• Primary tumor recurrence
  

• The development of a second primary tumor
  

There are more than one thousand deaths annually from head and neck cancer in Taiwan (excluding nasopharyngeal carcinoma) and the majority of treatment failures are related to recurrence of primary disease. Only patients with early-stage disease have high cure rates, but they remain at risk for the development of second primary tumors.

Second primary malignancies occur at a constant annual rate of 5% to 7% in all head and neck cancer patients1. Furthermore, because the mortality from primary disease recurrence plateaus after 2 to 3 years in patients with locally advanced disease, second primary tumors become the major cause of late cancer mortality.

Sporn et al defined chemoprevention as an effort to arrest or reverse premalignant cells during their progression to invasive malignancy2,3. The concept of chemoprevention has evolved to include the use of specific compounds, rather than general dietary changes, to prevent the development of cancer.

Hong et al studied the effects of 13-cis retinoic acid on patients with history of head and neck cancers 4. After treatment of head and neck primary cancers with either radiotherapy or surgery or both, 103 patients were randomized to receive either adjuvant 13-cis retinoic acid or placebo. In an update of this trial with 55 months of follow-up, 16 patients (31%) in the placebo group had developed second primary tumors, whereas 7 patients (14%) in the treatment group had developed second primary tumors (p=0.04) 5. Betel quid chewing becomes increasingly popular in Taiwan. Exposure to both smoking and betel quid significantly increases the risk of oral cavity cancer6. The hazard of developing second primary tumors is high in this population, therefore, chemoprevention is worthy of trial.

Use of 13-cis RA for chemoprevention of head and neck cancer only has been published by Hong et al. Their cases included a variety of head and neck cancers that are known to be not a homogenous group. The risk of second primary is different for different primary sites. Therefore, the value of 13-cis RA in chemoprevention is not conclusively addressed. In our proposal, only oral cavity cancer is included and the result will be more convincing. The result could be the basis of further chemoprevention clinical trial or guideline for clinical practice.