Treatment of Borderline Phyllodes Tumors

Primary Surgical Management

• The National Comprehensive Cancer Network recommends wide excision with clear margins as the definitive treatment for borderline phyllodes tumors 1, 2, 3
• Target surgical margins of ≥1 cm to minimize local recurrence risk 3, 4, 5
• Either breast-conserving surgery or mastectomy can be performed, depending on tumor size and location 1, 2
• No axillary staging or lymph node dissection is required, as phyllodes tumors rarely metastasize to lymph nodes 3, 4, 5
• Mastectomy is indicated only when adequate margins cannot be achieved with breast conservation 3, 5

Role of Adjuvant Radiotherapy

• The British Journal of Cancer guidelines suggest that adjuvant radiotherapy should be considered only in high-risk cases of borderline phyllodes, specifically large tumors (>5 cm) 1
• Adjuvant radiotherapy should also be considered for infiltrative margins 1
• Adjuvant radiotherapy should be considered for cases where clear margins could not be achieved surgically despite re-excision attempts 1
• Adjuvant radiotherapy improves local control but not survival in breast sarcomas 1, 2

Reconstruction Considerations

• Immediate reconstruction should be avoided in borderline phyllodes tumors with high-risk features 1, 2
• Delayed reconstruction is preferred when primary oncological management is completed and local recurrence risk has diminished 1, 2

Follow-up for Recurrence

• For locally recurrent disease, re-excision with wide margins without axillary staging is recommended 3
• Consider postoperative radiation therapy, especially if additional recurrence would create significant morbidity 3, 4

Key Clinical Pitfalls

• Core needle biopsy may not reliably distinguish borderline phyllodes from benign fibroadenoma preoperatively 3, 4, 5
• Avoid performing axillary staging—it is unnecessary and adds morbidity 3, 4, 5
• Avoid using adjuvant chemotherapy or endocrine therapy—these have no proven role in borderline phyllodes 6, 5
• Do not routinely recommend radiotherapy for all borderline tumors—reserve it for high-risk cases only 1, 2

Multidisciplinary Management

• Borderline phyllodes tumors should be referred to specialist sarcoma centers for pathology review and multidisciplinary team discussion 2, 7
• Close collaboration between breast cancer and sarcoma multidisciplinary teams is necessary 1, 2, 7
• This ensures appropriate risk stratification and treatment planning 2, 7

Radiotherapy Contouring Guidelines for Adjuvant Treatment of Phyllodes Breast Tumors

Indications and Target Volume

• For malignant or borderline phyllodes tumors with close (<5 mm) or positive margins after surgical resection, adjuvant radiotherapy should target the whole breast (after breast-conserving surgery) or chest wall (after mastectomy) to a dose of 50-60 Gy, using standard breast cancer radiotherapy contouring techniques without nodal irradiation, as recommended by the British Journal of Cancer guidelines 8
• The clinical target volume (CTV) should include the entire remaining breast tissue or chest wall, extending from the skin surface to the pectoralis major muscle posteriorly, and should not include axillary, supraclavicular, or internal mammary lymph nodes, according to the British Journal of Cancer guidelines 8
• Radiotherapy improves local control from 34-42% to 90-100% at 5 years, though does not improve overall survival, as stated in the British Journal of Cancer guidelines 8

Radiation Dose and Fractionation

• No specific radiation dose and fractionation guidelines are provided with associated citations.

Critical Technical Considerations

• Do not contour regional lymph nodes (axillary, supraclavicular, internal mammary) as phyllodes tumors are sarcomas, not epithelial breast cancers, and nodal metastases are exceedingly rare, as recommended by the British Journal of Cancer guidelines 8
• Do not perform immediate reconstruction in high-risk malignant phyllodes tumors; delay reconstruction until after radiotherapy completion and when local recurrence risk has diminished (typically 2 years), according to the British Journal of Cancer guidelines 8

Multidisciplinary Coordination

• All phyllodes tumors should be discussed at both breast cancer and sarcoma multidisciplinary team meetings to ensure appropriate risk stratification and treatment planning, as recommended by the British Journal of Cancer guidelines 8

