Abstract 272P
Background
Patients with LARC with tumor progression on interim restaging MRI (iMRI) and interim endoscopy (iEndo), typically obtained 5 weeks after induction chemoradiation (CRT), are referred directly to surgery at our institution. We aim to assess the outcomes of patients with poor response without progression on iMRI who completed TNT.
Methods
Patients with LARC, diagnosed 2015 -2021, with an iMRI tumor regression grade (mrTRG) of 4 who completed TNT were included. Pathologic response and disease-free survival (DFS) were calculated after completion of surgery. Univariate analysis was used to assess the impact of individual variables (clinical tumor and lymph node stage, clinical stage, tumor grade, extramural vascular invasion, final MRI response, and final endoscopy (fEndo) results) on pathologic complete response (pCR) and DFS.
Results
40 patients who completed induction therapy as part of TNT with an iMRI TRG of 4 were included. 37 (92.5%) and 3 (7.5%) had induction CRT or chemotherapy respectively. All 40 completed TNT. 5 (12.5%) and 35 (87.5%) had stage II and stage III cancer respectively. 26 patients had a concurrent iEndo with 1 (3.8%) complete response, 0 near complete response, 20 (76.9%) partial response and 5 (19.2%) poor response. 5 (12.5%), 3 (7.5%), 30 (75%), and 2 (5%) had complete, near complete, partial, and poor responses respectively on fEndo. 4 (10%), 21 (52.5%), and 15 (37.5%) had mrTRG of 2, 3, and 4, on final MRI respectively. 3 patients had a complete clinical response (cCR) and did not pursue surgery. Of the 37 patients who underwent resection, 10 (27%) had a pCR. After a median follow-up of 21 months, 2 (7.4%) had local recurrence and 8 (21.6%) had distant metastases, with a 1- and 2-year DFS rates of 89.1% (95% CI: 80%, 99) and 73.4% (95% CI: 57.3%, 94.0%) respectively. None of the variables had a statistically significant impact on pCR and DFS on univariate analysis. Of the 5 patients with iMRI mrTRG 4 and poor response on iEndo, all had ypT3N0 pathology.
Conclusions
Poor response on iMRI alone does not preclude pCR or cCR with TNT. Patients with poor TRG on iMRI and iEndo had residual cancer after TNT. Larger studies are needed to determine the cCR rate in this population.
Legal entity responsible for the study
The authors.
Funding
Cleveland Clinic.
Disclosure
All authors have declared no conflicts of interest.