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A 69-year-old male presented with early stage non-small cell lung cancer in 2016. The tumor was resected; however, the patient experienced recurrence 2 years later and subsequently received paclitaxel/carboplatin concurrently with radiotherapy. Within weeks of completing this treatment, he developed a symptomatic pancoast tumor secondary to disease progression and commenced second line nivolumab. Following the second dose of nivolumab, he developed acute unilateral right hearing loss. He commenced intravenous methylprednisolone followed by a slow taper of oral prednisolone. With steroids, he noted a gradual improvement in hearing, confirmed by audiology. Restaging imaging post-nivolumab demonstrated a complete metabolic response. Two prior cases have reported bilateral sensorineural hearing loss post-immune checkpoint inhibitor (ICI). We postulate the hearing impairment relates to the development of autoimmune inner ear disease. To our knowledge, this is the only case of a patient experiencing unilateral loss of hearing following an ICI.

Background: Reactive Oxygen Species (ROS) are by-products of normal cellular metabolic processes, such as mitochondrial oxidative phosphorylation. While low levels of ROS are important signalling molecules, high levels of ROS can damage proteins, lipids and DNA. Indeed, oxidative DNA damage is the most frequent type of damage in the mammalian genome and is linked to human pathologies such as cancer and neurodegenerative disorders. Although oxidative DNA damage is cleared predominantly through the Base Excision Repair (BER) pathway, recent evidence suggests that additional pathways such as Nucleotide Excision Repair (NER) and Mismatch Repair (MMR) can also participate in clearance of these lesions. One of the most common forms of oxidative DNA damage is the base damage 8-oxoguanine (8-oxoG), which if left unrepaired may result in G:C to A:T transversions during replication, a common mutagenic feature that can lead to cellular transformation. Objective: Repair of oxidative DNA damage, including 8-oxoG base damage, involves the functional interplay between a number of proteins in a series of enzymatic reactions. This review describes the role2 and the redox regulation of key proteins involved in the initial stages of BER of 8-oxoG damage, namely Apurinic/Apyrimidinic Endonuclease 1 (APE1), human 8-oxoguanine DNA glycosylase-1 (hOGG1) and human single-stranded DNA binding protein 1 (hSSB1). Moreover, the therapeutic potential and modalities of targeting these key proteins in cancer are discussed. Conclusion: It is becoming increasingly apparent that some DNA repair proteins function in multiple repair pathways. Inhibiting these factors would provide attractive strategies for the development of more effective cancer therapies.