2078 - Prediction Of Pathologic Tumor Response by MRI Restaging in Operable Soft Tissue Sarcoma following Preoperative Chemoradiotherapy
Presenter(s)
D. Greto1, M. Loi1, G. Roselli2, A. Palomba3, G. Scoccianti4, G. Francolini1, G. Simontacchi1, P. Bonomo5, M. Banini6, I. Desideri1, N. Bertini7, L. Visani1, C. Becherini8, C. Arilli9, C. Talamonti10, S. Pallotta11, D. A. Campanacci12, and L. Livi1; 1Radiation Oncology Unit, Azienda Ospedaliero Universitaria Careggi, University of Florence, Florence, Italy, 2Department of Radiology, Azienda Ospedaliero Universitaria Careggi, Firenze, Italy, 3Histopathology and Molecular Diagnostic Unit, Azienda Ospedaliero Universitaria Careggi, Firenze, Italy, 4Department of Orthopaedic Oncology and Reconstructive Surgery, Azienda Ospedaliera Universitaria Careggi, Firenze, Italy, 5Radiation Oncology Unit, Azienda Ospedaliero-Universitaria Careggi, University of Florence, Florence, Italy, 6Department of Experimental Clinical and Biomedical Sciences “Mario Serio”, University of Florence, Florence, Italy, 7Radiation Oncology Unit, Azienda Ospedaliero Universitaria Careggi, University of Florence, Firenze, Italy, 8Radiation Oncology, Careggi University Hospital, University of Florence, Florence, Italy, 9Medical Physics, Careggi University Hospital, University of Florence, Florence, Italy, 10Department of Biomedical, Experimental and Clinical Sciences “Mario Serio", University of Florence, Florence, Italy, 11University of Florence, Department of Biomedical, Experimental and Clinical Sciences “Mario Serio", Florence, Italy, 12Department of Health Sciences, Orthopedic Oncology and Reconstructive Surgery Unit, Careggi University Hospital, University of Florence, Florence, Italy
Purpose/Objective(s): In patients with resectable Soft Tissue Sarcoma (STS) treated with neoadjuvant radiotherapy (RT) or chemoradiotherapy (CRT), pathologic tumor response (pR) is correlated with the outcome. The aim of this study is to assess the correlation between imaging response (iR) at restaging MRI and pR.
Materials/Methods: Data from consecutive STS patients (2014-2023) treated with neoadjuvant CRT/RT were retrospectively collected. RT was delivered at a dose of 50 Gy in 25 fractions, in association with anthracycline-based chemotherapy in selected cases. Baseline and restaging MRI were performed within 4 weeks before the initiation and within 3 weeks after the end of preoperative treatment, respectively. The Objective Response Rate (ORR) was graded according to RECIST 1.0, while iR was evaluated as the percentage of tumor reduction in its major axis. In resected tumors, pR was assessed in terms of necrosis rate, using a =90% threshold for near-complete response (n-pCR). Spearman correlation for continuous variables and Kruskall-Wallis test for median comparison was performed. ROC curves were calculated to assess Sensitivity (Se) and Specificity (Sp) of iR at different thresholds for detection of n-pCR.
Results: One-hundred-eight patients (median age: 55 years, range 18-91) were included. Fifty-nine patients (50%) received concurrent chemotherapy. All patients received the planned neoadjuvant treatment followed by resection after a median interval of 5 (range 3-12) weeks. Median iR and ORR were respectively 10% and 12%. Median necrosis rate was 80% (range 5-100%): n-pCR was observed in 47% of patients (n=56) and was significantly correlated with longer interval to surgery (median 6 versus 5 weeks, p=0.04). A moderate correlation between iR and pR was observed (r=-0.23, p=0.013). At ROC analysis, AUC was 0.658: a >15% tumor reduction was identified (Sp: 80%; Se: 52%) for n-pCR. In the subset receiving RT alone (n=59), a stronger correlation between iR and pR was found (r=-0.38, p=0.0041). At ROC analysis, AUC was 0.734: at >15% volume reduction threshold, Sp and Se were respectively 80% and 57%. In one patient wiht n-pCR, volumetric increase due to intralesional bleeding rather than tumor progression was identified at radiologic review.
Conclusion: Assessment of iR at MRI-based restaging is correlated with pR, particularly in STS patients treated with preoperative RT. Due to the time-dependent trend toward increased n-pCR following CRT/RT, repeating imaging at different time points may be useful to guide the timing of surgery. However, RECIST criteria may not be appropriate for this purpose, and a careful radiological review is recommended to identify actual tumor progression.