Compromised CT Detection of Extracranial Malignant Neoplasms by Steroid Treatment

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Abstract
Computed tomographic attenuation coefficients in 6 rabbit thigh V2 [squamous cell] carcinomas were studied before and after steroid [prednisolone] treatment. In 4 V2 tumors with effective steroid treatment, the density difference bvetween V2 carcinoma and normal muscles decreased on pre- and postcontrast scans (17.9 and 21.8 Hounsfield units, respectively; HU: 1000 scale) attributable mainly to altered tumor X-ray absorption; 3 wk after steroid withdrawal, normal and malignant tissue density differences increased and returned toward baseline. Two V2 tumors failed to respond to steroids; the precontract density difference between V2 carcinoma and normal muscle was nearly constant, and the postcontract density difference increased by 6.8 HU. In patients taking steroids, malignant tumors may become isodense with the surrounding normal tissue and be difficult or impossible to detect. Changes in tumor density may also be a useful marker of therapeutic efficacy.