(P 458) FREQUENCY IN CHANGE OF GRADING UPON LOCAL RECURRENCE OR DISTANT METASTASIS OF SOFT TISSUE SARCOMAS.

Objective: The rate of local recurrences (LRs) and distant metastases (DM) in soft tissue sarcoma (STS) patients amounts to 10% and 30%, respectively. There is currently little evidence on the 1) frequency and 2) prognostic impact of change in grading upon development of LR or DM. The current retrospective single-centre study aimed at investigating the frequency of upgrading in case of LR or DM in STS, as well as the impact of upgrading on post-recurrence-survival (PRS) in comparison to no upgrading.

Methods:

Methods: From initially 504 STS patients, 144 (median age at surgery: 65.6 [IQR: 52.9 – 74.9] years; 78 males [54.2%]) with primary localised STS of extremities and trunk, who had been treated with curative intent between 07/95 and 10/16 at a single tertiary sarcoma centre, and developed a local or distant recurrence during follow-up, were retrospectively included. Median follow-up from time of surgery until last follow-up or death was 34.5 (IQR: 12.5 – 89) months. Primary histology and grading (from naïve surgical specimen), as well as grading during first (and second) LR as well as DM were documented, together with potential changes in grading. Patients with and without changes in grading were compared with regards to PRS (based on the first recurrent event in case of both LR and DM) using log-rank test with last follow-up or death as endpoint.

Results: Thirty patients developed LR, 88 patients DM, and 26 both LR and DM. In altogether 83 patients, information on change in grading was available, whilst in the remaining 61 patients, recurrence had only been verified on imaging, with no histological confirmation.
Of the 83 patients with histological diagnosis of recurrence available, grading of primary tumour was G1, G2, and G3/high-grade per definition in 4 (4.8%), 18 (21.7%), and 61 (73.5%) individuals, respectively. Most common histological subtypes were myxofibrosarcoma (n=25; 30.1%) and MFH/UPS (n=17; 20.5%). Median time from surgery to any recurrence was 16 (6 – 32) months. Upon recurrence, change in grading was observed in 9 patients (10.8%), with 7 presenting with higher-grade lesions, and 2 with lower-grade lesions than the primary tumour. Five of the 7 “upgradings” were observed in LR, and 2 in DM. In 6 of 7 “upgradings”, primary tumour had been diagnosed as G2 (and recurrence as G3), whereas in one case, primary tumour grading had been G1. The two “downgradings” were found in LR (one primarily diagnosed leiomyosarcoma G1/2, LR diagnosed G1; one primarily diagnosed myxofibrosarcoma G3, LR diagnosed G2). There was no significant difference in PRS between patients without change in grading (3-year survival probability 52.6%) and those with “upgrading” (3-year survival probability 62.5%) or “downgrading” (3-year survival probability not reached; log-rank p=0.593).

Conclusion: The frequency of change in grading upon recurrence of STS is relatively low. Although “upgradings” are the logical consequence of recurrence, two “downgradings” in patients with LR were likewise observed. Bearing the limitations of a small patient number as well as sampling bias due to cases without histological workup of recurrences in mind, a change in grading does not seem to have an impact on post-recurrence survival.