THE "NEW" PROSTATE CANCER INFOLINK

Prostate cancer reports from the 50th annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), held in Boston, have kindly been provided by Eyad Abu-Isa, MD, a resident in radiation oncology at the University of Michigan

This year’s scientific sessions concluded on Wednesday with two sessions focused on prostate cancer therapies and long-term outcomes and one afternoon session focused on quality of life outcomes.

In Wednesday’s morning session, Dr. Crook presented the final report of a Canadian Phase III study of pre-radiation androgen deprivation. In this study, 378 men with low-, intermediate-, and high-risk prostate cancer were randomized to 3 months or 8 months of hormone therapy prior to starting radiation treatment. A longer period of neoadjuvant hormone treatment did not alter patterns of failure. When data were evaluated by risk group stratification, the high-risk population appeared to have an improvement in disease-free survival at 5 and 7 years. Around 90 percent of patients had recovery of testosterone after completion of androgen deprivation, with a slight absolute improvement in levels with patients getting 3 months of hormonal therapy. This study presented interesting data, but will likely not influence patterns of practice. The radiation dose in this study was below the current standard dose.

In the same session, Dr. Zietman presented data from a prospective randomized phase I/II trial known as ACR 0312. In this study, 85 men with localized prostate cancer were treated with high-dose proton beam irradiation (82 Gy). Only toxicity data from this study are available so far. Toxicity rates were acceptable with a 6 percent risk of severe late toxicity (grade 3 or 4) at 2 years. No data on control rates were presented, as time is required for data to mature. An important question asked of Dr. Zietman at the end of his presentation was whether there are plans for a trial directly comparing proton beam therapy with photon beam therapy, as this has never been performed. He stated that work is in progress to initiate a multi-institutional randomized trial.

In the afternoon, Dr. Kuban updated the data on a randomized dose escalation trial comparing 70 to 78 Gy in patients with prostate cancer. At a median follow-up of 10 years, results of this study show that patients treated with high-dose radiation had decreased rates of PSA failure, nodal failure, and distant failure. Patients with high-risk features or PSA >10 ng/ml who were treated in the high-dose arm also had a reduced risk of dying of prostate cancer. Dr. Beckendorf presented data from the Getug 06 trial ( a similar French study). In this trial, 306 patents with localized prostate cancer were randomized to receive 70 or 80 Gy. With a median follow-up of 59 months, patients receiving the higher dose had improved biochemical control, especially when pre-treatment PSA was > 15 ng/ml. Current clinical practice is to treat to doses in the higher dose range used in these two trials, and is supported by the data from these two presentations.

Dr. Mirmiran presented toxicity data from a phase I/II trial of weekly paclitaxel, concurrent radiation, and androgen ablation in patients with high-risk prostate cancer. A tyotal of 59 patients were enrolled; 30 were treated post-prostatectomy, and 29 were treated for locally advanced disease. Toxicity data showed a low rate of severe toxicity with this tri-modality regimen. Data from randomized trials are needed to establish whether addition of paclitaxel will improve outcomes in patients at high-risk for failure when treated with standard regimens of radiation + androgen deptivation.

Treatment outcomes were also explored in today’s scientific sessions. Dr. Park presented data on long-term survivors of prostate cancer. Grade 2 or greater side effects from treatment had all resolved with a median time to resolution of 25 months. There was no increase in cardiovascular events in patients receiving or not receiving androgen deprivation therapy. Secondary malignancies (mainly bladder cancers) were seen in 5.6 percent of patients at a median time of 11 years post-treatment. Dr. Kurshan presented 10-year data on urinary function after low dose rate brachytherapy. The international prostate symptom scores (a measure of urinary symptoms) of patients improved steadily following seed implantation with no rebound in symptoms. Finally, Dr. Calcaterra presented 3-year bowel and bladder quality of life data on patients receiving external beam radiation, high-dose rate radiation, and low dose rate seed implantation. Acute urinary toxicity was greatest in the high dose rate group. At 6 months, urinary symptoms had improved, were similar between the 3three arms, and were lower than at the time of diagnosis. Bowel symptoms were worst at the completion of radiation, and improved with time. Use of androgen deprivation therapy had no effect on urinary or bowel symptoms. Erectile function declined throughout the first year of treatment and remained low through 3 years. By modality, high dose rate implants had the highest maintenance of erectile function, followed by external beam, followed by low-dose rate implants.

Overall, excellent scientific data have been presented at ASTRO over the past 3 days. These data confirm that radiation-based treatment of prostate cancer is on the right track (use of higher dose RT and anti-androgen therapy in the locally advanced population). Also presented were some exciting new and emerging ideas in prostate cancer. These data will undergo rigorous testing in the future to help further advance prostate cancer management.

This concludes our series of prostate cancer reports from ASTRO this year. The “New” Prostate Cancer InfoLink would like to publicly thank Dr. Abu-Isa for his excellent commentaries. We hope he will be willing and able to provide us with similar reports from other radiotherapy meetings in the future as his career progresses.

Filed under: Management, Treatment | Tagged: androgen deprivation, ASTRO, brachytherapy, external beam radiation |