In a recent study titled “Response assessment in metastatic melanoma treated with ipilimumab and bevacizumab: CT tumor size and density as markers for response and outcome”, published in the Journal for the Immunotherapy of Cancer, researchers from the Dana-Farber Cancer Institute, Boston, investigated the relation between tumor diameter and changes in density with survival in advanced melanoma patients treated with ipilimumab plus bevacizumab.
Tumors treated with different types of immunotherapies have a specific response configuration on imaging, since immunotherapeutic agents preform their anti-tumoral effects by increasing the infiltration of T cells in the tumors. The configuration changes directly related to the efficiency of the immune response may not be properly detected by conventional tumor response criteria, such as RECIST and WHO criteria.
Recent studies have proposed an immune-related response criteria (irRC) to adequately depict the outcomes of immunotherapies. One such evaluation measurement is the Choi criteria, whichwas first used to define responses in density in patients with gastrointestinal stromal tumors treated with imatinib.
The Dana-Farber research team, led by Dr.F Stephen Hodi, analyzed a total of 59 lesions in 21 patients. They registered a total of 15 lung lesions, 14 peritoneal or retroperitoneal lesions, 11 liver, 9 subcutaneous, 5 nodes and 5 adrenal lesions.
The results showed that, during the first follow-up, 39% of lesions and 33% of patients met the Choi density criteria for response. Using RECIST and MASS, the response rates were of 14%, and when size and density criteria were used, the Choi criteria was 52%.
Importantly, the team observed that a wider baseline tumor diameter was significantly associated with an inferior progression-free survival (PFS) and overall survival (OS). Furthermore, diameter and density changes, or responses by RECIST, MASS or Choi criteria during the first follow-up, did not have a direct link with PFS or OS.
Based on their results, the authors concluded that using the Choi criteria tumor decrease was found in one-third of advanced melanoma patients undergoing ipilimumab plus bevacizumab therapy, after the first follow-up scan.
Furthermore, the only criterion associated with shorter survival was larger baseline tumor diameter, since alteration in diameter or density plus responses by three criteria, did not calculate survival.
“The limitations of the present study include retrospective design and a small number of patients treated at a single institution. The role of density changes in evaluating response during ipilimumab and bevacizumab therapy for advanced melanoma remains to be further established”, the authors concluded in their study.