Table 1.

Limiting dilution transplantation after 48 hours of treatment with IR demonstrates a significant increase in tumor initiation, and IR+HT demonstrates a marked reduction in the tumor initiation. T1 palpable tumors formed between 2 and 4 weeks after mock and IR, and between 3 and 5 weeks with IR+HT. T7 palpable tumors formed after all treatments in 2 to 7 weeks.

No. of cells injected	10,000	1000	100	10
	No. of tumors formed/total no. of transplants
Mock T1	6/6	6/6	1/6	0/8
Mock T7	6/6	6/6	1/6	0/6
Mock total	12/12	12/12	2/12	0/14
IR T1	6/6	6/6	4/6	3/8
IR T7	6/6	6/6	2/6	1/6
IR total	12/12	12/12	6/12	4/14*
IR+HT T1	6/6	3/6	0/6	0/8
IR+HT T7	6/6	3/6	0/6	0/6
IR+HT total	12/12	6/12	0/12	0/14†

^*P = 0.02

^†P = 0.002