Phase II trial
A phase II study of localized prostate cancer treated to 75.6 Gy with 3D conformal radiotherapy

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Abstract

Background and purpose

To prospectively evaluate toxicity, biochemical failure-free survival (bFFS) and biopsy-proven local control for prostate cancer patients treated with 75.6 Gy in 42 fractions using 6-field conformal radiotherapy to prostate alone.

Patients and methods

From 1997 to 1999, 140 patients with T1-2NxM0, Gleason score ≤8, and PSA ≤20 ng/ml prostate cancer were assessed using Radiation Therapy Oncology Group acute and late toxicity scores. bFFS was determined for 120 patients treated without hormones. Post-treatment prostate biopsies were performed at a median of 3 years and a late toxicity questionnaire was administered at a median of 5 years.

Results

Clinically important acute toxicities were gastrointestinal (GI) grade 2: 22% and 3: 0%, and genitourinary (GU) grade 2: 24% and 3: 2%. Late physician-assessed toxicities were GI ≥grade 2: 2%, and GU ≥grade 2: 1%. The 3-year bFFS of patients failure-free before biopsy was 93% (95% CI: 83–100) from a negative biopsy and 22% (95% CI: 0–56) from a positive biopsy (P=0.001). Patients reported significantly more late toxicity than physicians (GI: P=0.003, GU: P<0.001). At 5.0 years median follow-up, cause-specific survival was 98% (95% CI: 96–100), overall survival was 91% (95% CI: 86–97), and bFFS was 55% (95% CI: 45–64).

Conclusions

75.6 Gy caused modest levels of acute and late toxicity. Three-year biopsies predicted subsequent biochemical outcome.

Section snippets

Patients

The research ethics board at the Princess Margaret Hospital approved the clinical trial protocol, and all patients provided written consent before participation. Between December 19, 1997 and August 10, 1999, 140 patients entered the study. Eligibility criteria included clinical T1b-c or T2a-b, NX, M0 (UICC, 1997 [23]) adenocarcinoma of the prostate, Gleason score ≤8, a presenting serum prostate-specific antigen (PSA) ≤20 ng/ml, and an Eastern Cooperative Oncology Group performance status of 0,

Acute and late toxicity

In the first week of RT, no patient had acute GU toxicity and only 1/140 had GI grade 1 toxicity, as assessed by physician. The highest grade of physician-assessed acute toxicity for the 8.5-week course of RT is shown in Table 2. One of the two patients whose treatment was stopped pre-maturely due to grade 3 acute bladder toxicity had been treated previously for in situ bladder transitional cell carcinoma using intravesical bacille Calmette-Guerin (BCG). Table 2 also shows the highest grade of

Acute toxicity

The acute toxicity experienced by the Study Cohort compared favourably with the RTOG 9406 Group 1 (prostate only) dose levels 1 (71.2 Gy) and 2 (76.7 Gy). The vast majority of patients in the Study Cohort experienced little or no acute toxicity, and grade 3 toxicity was rare with our 6-field conformal technique.

Late toxicity

The RTOG scoring system is a well-established method of recording late radiation normal-tissue effects; however, it does not identify chronic rectal bleeding well [2]. The Fox-Chase

Conclusion

Patients treated with 75.6 Gy experienced modest levels of acute and late GI and GU toxicity. Patient and physician-reported late toxicity differ significantly, and future reports should include patient-assessed late toxicity in comparison to baseline patient-assessed function. At a median follow-up of 5 years, the bFFS for this largely intermediate-risk group of patients was 55%. Biopsy results at 3 years post-treatment, with HMWK staining of basal cells, were highly predictive of subsequent

References (31)

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Meeting Presentation: European Society of Therapeutic Radiology and Oncology, Prague, Czech Republic, September 17–21, 2002. Abstract 357.

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