Do we need a Positron Emission Tomography (PET) scan before stopping treatment in a patient with Human Epidermal growth factor Receptor 2 (HER2)-positive invasive ductal carcinoma?

PET Scan Before Stopping Treatment in HER2-Positive Invasive Ductal Carcinoma

PET scan is not recommended before stopping treatment in patients with HER2-positive invasive ductal carcinoma (IDC), as current guidelines do not support routine PET imaging for post-treatment surveillance or treatment discontinuation decisions in breast cancer. 1

Guideline-Based Recommendations

No Role for PET in DCIS or Early-Stage Breast Cancer Surveillance

• The American College of Radiology explicitly advises against routine performance of PET scans in the staging or surveillance of ductal carcinoma in situ (DCIS) and early-stage breast cancer. 1
• The ESMO (European Society for Medical Oncology) guidelines state that in asymptomatic breast cancer patients, there are no data indicating that PET or other advanced imaging tests produce a survival benefit during follow-up. 1
• PET/PET-CT should not be used routinely for post-therapy surveillance without clinical, biochemical, or radiographic evidence of disease, as this leads to a disproportionate fraction of false-positive findings and increased costs without proven benefit. 1

Appropriate Surveillance Imaging

• Annual ipsilateral (after breast-conserving therapy) and/or contralateral mammography with ultrasound is the recommended surveillance approach. 1
• Regular clinical visits are recommended every 3-4 months in the first 2 years, every 6 months from years 3-5, and annually thereafter. 1
• Routine blood tests, chest X-rays, bone scans, liver ultrasound, CT scans, or PET scans are not indicated in asymptomatic patients. 1

When PET May Be Considered (Limited Circumstances)

Suspected Recurrence Only

• PET/PET-CT should only be obtained when there is clinical suspicion of recurrence based on symptoms, physical examination findings, or equivocal/conflicting results from conventional imaging. 1
• PET can be useful for identifying or confirming isolated locoregional relapse or isolated metastatic lesions where aggressive multidisciplinary treatment might be beneficial. 1
• In patients with suspected recurrence and elevated tumor markers (CA 15-3 or CEA), PET/CT is more effective than conventional imaging in detecting locoregional or distant recurrence. 2

Staging Advanced Disease (Not Surveillance)

• FDG-PET/CT is useful for initial staging of breast cancer from clinical stage IIB and higher (T2N1 or T3N0), but this applies to pre-treatment staging, not post-treatment surveillance. 2
• For invasive ductal carcinoma specifically, PET/CT performs well for staging purposes, but again, this is for initial disease assessment, not for determining when to stop treatment. 2

HER2-Positive Disease Considerations

No Special PET Indication for HER2-Positive Tumors

• While HER2-positive DCIS and invasive breast cancer are associated with higher recurrence rates and more aggressive features, this does not change the recommendation against routine PET surveillance. 3, 4
• HER2 overexpression predicts increased risk of in situ breast cancer recurrence (hazard ratio 1.59), but clinical surveillance with mammography and physical examination remains the standard approach. 4
• The decision to continue or discontinue HER2-targeted therapy (such as trastuzumab) should be based on established treatment duration protocols (typically 1 year for adjuvant therapy), not on PET imaging findings. 1

Common Pitfalls to Avoid

• Ordering PET for routine surveillance: This leads to unnecessary radiation exposure, false-positive findings requiring additional workup, increased patient anxiety, and healthcare costs without improving outcomes. 1
• Confusing staging with surveillance: PET has a role in initial staging of advanced disease but not in routine post-treatment monitoring of asymptomatic patients. 2
• Misinterpreting HER2-positive status as requiring more intensive imaging: HER2-positive tumors require appropriate systemic therapy and standard clinical surveillance, not routine PET scans. 3, 4
• Using PET to decide treatment duration: Treatment duration for HER2-positive breast cancer should follow evidence-based protocols, not imaging-driven decisions in asymptomatic patients. 1

Algorithm for Post-Treatment Surveillance

For asymptomatic patients with treated HER2-positive invasive ductal carcinoma:

1. Clinical examination: Every 3-4 months for years 1-2, every 6 months for years 3-5, annually thereafter. 1
2. Mammography with ultrasound: Annually for ipsilateral and contralateral breasts. 1
3. Symptom-directed imaging only: Order CT, MRI, bone scan, or PET only if symptoms, physical findings, or abnormal mammography suggest recurrence. 1
4. No routine PET scans: PET should not be part of routine surveillance before stopping treatment. 1