case_images: PMC11099277_01
case_images: Timeline of disease progression including applied theranostics together with findings of clinical relevance and subsequent treatments.
case_images: fonc-14-1395618-g001.jpg
case_images: PMC11099277_01_fonc-14-1395618-g001.jpg
case_images: f1
case_images: She went on to receive hormone therapy with CDK4/6 inhibitor and subsequentially multiple lines of guideline-driven systemic therapy (the timeline of these is shown in  Figure 1 ). Despite administration of all guideline-based interventions, only short periods of stable disease were achieved over 3 years ( Figure 1 ). Imaging revealed partial response, which lasted for 13 months with excellent quality of life (QLQ-C30) [ Supplementary Figure 1 ]. There was a partial radiological and serological response to this regimen with acceptable quality of life ( Figure 1 ).
case_images: The pictures show the intestinal passage of the patient at month 70 (left) with stenosis and month 76 (right) with regular passage under trastuzumab-deruxtecan.
case_images: fonc-14-1395618-g002.jpg
case_images: PMC11099277_01_fonc-14-1395618-g002.jpg
case_images: f2
case_images: A 4th molecular profiling was performed based on a liver biopsy, as well as peripheral blood and IHC on cancer cells originating from ascites, revealing the known ERBB2 pV697L within a ctDNA relapse without evidence of HER2 amplification ( Supplementary Figure 2 ). This combination was ineffective, leading to progressive peritoneal carcinomatosis and extensive bowl stenosis in the jejunum and sigmoid region, requiring outflow PEG and complete parenteral nutrition ( Figure 2 ). Subsequently this antibody drug conjugate was commenced ( Figure 2 ). Interestingly, besides the known ERBB2 Pv697L mutation some others of VNS like ERBB2 D582N, FGFR1 Pv389I were revealed in malignant ascites, all decreasing or even disappearing over the course ( Supplementary Figure 2 ) This corresponds to partial radiological response to treatment, with good tolerability and quality of life (patient went swimming, no significant hair loss under scalp cooling) and lasted for a duration of 5 months. Clinically there was a significant improvement, with restoration of normal bowel function and undisturbed food intake and digestion ( Figure 2 ).