Changing trends in national practice for external beam radiotherapy for clinically localized prostate cancer: 1999 Patterns of Care survey for prostate cancer

Abstract

Purpose: To report changing trends in external beam radiotherapy (EBRT) delivery practice for clinically localized prostate cancer as determined from the 1999 survey from the American College of Radiology National Patterns of Care Study.

Methods and materials: The 1999 survey included a weighted sample of 36,496 patient records obtained from a stratified two-stage sample of 554 patient records. Patients were surveyed from 58 institutions and were treated between January 1999 and December 1999. Of these, 36% (weighted sample size, 13,293; unweighted sample size, 162) were treated with brachytherapy with or without EBRT and 64% (weighted sample size, 23,203; unweighted sample size, 392) were treated with EBRT only. The latter group is the subject of this report. The following trends in clinical practice were analyzed according to prognostic risk groups and other variables and compared with the results of the prior surveys: use of androgen deprivation therapy (ADT) in combination with EBRT, higher prescription dose levels, and administration of elective whole pelvic RT (WPRT).

Results: The incidence of ADT use for favorable, intermediate, and unfavorable-risk groups was 31%, 54%, and 79%, respectively. A multivariate logistic regression analysis revealed a statistically significantly increased likelihood of intermediate (p = 0.001) and unfavorable (p <0.0001) risk groups treated with ADT in conjunction with EBRT compared with favorable-risk patients. ADT use was more prevalent among treated patients in the 1999 survey than in the 1994 survey (51% vs. 8%, p <0.0001). Compared with the prior survey, a greater percentage of patients were treated with higher radiation doses in the 1999 survey (> or =72 Gy, 45% in 1999 vs. 3% in 1994, p <0.0001). In the 1999 survey, the proportion of patients with favorable, intermediate, and unfavorable tumors treated to doses > or =72 Gy was 43%, 38%, and 60%, respectively, compared with 4%, 3%, and 1%, respectively, in the 1994 survey. Compared with the 1994 survey, a large increase in the number of patients treated with brachytherapy (36% vs. 3%, p <0.0001). The frequency of WPRT use decreased from 92% in 1989 to 52% in 1994 to 23% in 1999. For the 1999 survey, a multivariate analysis indicated that unfavorable-risk patients (p = 0.016) and intermediate-risk patients (p = 0.018) were more likely to be treated with WPRT compared with favorable-risk patients. Nevertheless, even among unfavorable-risk patients, a substantial decline had occurred in the use of WPRT for the 1999 survey (70% for the 1994 survey compared with the 31% for the current survey; p = 0.003).

Conclusion: The significantly increased use of ADT for high-risk patients and higher radiation doses, especially for intermediate- and high-risk patients, reflects the penetration and growing acceptance of clinical trial results that have demonstrated the efficacy of these treatment approaches. The relatively high proportion of favorable-risk patients treated with high radiation dose levels was greater than expected. A large increase in brachytherapy was observed compared with prior surveys. Most treated patients with high-risk disease did not undergo elective WPRT, which likely reflects the influences of prior trials, stage migration, and the commonly held belief that WPRT provides minimal benefit in the setting of higher radiation doses.