Androgen ablation in addition to radiation therapy for prostate cancer: is there true benefit?

Survival benefit for early hormone ablation in biochemically recurrent prostate cancer

PURPOSE

To determine whether early initiation of androgen ablation in patients with biochemically recurrent prostate cancer, but without clinically evident metastases, is associated with improved overall or disease-specific survival. To describe subgroups, based on PSA kinetics, which are most likely to benefit from early androgen ablation.

MATERIALS AND METHODS

A retrospective cohort of 124 patients, who were definitively treated by external beam radiotherapy between 1988 and 1999, and subsequently received androgen ablation for biochemical (92 patients) or clinically metastatic (32 patients) failure, was reviewed. Median follow-up time was 6.2 years. Overall survival, disease-specific survival, and hormonal control were examined and compared for patients whose hormone ablation was started early (prostate-specific antigen [PSA] <or=15 ng/ml or PSA doubling time >7 months) or late in the course of their biochemical failure.

RESULTS

All patients had biochemical response to hormone initiation, with a median PSA nadir of 0.05 ng/ml. Early initiation of hormone ablation resulted in statistically significant improvement in all outcome measures. Multivariate analysis indicated that PSA doubling time at hormone initiation was the most consistent predictor of outcome. The 5-year overall survival was 78% for patients whose androgen ablation was initiated at doubling time <or=7 months and 93% for patients when initiated at doubling time >7 months. Mean survival improved from 84.9 +/- 4.6 (doubling time <or=7) to 115.3 +/- 8.4 months (doubling time >7). Survival for patients started on hormones with doubling time <5 months was similar to that of patients with clinical metastases.

CONCLUSIONS

This survival benefit justifies the use of androgen ablation in patients whose doubling time approaches 7 months. A randomized trial is needed to confirm these findings, investigate potential benefit for patients with longer doubling times, and gather data on the morbidity of early hormone ablation, including quality of life issues.

Report of a multicenter Canadian phase III randomized trial of 3 months vs. 8 months neoadjuvant androgen deprivation before standard-dose radiotherapy for clinically localized prostate cancer

PURPOSE

To evaluate the effect of 3 months vs. 8 months of neoadjuvant hormonal therapy before conventional dose radiotherapy (RT) on disease-free survival using prostate-specific antigen PSA and biopsies as end points for clinically localized prostate cancer.

METHODS AND MATERIALS

Between February 1995 and June 2001, 378 men were randomized to either 3 or 8 months of flutamide and goserelin before conventional-dose RT (66 Gy) at four participating centers. The median patient age was 72 years (range, 50-84 years). The stage distribution was 17% T1c, 35% T2a, 34% T2b-T2c, 13% T3-T4. The Gleason score (GS) was < or =6 in 51%, 7 in 38%, and 8-10 in 11%. The median baseline PSA level was 9.7 ng/mL (range, 1.3-189 ng/mL). Of the 378 men, 26% were low risk (Stage T1c-T2a, GS < or =6, PSA <10 ng/mL), 43% were intermediate risk (Stage T2b or GS 7 or PSA 10-20 ng/mL), and 31% were high risk (Stage T3 or GS 8-10 or PSA >20 ng/mL). The two arms were balanced in terms of age, GS, T stage, risk group, and presenting PSA level. The median follow-up was 44 months (range, 10-84 months), and 361 patients were available for evaluation.

RESULTS

The 8-month arm achieved a lower PSA level before starting RT (0.37 vs. 0.74 ng/mL, p < or =0.001) and had a greater downsizing of the prostate (mean volume 26.6 cm(3) vs. 30.5 cm(3), p < or =0.001). However, the actuarial freedom from failure rate (biochemical by American Society for Therapeutic Radiology and Oncology definition, local or distant) for the 3-month vs. 8-month arms at 3 years was 66% vs. 68% and by 5 years was 61% vs. 62%, respectively (p = 0.36). No statistically significant difference was noted in the types of failure between the two arms (crude final status): biochemical, 22.2% vs. 22.3%; local, 10.2% vs. 6.5%; and distant, 3.4% vs. 4.4% (p = 0.61). Two-year post-RT biopsies were done in 57% (n = 205). Negative biopsies were obtained in 68% of the 3-month and 77% of the 8-month patients; 18% and 14% had indeterminate biopsies and 14% and 9% were positive for residual cancer (p = 0.34) in the two arms, respectively. The median PSA level for nonfailing patients was 0.50 ng/mL in both the 3-months and 8-month arms. A suggestion of improvement was found in the 8-month arm for disease-free survival at 5 years for high-risk patients (39% vs. 52%) but did not achieve statistical significance.

CONCLUSION

A longer period of neoadjuvant hormonal therapy before standard-dose RT does not appear to confer a benefit in terms of disease-free survival or to alter failure patterns. Failure was delayed in the 8-month arm, but this advantage was lost by 5 years of follow-up. A suggestion of benefit was noted with a longer period of hormonal therapy for high-risk patients.

