Inner ear deficits in irradiated nasopharyngeal carcinoma survivors

Abstract

4.

Irradiated ears in nasopharyngeal carcinoma survivors: A review

“…Compared to 2DRT, both radiation dosages to the cochlea and radiation damage to the tissues surrounding the inner ear are lessened by IMRT . Using the 2DRT, estimated radiation dose of 50 Gy was delivered to the cochlea, which was more than 35 Gy to the cochlea by IMRT . Consequently, irradiated NPC survivors treated by IMRT (0.2%) have a significantly lower prevalence of PISD than those treated by 2DRT (2%) .…”

“…Compared to 2DRT, serious toxicities (i.e., xerostomia, trismus, and temporal lobe necrosis) are significantly lessened by IMRT. However, ear symptoms still remained in NPC survivors during the IMRT era …”

Evolution of postirradiated sudden deafness in nasopharyngeal carcinoma survivors during the past two decades

“…In this study, the prevalence of middle ear complication in group A (47%) did not differ significantly from group B (50%), probably because the medial half of the Eustachian tube receives > 95% of total radiation dose regardless of 2DRT or IMRT . Similarly, Chi and Young recently reported that most irradiated NPC survivors with inner ear deficits are attributable to the high prevalence (51%) of ROM. Although prevalence of middle ear complication in irradiated NPC survivors did not decrease from 2DRT to IMRT era, the prevalence of PISD in patients who received IMRT (0.2%) was 10‐fold lower than 2% in those treated by 2DRT, indicating that correlation between ROM and PISD is less.…”

“…The treated volume covered a column from the basal skull down to the clavicle . In contrast, IMRT offers more adequate tumor coverage, with mean radiation dosage reduced to 35.0 ± 0.4 Gy for the cochlea and internal auditory canal (Table ) . Nevertheless, mean radiation dosage to the nasopharynx did not significantly differ between 2DRT and IMRT (70 ± 1 Gy), indicating that effect of irradiation on the tissue depends on the amount of radiation absorbed rather than on the quantity of radiation delivered.…”

“…However, prevalence of otological symptoms such as OME, ROM, or inner ear deficits did not decline in NPC survivors after IMRT technique. 8,9 Via an inner ear test battery, significantly sequential decline in inner ear function from the saccule to the utricle, cochlea, and semicircular canals was identified in irradiated NPC survivors, 10 which mimics that in conventional chronic otitis media. 11 Restated, inner ear deficits in NPC survivors were probably attributable to the sequela of ROM, likely because the toxin and pathogens themselves enter the labyrinth via the round window membrane.…”