THE RELATIONSHIP BETWEEN BRACHYTHERAPY DOSE AND OUTCOME IN PATIENTS WITH BULKY ENDOCERVICAL TUMORS TREATED WITH RADIATION ALONE

Purpose: To evaluate the relationship between brachytherapy dose and outcome in patients treated with external radiotherapy (40 Gy to the whole pelvis) and intracavitary radium therapy for bulky endocervical tumors. Methods and Materials: Between 1962 and 1985, 98 patients with Stage IB-IIB bulky endocervical carcinomas (greater than or equal to 6 cm in diameter) treated with radiotherapy alone received 40 Gy to the whole pelvis followed by 2 or more intracavitary treatments. Twenty-five patients received < 6000 mg-hr of intracavitary treatment and 73 received greater than or equal to 6000 mg-hr (an average dose to point A of approximately 49 Gy). Brachytherapy exposures ranged from 4800-7885 mg-hrs, Results: Patients who received < 6000 mg-hr tended to have unfavorable (narrow) vaginal anatomy (p < 0.01) and to be treated in the later years of the study (p ( 0.01). The high-dose group included a somewhat greater proportion of patients with positive lymphangiograms or poor responses to initial external beam treatment. Despite having somewhat more favorable tumors, patients who received less than 6000 mg-hr had a higher rate of pelvic disease recurrence at 5 years (33%) than those who received higher doses (16%) (p = 0.03). Actuarial survival rates at 5 years were 44% and 60% for the low- and high-dose groups, respectively (p = 0.14). Among those who received more than 6000 mg-hr, there was no significant relationship between brachytherapy dose and pelvic disease control. Calculated actuarially, the rate of major (greater than or equal to 1 grade 3) complications at 5 years was 23% in the low-dose group and 10% in the high-dose group (p = 0.1). Conclusions: The relatively high incidence of pelvic disease recurrence and complications in patients who receive less than 6000 mg-hr reflects the narrow therapeutic window for complication-free pelvic disease control in patients with bulky central disease and unfavorable normal tissue anatomy. The results also demonstrate a high pelvic control rate and acceptable morbidity in patients with favorable anatomy treated with high-dose radiotherapy alone.