D. Lim Joon

PO-0674: Understanding the impact of two pharyngeal axis delineation guidelines for planning definition in head & neck IMRT

interval [CI]: 64-89%) and 95.8% (95% CI: 90-100%) respectively. Thirteen pts presented LR failures, of which 4 had isolated local failure, 4 had isolated regional failure, 2 had local and regional failures, and 3 had simultaneous LR and distant relapses. Of 13 pts with LR relapse, only 1 (8%) had marginal failure, with the remaining 92% failing truly in-field within the high-dose region. No patient recurred in vicinity of spared PG, SMG or OC. Surgical salvage for LR failure was attempted in 5 pts. Contralateral PG was spared in 98% of pts and ipsilateral PG in 54%. Concerning SMGs, 18 (26%) contralateral glands were spared and the ipsilateral SMG was spared in 5 pts. In other 13 (19%) pts doses to the SMGs below 50 Gy were obtained. The OC was spared to a dose ≤40 Gy in 26 pts (37%). None of the pts developed permanent xerostomia higher than grade 2 at the last follow-up visit. Conclusions: The majority of LR failures occurred in-field within the high dose region. Sparing SMGs and OC in addition to PGs does not seem to jeopardize the LR control in HNC IMRT.