Significance of Hypoechoic Lesions in the Irradiated Prostate

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Abstract
The ultrasonographic features of the irradiated prostate were evaluated in 22 patients undergoing salvage radical prostatectomy for persistent or recurrent cancer after definitive radiotherapy. Preoperative sonographic features were compared with the histopathologic findings of serially sectioned surgical specimens. The irradiated nonmalignant prostatic tissue had the same echo characteristics as the nonirradiated gland. Twenty-four discrete hypoechoic lesions greater than 5 mm in minimum diameter and suggestive of cancer were found on transrectal ultrasonography. Twenty-two were in the same position as the cancer seen on the corresponding histologic sections. The positive predictive value of a hypoechoic area was 91.7%. A total of 109 separate foci of tumor greater than 3 mm in minimum diameter in the whole mount histologic step-sections were identified and compared with the transrectal ultrasonogram; 72.5% were hypoechoic, 4.6% hyperechoic, and 22.9% isoechoic. There was a statistically significant correlation between tumor diameter and echogenicity (p < 0.01). We conclude that radiotherapy rarely produces hypoechoic foci in normal prostate tissue and that prostate cancer persisting after definitive radiotherapy retains its hypoechoic appearance. Transrectal ultrasonography is valuable for monitoring the response of prostate cancer to radiotherapy.