Abstract 101P
Background
The treatment of 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, optimal type of surgery and adjuvant treatments are still a matter of debate.
Methods
We conducted a single-center, retrospective study on the clinical outcomes and prognostic factors in 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 incidence of distant and local recurrences.
Results
131 patients were included. All received surgery, 5 underwent adjuvant 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, 5-16%), respectively. Tumor size ≥5 cm was associated with higher distant recurrences (p=0.05). Among small tumors (<5 cm), distant recurrences were higher in those with heterologous differentiation and/or multifocal disease (p=0.06). Evolution from and/or previous history of fibroadenomas, benign or borderline phyllodes tumors of the breast were associated with lower distant recurrences (p=0.014). 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).
Table: 101P
| Characteristic | N=131 |
| Age at diagnosis, median (IQR) | 46 (40-55) |
| At least one negative prognostic factor, n (%) | 81 (62%) |
| Size ≥5 cm, n (%) | 56 (43%) |
| Multifocal disease, n (%) | 14 (11%) |
| Heterologous differentiation, n (%) | 26 (20%) |
| Type of last breast surgery | |
| Excisional biopsy (no attempt at margins), n (%) | 12 (9%) |
| Lumpectomy (wide local excision with attention to margins), n (%) | 44 (34%) |
| Mastectomy, n (%) | 75 (57%) |
| Adjuvant radiotherapy, n (%) | 15 (11%) |
| Adjuvant chemotherapy, n (%) | 5 (4%) |
| Evolution from/previous history of fibroadenoma, benign or borderline phyllodes | 53 (40%) |
Conclusions
The natural history of B-MPT can be burdened by local and distant recurrences. Pathologic prognostic factors (i.e., tumor size, heterologous differentiation, multifocal disease, previous history of fibroepithelial tumors) more than the type of wide breast surgery (mastectomy vs. lumpectomy) seem to represent the most significant prognostic factors 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, Advisory Board, Advisory Board: Menarini, Gilead; 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, Personal, Officer, Italian National Health Council as Advisor for Ministry of Health: Consiglio Superiore di Sanità; Non-Financial Interests, Personal, Advisory Role, Member of the Scientific Council. Patient advocacy association: Europa Donna; Non-Financial Interests, Personal, Advisory Role, Cancer Research Foundation: Fondazione Beretta; Non-Financial Interests, Personal, 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, Personal, Officer, Member of the Advisory Council: EUSOMA; Non-Financial Interests, Personal, Officer, ESMO Clinical Practice Guidelines Chair: ESMO; Non-Financial Interests, Personal, Member of Board of Directors, Chair of Clinical Practice Guidelines Committee: ESMO. All other authors have declared no conflicts of interest.