1 Vol.:(0123456789) Scientific Reports | (2022) 12:3385 | https://doi.org/10.1038/s41598-022-07143-1 www.nature.com/scientificreports Computed tomography based analyses of body mass composition in HER2 positive metastatic breast cancer patients undergoing first line treatment with pertuzumab and trastuzumab Michela Palleschi 1 , Andrea Prochowski Iamurri 2* , Emanuela Scarpi 3 , Marita Mariotti 1 , Roberta Maltoni 1 , Francesca Mannozzi 3 , Domenico Barone 2 , Giovanni Paganelli 4 , Michela Casi 5 , Emanuela Giampalma 6 , Ugo De Giorgi 1 & Andrea Rocca 1 Body composition parameters (BCp) have been associated with outcome in different tumor types. However, their prognostic value in patients with HER2-positive metastatic breast cancer (BC) receiving first line treatment with dual anti-HER2 antibody blockade is unknown. Preclinical evidences suggest that adipocytes adjacent to BC cells can influence response to anti-HER2 treatments. We retrospectively analyzed Computed Tomography (CT)-based BCp from 43 patients with HER2-positive metastatic BC who received first line pertuzumab/trastuzumab-based treatment between May 2009 and March 2020. The impact of baseline CT-based BCp on progression-free survival (PFS) was tested using Kaplan–Meier estimates and univariate and multivariate Cox regression models. We found a significantly worse PFS for patients with high baseline subcutaneous fat index (median 7.9 vs 16.1 months, p = 0.047, HR = 2.04, 95%CI 1–4.17) and for those with high total abdominal fat index (8.1 vs 18.8 months, p = 0.030, HR = 2.17, 95%CI 1.06–4.46). Patients with baseline sarcopenia did not show shorter PFS compared to those without sarcopenia (10.4 vs 9.2 months, p = 0.960, HR = 0.98, 95%CI 0.47–2.03). Total abdominal fat index remained a significant predictor of PFS at multivariate analysis. Our findings suggest that a high quantity of total abdominal fat tissue is a poor prognostic factor in patients receiving trastuzumab/pertuzumab-based first-line treatment for HER2-positive metastatic BC. e association between obesity and early breast cancer (BC) has been described in various clinical trials: in both pre- and postmenopausal patients the excess of body weight is correlated with higher relapse and poorer survival with respect to normal-weight individuals. A number of meta-analyses have confirmed the negative prognostic impact of obesity, which is more evident in patients with estrogen receptor (ER)-positive BC 1–3 . e relation between body mass index (BMI) and prognosis has yet to be clarified for metastatic disease, although some studies have hypothesized possible protective effect of excess body weight, in conflict with data reported in early-stage BC 4–6 . is phenomenon called ‘’obesity paradox’’ has also been described in other tumor types, in particular gastrointestinal malignancies, and could be explained by the fact that body composition is highly variable between individuals sharing same BMI. OPEN 1 IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) “Dino Amadori”, Meldola, Italy. 2 Radiology Unit, IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) “Dino Amadori”, Meldola, Italy. 3 Unit of Biostatistics and Clinical Trials, IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) “Dino Amadori”, Meldola, Italy. 4 Nuclear Medicine Unit, IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) “Dino Amadori”, Meldola, Italy. 5 Nuclear Medicine Unit, Bufalini Hospital, AUSL Della Romagna, Cesena, Italy. 6 Radiology Department, Bufalini Hospital, AUSL Della Romagna, Cesena, Italy. * email: andrea.prochowskiiamurri@irst.emr.it