Photon-counting CT matched MRI for breast cancer staging but missed microcalcifications

Design

Prospective single-centre diagnostic comparison with pathology reference

Population

126 women with BI-RADS 4C or higher breast lesions

Primary outcome

Agreement with MRI and sensitivity for additional lesions and nodal metastasis

Effect

Additional lesions vs MRI +7% (−5 to 21); nodes vs MRI +10% (1 to 20); 44% of microcalcifications missed

In this prospective single-centre study, 126 women with BI-RADS 4C or higher lesions underwent breast MRI, digital mammography and multiphasic contrast-enhanced photon-counting CT; a subset with locally advanced disease also had FDG PET/CT. Four radiologists read the studies independently against pathology.

Photon-counting CT agreed well with MRI for T category (κ 0.86–0.88). For 46 pathologically confirmed additional lesions it was more sensitive than mammography (difference 44%, 95% CI 19–66) and similar to MRI (7%, −5 to 21). It was more sensitive than MRI for nodal metastasis (difference 10%, 1–20). But it missed 44% of microcalcifications seen on mammography.

One scan that stages breast, axilla and chest could suit patients who cannot have MRI. The microcalcification gap means mammography cannot be dropped, and photon-counting scanners remain scarce outside a few centres, including in India.

• Do not substitute photon-counting CT for mammography where calcifications matter, including suspected DCIS
• Consider it as an alternative staging test where MRI is contraindicated and the scanner is available
• Correlate axillary findings with ultrasound and biopsy before changing surgical plans
• Note radiation and iodinated contrast exposure when choosing it over MRI

Why it matters

A single contrast CT that stages breast and axilla as well as MRI would change access, if its calcification blind spot is respected.

Don't overread it

A single-centre feasibility study — it does not show that staging with photon-counting CT changes treatment or outcomes.

The statistics, in plain English

The difference with MRI for additional lesions (7%, interval −5 to 21) crosses zero, so the two may be equivalent. The nodal advantage over MRI has a lower bound of 1%, so it is real but could be small. With 126 women at one centre, these estimates need confirming elsewhere.

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