Does initial FDG-PET/CT reveal more distant metastases in women under 40 y.o. than in women over 40 y.o. with breast cancer?

Objectives Current guidelines for the management of women with stage I and II breast cancer (BC) recommend against the routine use of imaging to detect asymptomatic distant metastases at the time of diagnosis. The higher specific mortality of BC in young women (<40y) raises the issue of possible undetected metastasis at the time of diagnosis. Our objectives have been: (i) to determine the distant metastasis rate revealed by initial FDG-PET/CT in a population of BC patients younger than 40 yo (<40y group), (ii) to compare this rate with a group of BC patients older than 40 yo (>40y group), (iii) to compare this distant metastasis rate with initial clinical/local stage.

Methods Retrospective single-institution study of BC initially diagnosed between 2006 and 2015. Inclusion criteria for the <40y group were: BC women without history of prior malignancy, asymptomatic for metastatic lesions on initial clinical exam, initial FDG-PET/CT realized within 3 months after pathologic BC diagnosis and before initial chemotherapy/hormonotherapy/radiation therapy treatment, <40yo at the time of FDG-PET/CT. Inclusion criteria for the >40y group were identical except for the age. All FDG-PET/CT exams were reviewed by experienced nuclear medicine physicians and the rate of distant metastasis findings (M+ rate) was recorded for each clinical stage subgroup (stage I to III). Statistical differences in M+ rate between <40y and >40y groups were calculated using Fisher’s exact test.

Results For each group of patients (<40y and >40y group), 107 patients were included, with the same number of patients in each clinical stage subgroup (12 stage I patients, 32 stage IIA patients, 30 stage IIB patients and 33 stage III patients). Mean age was 34.5±4.0y and 56.0±10.7y for the <40y group and the >40y group, respectively. The M+ rate for each group and stage subgroups is shown on Table 1. No significant difference was observed in M+ rate between the <40y and the >40y group for any stage. Altogether M+ restaging as compared to clinical stage in patients unselected for age was 8% for stage I, 11% for stage IIA, 15% for stage IIB and 44% for stage III.

Conclusions The rate of M+ revealed by initial FDG PET/CT is not significantly higher in young BC patients than in older patients, ruling out the idea of undetected metastasis at diagnosis to explain the poorer outcome of young women with BC. However, our results highlight the high yield of FDG-PET/CT for initial BC staging, even in stage II patients whatever their age.

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