PB.38: In the context of overdiagnosis, does size matter?
KeywordsCarcinoma Cancer Research Retrospective Review Invasive Cancer Invasive Carcinoma
The Marmot Review showed that although breast screening saves lives, it is harmful through overdiagnosis - treating cancers that would not otherwise have ever become clinically apparent. Currently, there is no size threshold for recalling screening patients with calcifications. Our aim was to assess whether a minimum size threshold would reduce overdiagnosis.
We conducted a retrospective review of 375 screening patients with microcalcifications over 24 months. We assessed all patients with pure calcifications ≤10 mm documenting core biopsy, final histology and treatment.
Sixty-one cases of microcalcifications ≤10 mm: eight benign, 40 in situ cancers and 13 invasive cancers. This group was subcategorised into calcifications: 0 ≤5 mm (24 patients) and 5 ≤10 mm (37 patients). In the 0 ≤5 mm group, there were 16 in situ (low-grade, one; intermediate grade, seven; high grade, eight) and two invasive cancers (G2 ductals ER/PR+Her2- node-negative). In the 5 ≤10 mm group, there were 24 in situ (low-grade, three; intermediate grade, 12; high grade, nine) and 11 invasive cancers (four G1ER+Her2- node-negative, six G2ER+Her2-, one triple-negative). One of these six cases was node-positive (micrometastasis) and one G3ERPR+Her2- node-negative. All underwent wide local excision, and all but one patient with invasive carcinoma received radiotherapy.
Recalling focal clusters of microcalcifications (<10 mm) identified a high rate of cancers: 66% (40/61) in situ and 21% (13/61) invasive. With regards to overdiagnosis: 51% (27/53) of cancers were low/intermediate-grade DCIS or G1 invasive and 49% (26/53) were high-grade DCIS or invasive G2/3. Therefore size is not a key factor in reducing overdiagnosis.
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