THREE OR FOUR FRACTIONS PER WEEK IN POSTOPERATIVE HIGH DOSE RATE BRACHYTHERAPY (HDRBT) FOR ENDOMETRIAL CARCINOMA (EC). Rovirosa A1, Vargas M1, Ascaso C2, Sánchez-Reyes A3, Martinez F1, Herreros A1, Francisco R1, Piñeiro M2, Arenas M4, Biete A1. 1- Radiation Oncology Dpt., Hospital Clinic i Universitari, Barcelona. 2- Public Health Dpt, University of Barcelona. 3- Radiation Oncology Dpt, Hospital Platón, Barcelona. 4- Oncology Dpt., Hospital Sant Joan Reus, Tarragona. SPAIN. PURPOSE: To evaluate the HDRBT in postoperative treatment of EC using a schedule of 3 or 4 fractions / week. PATIENS AND METHODS 89 PATIENS (pts) Between June 2003 and December 2006. Mean follow-up 31 months (6 to 70 months). AGE: median 69 years (y), range between 38 and 89 y. SURGERY: 30/89 Vaginal hysterectomy + bilateral salpingo-Ooforectomy (HTSO) & laparoscopic pelvic +/- para-aortic lymphadenectomy; 30/89 abdominal HTSO & pelvic lymphadenectomy; 20/30 abdominal HTSO, lymphadenectomy & omentectomy, 7/89 vaginal HTSO and 2/789 abdominal HTSO lymphadenectomy + omentectomy. FIGO STAGE: 24 IB, 45 IC, 4 IIA, 6 IIB, 4IIIA, 1 IIIB, 5 IIIC. PATHOLOGY: 77 Endometrioid, 6 Serous, 2 Clear cell, 3 mixed types, 1 miscelaneous. 17G1, 43G2, 29G3 RADIOTHERAPY: TWO GROUPS GROUP 1: 67/89 PTS 11 IB, 37 IC, 4 IIA, 5 IIB, 4 IIIA, 1 IIIB, 5 IIIC 26/67 Grade 3 (13 IC, G3) EXTERNAL BEAM IRRADIATION (EBI) Linac of 6-18 MV. Median dose 45Gy, range 44 to 50 Gy, 1.8-2Gy/day.2 to 4 pelvic fields (para-aortic lymph nodes included when necessary) . If N+: boost with small fields until 50 to 60 Gy. HDRBT 3 fractions of 4 to 5 Gy. GROUP 2: 22/89 PTS 13 IB, 8 IC, , 1 IIB. 3/22 Grade 3 (1IC,G3) HDRBT alone: 6 fractions of 4 to 5 Gy. BRACHYTHERAPY 3 to 4 fractions per week when possible. I192 HDR, MicroHDR afterloading system (Nucletron®) Technique: 6/89 colpostats, 83/89 cylinders (1/83 2cm, 8/83 2.5 cm, 33/83 3 cm, 41/83 3.5 cm). Median treated length 3 cm. OVERALL TREATMENT TIME GROUP 1 (3 FRACTIONS). 32/ 67 pts ≤ 5 DAYS (median 5 days, range 3 to 5 days). 35/67 pts > 5 DAYS (median 7 days, range between 6 and 23 days). GROUP 2 (6 FRACTIONS). 11/22 pts ≤ 5 DAYS (median 14 days, range 9 to 15 days). 11/22 pts > 15 DAYS (median22 days, range 16 to 28 days). TOXICITY Rectum and bladder: RTOG Late Vagina. G1: Telangiectasia without bleeding, slight pigmentation change, vaginal scar fibrosis. G2: Telangiectasia with bleeding, dryness, slight atrophy, ulceration, partial synechiae, marked pigmentation change, symptomatic fibrosis. G3: Stenosis, complete synechiae, intermitent bleeding. G4: Obliteration, fistulae, Diffuse atrophy, persistent bleeding, total dysfunction. BED vaginal surface dose Study STATISTICS Non parametric ANOVA, Chi-square & ROC curves RESULTS FIG. 1 GROUP 2 1/89 Vaginal relapse and died at 1 y. 1/89 was lost in follow-up at 50 months. 4 patients died at 16 and 37 months without relationship with EC. Early Toxicity was resolved in all de pts. in 2 months. Vagina (8/89, 9%): 91% G0, 8% G1, 1% G2. No relationship with BED at vaginal surface. Rectum 2/89 G1( 2%), 1/89 (1%)G2. Bladder 5/89 (5.5%) had G1 urinary problems. Late Toxicity appeared in 13/89 (14%). Rectum 2/89 pts (2%): 2 G1. Bladder 4/89 pts (4%): 2G1, 2 G2. Vagina 11/89 pts (12%): 7G1, 3G2, 1G4 (obliteration). BED vaginal mucosa. Group 1: Mean 63 Gy (41- 146Gy). Group 2: Mean 120 Gy, range 82 to 188 Gy. The relationship between BED and late toxicity is shown in Fig. 1 for Group 1 and 2. Overall interval time. No differences in toxicity were found in Group 1 for ≤ 5 days or > 5 days, and in Group 2 for ≤ 15 days or > 15 days. GROUP 1 BED VAGINAL SURFACE DOSE AND LATE TOXICITY FOR GROUPS 1 & 2. CONCLUSIONS 1- 3 FRACTIONS OF 4 TO 5 Gy IN 3 TO 5 DAYS AFTER EBI OR 6 FRACTIONS IN LESS THAN 15 DAYS SEEMS A SAFE TREATMENT IN RELATION TO TOXICITY AND LOCAL CONTROL IN HDRBT FOR EC. 2- CASES WITH G2 LATE VAGINAL TOXICITY SHOWED VAGINALSURFACE BED HIGHER THAN 60 Gy AFTER EBI OR MORE THAN 120 GY FOR HDRBT ALONE.