Prognostic impact of ¹⁸F-FDG PET/CT staging and of pathological response to neoadjuvant chemotherapy in triple-negative breast cancer

Mortality is high in patients with locally advanced triple-negative breast cancer (TNBC), especially in those with residual tumour after neoadjuvant chemotherapy (NAC). The aim of this study was to determine if pretreatment ¹⁸F-FDG PET/CT staging and pathological findings after NAC could together allow stratification of patients into prognostic groups.

Initial staging with ¹⁸F-FDG PET/CT was performed prospectively in 85 consecutive patients with stage II/III TNBC. Correlations between PET findings and disease-specific survival (DSS) were examined. In patients without distant metastases on PET staging, the impact of pathological response to NAC on DSS was examined. Patterns of recurrence were also analysed.

¹⁸F-DG PET/CT revealed distant metastases in 11 of 85 patients (12.9 %). Among 74 M0 patients, 23 (31.1 %) showed a pathological complete response (pCR) at surgery, while 51 had residual invasive disease (no pCR). DSS differed considerably among the three groups of patients (log-rank P < .001): among patients with occult metastases on baseline PET/CT, 2-year DSS was 18.2 %, and among patients without initial metastases on PET/CT, 5-year DSS was 61.3 % in patients without pCR after NAC and 95.2 % in those with pCR. Of the 51 patients who did not achieve pCR, 21 relapsed (17 developed distant metastases). The sites of distant recurrence were: lung/pleura (nine patients), brain (eight patients), liver (six patients), distant lymph nodes (six patients) and bone (five patients).

In patients with clinical stage II/III TNBC, ¹⁸F-FDG PET/CT findings at initial staging and pathological response at the end of NAC allow three groups of patients with quite different prognoses to be defined. Extraskeletal recurrences predominated. Specific follow-up strategies in patients with TNBC who do not achieve pCR deserve investigation.