eMRI-measured prostate tumor changes show prognostic value

September 1, 2007

Tumor volume changes measured by endorectal magnetic resonance imaging (eMRI) independently predict PSA recurrence in men with intermediate or high-risk prostate cancer being treated with radiotherapy plus 6 months of androgen suppression therapy.

To determine whether changes in tumor volume measured with 1.5 Tesla eMRI were associated with biochemical recurrence, researchers from the National Cancer Institute-sponsored Cancer and Leukemia Group B (CALGB) 9682 study analyzed data from a CALGB study that enrolled 180 men with nonmetastatic T1c to T3c prostate cancer between May 1996 and April 2001. About three-fourths of the cohort had a Gleason score of 7 or higher, three-fourths of the men had palpable disease, and about 20% had locally advanced prostate cancer. Median baseline PSA was 10.7 ng/mL.

Excluding 15 ineligible men, the remaining study participants had eMRI at baseline and again after completing 2 months of AST. Change in tumor volume could be analyzed in 133 men, and eMRI progression during neoadjuvant AST, defined as a >10% increase in the volume of all lesions consistent with prostate cancer, occurred in 22 (17%) of those patients.

"These results indicate that eMRI allows early documentation of men with androgen-insensitive prostate cancer, and suggest it could be used to select patients for clinical trials aiming to evaluate the efficacy of non-AST-based approaches, such as docetaxel [Taxotere], combined with radiation for prolonging survival in men with hormone-refractory disease," said first author Anthony V. D'Amico, MD, professor and chief of genitourinary radiation oncology, Harvard Medical School, Boston.

Dr. D'Amico told Urology Times that a limitation of the study is that its design did not include re-measurement of PSA levels at the end of the first 2 months of neoadjuvant AST. Thus, it remains unknown whether eMRI is providing information independent of PSA kinetics or is acting as a surrogate for it.

"This is an important issue, because eMRI is expensive and PSA is not. However, during the years when men were being enrolled in this trial, the prognostic significance of PSA nadir was not yet recognized," he explained.

"It seems reasonable that eMRI and PSA are giving different information because the eMRI appears to identify hormone-refractory disease that is known to produce PSA differently than hormone-sensitive prostate cancer. Therefore, a hormone-refractory tumor could still be progressing even though PSA is undetectable."

Also notable was the finding that eMRI tumor progression occurred in 17% of men although the prostate shrunk after neoadjuvant AST in all patients.

"We have never thought of prostate cancer as disease that could be visualized radiographically. Perhaps with the perturbation of AST and the comparison of two scans, we may now be able to make some sense of prostate cancer in terms of imaging," Dr. D'Amico said.