Significance of different response evaluation criteria in predicting progression‐free survival of lung cancer with certain imaging characteristics

BACKGROUND: Certain radiographic signs of a treatment response, such as cavitation, changes in density, or tumor change along a short axis, are not considered by Response Evaluation Criteria in Solid Tumors (RECIST). This study evaluates what additional prognostic information can be obtained by including these criteria in tumor assessment. METHODS: Data of 105 patients were included. Tumor cavitation was observed in 51 patients at baseline. An additional 23 patients developed tumor cavitation during treatment. A change in tumor density was the only radiographic treatment response observed in 22 patients. The only measureable treatment response in nine patients was a decrease along the short axis size of the tumor. Tumor response was assessed using various criteria. RESULTS: In patients with basic tumor cavitation, RECIST1.1 scores accurately predicted differences in progression‐free survival (PFS; P = 0.076) while modified (m) RECIST did not (P = 0.550). mRECIST detected a significant difference between PFS in patients with post‐therapeutic cavitation with different responses, but no significant difference using RECIST1.1 (P = 0.004 vs. P = 0.477). In patients with only tumor density changes, there was no significant difference in PFS when either RECIST1.1 or density criteria were used (P = 0.419). In patients with a change in size along the tumor's short axis, short axis criteria could predict significant difference in PFS (P = 0.004). CONCLUSIONS: RECIST1.1 provides the best assessment of tumor response and prediction of PFS in patients with basic tumor cavitation. mRECIST provides better PFS prognostic information in patients with post‐therapeutic cavitation. Short axis criteria provides better PFS prognostic information in patients with changes in the short axis of tumor diameter. Changes in tumor density were not a useful prognostic sign.