Biochemical Relapse Free Survival After External Beam Radiotherapy for Clinical Stage T1-3 Prostate Cancer in the PSA Era: What Should We Expect

English

Reviewer: Ryan Smith, MD
OncoLink
Ultima Vez Modificado: 6 de octubre del 2002

Presenter: Kuntia, Deepak
Presenter's Affiliation: Cleveland Clinic
Type of Session: Scientific

Background

Past studies in prostate cancer reflecting on Relapse Free Survival (RFS) have done so using the development of symptoms-either local or distant (usually by bone pain). It has differed as to whether this included radiographic evidence of disease without the development of symptoms. As prostate cancer is a relatively slow growing disease, it requires long follow-up. This fact, along with the widespread use of PSA within the past 15 years, means that there is a relative paucity of data concerning RFS using PSA as an endpoint from the start. This study reports of the bRFS (biochemical Relapse Free Survival) as determined by PSA failure in men with stage T1-3 prostate cancer treated by XRT.

Materials and Methods

The study group consisted of 1344 patients.
All patients had a pretreatment PSA value and GS (Gleason Score)
No patient received hormonal therapy of greater than 6 months
There was a minimum of 12 months of follow up with a median follow up of 51 months
T1/T2a patients made up 65% of the patients.
PSA values were well distributed among the patients, with the majority with values of 4-20
GS was well distributed among patients, with the majority with GS 6 or lower disease, though with 44% having GS 7 or greater

Results

15% were treated with doses of <68 Gy, 25% were treated with doses of 68-72 Gy, with 60% treated with doses >72 Gy (all delivered by conformal therapy or IMRT)
bRFS for all cases was 62% at 5 years and 59% at 7 years
T stage, PSA, and GS >7 were significant predictors of failure
Low risk patients (T1-2a, GS < 7, PSA <10) had an 80% bRFS
Intermediate risk patients (T2b, GS=7, PSA 10-20) had a bRFS of 60%
High risk patients (T3, GS > 7, PSA > 20) had a bRFS of 40-50%
Patients treated with conformal treatment or IMRT did better
Patients treated with doses >72 Gy did better, with a bRFS of >91%

Author's Conclusions

XRT dose was the most significant prognostic indicator, with doses less than 72 Gy inadequate for optimal control of disease
Classic prognostic indicators (T stage, PSA, GS) continue to also predict for outcome
Need further follow up to validate the data

Clinical/Scientific Implications

This study made the use of PSA values to determine bRFS in prostate cancer patients treated with XRT. Although PSA, GS, and T stage remain significant prognostic factors, the most significant prognostic factor in this study was radiation dose. Although the use of IMRT and conformal therapy was also linked to better outcome, this is simply a restatement of the fact that patients treated with higher doses do better than those treated with lower doses. However, because the patients treated with the higher doses of radiation therapy have a shorter follow-up then those treated in earlier years, these data must be viewed with some caution as with longer follow-up there will be more failures in the high dose patients. Taken as a whole, the survival figures from this study are relatively poor compared to what we have come to expect in the year 2002. However, it should be kept in mind that the majority of those who failed were treated with inadequate doses of XRT of less than 72 Gy (again with longer follow-up). Those that were treated with doses of greater than 72 Gy had a bRFS of >90%. Hence, XRT remains a valid option for the treament of prostate cancer, especially in the light of this study which had a large number of patients with high GS and higher PSA. Prospective studies with long-term follow-up evaluating dose escalation with radiation for the treatment of prostate cancer are needed to fully answer this question.

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