Introduction Volume changes induced by selective internal radiation therapy (SIRT) may increase the possibility of tumor
resection in patients with insufficient future liver remnant (FLR). The aim was to identify dosimetric and clinical parameters
associated with contralateral hepatic hypertrophy after lobar/extended lobar SIRT with 90Y-resin microspheres.
Materials and methods Patients underwent 90Y PET/CT after lobar or extended lobar (right + segment IV) SIRT. 90Y voxel
dosimetry was retrospectively performed (PLANET Dose; DOSIsoft SA). Mean absorbed doses to tumoral/non-tumoral-treated
volumes (NTL) and dose-volume histograms were extracted. Clinical variables were collected. Patients were stratified by FLR at
baseline (T0-FLR): < 30% (would require hypertrophy) and ≥ 30%. Changes in volume of the treated, non-treated liver, and FLR
were calculated at < 2 (T1), 2–5 (T2), and 6–12 months (T3) post-SIRT. Univariable and multivariable regression analyses were
performed to identify predictors of atrophy, hypertrophy, and increase in FLR. The best cut-off value to predict an increase of
FLR to ≥ 40% was defined using ROC analysis.
Results Fifty-six patients were studied; most had primary liver tumors (71.4%), 40.4% had cirrhosis, and 39.3% had been
previously treated with chemotherapy. FLR in patients with T0-FLR < 30% increased progressively (T0: 25.2%; T1: 32.7%;
T2: 38.1%; T3: 44.7%). No dosimetric parameter predicted atrophy. Both NTL-Dmean and NTL-V30 (fraction of NTL exposed
to ≥ 30 Gy) were predictive of increase in FLR in patients with T0 FLR < 30%, the latter also in the total cohort of patients.
Hypertrophy was not significantly associated with tumor dose or tumor size. When ≥ 49% of NTL received ≥ 30 Gy, FLR
increased to ≥ 40% (accuracy: 76.4% in all patients and 80.95% in T0-FLR < 30% patients).
Conclusion NTL-Dmean and NTL exposed to ≥ 30 Gy (NTL-V30) were most significantly associated with increase in FLR
(particularly among patients with T0-FLR < 30%). When half of NTL received ≥ 30 Gy, FLR increased to ≥ 40%, with higher
accuracy among patients with T0-FLR < 30%