Evaluation of Sensorineural Hearing Loss as a Consequence of Conventional Radiotherapy in Head and Neck Cancer MC01-MC04
Dr. Abhay D Havle,
Somwar Peth, Karad, Maharashtra, India.
Introduction: Sensorineural Hearing Loss (SNHL) is potentially disabling and yet overlooked, while subjecting patients of head and neck cancer to conventional ionising radiation at most tertiary care centers. The demand for cancer care, along with the rising cost of therapy using newer treatment technologies such as intensity modulated radiotherapy is a concern to the health care system in India. Cochlea often remains in the field of radiation and hence need to be shielded to prevent development of SNHL.
Aim: To assess role of radiotherapy causing sensorineural hearing loss in patients of head and neck cancer.
Materials and Methods: A prospective study was initiated on 110 cases with normal hearing requiring Radiotherapy (RT), for biopsy proven tumours of head and neck in the Department of Otorhinolaryngology. All cases were treated with external beam conventional radiotherapy using telecobalt machine and a shielding collimator. Out of 110 cases treated by either curative or palliative dose of RT which was around 60 Gray (Gy) and 30 Gray (Gy) respectively, 16 did not come for follow-up. The study was concluded with remaining 94 cases who completed the follow-up. Hearing acuity was assessed using 500, 1000 and 2000 Hz frequency before start of radiotherapy, immediately following radiotherapy and at first follow-up after six months in all cases. Quantification of the degree of SNHL was done using one-way analysis of variance (ANOVA). During follow-up the hearing loss noted was graded into mild and moderate.
Results: The ototoxic effect after RT was found amongst the cases who received curative dose of 60 Gy, while none in cases who received palliative dose of 30 Gy. Out of 188 ears in 94 cases, 59 ears (31.38%) had SNHL, including newly developed SNHL in 44 ears during the 6 month post-RT follow-up period. The number of ears having SNHL was 18 at immediate post-RT which further increased to 59 at 6 month follow-up as compared to pre-RT normal hearing levels.
Conclusion: In cases of head and neck cancer treated by conventional radiotherapy using telecobalt machine and shielding, the risk of consequent sensorineural hearing loss -SNHL was about just less than one third (31.38%). The tolerance of cochlea to total dose of radiotherapy was less than 60 Gray in cases of head and neck cancer treated by conventional radiotherapy.