Breast telecobalt beam therapy using multi-isocentric technique

ABSTRACT Aim To treat breast cancer patients in telecobalt unit with image based conformal radiotherapy planning using the multi-isocentric technique. Background Breast cancer is the leading cancer among all the female cancers. With improved screening techniques, many patients are being diagnosed at an early stage and the need for radiotherapy in such patients has increased. The telecobalt machine is still a preferred machine in many of the low income countries as it is cost-effective and can offer uninterrupted treatment to large number of patients. Materials and Methods Three hundred patients requiring radiotherapy had a computed tomography based planning. Patients were immobilized using a breast board with a thermoplastic mould. Three dimensional planning was done with the multi-isocentric technique. These patients were then simulated using a Nucletron Simulix digital simulator for field verification and were treated in a Theratron Phoenix telecobalt treatment unit. Results The doses to the heart, ipsilateral lung and the conformity index were within the recommended values. The homogeneity index was not comparable; however, a section by section qualitative analysis was done and a final plan approved. As per the RTOG toxicity grading system, acute skin reaction grade 3 was observed in 3.6% of treatments to intact breast including nodal regions and in 3.5% of post mastectomy radiation patients. Conclusion Single isocenter technique was not feasible as the telecobalt unit did not have multileaf collimators and asymmetric jaws. With improved image based planning, a multi-isocentric technique was planned. By evaluating the dose distribution, beam modifications can be made and treatments can be given with acceptable toxicity.