INFLUENCE OF BLADDER VOLUME AND CENTRAL TANDEM LENGTH ON OPTIMUM DOSE TO OAR IN INTRACAVITARY BRACHYTHERAPY OF CARCINOMA CERVIX

Dr. Hepsiba Priyadarshini, Dr. Hasib A. G

Abstract


PURPOSE: The aim of this study is to find an optimum bladder volume and central tandem length to minimize the dose to pelvic OARs.
METHOD : This study was done between 2017-2018 among 40 histologically proven squamous cell cervical cancer patients who received
concurrent chemoradiation of dose 50Gy in 25 fractions, 2Gy per fraction over 5 weeks along with weekly Inj.Cisplatin of dose 40mg/m2 followed
by 3 sessions of HDR intracavitory brachytherapy with dose 7.5Gy per session once weekly from the Department of Radiation oncology, Father
Muller Medical College. Patients were classified into four groups based on their bladder volumes measured – (i) Group A with less than 70 cc, (ii)
Group B with 70 to 110 cc, (iii) Group C with 110 to 170 cc, and (iv) Group D with greater than 170 cc. The rational for this type of patient
classification was to calculate the bladder, rectal and sigmiod doses based on different bladder volumes and to fix a routine filling protocol. Another
classification was made based on the physical tandem length into two groups (a) the patients who were treated with tandem lengths equal to or less
than 4 cm,and (b) those who were treated with tandem lengths longer than 4 cm. The bladder, rectum, and sigmoid DVH parameters such as D0.1cc
, D2cc and D10, D30, D50 were recorded in terms of percentages of the planning aim dose after each treatment plan.
RESULTS - BLADDER: The results of this study indicate that the minimum dose to the most exposed small volumes of the bladder (i.e., D0.1cc
and D2cc),increased as the bladder volume enlarges. On the other hand, large volume doses (i.e., D10, D30, and D50) decreased by increasing
bladder volume. Tandems longer than 4 cm increase the dose to the bladder up to about 4% more (of the planning aim dose) compared to the shorter
tandems.
RECTUM: Rectum dose reaches its minimum and maximum levels for <70cc and 110-170 cc bladders, respectively. Choosing a longer tandem
leads to about 5% more dose to the rectum.
SIGMOID: When the bladder volume is 70-110 cc, the sigmoid dose will be minimum. Tandem lengths have a direct relationship with sigmoid
dose.
CONCLUSION : In conclusion, choosing a bladder with a volume of about 70 cc or less and tandem length of <4cm is recommended when taking
into account the high dose volume parameters for bladder, rectum, and sigmoid.


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