Clinical significance of cumulative biological effective dose and overall treatment time in the treatment of carcinoma cervix

The purpose of this retrospective study is to report the radiotherapy treatment response of, and complications in, patients with cervical cancer on the basis of cumulative biologic effective dose (BED) and overall treatment time (OTT). Sixty-four (stage II - 35/64; stage III - 29/64) patients of cervical cancer were treated with combination of external beam radiotherapy (EBRT) and low dose rate intracavitary brachytherapy (ICBT). The cumulative BED was calculated at Point A (BED(10)); and bladder, rectal reference points (BED(2,5)) using the linear-quadratic BED equations. The local control (LC) rate and 5-year disease-free survival (DFS) rate in patients of stage II were comparable for BED(10) <84.5 and BED(10) >84.5 but were much higher for BED(10) >84.5 than BED(10) <84.5 (P< 0.01) in stage III patients. In the stage II patients, The LC rate and 5-year DFS rate were comparable for OTT <50 days and for OTT >50 days but were much higher in stage III patients with OTT < 50 than OTT >50 days (P< 0.001). It was also observed that patients who received BED(2.5) <105 had lesser rectal (P< 0.001) and bladder complications than BED(2.5) >105. Higher rectal complication-free survival (CFS(R)) rate, bladder complication-free survival (CFS(B)) rate and all-type late complication-free survival rate were observed in patients who received BED(2.5) < 105 than BED(2.5) >105. A balanced, optimal and justified radiotherapy treatment schedule to deliver higher BED(10) (>84.5) and lower BED(2.5) (< 105) in lesser OTT (< 50 days) is essential in carcinoma cervix to expect a better treatment outcome in all respects.