68Ga-DOTATOC PET/CT Uptake and Physiological Impairment in DIPNECH: An Exploratory Case Series

Background/Objectives: Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) can cause respiratory symptoms and physiological impairment. We explored whether quantitative somatostatin-receptor imaging by positron emission tomography/computed tomography with gallium-68-labelled DOTATOC (68Ga-DOTATOC PET/CT) is associated with pulmonary physiology and nodule count in histologically confirmed DIPNECH. Methods: This retrospective, single-centre, hypothesis-generating series included six consecutive adults diagnosed during 2020–2025. Spearman correlations with exact permutation p-values and 95% confidence intervals related the maximum standardised uptake value (SUVmax) of the most avid lesion to diffusing capacity for carbon monoxide (DLCO), forced expiratory flow between 25% and 75% of forced vital capacity (FEF25–75) and the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC); index-lesion diameter and expected partial-volume recovery were examined. Analyses were exploratory and unadjusted for multiple comparisons. Results: All patients were women. SUVmax correlated inversely with DLCO (ρ = −0.90; p = 0.028) and FEF25–75 (ρ = −0.84; p = 0.044); the nodule-count–DLCO association was uncertain (ρ = −0.37; p = 0.50). Index lesions measured 3.6–4.7 mm, below the resolution of the PET system; lesion diameter was unrelated to SUVmax (ρ = −0.20), and the association with DLCO persisted after crude recovery correction (ρ = −0.66). Conclusions: Higher 68Ga-DOTATOC uptake of the most avid lesion accompanied greater physiological impairment in this six-patient series, and the differences in uptake were not explained by lesion size. Given the sample size, wide confidence intervals, multiple unadjusted comparisons, unadjusted comorbidities and sub-resolution lesions, these findings are hypothesis-generating only; they do not establish SUVmax as a marker of disease severity, an actionable threshold or a guide to biopsy, but support prospective investigation of somatostatin-receptor imaging in DIPNECH.