Radiotherapy in Malignant Phyllodes Tumors

Primary Indications for Radiotherapy

• Local recurrence after salvage mastectomy is an indication for radiotherapy, as additional recurrence would create significant morbidity, such as chest wall recurrence, according to the National Comprehensive Cancer Network 9

Evidence Supporting Radiotherapy Use

• The National Comprehensive Cancer Network recommends radiotherapy for local control in malignant phyllodes tumors, with evidence showing a reduction in local recurrence, although it does not impact disease-free survival or overall survival 9

Follow‑Up After Mastectomy for Borderline Phyllodes Tumor

Clinical Surveillance Schedule

• Perform a structured clinical examination schedule: every 3–4 months during the first 2 years, every 6 months for years 3–5, and then annually for lifelong follow‑up. This schedule is recommended by the oncology community (Annals of Oncology, 2015) 10.
• During each visit, focus the physical exam on the chest wall and mastectomy scar; local recurrence of borderline phyllodes tumors occurs in approximately 1–2 % of patients per year (Journal of the American College of Radiology, 2020) 11.

Chest‑Wall Imaging Strategy

• Routine imaging of the mastectomy site is not recommended in asymptomatic patients; surveillance relies on clinical examination (Journal of the American College of Radiology, 2020) 11.
• If a palpable abnormality is detected, targeted ultrasound or magnetic resonance imaging of the chest wall should be obtained to characterize the lesion (Journal of the American College of Radiology, 2020) 11.

Pulmonary Surveillance

• Annual chest imaging (plain radiograph or low‑dose CT) is advised to detect pulmonary metastases, the most common distant site for phyllodes tumors. This recommendation contrasts with standard breast‑cancer follow‑up, where routine metastatic imaging is not advised (Annals of Oncology, 2015) 10.

Contralateral Breast Surveillance

• Conduct annual mammography (2‑D or digital breast tomosynthesis) together with adjunctive ultrasound of the remaining native breast, following standard breast‑cancer screening guidelines for the contralateral breast (Annals of Oncology, 2015; Journal of the American College of Radiology, 2020) [10][11].

Imaging Modalities to Avoid in Routine Surveillance

• Do not perform PET‑CT or bone‑scan studies for routine surveillance in asymptomatic patients, as these modalities have no proven benefit for phyllodes‑tumor follow‑up (Annals of Oncology, 2015; Journal of the American College of Radiology, 2020) [10][11].

NCCN Guidelines for Management of Borderline Phyllodes Tumors

Surgical Management

• Perform wide excision with surgical margins ≥ 1 cm as the definitive treatment for borderline phyllodes tumors; axillary staging is not indicated. 12
• Breast‑conserving surgery (lumpectomy or partial mastectomy) is preferred when a ≥ 1 cm margin can be achieved. 12
• Mastectomy is reserved for cases where negative margins cannot be obtained with breast‑conserving surgery. 12

Margin Management

• Margins < 1 mm are considered inadequate and are associated with a higher risk of local recurrence. 12
• Positive margins (tumor at ink) mandate re‑excision to obtain clear margins. 12
• If the initial excision achieves ≥ 1 cm margins, no further surgery is required. 12
• When margins are < 1 cm but the tumor appears well‑circumscribed on pathology, clinicians may consider re‑excision versus close surveillance based on individual risk factors. 12

Adjuvant Radiotherapy

• Radiotherapy is not routinely recommended for all borderline phyllodes tumors; it is reserved for high‑risk scenarios. 12
• High‑risk indications for adjuvant radiotherapy include:
• In high‑risk cases, radiotherapy improves 5‑year local‑control rates from approximately 34‑42 % to 90‑100 % but does not affect overall survival. 12
• Recommended radiation fields: whole breast after breast‑conserving surgery or chest wall after mastectomy, delivering 50‑60 Gy; axillary, supraclavicular, and internal‑mammary nodes are omitted. 12

Reconstruction Timing

• Immediate reconstruction should be avoided in borderline phyllodes tumors with high‑risk features (large size, infiltrative or close margins). 12
• Delayed reconstruction is preferred after completion of oncologic treatment, typically waiting until the local‑recurrence risk has diminished (≈ 2 years). 12

