E1583. Does PET-CT Response to DEBIRI Chemoembolization in Colorectal Metastases Influence Lesion Progression-Free Survival?
  1. Rishi Thakkar; University of Saskatchewan
  2. Brent Burbridge; University of Saskatchewan
  3. Rajan Rakheja; University of Saskatchewan
  4. Prosanta Mondal; University of Saskatchewan
  5. Shahid Ahmed; Saskatchewan Cancer Agency
  6. Kiat Tan; University of Saskatchewan; Western University
Chemoembolization with irinotecan drug-eluting beads (DEBIRI) is used to treat selected patients with hepatic metastases from colorectal cancer. However, the role of PET-CT in the post-procedural assessment of these patients is uncertain. In addition, the authors have noticed that there is heterogeneity in the PET-CT response in these patients, whereby tumors that demonstrate a response on PET-CT may coexist with lesions that demonstrate progression or no response (1). The authors, therefore, hypothesize that lesions which demonstrate a response on PET-CT demonstrate slower progression than those that do not. For the purpose of this study, the term lesion progression-free survival (LPFS) is used to denote the number of months a lesion does not progress while the patient is alive.

Materials and Methods:
This retrospective study involved 10 subjects (7 males and 3 females) with a total of 40 marker lesions. Patients underwent 1-4 rounds of chemoembolization between March 2014 and December 2016. LPFS (in months) was determined by comparing pre- and post-treatment CT scans.

Of the 40 marker lesions identified, 22 lesions had an LPFS <3 months (55%) and 18 lesions had a LPFS of >3 months (45%). Lesions were classified into three categories based on PET-CT results; complete response, partial response, and progression. Of the 22 lesions that demonstrated an LPFS <3 months, 0 showed a complete response, 1 demonstrated a partial response and 21 demonstrated progression of the disease. Of the 18 lesions that demonstrated a LPFS > 3 months, 9 demonstrated complete response 7 demonstrated partial response and 2 demonstrated progression. Lesion classification was significantly associated with LPFS (P<0.0001). Mean PFS and OS were 4.20 +/- 9.41 months and 20.50 +/- 19.31 months, respectively.

Lesions that demonstrated a complete response to treatment on PET-CT are associated with an increased LPFS. Previous research has shown that the heterogeneity of PET-CT response after chemoembolization may be due to incomplete treatment of certain lesions due to the uneven distribution of chemoembolic agent during the procedure. Therefore, the result from our current study suggests that follow-up PET-CT can be done to identify residual tumor ‘hot spots’ that may require additional treatment, through sub-selective chemoembolization of these lesions.