Radioactive alginate gel skin patch for the treatment of skin cancer

Basal cell carcinoma (BCC) is the most common skin cancer and originates from the lowest layer of epidermis. External radionuclide based radiation therapy with locally applied radioactive patch is an useful way to treat superficial skin cancers. We evaluated the utility of P-32 alginate gel patches, as an inert solid matrix, to immobilize radionuclide. Sodium alginate solutions (4%) was spread on parafilm and dipped into anhydrous CaCl₂ (0.2 M) solution. The patches were washed and air dried. Radioactive solution in the form of Tc-99m or P-32 colloid was spread on the gel to uniformly distribute the radioactivity on pre marked 1 cm² area and was left undisturbed to allow drying and avoid alteration in distribution. The image of alginate patches of Tc-99m colloid incorporated was acquired under gamma-camera, ROIs were drawn and counts were recorded to study radioactivity distribution. A teflon sheet of size bigger than patch (~2 cm) was placed over the outer surface over parafilm and exposure rate was observed. Dose delivered to the patient was calculated based on MIRD. Customized P-32 patch was applied for 3 h on a patient of biopsy proven basal cell carcinoma. The same patch was reapplied on 4th and 7th day. Clinical assessment, photographic recording and hematologic monitoring were done during the follow-ups. Tc-99m colloid was used to study the distribution pattern of radioactivity on alginate film. The counts registered were almost similar. Radioactivity (P-32) was uniformly adsorbed on the gel layer. Exposure rate above the parafilm surface was reduced by covering the patch with teflon sheet. More than 20% relief of clinical symptoms was experienced by the patient after first application. On follow ups, significant symptomatic relief was observed. The alginate gel patch can be stable and suitable alternatives for radionuclide patch preparation for superficial skin cancers. Also our single patient observation demonstrated that P-32 patch therapy can be simple, non invasive and safe out-patient therapeutic procedure in treating patients of BCC. (author)