A TCP-based early regression index predicts the pathological response in neo-adjuvant radio-chemotherapy of rectal cancer

• Published in: Radiotherapy and oncology 2018-09, Vol.128 (3), p.564-568
• Main Authors: Fiorino, Claudio, Gumina, Calogero, Passoni, Paolo, Palmisano, Anna, Broggi, Sara, Cattaneo, Giovanni M., Di Chiara, Alessandra, Esposito, Antonio, Mori, Martina, Raso, Roberta, Ronzoni, Monica, Rosati, Riccardo, Slim, Najla, De Cobelli, Francesco, Calandrino, Riccardo, Di Muzio, Nadia G.
• Format: Article
• Language: English
• Subjects: Adaptive radiotherapy; Magnetic resonance imaging; Modeling; Rectal cancer; Tumor control probability
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2018.06.019

Introducing a radiobiological index based on early tumor regression during neo-adjuvant radio-chemotherapy (RCT, including oxaliplatin) of rectal adenocarcinoma and testing its discriminative power in predicting the tumor response. Seventy-four patients were treated with Helical Tomotherapy following an adaptive (ART) protocol (41.4 Gy/18 fr, 2.3 Gy/fr) delivering a simultaneous integrated boost on the residual tumor in the last 6 fractions up to 45.6 Gy. T2-weighted MRI were taken before (MRIpre) and at mid (MRImid) therapy and the corresponding tumor volumes were considered (Vpre,Vmid). The “Early Regression Index” (ERITCP=-ln[(1-(Vmid/Vpre))Vpre]) was introduced and its discriminative power was assessed in terms of AUC, sensitivity/specificity, positive/negative predictive value (PPV/NPV). Two end-points were considered: (a) pathological complete response (pCR) or clinical complete response followed by watch-and-wait, (cCR); (b) limited response (residual vital cells (RVC) in the surgical specimen >10%). Complete data were available for 65 patients: pCR, cCR and RVC >10% were 20, 2 and 19 respectively. The discriminative power of ERITCP was moderately high (AUC = 0.81/0.75 for /pCRorcCR/RVC >10% respectively, p