1942P - Non-metastatic malignant phyllodes tumors of the breast (B-MPT): A retrospective analysis from a referral center

Background

B-MPT accounts for <1% of breast neoplasms. The standard treatment for non-metastatic disease consists of wide local excision. Type of excision and adjuvant treatments are still matter of debate. Because of its rarity, only few case series with less than 100 B-MPT patients (pts) are available.

Methods

We conducted a retrospective single-centre observational study to describe outcomes and possible prognostic factors of pts with B-MPT. Data of consecutive patients aged ³18 years old, with a histologically confirmed diagnosis of non-metastatic B-MPT, who underwent surgery from January 2000 to December 2021, were collected. The primary endpoint was recurrence-free survival (RFS). Survival was calculated using Kaplan–Meier method. Multivariable analysis was performed with Cox proportional hazards model (significance at p-value<0.05).

Results

131 pts were included. Patient characteristics are reported in table. All patients received a surgery, 5 adjuvant anthracycline-based chemotherapy and 15 radiation therapy. After a median follow-up of 6.8 years, 36 (28%) pts experienced a disease recurrence: 19 (15%) a distant and 23 (18%) a loco-regional relapse. The median RFS, distant RFS (DRFS) and local RFS (LRFS) were not reached. The 5-year RFS, DRFS and LRFS rates were of 72%, 85% and 82%. At univariate analysis DRFS significantly correlated with the presence of at least one negative pathological prognostic factor (i.e., Size >5 cm, Multifocal disease or Heterologous differentiation [SMH]) (p=.03). If adjusted for type of breast surgery, SMH was associated also with LRFS (HR 3.3; 95%CI, 1.4-7.8; p=.008). The type of surgery was not prognostic for RFS, DRFS and LRFS.

Table: 1942P

Patient characteristics

Conclusions

Natural history of B-MPT is burdened by local and distant recurrences. Pathological features more than the type of wide local excision seem to represent the most significant prognostic factor for recurrences.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

G. Curigliano: Financial Interests, Personal, Invited Speaker: Roche, AstraZeneca, Daiichi Sankyo, Novartis, Pfizer, Pfizer; Financial Interests, Personal, Advisory Board: Roche, AstraZeneca, Daiichi Sankyo, Lilly, Pfizer, Veracyte, BMS, Merck, Exact Sciences, Celcuity; Financial Interests, Personal, Other, Advisory Board: Ellipsis; Financial Interests, Institutional, Research Grant, Investigator Initiated Trial: Merck; Financial Interests, Institutional, Funding, phase I studies: BMS, Novartis, AstraZeneca, Daiichi Sankyo, Roche, Blueprint Medicine, Kymab, Astellas, Sanofi, Philogen; Financial Interests, Institutional, Invited Speaker, phase I clinical basket trial: Relay Therapeutics; Non-Financial Interests, Member of Board of Directors, No compensation for this role. This a public national company for cancer prevention: Lega Italiana Lotta ai Tumori; Non-Financial Interests, Officer, Italian National Health Council as Advisor for Ministry of Health: Consiglio Superiore di Sanità; Non-Financial Interests, Advisory Role, Member of the Scientific Council. Patient advocacy association: Europa Donna; Non-Financial Interests, Advisory Role, Cancer Research Foundation: Fondazione Beretta; Non-Financial Interests, Officer, Member of the Advisory Council: EUSOMA; Non-Financial Interests, Officer, ESMO Clinical Practice Guidelines Chair: ESMO. All other authors have declared no conflicts of interest.