Therapeutic options in the management of incidental carcinoma of the prostate

Estimating the optimal external-beam radiotherapy utilization rate for genitourinary malignancies

BACKGROUND

Benchmark radiotherapy utilization rates for genitourinary malignancies are largely unknown, despite the finding that genitourinary cancers comprise approximately 19% of all registered malignancies in Australia.

METHODS

To develop an evidence-based benchmark of the optimal proportion of patients with genitourinary malignancies who should receive at least one course of radiotherapy at some time during their illness, the authors studied treatment guidelines and treatment reviews regarding genitourinary malignancies. Optimal radiotherapy utilization trees were constructed to show the clinical attributes that indicated possible benefit from radiotherapy based on evidence. Epidemiologic incidence data for each of these clinical attributes were obtained to calculate the optimal proportion of all patients with genitourinary cancer for whom radiotherapy was considered appropriate.

RESULTS

The proportion of patients with genitourinary malignancies for whom radiotherapy was indicated at some point in their illness, according to the best available evidence, was estimated to be 27% of patients with renal cancer, 58% of patients with bladder cancer, 60% of patients with prostate cancer, and 49% of patients with testicular cancer. The occurrence of ureteric and penile cancers among patients was too rare, and, therefore, these patients were not included in the current study.

CONCLUSIONS

There was a large discrepancy between actual radiotherapy utilization and the evidence-based optimal rate. The authors recommended strategies to implement the evidence-based guidelines. Evidence-based benchmarks for radiotherapy utilization rates such as the ones described in the current study were important in the evaluation of the appropriate use of radiotherapy.

Prostate cancer

This synthesis of the literature on radiotherapy for prostate cancer is based on 53 scientific articles, including 4 randomized studies, 3 prospective studies, and 44 retrospective studies. These studies involve 52005 patients. The literature provides no apparent evidence to motivate radiotherapy, or any treatment, for highly differentiated T0 tumors. Some findings suggest that radiotherapy or surgery may be indicated for poorly differentiated tumors. The literature however shows no differences in tumor effects between these two methods for treating T0 tumors. Radiotherapy is milder and less mutilating. Conclusions cannot be drawn from the literature concerning whether surgery (radical prostatectomy) or external radiotherapy is preferable for T1 and T2 tumors. Most probably, some patients are more suitable for surgery, others for radiotherapy. More patients are, nevertheless, candidates for radiotherapy. The value of external radiotherapy for T3 tumors is documented. Radiotherapy is valuable as palliative treatment for T4 tumors. Radiotherapy may be valuable as localized, symptom-relieving treatment for generalized prostate cancer. Treatment given via a few high fractions saves patients' time, hospitalization, and resources. Concerning individualized treatment, the differentiation grade is important for the choice of treatment method, mainly in early, but even in late clinical stages. This may involve choosing between radiotherapy and endocrine therapy, or even choosing between radiotherapy and surgery. The value of external radiotherapy increases as the differentiation grade of the tumor decreases. It is essential to treat patients at facilities that have the diagnostic potential to establish the differentiation grade of tumors. The value of postoperative radiotherapy has not yet been demonstrated at any clinical stage of prostate cancer. Treatment results from interstitial brachytherapy alone appear to be clearly inferior to the results from other methods. The value of combining interstitial/external radiotherapy should be studied further.

Prostate cancer

Prostate cancer is the most common noncutaneous malignancy diagnosed in American men, and in 1994 it will pass lung cancer as the most common cancer diagnosed in the United States, with an estimated 200,000 new cases. The molecular biology of prostate carcinogenesis is rapidly advancing, and it is clear that, to a degree, prostate cancer is a heritable disease. The use of serum prostate-specific antigen (PSA) as a screening tool has been widely accepted by the medical community, although the evidence to support the efficacy of screening is not yet available. The curative approaches to organ-confined, clinically localized prostate cancer include radiation therapy, radical prostatectomy, and close observation in selected patients. The absence of well-designed clinical trials contributes to the confusion surrounding which curative treatment is the best option in individual patients. The standard approach to patients with evidence of extracapsular spread without distant metastases has been external-beam radiotherapy, although the results with radiation therapy alone in these patients has left considerable room for improvement. Innovative combined-modality approaches are currently being investigated at a number of institutions for these poor-prognosis patients. Three-dimensional conformal radiation therapy is currently being investigated at multiple institutions and offers some hope for improved results. The treatment of metastatic disease remains hormonal manipulation, although the exact nature of optimal androgen deprivation is currently a matter of considerable debate. In patients with hormone-refractory disease newer regimens using novel chemotherapy regimens offer some promise.

Patient age as a prognostic factor in prostate cancer

Whether patient age per se is a prognostic factor of significance in prostate cancer is controversial. To investigate this issue age-specific relative survival was analyzed, and the number of years lost due to this disease was calculated in a large and unselected cohort of 6,890 prostate cancer patients diagnosed between 1971 and 1987 in the northern region of Sweden. The tumor grade was derived from filed notification forms, which showed 26.4% well (grade 1), 40.0% moderately (grade 2) and 17.7% poorly (grade 3) differentiated tumors. There was an overrepresentation of grade 3 tumors among the youngest patients. The age-specific relative survival rate did not differ significantly among different age groups and slight differences almost vanished when adjusting for tumor grade. This finding does not support the view that tumors appearing in younger patients are more aggressive per se. However, loss of life expectancy differed significantly among all age classes and in all 3 grades. In patients with grade 1 tumors the years lost due to prostate cancer ranged from 11.0 to 1.2 in the youngest and oldest age strata, even though the relative survival was approximately 0.70 in all age classes. It was concluded that even if relative survival is constant with patient age, the absolute impact of prostate cancer at different ages varied substantially as indicated by loss of life expectancy. This finding might indicate that younger prostate cancer patients should be given more aggressive treatment than older patients.

