Concept is withdrawn and a different concept will be submitted the near future.

This is a Phase II treatment, randomized 3:1 ratio, open label clinical trial to study the effect of short duration administration of N-acetyl cysteine on oral microbiome and on mucositis caused by concurrent chemotherapy and radiotherapy.

Primary Objective(s) I. To determine whether short duration pre-treatment with N-acetyl cysteine reduces the rate of severe mucositis that develops during the standard concurrent chemoradiotherapy in patients with locally advanced Head and Neck Squamous Cell Cancer.

Secondary Objective(s) I. Identify the effect of N-acetyl cysteine on the oral microbiome.

II. Identify the effect of short duration pre-treatment with N-acetyl cysteine on the duration and delay onset of severe radiation-induced mucositis developed during the standard concurrent chemoradiotherapy in patients with locally advanced Head and Neck Squamous Cell Cancer.

III. Bank saliva and blood for future studies of biomarkers that will be correlated with changes in the oral microbiome and the duration of mucositis.

IV. Determine if there is any effect of short duration pre-treatment with N-acetyl cysteine on tumor response to standard CRT as measured within the first year of treatment.

V. Determine the relationship between human papillomavirus status and smoking status and the baseline microbiome as well as well as the possible differential effect of N-acetyl cysteine on the structure of the oral microbiome in human papillomavirus positive patients vs smokers.

VI. Gather data on the incidence, severity, duration and onset of severe radiation-induced mucositis as well as data on saliva and blood biomarkers and evaluation of the oral microbiome in patients receiving standard of care primary or adjuvant chemoradiotherapy to gather preliminary data for use in designing future Phase 3 studies.

Inclusion Criteria:

• Patients must have histologically or cytologically confirmed HNSCC.
• Patients must be scheduled for definitive or adjuvant concurrent drug therapy and radiotherapy to include the oral cavity in the field and have a window of at least 14 days between the treatment decision and beginning of treatment.
• Patients must be ≥ 18 years old.
• Willing to provide consent for collection of samples of blood and saliva as scheduled through the treatment.
• Subject is willing and able to comply with the protocol for the duration of the study.
• Ability to understand and the willingness to sign an IRB-approved informed consent document.

Exclusion Criteria:

• Patients who have used NAC as a supplement or as a treatment within the last 6 months.
• Patients who have participated in another clinical study with an investigational product during the last 8 weeks.
• Receipt of anti-cancer therapy (chemotherapy, immunotherapy, endocrine therapy, targeted therapy, biologic therapy, tumor embolization, monoclonal antibodies, other investigational agent) within the last 8 weeks.
• Patients who are unable to swallow pills.
• Patients Patient is on medications that need to be continued and that might interact with NAC.
• Uncontrolled pre-existent illness of the digestive tract such as PUD, GERD.
• Any condition that, in the opinion of the investigator, would interfere with evaluation of study treatment or interpretation of patient safety or study results