Rectal morbidity after permanent prostate brachytherapy with dose escalation to biologic target volumes identified by SPECT/CT fusion

Purpose: To evaluate rectal morbidity after dose escalation to biologic target volumes identified by capromab pendetide (ProstaScint) single-photon emission tomography images coregistered with computed tomography (SPECT/CT). Methods and materials: Two hundred thirty-nine consecutive patients diagnosed with T1c-T3b NxM0 adenocarcinoma of the prostate were treated with brachytherapy seed implant (SI) dose escalation to SPECT/CT-identified biologic target volumes, from February 1997 through December 2002. Patients received SI (n = 150) or external beam radiation therapy plus SI (n = 89). Rectal morbidity was evaluated by clinician scoring using the modified Radiation Therapy Oncology Group criteria. The median followup was 47.2 (range 24.8-96.1) months. Results: The rate of acute Grades I and II toxicity was 29.9% and 3.7%, respectively, and chronic Grade I toxicity was 15.4%, 12.4%, 2.3%, and 1.8% at 1, 2, 3, and 4 years postimplant, respectively. Chronic Grade II toxicities were 1.8%, 1.9%, 1.5%, and 0.9% at 1, 2, 3, and 4 years, respectively. No Grade III rectal toxicity was reported. Chronic Grade IV rectal toxicity was 0.5% and 0.6% at 1.5 and 2.5 years, respectively. Ninety-six percent of patients reported freedom from all rectal toxicity after 3 years. Conclusions: Dose intensification to occult tumor targets without increasing rectal toxicity may be achieved using SPECT/CT ProstaScint. Additional research to define the role of molecular imaging in prostate cancer is warranted.