Nonrandomized evaluation of pelvic lymph node irradiation in localized carcinoma of the prostate.

PURPOSE

A great deal of controversy exists regarding the potential benefit of pelvic lymph node irradiation compared with treatment to the prostate only in patients with localized prostate cancer. Despite numerous reports, including a randomized study, this issue has not been completely elucidated.

METHODS AND MATERIALS

A total of 963 patients with histologically proven localized adenocarcinoma of the prostate treated with definitive radiation therapy alone were analyzed. Median follow-up was 6.5 years (minimum: 2 years, maximum: 22 years). Pelvic lymph nodes received 40 to 55 Gy with anteroposterior/posteroanterior and sometimes lateral stationary portals in 1.8 Gy daily fractions; an additional dose was delivered to the prostate with 120 degrees bilateral are rotation to complete doses of 65 to 68 Gy for Stage A2 and B tumors and 68 to 71 Gy for Stage C tumors. The same total doses were delivered with smaller fields when the prostate only was treated.

RESULTS

In Stage A2 (T1b,c) the 10-year clinical pelvic failure rate was 16% regardless of the volume irradiated or tumor differentiation. With Stage B (T2) well- or moderately differentiated tumors, the 10-year pelvic failure rates were 22% when pelvic lymph nodes were irradiated and 32% when prostate only was irradiated (p = 0.41). With Stage A2 (T1b,c) and B (T2) poorly differentiated tumors, the 10-year pelvic failure rates were 32% and 7%, respectively (p = 0.72). With clinical stage C (T3) well-differentiated tumors treated with 50 to 55 Gy to pelvic lymph nodes, the pelvic failure rate was 22% compared with 37% in those receiving 40 to 45 Gy (p < or = 0.07). A significant reduction in pelvic failures was noted with Stage C poorly differentiated tumors when the pelvic lymph nodes received doses higher than 50 Gy (23%) compared with lower doses (46%) (p < or = 0.01). Volume or doses of irradiation did not influence incidence of distant metastases in any stage or tumor differentiation group. Disease-free survival did not correlate with volume treated in any clinical stage or tumor differentiation group. In 317 patients on whom pretreatment prostate-specific antigen levels were available, there is a suggestion that those treated to the pelvic lymph nodes had a higher chemical disease-free survival than those receiving prostate irradiation only. Follow-up is short, and differences are not statistically significant in any of the groups. Morbidity of therapy was slightly higher in patients treated to the pelvic lymph nodes, but in Stages A2 (T1b,c) and B (T2) differences are not statistically significant (4 to 6%). Stage C patients treated to the pelvic lymph nodes with 50 Gy had a 12% incidence of Grade 2 rectosigmoid morbidity compared with 6% in those treated with 40 Gy (p = 0.26).

CONCLUSIONS

In this retrospective analysis, pelvic lymph node irradiation did not influence local/pelvic tumor control, incidence of distant metastases, or disease-free survival in patients with clinical Stage A2 (T1b,c) or B (T2) localized carcinoma of the prostate. In patients with Stage C (T3) disease, irradiation of the pelvic lymph nodes with doses of 50 to 55 Gy resulted in a lower incidence of pelvic recurrences and improved disease-free survival. Morbidity of therapy was acceptable, although patients with Stage C disease had a somewhat higher incidence of Grade 2 rectosigmoid morbidity. Pelvic lymph node irradiation is being elucidated in properly designed prospective, randomized protocols.