2.3. Tumor Recurrence Determination
BrICS-LIT, tumor, necrosis
DISEASE PROGRESSION, TUMOR, PROLIFERATION, TUMOR PROGRESSION, NECROSIS, PATHOLOGY, TUMOR RECURRENCE
With BrICS-LIT, we graphed lesion volumes and BT-RADS scores over each patient’s follow-up period to observe long-term trends. As tumor-mimicking treatment effects such as pseudo-progression and radiation necrosis are commonly associated with high-dose radiation, we sought to use BrICS-LIT and clinical pathology reports to determine true tumor recurrence dates on a case-by-case basis. The following criteria were established across all patients to label the date of first disease progression. First, if the patient received any follow-up surgery and biopsy, then their pathology report served as the ground truth for tumor progression. If the re-resection or biopsy specimens contained over 20% tumor as described in the pathology report, the previous date was labeled as progression. When the pathology report did not include a percentage but mentioned positive tumor presence, the previous follow-up was labeled as progression. While other factors included in pathology reports such as mitosis or elevated proliferation index could have been used as cutoff points for progression, these factors were not present in every report we received. Therefore, we used a defined cutoff based on information that every report shared. This cutoff was set a priori and not changed in the analysis. For patients who did not receive re-resection, follow-up imaging was evaluated by comparing volumetric changes of contrast-enhancing and FLAIR lesions over time. Dates where significant increases in segmented tumor volume leading to BT-RADS scores of 3c and 4 were further examined using RT dose map overlays. By overlaying an RT dose map over follow-up anatomic imaging, we could look for cases where an enhanced lesion continued to expand and significantly spread outside of the high-dose target (appearing red in the overlaid dose maps). If the enhancing lesion spread outside the high-dose radiation field, the corresponding follow-up date was defined as the tumor recurrence date. Otherwise, if the enhancing lesion volume stabilized within the high-dose region of the brain, the enhancement was attributed to radiation necrosis. Every case where the enhancing lesion extended past the high-dose radiation target was verified and agreed upon by a neuro-radiologist and the patient’s treating radiation oncologist.