The guideline regarding the maximum tolerated lung dose for Yttrium-90 (Y90) radioembolization
is an expert opinion (level 5 evidence) based on a case series of 5 patients and recommends
keeping the absorbed radiation dose to the lungs below 30 Gy per treatment and 50
Gy in a lifetime to prevent radiation pneumonitis (RP). The current understanding
of the risks of RP is minimal despite its debilitating nature and high mortality rate.
This review evaluates the available evidence of lung dosimetry and RP.A systematic
literature review was conducted in PubMed, Embase, Cochrane database, and Google Scholar
for reported cases of RP. A database of 48 RP cases was compiled and analyzed.Thirty
patients were treated with resin and 16 patients with glass Y90-microspheres. The
treatment device was not reported in 2 cases. RP developed a median of 3 months after
radioembolization. The mortality rate was 40%. The hepatopulmonary shunt was not significantly
different between the glass and the resin group (21.2±14% vs. 15.6±7.5%, p=0.24).
The radiation dose to the lungs was significantly higher in patients treated with
glass compared to resin Y90-microspheres (41.4±18.4 Gy vs. 21.5±9.9 Gy, p=0.003).The
dose toxicity threshold for resin microspheres is lower than that of glass microspheres.
The established 30 Gy dose limit may not be uniformly applicable in all cases and
for both devices. The maximum tolerable lung doses should be re-evaluated and the
shortcomings of the hepatopulmonary shunt calculation need to be corrected.