Management of Local Recurrence

• Diagnostic work‑up for suspected recurrence includes:
• Therapeutic approach:

Common Pitfalls (What NOT to Do)

• Do not rely on core‑needle biopsy or fine‑needle aspiration alone to definitively exclude a phyllodes tumor preoperatively. 12
• Do not perform routine axillary staging or lymph‑node dissection. 12
• Do not use adjuvant chemotherapy or endocrine therapy, as they have no proven benefit in borderline phyllodes tumors. 12
• Do not recommend radiotherapy for all borderline tumors; reserve it for the high‑risk situations described above. 12
• Do not accept inadequate surgical margins; achieving ≥ 1 cm margins is the most important modifiable factor for preventing local recurrence. 12

Surveillance Strategy

• Follow‑up schedule after definitive treatment:
• Surveillance components at each visit: clinical examination of the surgical site and chest wall; annual mammography of the contralateral breast; annual chest imaging (plain radiograph or low‑dose CT) to detect pulmonary metastases; targeted ultrasound or MRI only if a palpable abnormality is identified. 12

Multidisciplinary Management

• Refer patients with borderline phyllodes tumors to specialist sarcoma centers for:

Management of Recurrent Phyllodes Tumor After Mastectomy

Surgical Management

• Re‑excision of the chest‑wall recurrence with surgical margins of ≥ 1 cm is the definitive treatment to prevent further recurrence in patients with recurrent phyllodes tumor after mastectomy. Strong recommendation. 13
• Axillary staging or lymph‑node procedures are not required, because nodal metastasis occurs in < 1 % of phyllodes tumors. 13
• If the initial re‑excision yields margins < 5 mm or positive, a repeat surgery should be performed to achieve adequate clearance. 13
• The majority of recurrences (≈ 98 %) are located within 2 cm of the original mastectomy scar or tumor bed, indicating true local recurrence rather than a new lesion. 13

Adjuvant Radiotherapy

• Adjuvant chest‑wall radiotherapy after surgical re‑excision is strongly recommended for recurrent disease to reduce the risk of additional local events. Strong recommendation. 13
• Delivering 50–60 Gy to the entire chest wall (standard techniques) improves 5‑year local control rates from 34–42 % to 90–100 %, although it does not affect overall survival. 13
• The radiation field should exclude axillary, supraclavicular, and internal‑mammary nodes, reflecting the sarcoma‑type behavior of phyllodes tumors and the rarity of nodal spread. 13

Systemic Therapy (What Not to Do)

• Adjuvant chemotherapy and endocrine therapy (e.g., tamoxifen, aromatase inhibitors) have no proven benefit and should not be used in phyllodes tumors, irrespective of hormone‑receptor status. 13
• Axillary staging or sentinel‑node biopsy should be omitted because nodal involvement is exceedingly rare. 13
• Management should follow sarcoma‑directed principles, not those used for epithelial breast cancer. 13

Management of Distant Metastases

• When pulmonary or other distant metastases are identified, surgical resection or local ablative therapies (e.g., radiofrequency ablation, stereotactic radiotherapy) are preferred first‑line options, given the relatively indolent nature of phyllodes tumor metastases. 13
• Sarcoma‑directed chemotherapy (e.g., doxorubicin‑ifosfamide) is reserved for unresectable metastases or disease progression after local therapy. 13
• Conventional breast‑cancer chemotherapy regimens should not be employed. 13

Reconstruction Considerations

• Delayed reconstruction is strongly preferred over immediate reconstruction in high‑risk phyllodes tumors; reconstruction should be postponed until ≥ 2 years after completion of primary oncologic treatment (including radiotherapy) to allow the local recurrence risk to diminish. Strong recommendation. 13

Multidisciplinary Coordination

• Cases should be reviewed jointly by breast‑cancer and sarcoma multidisciplinary teams for expert pathology review, risk stratification, and treatment planning. Strong recommendation. 13
• Patients should be referred to a specialist sarcoma center if they are not already under its care, ensuring access to sarcoma‑specific expertise. 13