A DOSIMETRIC COMPARISION OF BLADDER AND RECTAL VOLUMETRIC DOSES IN 3D– CT BASED HDR INTRACAVITARY BRACHYTHERAPY FOR CERVICAL CANCER USING TWO RECTAL RETRACTION METHODS

Introduction: Cervical cancer is a common malignancy among women in India. For locally advanced stages, standard treatment consists of concurrent chemoradiation along with brachytherapy. Most commonly, intracavitary brachytherapy is used. To reduce the radiation dose to the rectum, a rectal retractor is often used. This is sometimes done with vaginal gauze packing also.

Aims: To find out the variation in dosimetric parameters in patients who received 3D CT based intracavitary brachytherapy for cervical cancer based on two rectal retraction methods and if one is dosimetrically non inferior to the other.

Methods: FIGO Stage IIB cervical cancer patients, who received intracavitary brachytherapy with Manchester-style applicator after concurrent chemoradiation, were randomised to either rectal retractor or vaginal gauze packing. Dosimetric parameters of D_2cc, V50, Dmax, for rectum and bladder were obtained, along with volume contoured. Paired t-test done for results.

Results: Using t test, the variation in V₅₀ for bladder with and without rectal retractor was significant (p=0.017), favouring the arm with packing, but for rectum, it was not statistically significant (p=0.08). Variation in D_2cc for bladder (p=0.09) and rectum (p=0.1) was not significant between the two arms.

Conclusion: Vaginal gauze packing may be considered a dosimetrically non inferior substitute to rectal retractor, provided it is done in an adequate manner.