A comparative study of Conventional and CT based planning of Target volumes and organs at risk in Intra cavitary brachytherapy for Carcinoma of cervix

Introduction: Cervical cancer is the third most common malignancy in women worldwide, and it remains the leading cause of cancer related deaths in women in developing countries. In the management of cervical cancer, both intracavitary brachytherapy (ICBT) and external radiotherapy (ERT) are essential as they deliver a high dose to the primary tumor and low doses to adjacent organ. The dose can be delivered either by conventional orthogonal radiograph mapping or by the 3-dimensional computed tomography mapping. In the present study, we have compared both the techniques. Aim and objectives: To compare intracavitary brachytherapy (ICBT) planning methods for cervical cancer based on orthogonal radiographs (conventional plan) and computed tomography sections (CT plan). Materials and methods: This was a prospective study, conducted in the department of Radiotherapy, MNJ Institute of Oncology and Regional Cancer Centre, over a period of two years from November 2012 to November 2014. The study consisted of total 25 registered patients having confirmed diagnosis of Squamous cell carcinoma of cervix. All the patients underwent conventional and CT planning for brachytherapy. One arm received the conventional plan of radiotherapy while the other arm received computed tomography (CT) based plan. Results: The patient age ranged from 35 to 65 years. The mean age was 47 years. The results of the study demonstrates that CT-guided brachytherapy planning is superior in terms of both conformity of target coverage and evaluation of OARs .Although this superiority was clear for small GTVs, for large GTVs both the conventional and CT-Plans had the drawbacks of inadequate target coverage and /or excessive radiation doses to normal organs. Conclusions: The conventional plan with the point A calculation relies on reference points on orthogonal films ,not tumor volumes defined on CT, which may cause underestimation of tumor doses. Likewise, the calculation of rectum and bladder doses made with ICRU reference points, not with bladder and rectal volumes may not reflect the actual organ doses. To overcome such problems, 3D CT-guided brachytherapy treatment planning is recommended.