(P 231) INCREASED LIFETIME RISK (LTR) OF SOFT TISSUE SARCOMAS (STS) IN PATIENTS WITH LOW-RISK GASTROINTESTINAL STROMAL TUMORS (GIST): A RETROSPECTIVE ANALYSIS FROM THE ITALIAN SARCOMA GROUP (ISG)

Author(s)

Lorenzo D'Ambrosio, MD PhD

Medical Oncologist and Associate Professor
University of Torino
Orbassano, Piemonte, Italy

Co-Author(s)

EF

Elena Fumagalli, MD

Medical Oncology Unit 2, Medical Oncology Department, Fondazione IRCCS Istituto Nazionale dei Tumori di Milano
Milan, Lombardia, Italy
TD

Tommaso Martino De Pas, MD

Medical Oncology Division, Cliniche Humanitas Gavazzeni, Bergamo, Italy; previously at Unit of Sarcomas and Thymomas, European Institute of Oncology, Milan
Bergamo, Lombardia, Italy
MN

Margherita Nannini, MD

Oncology Unit. Department of Medical and Surgical Sciences, University of Bologna
Bologna, Emilia-Romagna, Italy
AB

Alexia Bertuzzi, MD

Medical Oncology, Humanitas Cancer Center
Rozzano, Lombardia, Italy
SC

Silvia Carpano, MD

Division of Medical Oncology 2, IRCCS Regina Elena National Cancer Institute
Roma, Lazio, Italy
AB

Antonella Boglione, MD

Oncology Department, ASL Città di Torino
Torino, Piemonte, Italy
AB

Angela Buonadonna, MD

Sarcoma and gastrointestinal tumors Unit, Centro di Riferimento Oncologico di Aviano
Aviano, Friuli-Venezia Giulia, Italy
DC

Danila Comandini, MD

Medical Oncologist
Medical Oncology 1, Ospedale Policlinico San Martino, University of Genova
Genova, Liguria, Italy
SG

Silvia Gasperoni, MD (she/her/hers)

Coordinator regional Organizative Centre Of Rare Tumors
Clinical Oncology Unit, Oncology Department and Robotic Surgery, AOU Careggi
Firenze, Toscana, Italy
Bruno Vincenzi, Prof.

Full professor
Fondazione Policlinico Universitario Campus Bio-Medico
Rome, Lazio, Italy
Antonella Brunello, MD (she/her/hers)

Medical Oncologist
Istituto Oncologico Veneto
Padova, Veneto, Italy
Giuseppe Badalamenti, Prof

Associate Professor
University of Palermo
Palermo, Sicilia, Italy
EM

Elena Maccaroni, MD

Department of Oncology, Azienda Ospedaliero-Universitaria delle Marche
Ancona, Marche, Italy
Giacomo Giulio G. Baldi, MD

Medical Oncologist
Department of Oncology, Hospital of Prato, Azienda USL Toscana Centro
Prato, Toscana, Italy
Alessandra Merlini, MD (she/her/hers)

Assistant Professor
University Hospital S. Luigi Gonzaga
Orbassano, Piemonte, Italy
AM

Andrea Mogavero, MD

University Hospital S. Luigi Gonzaga
Orbassano, Piemonte, Italy
EP

Elisabetta Pennacchioli, MD

European Institute of Oncology, IRCCS
Milan, Lombardia, Italy
MR

Martina Rabino, MD

University Hospital S. Luigi Gonzaga
Orbassano, Piemonte, Italy
SA

Sandra Aliberti, MD

Oncology Unit, Candiolo Cancer Institute, FPO-IRCCS
Turin, Piemonte, Italy
FT

Francesco Tolomeo, MD (he/him/his)

Medical Doctor
Oncology Unit, Candiolo Cancer Institute, FPO – IRCCS
Candiolo, Piemonte, Italy
Tiziana Robba, MD (she/her/hers)

physician
Radiology, Ospedale CTO, AOU Città della Salute e della Scienza di Torino
Torino, Piemonte, Italy
Marco Fiore, MD, FACS, FEBS

Surgeon
Fondazione IRCCS Istituto Nazionale dei Tumori
Milano, Lombardia, Italy
MS

Marta Sbaraglia, MD (she/her/hers)

Associate Professor
University of Padua, Padua, Italy
Padua, Veneto, Italy
AD

Angelo Paolo Dei Tos, Prof.

Azienda Ospedaliera di Padova
Padova, Veneto, Italy
Silvia Stacchiotti, MD

Medical Oncologist
Fondazione IRCCS Istituto Nazionale dei Tumori
Milan, Lombardia, Italy
Maria Abbondanza A. Pantaleo, N/A, MD

Associate Professor
Oncology Unit. Department of Medical and Surgical Sciences, University of Bologna
Bologna, Emilia-Romagna, Italy
Alessandro Gronchi, MD (he/him/his)

Surgical Oncologist
Fondazione IRCCS Istituto Nazionale Dei Tumori, Milan
Milano, Lombardia, Italy
Giovanni Grignani, Dr

Medical Oncologist
Candiolo Cancer Institute, FPO-IRCCS
TORINO, Piemonte, Italy

Objective: Several studies consistently showed an increased incidence of second primary neoplasms (SPNs) in patients with GIST. ISG previously reported that 25.4% of patients developed an SPN either before or after diagnosis. We investigated whether the LTR of developing an SPN was different across tumor types and exceeded that expected in the general population.

Methods: We included patients with histologically confirmed, surgically resected GIST, classified as low risk of relapse according to AFIP criteria, who were treated at ISG centers and did not receive neo/adjuvant imatinib. We analyzed the incidence and subtype distribution of SPNs, comparing observed rates with the expected LTR in the general population using data from the SEER database using Mantel-Haenszel odds ratios (ORs) with corresponding 95% confidence intervals (CIs).

Results: A total of 737 patients with low-risk GIST were included, with a median follow-up of 69.2 months. Among them, 187 patients (25.4%, 95% CI: 22.2–28.7%) were diagnosed with an SPNs (80 before, 51 synchronous with, and 56 after GIST diagnosis) (Table 1). Notably, 8 patients (1.1%; M/F 3/5) were diagnosed with STS: 1 before GIST, 4 synchronously, and 3 during follow-up. Histologic subtypes included solitary fibrous tumor (2), MDM2-amplified liposarcoma (2), soft tissue leiomyosarcoma (2), uterine leiomyosarcoma (1), and endometrial stromal sarcoma (1). When compared with SEER-based LTR data, the risk of developing STS was the only significantly increased in our cohort (OR 3.22, 95% CI: 1.48–6.97, p=0.0031).(Table 1)

Conclusion: Our findings showed increased risk of STS in patients with low-risk GIST compared to the general population. This observation is consistent with previous reports and supports the hypothesis that patients with GIST may share a common genetic predisposition to mesenchymal tumor development.

Table 1. Second Primary Neoplasms (SPNs) in Low-Risk GISTs and Odds Ratios (OR) for SEER Database Tumor-specific Lifetime Risk.
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