Predictive value of linear-quadratic model in the treatment of cervical cancer using high-dose-rate brachytherapy.
OBJECTIVE
To determine whether a dose-response relationship exists between the biologic effective dose (BED) at Point A and the bladder and rectum and the clinical outcomes in our experience with external beam radiotherapy (EBRT) and high-dose-rate brachytherapy in the treatment of cervical carcinoma.


METHODS
This was a retrospective study. A total of 49 patients with cervical cancer were treated with a combination of EBRT (median 45 Gy, range 41.4-50.4) and high-dose-rate brachytherapy (median 18 Gy; range 18-19, in two fractions). Twenty-three patients received concomitant cisplatin-based chemotherapy. The cumulative BEDs were calculated at Point A (BED10) and at bladder and rectal reference points (BED3) using the linear-quadratic equation. The BED10 values, after incorporating a time factor (BED10tf) in the formula, were also calculated.


RESULTS
In patients treated with RT alone, the local failure rate was 10% (1 of 10) and 19% (3 of 16) in patients receiving a BED10 >89 Gy10 or <89 Gy10 to Point A, respectively (p = 0.2). The corresponding local failure rates were 20% (3 of 15) and 0% (0 of 8) in patients treated with concomitant chemotherapy (p = 0.3). In patients treated with RT alone, the local failure rate was 7.7% (1 of 13) and 23% (3 of 13) in patients with a BED10tf >64 Gy10 or <64 Gy10 (p = 0.1), respectively. The median BED3 values at the rectal and bladder point was 95.5 Gy3 and 103.6 Gy3, respectively. Only 1 case of Grade 2 late rectal toxicity (2%) and no late bladder toxicity occurred.


CONCLUSIONS
In patients treated with RT alone, a BED10 >89 Gy and a BED10tf >64 Gy indicated a trend toward a better local control rate. This difference was not observed in patients receiving chemotherapy. A BED3 <100 Gy3 was associated with negligible late toxicity. Although the BED10 in our study was about 10-15 Gy10 less than that in the published data, the 4-year local control rate of 80% and 83% and disease-free survival rate of 75% and 70% with and without chemotherapy, respectively, compare well with the rates in other studies in the literature.
Sood
Brij
B
Department of Radiation Oncology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY 11355-5095, USA. brijmsood@aol.com
Garg
Madhur
M
Avadhani
Jai
J
Gorla
Giridhar
G
Malhotra
Harish
H
Guha
Chandan
C
Deore
Shivaji
S
Vikram
Bhadrasain
B
D000230:Adenocarcinoma / Q000532:radiotherapy; D000328:Adult; D001918:Brachytherapy / Q000379:methods*; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy; D002945:Cisplatin / Q000627:therapeutic use*; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D008962:Models, Theoretical; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
D011838:Radiation-Sensitizing Agents; D002945:Cisplatin