Patterns of radiotherapy for cancer patients in south-eastern Netherlands, 1975-1989

Radiotherapy patterns were determined in all 34,487 cancer patients diagnosed between 1975 and 1989 in south-eastern Netherlands, a densely populated and prosperous area with a greying population of almost 1 million inhabitants. Specialised care was available in 10 community hospitals with expanding staffs and in a non-academic radiotherapy centre, the distance never exceeding 50 km. With respect to western Europe the cancer incidence rates for this area were relatively high for males and average for females during this period. We computed overall and tumour-specific percentages of patients receiving radiotherapy as primary treatment (RT1a) and estimated this for initial treatment of recurrence or metastasis (RT1b). The total number of patients receiving RT1a increased by about 2% per year, but age-adjusted figures remained stable at 36% for females and increased from 28% to 32% for males. Since 1986 about 40% of all new cases receive RT1a and RT1b and about 40% of all RT1a undergo secondary radiotherapy for recurrence or metastasis. Of all male and female patients 70% and 50%, respectively, were over 60. Diverse underlying tumour-specific trends in RT1a were observed: children and adolescents with cancer received RT1a less often (25% vs. 40%) as did patients with cervical (55% vs. 80%), ovarian (9% vs. 17%), small cell lung (25% vs. 55%) and non-melanoma skin cancer (5% vs. 55%); patients with stage 1 breast (70% vs. 45%), rectal (30% vs. 10%) and prostate cancer (31% vs 13%) and adenocarcinoma of the lung (40% vs. 20%) received RT1a more often.(ABSTRACT TRUNCATED AT 250 WORDS)

Linear regressive analysis using prostate-specific antigen doubling time for predicting tumor biology and clinical outcome in prostate cancer

BACKGROUND

This study was undertaken to calculate the prostate-specific antigen doubling time (PSA-DT) of prostate cancers recurrent after external beam radiation therapy and to investigate if a correlation exists between the PSA-DT and the clinical behavior of prostate cancer as a possible reflection of the tumor doubling time.

METHODS

Twenty-two patients treated with external beam radiation between October 1985 and October 1990 for clinical stages B1, B2, and C (T2a, T2b, T3) prostate cancer experienced PSA elevation as their only sign of failure. Serial PSA determinations are available before initiation of any secondary treatment and these have been used to calculate PSA-DT.

RESULTS

The results of this study reveal that the PSA-DT is a constant (r > or = 0.98). Mathematically, this means the PSA value is growing exponentially and may represent tumor growth in the exponential phase. Second, the PSA-DT was found to be linearly correlated (r = 0.86) with the interval to clinical relapse after PSA failure. Graphically, the slope of this correlation is equal to the number of PSA-DT (4.5 with 95% confidence interval [3.6]) required before clinical disease manifests after PSA failure. Using this relationship, one can delineate those patients with aggressive tumor biology (PSA-DT < 3.8 months) who require immediate therapeutic intervention versus a relatively indolent tumor biology (PSA-DT > or = 3.8 months) who can be spared the morbidity and expense of androgen deprivation therapy until clinical recurrence manifests. Furthermore, in the pretreatment setting, observation rather than treatment may be indicated for patients with PSA-DT for 18 months or more, because the disease may not become clinically apparent during the patient's lifetime.

CONCLUSION

PSA-DT after radiation therapy may reflect the tumor doubling time and has implications in the posttherapy setting regarding the optimal time of intervention with androgen deprivation and in the pretreatment setting regarding the necessity for treatment rather than observation.

External beam radiotherapy for incidental adenocarcinoma of the prostate discovered at transurethral resection

This paper updates the results of 89 patients treated between 1967 and 1989 for incidental carcinoma discovered at transurethral resection of the prostate (Stanford stage T0 or AJC-UICC stage T1) with external beam irradiation. Twenty-two patients had Stanford T0 focal (less than 5% involvement of the prostatic chips) and 67 presented with Stanford T0 diffuse (5% or more involvement). Follow-up ranges from 4 months to 25.1 years, with a mean follow-up of 9.8 years. The actuarial local control for Stanford T0 focal is 100%, and 70% for Stanford T0 diffuse at 15 years. There was no difference in survival between Stanford T0 diffuse and T0 focal and the expected survival of an age-matched control population. Patients who were treated when younger than 65 had a similar local control and distant relapse when compared to those treated when 65 or older. There was no difference in local control, freedom from relapse, or disease-specific survival when the 38 patients who received irradiation to the prostate only are compared with the 29 who also received pelvic irradiation for Stanford T0 diffuse carcinoma. Patients with a Gleason score of 6 or more, when compared with those with a score of 5 or less, experienced more distant relapses and similar local control, suggesting that patients with a high grade tumor have occult metastases at presentation.