Evaluating surveillance CT scans and reassuring other providers after lung SABR can be frustrating to say the least. That’s because ablative radiation often causes significant parenchymal consolidation around the tumor months after treatment. At the same time, we know that only a small fraction of these patients will actually have recurrent disease. In this study of 88 lung lesions treated with SABR, 66% met RECIST criteria for progression after treatment. However, only 16% actually developed a confirmed recurrence. The positive predictive value of RECIST criteria was a disappointing 0.16 meaning fewer than 20% of RECIST positive lesions were true recurrences. As we’ve seen before, the timing of changes is also important. The PPV of RECIST was just 0.08 within 12 months of treatment compared to 0.21 beyond 12 months. Long story short, RECIST criteria performs poorly in predicting progression in lung tumors treated with SABR. | Gulstene, Radiother Oncol 2023
