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Until recently, clinical trials for locally advanced cervix cancer have utilized clinical evaluation and symptom directed imaging (standard response evaluation; SRE) to determine disease free survival (DFS). Recent drug trials use Response Evaluation Criteria in Solid Tumors (RECIST 1.1).This study was undertaken to compare SRE and RECIST 1.1

Between November 2017 to March, 2020 patients recruited in clinical trials that used chemo radiation and brachytherapy were screened. For study inclusion, MRI at diagnosis and at least one follow up imaging between 6-18 months of treatment completion was mandatory. Response to treatment and resultant disease-free status was determined using SRE and RECIST 1.1. For RECIST 1.1, at baseline, cervical lesions with ³ 10mm and lymph nodes with a short axis ³15 mm were considered target lesions, and lymph nodes with a short axis < 15 mm as non-target lesions. In SRE, any measurable primary lesion and any node with short axis ³ 10 mm was considered pathological. Any residual lesion after 6 months of treatment completion or any clinic-radiological increase in the size of primary lesion was categorized as an event for SRE. Similarly, any increase in the size of nodal disease or persistent nodes with short axis³ 10 mm was considered as an event. Pathological verification of recurrence was performed as per treating physician. RECIST 1.1, categorized response as complete response (CR), partial response (PR), stable disease (SD) or progressive disease (PD). PR, SD and PD was considered an event for DFS estimation. SRE categorized patient’s disease free vs not. DFS was calculated using SRE and RECIST 1.1 and agreement was estimated using kappa value.

Sixty-eight patients were eligible for the study inclusion. At diagnosis, each patient had one tumor target lesion. Thirty-three patients (48.5%) had pathological lymph nodes at diagnosis. However, out of these 33 patients, RECIST 1.1 considered only 18% (6/33) to have “target nodal lesions” at diagnosis. In all other patients nodes were classified as “non-target” for response evaluation. On an average, each patient had two follow-up scans (1-4). Using RECIST 1.1, CR was noted in 57, PR in 7, SD in 0, and PD in 4 patients, and on standard evaluation, disease persistence or progression was reported in 9 patients. There were therefore 11(16.1%) and 9 (13.2%) disease events using RECIST 1.1 and standard evaluation. The disease-free survival at 12, 18, and 24 months using RECIST 1.1 were 96%, 87%, 85% and with SRE were 96%, 89%, 88% respectively (p= 0.653) (Figure 1). Kappa value was 0.88, showing strong agreement between the two methods in assessing DFS. However, absolute difference of 2% was noted at 18 and 24 months. 

The study showed 2% absolute difference in DFS at 24 months between RECIST 1.1 and SRE in a population with low event rate. Further investigation of the differences is needed in population with higher event rate to understand impact of this transition.