Value of endocrine therapy for early and locally advanced prostate cancer

Prostate-specific antigen-based screening and increased public awareness of prostate cancer have led to earlier detection of localised and potentially curable tumour stages. Nevertheless, disease recurrence after radical treatment of prostate cancer remains a problem for a considerable number of patients. Endocrine therapy plays a role in the treatment of almost all stages of prostate cancer, either as definitive or as temporary therapy. Neoadjuvant hormonal treatment has its place mainly in the external beam radiotherapy setting, where it reduces target volume and adverse effects. When used prior to and during external beam radiotherapy, endocrine therapy has shown a survival advantage in the subset of patients with locally advanced prostate cancer (cT2-4, N0-1, M0) with Gleason scores 2-6. Several studies have shown that adjuvant endocrine treatment is able to delay disease progression in any stage. There is, however, an ongoing controversy regarding the possible survival benefit of such treatment that has to be balanced against its considerable adverse effects and costs. Survival improvements associated with adjuvant hormonal treatments have mainly been seen in patients with lymph node metastases or those with a high probability of micrometastatic disease. Several large studies are under way to investigate the role of adjuvant treatment in the field of early prostate cancer.

Primary radiation therapy for localized prostate cancer

Prostate cancer in men is similar to breast cancer in women; both cancers rank first, respectively, in incidence and are normally responsive to radiation therapy. In addition, advances in mammography help detect earlier breast cancers, and the development and refinement of prostatic specific antigen (PSA) has resulted in early detection of low-stage localized prostate cancers. This has generated debate over the proper management of localized prostate cancer. While there have not been any controlled, prospective, randomized trials of sufficient power to compare the various local therapies, based on the current available data, the three commonly used local modalities, surgery, and external beam radiation therapy and brachytherapy (radioactive seed implant), have similar efficacy controlling the disease up to 10 years in many patients. Technological advances in treatment delivery and planning have improved the treatment of prostate cancer with external-beam radiotherapy using three-dimensional conformal radiotherapy (3DCRT), ultrasound-guided transperineal implant, or intensity-modulated radiotherapy (IMRT), as well as proton or neutron beam based therapies.

Signaling for the caspases: their role in prostate cell apoptosis

PURPOSE

The caspases are an evolutionary conserved family of cell death proteases. Their activation during apoptosis is an important underlying theme in prostate cancer therapy. We summarize the signaling pathways leading to the recruitment of the caspases and address the importance of recent therapeutic strategies aimed at specifically targeting these proteases in relation to prostate cancer.

MATERIALS AND METHODS

We present a background introduction into the role of the caspases in apoptosis and how failure to signal effectively their activation may contribute to prostate cancer progression. Key studies aimed at specifically targeting the caspases as cancer therapy are discussed.

RESULTS

Prostate carcinogenesis and apoptosis are related. The deregulation of apoptosis contributes to tumor initiation, metastasis and progression to the androgen insensitive state. Conversely the effectiveness of therapy often depends on its ability to induce apoptosis in prostate cancer cells. Identifying abnormalities in the apoptotic signaling pathway has greatly contributed to understanding the biology of prostate cancer. Elucidating caspase regulation has contributed to the design of novel therapies for prostate cancer.

CONCLUSIONS

We summarize the physiological and pathological pathways leading to caspase activation in the prostate and describe novel approaches that target these proteases.

Importance of high radiation doses (72 Gy or greater) in the treatment of stage T1-T3 adenocarcinoma of the prostate

OBJECTIVES

To analyze the effect of total radiation dose on the outcome of patients treated with external beam radiotherapy for early-stage prostate cancer.

METHODS

The records of a total of 738 patients with localized prostate cancer treated with external beam radiotherapy (RT) and no androgen deprivation at our institution between July 1986 and February 1999 were reviewed. Two risk groups were defined: favorable (Stage T1-T2, pretreatment prostate-specific antigen [PSA] level 10.0 ng/mL or less, and biopsy Gleason score 6 or less) and unfavorable (Stage T3 lesion or pretreatment PSA level greater than 10.0 ng/mL or biopsy Gleason score 7 or greater). The median RT dose was 70.0 Gy (range 57.6 to 78.0), with 192 patients (26%) receiving at least 72.0 Gy. The mean follow-up was 45 months.

RESULTS

The 5-year biochemical relapse-free survival (bRFS) rate was 58%. The 5-year bRFS rate for patients who received radiation doses of 72 Gy or greater versus less than 72 Gy was 85% and 54%, respectively (P <0.001). On multivariate analysis of factors affecting bRFS rates, the number of follow-up PSA levels (P <0.001), tumor stage (P <0.001), pretreatment PSA (P <0.001), biopsy Gleason score (P <0.00 1), and RT dose (P = 0.001) were the only independent predictors of outcome. For favorable tumors, the 5-year bRFS rate for patients who received radiation doses of 72 Gy or greater versus less than 72 Gy was 98% and 81 %, respectively (P = 0.023). For unfavorable tumors, the 5-year bRFS rate for patients who received radiation doses of 72 Gy or greater versus less than 72 Gy was 75% and 41 %, respectively (P = 0.001).

CONCLUSIONS

Patients receiving radiation doses of 72 Gy or higher had a significantly better outcome. The improvement was seen in all subgroups of patients. If these results are confirmed, radiation doses exceeding 72 Gy should be considered the standard of care. Inc.

Neoadjuvant therapy in localized prostate cancer before surgery and radiotherapy

Neoadjuvant hormonal therapy brings the possibility of improving the results of radical treatment of clinically localized prostate cancer. While the advantages of this therapy combined with radiotherapy and cryosurgery are encouraging, as yet the positive effects of initial hormonal ablation before radical prostatectomy are still not proven.