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Prelimimary results of a randomized dose-escalation study comparing 70 Gy to 78 Gy for the treatment of prostate cancer

Albert DeNittis, MD
OncoLink Assistant Editor
Ultima Vez Modificado: 1 de noviembre del 1999

Presenter: Alan Pollack
Affiliation: MD Anderson Cancer Center

Summary:
- The purpose of this study was to compare the impact of 70 Gy versus 78 Gy on relapsing/rising PSA and biopsy positivity.

Methods:

• 298 patients were enrolled in a single institution randomized clinical trial comparing 70 Gy vs. 78 Gy in the treatment of prostate cancer.
• Patients were eligible if they had T1-T3 disease, no history of pelvic radiation therapy or androgen ablation
• Treatments consisted of 70 Gy using a four field technique. Initial fields were treated to 46 Gy to the whole pelvis with a boost to prostate and seminal vesicles with 24 Gy. The 78 Gy arm used a 6 field arrangement initially to 46 Gy with a boost to the prostate and seminal vesicles. The 76 Gy isodose line covered the prostate.

Results:

• Demographics were equal for both groups
• Median follow up was 40 months for the entire group and median PSA was 7.8
• Freedom from failure (FFF) at 5 years was 79% for 78 Gy compared to 69% for 70 Gy. This was of borderline statistical significance.
• Multivariate analysis demonstrated that PSA, stage, and gleason score were all significant factors.
  • T1/T2 patients had a FFF rate at 5 years of 87% for 78 Gy and 77 % for 70 Gy.
  • T3 patients had a 61% FFF for 78 Gy and 35% for 70 Gy.
  • For Gleason <6 the 5 year FFF was 93% and 75% for 78 Gy and 70 Gy respectively.
• Pretreatment PSA <10 was not significant. For PSA >10 there again was a significant FFF at 5 years. For 78 Gy it was 75% versus 48% for 70 Gy.
• In addition there was no significant difference in freedom from distant metastases (FFDM) for patients with PSA >10. However there was a trend which would suggest an effect on biochemical failure that translates into decreased DM.
• The probability of positive biopsy was not significantly different between the two groups. Both groups had a positive biopsy of 30%.

Clinical/Scientific Implications:

• The preliminary results of this dose escalation study indicate that for patients with PSA>10 or T1/T2 disease NED rates are improved
• In addition the data suggests a difference in FFDM
• It seems that for this study the intermediate risk patient benifits from dose escalation however further dose escalation studies are needed.

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