POSTOPERATIVE RADIATION-THERAPY FOR SURGICALLY STAGED ENDOMETRIAL CANCER - IMPACT OF TIME FACTORS (OVERALL TREATMENT TIME AND SURGERY-TO-RADIATION INTERVAL) ON OUTCOME

Purpose: To evaluate the impact of prolonged overall radiation treatme nt (RT) time and surgery-to-radiation interval on local control (LC) a nd disease-specific survival (DSS) of surgically staged endometrial ca ncer patients in relation to known prognostic factors. Methods and Mat erials: Between 1971 and 1993, 195 endometrial cancer patients receive d postoperative RT at the Fox Chase Cancer Center, All patients underw ent total abdominal hysterectomy (TAH), with 38% also having lymph nod e sampling, All patients received whole pelvic external beam RT to a m edian dose of 45 Gy (range 40 to 60 Gy). Sixty-nine percent received a vaginal cuff boost with either low dose rate or high dose rate brachy therapy, Tumor and treatment factors were analyzed for impact on LC an d DSS, Median follow-up was 47 months (range: 6 to 187 months). Result s: The overall actuarial 5-year LC rate was 85%. In multivariate analy sis, tumor grade, pathologic stage, external radiation dose, and surgi cal lymph node evaluation were independent prognostic variables for im proved LC. Surgery-to-radiation interval of greater than 6 weeks was a marginally significant factor for decreased LC (p = 0.06), Overall RT time and external beam treatment time did not appear to impact LC rat es, The overall actuarial 5-year DSS rate was 86%. In multivariate ana lysis, depth of myometrial invasion, tumor grade, and pathologic stage were independent prognostic variables for DSS, In addition, a surgery -to-radiation interval of greater than 6 weeks was significantly assoc iated with decreased DSS (p < 0.005). Conclusions: Surgery-to-radiatio n interval of greater than 6 weeks is a significant independent progno stic variable for decreased DSS and a marginally significant variable for decreased LC in patients irradiated postoperatively for endometria l cancer, Other time factors (overall RT time and external beam treatm ent time) did not appear to impact outcome, Based on this analysis, po stoperative radiation therapy for endometrial cancer should be initiat ed within 6 weeks following surgery.