Research ArticleClinical Investigation

Optimal [18F]FDG PET/CT Cutoff for Pathologic Complete Response in HER2-Positive Early Breast Cancer Patients Treated with Neoadjuvant Trastuzumab and Pertuzumab in the PHERGain Trial

Geraldine Gebhart, Marleen Keyaerts, Thomas Guiot, Patrick Flamen, Manuel Ruiz-Borrego, Agostina Stradella, Begoña Bermejo, Santiago Escriva-de-Romani, Lourdes Calvo Martínez, Nuria Ribelles, María Fernandez-Abad, Cinta Albacar, Marco Colleoni, Laia Garrigos, Manuel Atienza de Frutos, Florence Dalenc, Aleix Prat, Frederik Marmé, Peter Schmid, Khaldoun Kerrou, Sofia Braga, Petra Gener, Miguel Sampayo-Cordero, Javier Cortés, José Manuel Pérez-García and Antonio Llombart-Cussac
Journal of Nuclear Medicine May 2024, 65 (5) 708-713; DOI: https://doi.org/10.2967/jnumed.123.266384

Article Figures & Data

Figures

  • Figure
  • FIGURE 1.
    FIGURE 1.

    PHERGain study design. PHERGain assesses potential of metabolic imaging to identify candidates for chemotherapy deescalation in HER2+, stage I–IIIA, invasive, operable breast cancer with at least 1 breast lesion evaluable by [18F]FDG PET/CT. Asterisk indicates patients with hormone receptor–positive tumors who received endocrine therapy concomitantly with HP (except those receiving chemotherapy). Number symbol indicates patients who were RECIST responders after cycle 2 with SUVmax reduction ≥ 40%. Dagger represents patients who obtained pCR in breast and axilla (ypT0/isN0). Encircled areas indicate decreased lesion uptake after treatment cycles. Etx = endocrine therapy (letrozole for postmenopausal women and tamoxifen for premenopausal women; adjuvant ETx up to 3 y from surgery); R = randomization; TCHP = trastuzumab, pertuzumab, docetaxel, and carboplatin.

  • FIGURE 2.
    FIGURE 2.

    Receiver-operating-characteristic curve of sensitivity and specificity values to predict pCR for different cutoffs for ΔSUVmax at 6 wk among metabolic responders in arm B. AUC = area under curve.

  • FIGURE 3.
    FIGURE 3.

    pCR rate for patients with ΔSUVmax higher than or equal to cutoff values in arm B compared with pCR rate in whole arm A. P values compare pCR rate for arm B at different cutoffs vs. pCR rate for whole arm A (reference). Imputed and raw ΔSUVmax for arm B are presented. We reported higher P values for both analyses. In [18F]FDG PET nonresponders for arm B (blue line), there were no patients with ΔSUVmax ≥ 40% and only 8 patients had ΔSUVmax between 35% and 40%. We reported pCR for patients with ΔSUVmax ≥ 26% (29.4%; 5/17 patients). Line was interpolated between 26% and 40% cutoffs. Of note, each data point contains pCR rate for patients with ΔSUVmax ≥ cutoff. *P < 0.05. **P ≤ 0.01. ns = P > 0.05.

Tables

  • TABLE 1.

    Association Between ΔSUVmax Cutoff and Chemotherapy Treatment in Arm B

    ΔSUVmax cutoff to avoid chemotherapyReceived neoadjuvant chemotherapyNeed adjuvant chemotherapy in patients without neoadjuvant chemotherapyChemotherapy deescalation
    Yes (n = 285)No (n = 285)YesNoYes (n = 285)
    ≥77%211 (74.0)74 (26.0)30 (40.5)44 (59.5)44 (15.4)
    ≥64%145 (50.9)140 (49.1)70 (50.0)70 (50.0)70 (24.6)
    ≥51%93 (32.6)192 (67.4)113 (58.9)79 (41.1)79 (28.0)
    ≥40%58 (20.4)227 (79.6)141 (62.1)86 (37.9)86 (30.2)

    • Clinical outcomes were compared between the PHERGain cutoff (40%), selected cutoff in study sample (64%), and population-based cutoffs (51% and 77%). Data are number followed by percentage in parentheses.

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