Quest for excellence: the ultimate goal of the radiation oncologist: ASTRO Gold Medal Address, 1992

Impact of Elapsed Treatment Time on Outcome of External-Beam Radiation Therapy for Localized Carcinoma of the Prostate

PURPOSE

The purpose of this study was to evaluate the impact of elapsed treatment time in external-beam radiation therapy for localized prostate carcinoma.

MATERIALS AND METHODS

The medical records of 1083 patients with localized prostate carcinoma treated between 1970 and December 1999 with external irradiation alone were reviewed. Median follow-up was 6 years (range, 4-24 years). Since 1987, prostate-specific antigen levels were obtained in 687 patients before the initiation of radiation therapy, and all patients seen in follow-up had prostate-specific antigen determinations. There were 344 patients with T1c, 496 with T2, and 243 with T3 tumors. The elapsed treatment time was divided into < or = 7, 7.1-9, or > 9 weeks. Local tumor control was determined by rectal examination and cause-specific survival or prostate-specific antigen failure according to American Society of Therapeutic Radiology and Oncology consensus criteria. Because of dose-escalation studies, tumor dose levels ranged from 66-73.8 Gy, given in 1.8- to 2-Gy fractions.

RESULTS

In patients with stage T1c, local failure ranged from 0% to 10% with doses < or = 72 Gy with; elapsed treatment time had no impact. No pelvic failures were detected in 88 patients receiving doses > 72 Gy. In patients with T2 who received < or = 70 Gy, overall pelvic failure rate was 4% (12/306) in those with an elapsed treatment time of < or = 9 weeks, in contrast to 27% (12/44) for those with an elapsed treatment time > 9 weeks; at 10 years, patients with T2 tumors treated in > 9 weeks had a higher actuarial pelvic failure rate (35%), in contrast to 5% to 18% with shorter treatment times. For patients with T2 tumors who received 70-72 Gy, pelvic failure rate ranged from 0% to 32%, and there were no failures in 37 patients treated to higher doses. In patients with prostate-specific antigen values whose tumors were stage T1c, the chemical failure rate was 41% (60/147) with a tumor dose < 70 Gy, compared with 17% (4/24) in those who received higher doses. In patients with stage 2 disease who were treated with < 70 Gy, the chemical failure rate was 31%, and the rate was 12%-18% in those who received higher doses. In stage T3, the clinical pelvic failure rate ranged from 25% to 32% in the three elapsed time groups, and the chemical failure rate ranged from 48% to 69%, and there was no significant correlation with elapsed time or total irradiation dose. Cause-specific survival without chemical failure in patients with stage T1c disease at 10 years was 85%-90% in the three elapsed treatment time groups. In patients with stage T2 disease, the corresponding values were 80% and 90% for elapsed treatment times < 9 weeks, in contrast to 65% for patients treated > 9 weeks. In patients with stage T3 disease, cause-specific survival was about 60% in all elapsed treatment groups. There was no significant correlation of elapsed treatment time with urinary or rectal morbidity.

CONCLUSIONS

Patients treated with radiation therapy for stage T2 localized prostate carcinoma showed a greater incidence of pelvic and chemical failures and a lower cause-specific survival when elapsed treatment time was > 9 weeks in comparison with the failure and survival rates occurring with shorter times. Higher doses of irradiation (> 72 Gy) eliminate the influence of prolongation of treatment time on outcome.

Three-Dimensional Conformal Therapy Versus Standard Radiation Therapy in Localized Carcinoma of Prostate: An Update

