Table 2. Clinical status of NPC cases detected.

		AJCC/UICC stage
Detection	Number of NPC cases	I	II	III	IV	% I and II
Routine screening:	74	44	6	16	8	67.6
After onset of symptoms	97	7	12	38	40	19.6
New cases referred to our clinic	1629	173	164	578	714	20.7

AJCC/UICC=American Joint Committee of Cancer/International Union Against Cancer; NPC=nasopharyngeal carcinoma.

One hundred and seventy-one NPC cases were detected from study subjects either by clinical examination during routine screening, or when patients presented with symptoms of NPC (see Table 1 for details). Newly diagnosed cases, usually with presence of symptoms and referred to our out-patients clinics during the same time, served as concurrent control cases. Percentage of stages I and II cases detected by routine screening is significantly higher than that detected after onset of symptoms (χ²=154.88, P=0.000), and that of the latter is similar as new cases referred to our clinics (χ²⁼1.984, P=0.576).