (post surgery controls) • PET was true positive in 32 patients • …. so 80 % correlation to CT scan and Clinic !!

14. Results (3) • PET was false negative in 9 /45 patients (20 %) • PET was true negative in 4 patients (post surgery controls) • PET was true positive in 32 patients • Repeat PET used for response assessment in 23 patients

15. Results (4) • Repeat PET for response assessment in 23 patients • 19 patients PET confirmed good response • 3 unchanged PET activity confirmed active SD on CT • …. so if 1st PET shows disease activity • 95 % correlation to CT scan and Clinic !!

16. Results (4) • Repeat PET for response assessment in 23 patients • 19 patients confirmed good response • 3 unchanged PET activity confirmed active SD on CT • 1 discrepancy

17. Case presented at CTOS 2006 in Venice • 33 yr male • dec 2005 resection of high grade small bowel GIST • randomized in 62024 to control group

18. Case presented at CTOS 2006 in Venice • 33 yr male • dec 2005 resection of high grade small bowel GIST • randomized in 62024 to control group • aug 2006: peritoneal recurrence • Start Imatinib 400 mg

19. Case presented at CTOS 2006 in Venice

20. After Glivec After Glivec August 2006: Start (neoadjuvant)Imatinib 400 mg October 2006: effect ??? Before Glivec Or response ? Progression ? So he went for surgery

21. After Glivec After Glivec Bad message: At pathology the PET negative tumor more than 90% vital GIST Before Glivec

22. Bad message: At pathology the PET negative tumor more than 90% vital GIST Good message: Exon 9 mutation Now 1 year later on 800 mg Imatinib: NO ACTIVE DISEASE So maybe PET did predict a favourable outcome very early ??

23. Survival related to PET scanning

24. PET response correlated to outcome at FU

25. Conclusions • PET had a 80 % correlation to active GIST • but PET was false negative in 20 % • If PET is positive: 95% correct response correlation • No change or PD at response assessment predicts a poor outcome

26. Thank you