This study updates technical principles and results of 3-dimensional conformal radiation therapy (3D-CRT) in localized carcinoma of the prostate. Between January 1992 and December 1999, 312 patients were treated with 3D-CRT and 135 patients were treated with bilateral arcs standard radiation therapy (SRT) alone for clinical stage T1b-c or T2 histologically confirmed prostate cancer. None of these patients received hormonal therapy. Mean follow-up for patients in the 3D-CRT group was 3.2 years (range, 2-5.9 years) and for SRT patients, 4.7 years (range, 4-7 years). For 3D-CRT, 7 intersecting fields were used (cerrobend blocking or multileaf collimation) to deliver 68-74 Gy to the prostate. Standard radiation therapy consisted of bilateral 120 degree rotational arcs, with portals using 2-cm margins around the prostate to deliver 68-70 Gy to the prostate. The criterion for chemical disease-free survival was a postirradiation prostate-specific antigen (PSA) value following the American Society for Therapeutic Radiology and Oncology guidelines. Symptoms during treatment were quantitated weekly, and late effects were assessed every 4-6 months. Dose-volume histograms showed a two-thirds reduction with 3D-CRT in normal bladder or rectum receiving > or = 70 Gy with 3D-CRT. Higher 5-year chemical disease-free survival was observed with 3D-CRT (75%; for T1b-c and 79%; for T2 tumors) compared with SRT (61% and 65%, P = 0.01 and P = 0.12, respectively). There was no statistically significant difference in chemical disease-free survival in patients with Gleason score of < or = 4 (P = 0.85), but, with Gleason score of 5-7, the 5-year survival rates were 83% with 3D-CRT and 59% with SRT (P < or = 0.01). In 245 patients with pretreatment PSA of < or = 10 ng/mL treated with 3D-CRT, the chemical disease-free rate was 80% versus 72% in 98 patients treated with SRT (P = 0.21). In patients with PSA of 10.1-20 ng/mL, the chemical disease-free survival rate for 50 patients treated with 3D-CRT was 71% compared with 43% for 20 patients treated with SRT (P = 0.02). The corresponding values were 59% and 16%, respectively, for patients with PSA levels > 20 ng/mL (P = 0.09). On multivariate analysis, the most important prognostic factors for chemical failure were pretreatment PSA (P = 0.004), nadir PSA (P = 0.001), and 3D-CRT technique (P = 0.012). Moderate dysuria was reported by 2%-5% of patients treated with 3D-CRT in contrast to 6%-9% of patients treated with SRT. The incidence of moderate loose stools or diarrhea, usually after the fourth week of treatment, was 3%-5% in the 3D-CRT patients and 8%-19% in the SRT group. Late intestinal grade 2 morbidity (proctitis or rectal bleeding) was 1% in the 3D-CRT group in contrast to 7% in SRT patients. The 3D-CRT spares more normal tissues, yields higher chemical disease-free survival, and results in less treatment morbidity than SRT in treatment of stage T1-T2 prostate cancer. Follow-up at > or = 10 years is needed to confirm these observations.

Three-dimensional conformal therapy or standard irradiation in localized carcinoma of prostate: preliminary results of a nonrandomized comparison

PURPOSE

We present preliminary results of a nonrandomized comparison of three-dimensional conformal radiation therapy (3D CRT) and standard radiation therapy (SRT) in localized carcinoma of the prostate in two groups of patients with comparable prognostic factors treated during the same period.

METHODS AND MATERIALS

Between January 1992 and December 1997, 146 patients were treated with 3D CRT and 131 with SRT alone for clinical stage T1c or T2 histologically confirmed carcinoma of the prostate. None of these patients received hormonal therapy. Mean follow-up for all patients is 3 years (range, 1-6 years). For 3D CRT, 7 intersecting fields were used (Cerrobend blocking or multileaf collimation) to deliver 68-73.8 Gy to the prostate; 3D dose distributions and dose-volume histograms (DVHs) of the planning target volume, bladder, and rectum were obtained. SRT consisted of bilateral 120 degrees rotational arcs, with portals with 2-cm margins around the prostate to deliver 68-70 Gy to the prostate. The criterion for chemical disease-free survival was a postirradiation prostate-specific antigen (PSA) (Tandem-R, Hybritech) value following the American Society for Therapeutic Radiology and Oncology guidelines. Symptoms during treatment were quantitated weekly, and late effects were assessed every 4-6 months.

RESULTS

DVHs showed a two-thirds reduction in normal bladder or rectum receiving 70 Gy or more with 3D CRT. Higher 5-year chemical disease-free survival was observed with 3D CRT (91% for T1c and 96% for T2 tumors) compared with SRT (53% and 58%, respectively). There was no statistically significant difference in chemical disease-free survival in patients with Gleason score of 4 or less (p = 0.83), but with Gleason score of 5-7, the 5-year survival rates were 96% with 3D CRT and 53% with SRT (p < or = 0.01). In 111 patients with pretreatment PSA of 10 ng/mL or less, treated with 3D CRT, the chemical disease-free rate was 96% vs. 65% in 94 patients treated with SRT (p < or = 0.01). In patients with PSA of 10. 1-20 ng/mL, the chemical disease-free survival rate for 26 patients treated with 3D CRT was 88% compared with 40% for 20 patients treated with SRT (p = 0.05). The corresponding values were 71% and 26%, respectively, for patients with PSA levels of greater than 20 ng/mL (p = 0.30). On multivariate analysis, the most important prognostic factors for chemical failure were pretreatment PSA (p = 0. 023), nadir PSA (p = 0.001), and 3D CRT technique (p = 0.033). Moderate dysuria and difficulty in urinating were reported by 2-5% of patients treated with 3D CRT in contrast to 6-9% of patients treated with SRT; moderate urinary frequency and nocturia were reported by 18-24% treated with 3D CRT and 18-27% of patients in the SRT group. The incidence of moderate loose stools/diarrhea, usually after the 4th week of treatment, was 3-5% in the 3D CRT patients and 8-19% in the SRT group. Late intestinal morbidity (proctitis, rectal bleeding) was very low (1.7%) in the 3D CRT group in contrast to the SRT patients (8%).

CONCLUSION

Three-dimensional CRT spares more normal tissues, yields higher chemical disease-free survival, and results in less treatment morbidity than SRT in treatment of Stage T1-T2 prostate cancer. Longer follow-up is needed to confirm these preliminary observations.