Aim To prepare ³²P-based user-friendly mould brachytherpy sources for the treatment of superficial tumors.
Methods ³²P as orthophosphoric acid was adsorbed on 15–25mm (diameter) circular sheets of cellulose-based adsorbent paper to prepare sources containing approximately 37–74MBq of ³²P per cm² of strip. The sources were immobilized between plastic sheets of 40 lm thickness. Autoradiography studies were carried out to determine the uniformity of ³²P deposition in the source. Dosimetric evaluation of the sources was also carried out. Bioevaluation studies were carried out in C57BL6 mice bearing melanoma using 37–74MBq sources.
Results Cellulose-based sources containing 37–74MBq of ³²P per cm² could be prepared from which no radioactivity leakage could be detected in water or saline. Autoradiography studies revealed ³²P to be uniformly distributed in these sources. Dosimetric evaluation showed that the contact dose imparted was 10 Gy/h, sufficient for treatment of superficial tumors. In mice bearing melanoma, complete tumor regression could be achieved with two applications of 37–74MBq sources, at an interval of 3 days. Histopathological examination of the skin tissue from the treated area proved the absence of tumor as compared with the controls.
Conclusion Preparation of ³²P sources of various shapes and sizes (based on the tumor size) having uniform ³²P activity distribution could be achieved. Efficacy of these sources in treating melanoma tumors could be established in the animal model.