Cervix: Poster Abstract: Comparative dosimetric study between point and volume based brachytherapy in definitive treatment of de novo carcinoma cervix
This article was originally published by Wolters Kluwer - Medknow and was migrated to Scientific Scholar after the change of Publisher.
Cervical cancer has a high incidence in developing countries including India. Brachytherapy (BT) is an important component in the curative management of carcinoma of the cervix, and significantly improves survival. In gynaecologic BT, correlation between the radiation dose and the normal tissue effects have been assessed using point doses. Since 1985, these points have been defined in the international commission of radiation units and measurements (ICRU-38) report. However GEC-ESTRO recommended volume based treatment planning in their respective series (I-IV). For cervical cancer BT, the correlation of ICRU point doses and volume based treatment planning is investigational till date. Analysis becomes feasible when cross sectional image-based treatment planning for BT using computerized tomography (CT) or magnetic resonance imaging (MRI) is utilised as per GEC-ESTRO recommendation.
It is a retrospective pilot study includes patients (pts.) of carcinoma cervix treated with high dose rate (HDR) BT 9 Gy in 2 fractions 1 week apart. All volume based dosimeteric parameters regarding high risk clinical target volume (HRCTV), intermediate risk clinical target volume (IRCTV) like D90, D100 and for organ at risk (OAR) D 0.1 cc, D 1.0 cc and D 2.0 cc were delineated and dose coverage was analysed in point dose based planning.
We have analysed twenty pts. of squamous cell carcinoma (SCC) cervix. The median age was 52 yrs. (41-65 yrs), stage II B 10 pts. & III B 10 pts. The mean value of D90 & D100 in HRCTV during I and II session were 8.64, 6.75 and 5.76, 4.36 Gy respectively. Same values for IRCTV were 6.31, 4.91 and 3.68, 3.15 Gy respectively. Analysis of OARs demonstrated that mean dose received by 0.1, volume of bladder during I and II session received 10.68, 9.47, by 1 cc volume 8.39, 7.57 and by 2 cc volume 6.84, 6.21 Gy respectively. The mean dose received by 0.1 cc of rectum were 11.59, 10.12, by 1 cc volume 9.53, 8.19 and by 2 cc volume 7.76, 6.81 Gy respectively. In point based analysis mean dose delivered to bladder point during I and II session were 5.63, 6.02 and to rectum point were 5.98, 5.46 Gy respectively. Doses to 0.1 cc volume of bladder and rectum were higher in volume based BT as compared to point based BT in respective fractions.
Both HRCTV and IRCTV had better dose coverage in 1st fraction as compared to 2nd fraction. Point doses to bladder and rectum is underestimated in point based (ICRU-38) BT. We need more number of pts in prospective randomized trial for more consistent result.