Human papilloma virus-related oropharynx cancer is increasing in incidence and is now the most common indication for LASCCHN CRT. It more commonly affects younger patients without other comorbidities and is associated with high rates of cure. This creates a survivorship dilemma, as these patients suffer a greater and more prolonged impact from chronic treatment effects such as hearing loss on their HRQOL. Furthermore, this cohort of patients is more likely to be engaged in contributing to societal and economic productivity for a more prolonged period of time. Minimizing long term side effects through strategies to better individualize treatment has been recognized as a priority by the US NIH.

Efforts to identify risk factors for cisplatin toxicity have been previously reported in pediatric cancer patients. Pussegoda and colleagues identified greater risk of hearing loss with cisplatin in children who carried single nucleotide polymorphisms (SNPs) in thiopurine S-methyltransferase (TPMT) and catechol-O-methyltransferase (COMT) genes. However, the role of these genes in predicting ototoxicity risk has remained controversial with both confirmatory and conflicting reports. Two independent studies identified SNPs in the gene acylphosphatase 2 (ACYP2) as being predictive of ototoxicity in pediatric populations. Additional studies have implicated drug transporters involved in cisplatin disposition including the multidrug and toxin extrusion protein 1 (MATE1) to be associated with platinum response and toxicities. In vitro experiments and know-out studies identified cisplatin as a substrate of MATE1. To date, there remains a paucity of data investigating the association between genetic factors and hearing loss in adult LASCCHN patients. A prospective cohort study conducted at LHSC in collaboration with Dr. Richard Kim studied 206 adult LASCCHN patients receiving CRT with cisplatin and identified four independent risk factors for cisplatin-related hearing loss. Risk of hearing loss was increased with the presence of COMT SNPs (HR = 1.75; 95% CI, 1.17 - 2.52) while MATE1 reduced the risk (HR = 0.46; 95% CI, 0.26 - 0.84). The risk of hearing loss was reduced with cisplatin administered on a weekly low dose (LD) compared to a HD schedule. PFS and OS were similar between SNP cohorts and patients treated with weekly LD cisplatin and HD cisplatin regimens. To validate these results and confirm benefits on the pragmatic endpoint of hearing-related QOL, the investigators propose a prospective randomized clinical trial comparing HD and weekly LD cisplatin.

Opinion leaders such as the National Comprehensive Cancer Network guidelines endorse the use of weekly LD cisplatin as a reasonable alternative to HD cisplatin when administered concurrently with radiation. While the study conducted at LHSC observed weekly LD patients had reduced ototoxicity with similar efficacy compared to HD patients, there is no randomized control trial data in LASCCHN to support this practice. Current American Society of Clinical Oncology (ASCO) guidelines support HD cisplatin in this setting based strength of evidence. Therefore, the optimal schedule and dosing of cisplatin when administered as part of CRT in the curative intent treatment of patients with LASCCHN remains unresolved supporting clinical equipoise as to which constitutes the "best" approach.

The investigators primary hypothesis is that LD weekly cisplatin 40 mg/m² is associated with reduced frequency of severe hearing loss and improved hearing-related QOL when compared to conventional HD cisplatin 100 mg/m² days 1, 22 \& 43 (control arm) in LASCCHN patients treated with CRT. Furthermore, the investigators hypothesize that a significant proportion of the risk of cisplatin-related hearing loss is attributable to individual differences in pharmacogenomics factors affecting cisplatin disposition that could be identified prior to treatment.