(P 457) LONG-TERM FOLLOW-UP OF PATIENTS WITH ATYPICAL LIPOMATOUS TUMOR (ALT) TREATED WITH MARGINAL RESECTION IN A REFERRAL CENTER

Objective: Atypical Lipomatous Tumor(ALT) of the extremities and superficial trunk, is a rare soft tissue tumor. The main treatment is marginal resection(MR). ALT have a propensity for to late local recurrence(LR) but unusually metastasize distantly. Our objective was to gain further insights into the timing of LR through the analysis of a cohort with a long follow-up (FU).

Methods: Data from 205 patients who underwent MR for ALT of the extremities or trunk at IRCCS Humanitas Research Hospital (Jan 1998-Jan 2023), were analyzed. Patients already published in 2014 were included, excluding 10 patients(9 spermatic cord liposarcoma,1 lost on FU). All patients had at least 10 years of FU. We included primary, recurrent tumors, and patients who underwent unplanned surgery(US) at another center, selected for re-excision. All patients were treated with MR, removing the tumor en bloc while preserving a slight cuff of muscle and/or surrounding soft tissues. Tumors were subclassified as lipoma-like or sclerosing subtypes. Tumor grade was assessed according to the Federation Nationale des Centres de Lutte Contre le Cancer (FNCLCC) criteria. The Clavien-Dindo Classification (CDC) was used for complications. After surgery, FU comprised physical examination and contrast-enhanced magnetic resonance imaging or ultrasonography in selected cases, every 6 months for 5 years and once a year thereafter. The primary outcome was local recurrence free survival (LRFS); overall survival (OS) was also calculated.

Results: A total of 111 patients were analyzed (Table 1). All ALT were FCNLCC Grade 1. Postoperative complications (CDC 1-2) were observed in 15 cases (13.5%). Median FU was 170.5months (IQR 132-199) for alive patients, and 134months (IQR 75-170) for dead patients. Median OS was not reached. Twenty-five patients(22.5%) died for ALT-unrelated causes. The 5-,10-,and 20-years OS rates were 97.3%,88.8%,69.2%, respectively. Median LRFS was not reached for either primary or recurrent tumors. At the last FU, 7 patients (6.3%) experienced LR. The 5-,10-,and 20-years LRFS rates for primary tumors were 94.7%,94.7%,94.7%, respectively. The 5-,10-,and 20-years LRFS rates for recurrent tumors were 100.0%,100.0%,69.2%, respectively (Figure 1). Among 98 patients with primary tumors, 5(5.1%) had recurrence. Median time to recurrence was 42months (IQR 12-44). Among 13 patients with recurrent tumors at presentation, 2(15.4%) had recurrence. Median time of recurrence 210.5months (IQR 202-219). In general, no additional recurrence was observed during the FU period after the initial recurrence. Characteristics of the 7 patients who experienced a recurrence after surgery at our center are described in table 2. After diagnosis of recurrence, 1/7 patient (14.3%) did not receive any treatment, because of the clinical condition. However, 2/7 recurred patients (28.6%) underwent immediate surgical intervention. In the remaining 4/7 cases (57.1%), a wait and see approach was adopted. In these cases, surgical management was pursued upon evidence of dimensional progression of disease.

Conclusion: In our study, ALTs of the extremities and superficial trunk exhibited a LR rate around 6%. Through a long FU period, we observed a wide range of LR time (from few months to nearly 20 years). LR can be successfully managed with surgery. However, considering the rarity of secondary dedifferentiation and metastasis in ALT, a wait and see approach can be considered. Interestingly, we noted that patients who experienced late LR were initially treated at another center. According to our findings, it could be expected that after treatment for primary tumor, a LR may occur within the first 5 years. However, for patients who experienced a recurrence following an inadequate initial surgery, a late LR could be expected, potentially manifesting even up to 20 years later. This highlights the importance of long-term surveillance to ensure early detection and appropriate intervention.