The primary endpoint planned in the protocol was the percentage of participants with an oral mucositis score greater than or equal to 3 using the WHO oral mucositis severity scale at a cumulative radiation dose of 50 Gy. This was modified by protocol amendment to the cumulative radiation dose at which a WHO score greater than or equal to 3 was first observed. This change was made to account for the fact that in real practice most patients receive a cumulative dose between 60 and 70 Gy. The presence of grade 3 or 4 oral mucositis was assessed twice weekly during the active phase (radiotherapy) by a trained radiation oncologist or an ear nose and throat specialist who took into account the field of radiation treatment. WHO score 3 = oral ulcers, liquid diet only; WHO score 4 = oral alimentation impossible. Each assessment was associated with the actual cumulative dose of radiotherapy.

The analysis was conducted on the Intent to treat population, defined as all participants who received at least one dose of investigational drug.

Opioid use was recorded twice weekly during the active phase (radiotherapy)

Opioid use was recorded twice weekly for up to 8 weeks during the active phase (radiotherapy). The sum of non-missing total cumulative doses across all class 3 analgesics recorded for the considered participant is reported.

Participants with at least one use of an opioid during the active phase with evaluable data.

Opioid use was recorded twice weekly for up to 8 weeks during the active phase (radiotherapy). The sum of non-missing total cumulative doses across all class 3 analgesics recorded for the considered participant is reported.

Participants with at least one use of an opioid during the active phase with evaluable data.

After the end-of study visit, the investigator center collects OS follow-up data for each patient who has consented to participate in the follow-up data collection. the OS follow-up period was still ongoing at time of the primary analysis and ended in Nov 2016. The analysis was condicted on the ITT population. The overall survival was evaluate every 6 months after last subject completed in patients who has consented to participate .

The population for the 2-year OS follow-up was the ITT defined as all patients who received at least 1 dose of investigational drug.

Time to onset is the duration until first Severe Oral Mucositis. Severe Oral Mucositis was defined as a Grade 3 or Grade 4 score on the World Health Organization (WHO) oral mucositis severity scale. Participants were assessed twice weekly during the active phase (radiotherapy) by a trained radiation oncologist or an ear nose and throat specialist who took into account the field of radiation treatment. WHO score 3 = ulcers, extensive erythema, and the inability of the participant to swallow a solid diet; WHO score 4 = mucositis to the extent that alimentation was not possible.

Participants were assessed using the World Health Organization (WHO) oral mucositis severity scale twice weekly during the active phase (radiotherapy) by a trained radiation oncologist or an ear nose and throat specialist who took into account the field of radiation treatment. The WHO scores were as follows: 0 = None; 1 = oral soreness, erythema; 2 = oral erythema, ulcers, solid diet tolerated; 3 = oral ulcers, liquid diet only; 4 = oral alimentation impossible. The maximum severity was the maximum score reported during the active phase.

The presence of grade 3 or 4 oral mucositis on the World Health Organization (WHO) oral mucositis severity scale was assessed twice weekly during the active phase (radiotherapy) by a trained radiation oncologist or an ear nose and throat specialist who took into account the field of radiation treatment. WHO score 3 = ulcers, extensive erythema, and the inability of the participant to swallow a solid diet; WHO score 4 = mucositis to the extent that alimentation was not possible.The number of participants with at least one Grade 3 or Grade 4 mucositis score during the active phase is reported.

Missing = participants without a WHO score during the active phase

Salivary flow was assessed and scored by the investigator weekly using the NCI-CTC scale for xerostomia for up to 8 weeks during the active phase (radiotherapy). Time to appearance of Grade 2 or higher on the following 4-point scoring scale is reported: 0 = normal; 1 = symptomatic (dry or thick saliva) without significant dietary alteration (unstimulated saliva flow greater than 0.2 mL/minute); 2 = symptomatic and significant oral intake alterations (e.g. copious water, other lubricants, diet limited to purees and/or soft, moist foods) (unstimulated saliva 0.1 to 0.2 mL/minute); and 3 = symptoms leading to inability to adequately aliment orally, intravenous fluids, tube feedings, or total parenteral nutrition indicated (unstimulated saliva < 0.1 mL/minute).

Two of the 183 participants received study treatment but withdrew early without any safety assessments (1 in the clonidine Lauriad 50 μg group and 1 in the clonidine Lauriad 100 μg group). The safety population therefore included 181 participants.

All participants complete a daily questionnaire during the active phase (radiotherapy). Compliance = [ number of tablets / (end date of treatment - start date treatment + 1 ) ] * 100. The "number of tablets" is the number of days with a tablet applied and treatment start and end dates are the first and last dates of the patient diary with a tablet applied.

Participants with evaluable data.