ASCO 2018: PET imaging may top CT in predicting therapy response in melanoma patients

PET imaging may better predict long-term benefits and guide discontinuation of therapy compared to standard contrast CT for patients with metastatic melanoma, according to findings presented Monday, June 4, at the 2018 American Society of Clinical Oncology (ASC0) annual meeting in Chicago.

Researchers—led by Alexander Menzies, PhD, a medical oncologist and senior research fellow at Melanoma Institute Australia—found that most metastatic melanoma patients who survived one year with PD1-based therapy had a complete metabolic response shown through PET imaging and 96 percent of patients had an ongoing response to therapy.  

Although PD1-based therapy has proven successful for many metastatic melanoma patients, determining whether these patients will have a long-term response to the therapy remains unclear, wrote Menzies and his colleagues.

A cohort of 104 metastatic melanoma patients (67 percent male, average age of 65 years) treated with PD1-based therapy was recruited from the Melanoma Institute Australia between May 2013 and April 2018 for analysis, wrote Menzies et al. Patient data, including demographics, disease features, treatment, response and outcome, were collected.  

Additionally, one-year response to therapy was determined using RECIST criteria for CT and EORTC criteria for PET and was coded for complete response (CR or CMR), partial response (PR or PMR), stable disease (SD or SMD) or progressive disease (PD or PMD) on CT and PET, respectively, the researchers wrote.

Findings included:  

  • At one year since treatment, 25 percent of patients had CR, 60 percent had PR and 15 percent had SD/PD on CT versus 68 percent having CMR, 17 having PMR and 15 percent SMD/PMD on PET.  
  • RECIST progression-free survival (PFS) was improved in patients with CMR versus non-CMR. In the patients with CMR, PFS was not statistically different between patients with CMR plus CR versus CMR plus PR/SD.  
  • In patients with PR on CT, PFS was improved in patients with PR plus CMR versus PR plus non-CMR.  
  • In the 80 patients with CMR, average time of treatment was 14.8 months and 60 percent had discontinued treatment with median follow-up post discontinuation after 9.9 months.