The Prognostic Value of Interim PET Scan in Patients with Classical Hodgkin Lymphoma
Authors: Oki Yasuhiro , Chuang Hubert , Chasen Beth , Pan Tinsu , Fanale Michelle A. , Dabaja Bouthaina S. , Fowler Nathan H , Romaguera Jorge Enrique E , Fayad Luis E , Hagemeister Fredrick B , Rodriguez Alma , Neelapu Sattva S. , Samaniego Felipe , Kwak Larry W , Younes Anas 
Published: October 2019

Abstract
Abstract 1529
The interim PET scan has prognostic value in pts with cHL. Because the outcome of ptswho have positive interim PET scans was dismal in previous reports, multiple clinical trials are ongoing using the interim PET to guide treatment decisions, but these are mostly non-randomized studies. We performed a retrospective study analyzing the prognostic role of the interim PET scan for predicting event free survival (EFS) for early stage (I and II non-bulky) and advanced stage (II-bulky, III and IV) cHL treated with standard ABVD with or without radiation therapy. This study was approved by the institutional review board.
Interim PET results (positive or negative) were collected from the clinical reports of PET scans which were based on visual interpretation. A total of 327 pts diagnosed between 01/2001 and 05/2011, and had interim PET scan after 2 (PET2; n=231) or 3 (PET3; n=96) cycles were reviewed. The median follow up duration of surviving pts was 45 months (range 2–130 months).
For pts with advanced stage disease, 5-year EFS rates in PET2-negative (n=79) and PET2-positive (n=20) groups were 75% and 54%, respectively (p=0.027). For pts with low IPS scores (0–2), 5-year EFS rates in PET2-negative (n=60) and PET2-positive (n=15) groups were 77% and 53%, respectively (p=0.02). For pts with high IPS scores (3–7), 5-year EFS rates in PET2-negative (n=19) and PET2-positive (n=5) groups were 69% and 50%, respectively (p=0.76). In pts with early stage disease, 5-year EFS rates in PET2-negative (n=107) and PET2-positive (n=25) groups were 98% and 65%, respectively (p<0.01). PET3 had little prognostic value for EFS for pts with early stage or advanced stage diseases, though the number of pts analyzed was smaller.
There have been significant changes in PET technology, methodology, and interpretation criteria. To minimize these factors, we next selected 118 pts whose PET2 were performed between 03/2008 and 05/2011. The PET scans from theres patients were blindly and independently re-reviewed without information on clinical outcome, by two nuclear radiologist based on Deauville criteria. For pts with advanced stage disease, 2-year EFS rates for pts with negative PET2 (n=47) and positive PET2 (n=5) scans were 68% and 60%, respectively (p=0.59). For pts with early stage diseases, 2-year EFS rates for pts with negative PET2 (n=55) and positive PET2 (n=11) scans were 98% and 47%, respectively (p<0.01).
In conclusion, this study confirmed that PET2 results remain prognostic, not only for advanced stage disease but more significantly for early stage cHL. However, pts with advanced stage disease whose PET2 was positive had 5-year EFS of 54% (2001–2011), which seems far better than previous reports. Interim-PET guided treatment decisions are not currently recommended outside of clinical trials. Randomized trials will be required to determine whether change of therapy based on PET2 status will improve treatment outcome.

Disclosures:
Fanale: MedImmune: Research Funding.