J.A. Cesaretti

Prognostic Significance of 5-Year PSA Value for Predicting Prostate Cancer Recurrence After Brachytherapy Alone and Combined With Hormonal Therapy and/or External Beam Radiotherapy

PURPOSEnTo analyze the prognosis and outcomes of patients who remain free of biochemical failure during the first 5 years after treatment.nnnMETHODS AND MATERIALSnBetween 1991 and 2002, 742 patients with prostate cancer were treated with brachytherapy alone (n = 306), brachytherapy and hormonal therapy (n = 212), or combined implantation and external beam radiotherapy (with or without hormonal therapy; n = 224). These patients were free of biochemical failure (American Society for Therapeutic Radiology and Oncology [ASTRO] definition) during the first 5 post-treatment years and had a documented 5-year prostate-specific antigen (PSA) value. The median follow-up was 6.93 years.nnnRESULTSnThe actuarial 10-year freedom from PSA failure rate was 97% using the ASTRO definition and 95% using the Phoenix definition. The median 5-year PSA level was 0.03 ng/mL (range, 0-3.6). The 5-year PSA value was <or=0.01 in 47.7%, >0.01-0.10 in 31.1%, >0.10-0.2 in 10.2%, >0.2-0.5 in 7.82%, and >0.5 in 3.10%. The 5-year PSA value had prognostic significance, with a PSA value of <or=0.2 ng/mL (n = 661) corresponding to a 10-year freedom from PSA failure rate of 99% with the ASTRO definition and 98% with the Phoenix definition vs. 86% (ASTRO definition) and 81% (Phoenix definition) for a PSA value >or=0.2 ng/mL (n = 81; p < .0001). The treatment regimen had no effect on biochemical failure. None of the 742 patients in this study developed metastatic disease or died of prostate cancer.nnnCONCLUSIONnThe results of this study have shown that the prognosis for patients treated with brachytherapy and who remain biochemically free of disease for >or=5 years is excellent and none developed metastatic disease during the first 10 years after treatment. The 5-year PSA value is prognostic, and patients with a PSA value <0.2 ng/mL are unlikely to develop subsequent biochemical relapse.

Urinary symptom flare after brachytherapy for prostate cancer is associated with erectile dysfunction and more urinary symptoms before implantation.

To examine the relationship of ‘symptom flare’ with sexual function and lower urinary tract symptoms (LUTS) before brachytherapy, as we noted that after brachytherapy for prostate cancer, some patients had recurrent LUTS after an asymptomatic period; this secondary exacerbation of symptoms (‘symptom flare’) occurred at ≈2u2003years after implantation and was transient in most patients.

SU‐FF‐T‐12: Comparison of Biological Effective Dose Between Protons and Seed Implant Plus IMRT for Prostate Treatment

Purpose: To use biological effective dose (BED) as a metric to compare the dosimetric difference between mixed modality photon treatment (LDR seed implant followed by IMRT treatment) and intensity‐modulated proton therapy (IMPT) for prostate cancer.Methods and Material: An in‐house program was developed to calculate the total BED for three patients who received mixed modality photon treatment (MMPT). These patients first received brachytherapy using Pd‐103 prescribed to a dose of 100 Gy to 90% of the prostate volume (112 Gy BED) followed by IMRT prescribed to a dose of 45‐Gy IMRT (85.5 Gy BED) to 95% of the PTV (6‐mm margin posteriorly and 1 cm elsewhere). To simulate IMPT, the inverse treatment planning system KonRad from German Cancer Research Center was used to design a two‐field opposed lateral IMPT plan delivered using the spot scanning technique and was prescribed to a total dose of 81 Gy to 95% of the PTV volume (153.9 Gy BED). Results: In all three cases, MMPT shows minimal difference in target coverage (98% of the prostate) compared to IMPT. MMPT had higher dose heterogeneity due to the high dose gradient close to the implanted seeds, but the areas of high dose are completely confined within the target borders The rectal and bladder biological effective DVH (BEDVH) both show that the histogram curve is higher for BEDs less than 100 Gy for MMPT compared to IMPT. The curves cross at 100 Gy and the MMPT histogram curve is lower than IMPT for all doses greater than 100 Gy. Conclusion: MMPT provides superior high BED (>100 Gy) normal tissue sparing compared to proton therapy for similar target coverage. In addition, considering the high‐cost of a proton facility, MMPT provides a more financially viable alternative to prostate cancer treatment.

SU‐GG‐T‐413: Combined Biological Effective Dose Based Treatment Planning for Low Dose Rate Prostate Brachytherapy and IMRT

Purpose:Brachytherapy with seed implants followed by intensity‐modulated radiotherapy provides an effective treatment for prostate cancer. However, it is difficult to quantify the effectiveness of the combined treatment because of the different dose rates of brachy and IMRT. We developed a simple pc‐based system using the α/β model for the biological effective dose (BED) as an additional quality index to evaluate treatment plans. Method and Materials:Dose grids and organ contours from a commercial brachy planning system (Variseed) and external beams systems (Eclipse and Brainscan) were exported to our in‐house system where physics doses were converted to BED. Iso‐BED derived from the brachy, IMRT, and the combined treatment of brachy + IMRT were displayed using our software. The in‐house system was implemented by using Interactive Data Language (IDL). The IDL provides the capability of importing treatment plans and the graphical interface for navigating the combined results. Results: Contours and isodose curves generated from the commercial software were unchanged after being transferred to the in‐house planning system. Iso‐BED curves were verified with hand calculation method. Our system allows users to customize the α/β values and iso‐BED curves, zoom in and out on each available plane, view BED‐volume histograms, and display 2D/3D at any angle to detail the target and normal tissuesdoses. Because BED is more appropriate to correlate with tissue injury, knowing the BED of the prior treatment, we can design dose‐mapping plans to compensate for under‐ or over‐dose regions in the previous treatments. Conclusion: This combined BED based treatment planning system will allow for clinicians to make more informed judgments regarding the therapeutic ratio of any given give treatment plan which uses two different modalities of radiotherapy delivery.