Primary malignant phyllodes tumors of the breast: A retrospective analysis from a referral center.

Background: The treatment for primary malignant phyllodes tumors of the breast (B-MPT) consists of wide local excision with negative margins (≥1 cm). However, because of their rarity, prognostic factors, type of surgery and adjuvant treatments are still a matter of debate.
Methods: We conducted a single-center retrospective study to describe outcomes and prognostic factors of patients with primary B-MPT, who underwent breast surgery from January 2000 to December 2021. The primary endpoint was the cumulative incidence of any recurrence. Secondary endpoints were the cumulative incidences of distant and local recurrences.
Results: 131 patients were included, of whom all received surgery, 5 adjuvant anthracycline-based chemotherapy and 15 radiation therapy. After a median follow-up of 6.4 years, the cumulative incidences at 5-years of any, local and distant recurrences were of 26% (95% Confidence Interval [CI], 4-34%), 16% (95%CI, 10-24%) and 10% (95%CI, 5.3-16%), respectively. Tumor size ≥ 5 cm was associated with higher distant recurrences (p = 0.05); instead, among small tumors (<5 cm), distant recurrences were higher in those with heterologous differentiation and/or multifocal disease (p = 0.06). Type of breast surgery (mastectomy vs. lumpectomy/excision) was not found to be significantly associated with distant (p = 0.32) or local (p = 0.17) recurrence, even after controlling local recurrence incidence for negative pathologic prognostic factors (p = 0.17).
Conclusions: The natural history of B-MPT is burdened by local and distant recurrences. Pathologic prognostic factors (i.e., tumor size, heterologous differentiation and multifocal disease) more than the type of wide breast surgery (mastectomy vs. lumpectomy) seem to represent the most significant prognostic factor for recurrences.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: GC reports honoraria for speaker's engagement: Roche, Seattle Genetics, Novartis, Lilly, Pfizer, Foundation Medicine, NanoString, Samsung, Celltrion, BMS, MSD; honoraria for providing consultancy: Roche, Seattle Genetics, NanoString; Honoraria for participating in Advisory Board: Roche, Lilly, Pfizer, Foundation Medicine, Samsung, Celltrion, Mylan; honoraria for writing engagement: Novartis, BMS; Honoraria for participation in Ellipsis Scientific Affairs Group; institutional research funding for conducting phase I and II clinical trials: Pfizer, Roche, Novartis, Sanofi, Celgene, Servier, Orion, AstraZeneca, Seattle Genetics, AbbVie, Tesaro, BMS, Merck Serono, Merck Sharp Dome, Janssen-Cilag, Philogen, Bayer, Medivation, Medimmune. All the competing interests were outside the submitted work. All other authors have no potential conflict of interest to disclose.
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