Transrectal ultrasound for staging prostate carcinoma prior to radiation therapy: an evaluation based on disease outcome.

BACKGROUND: Despite its subjectivity and inaccuracy, digital rectal examination (DRE) has a long history of well-documented prognostic significance in patients with prostate carcinoma. To the authors' knowledge, very few studies have evaluated the relative prognostic merits of transrectal ultrasound (TRUS) versus DRE. This question is addressed in this study. METHODS: The outcome for 558 men with T1-T3, N0, M0 adenocarcinoma of the prostate who underwent both DRE and TRUS and received external beam radiation without androgen ablation was evaluated relative to the prognostic information from DRE, TRUS, or both. The outcome endpoints were no evidence of disease (NED) (no relapse or rising prostate specific antigen level) and freedom from metastases. Prognostic factors were evaluated with univariate and multivariate techniques. The median follow-up was 55 months. RESULTS: Both purely DRE-based and purely TRUS-based T categories correlated significantly with NED status. For DRE T categories, 6-year NED rates for T1/T2 and T3 disease were 64% and 36%, respectively (P < 0.001). For TRUS T categories, the rates for T1/T2 and T3 were 63% and 39%, respectively (P < 0.001). There were significant differences in patient composition between DRE and TRUS T categories. Only 40% of patients were in the same DRE and TRUS category, but the majority of the reclassification based on TRUS was within rather than between major T categories (T1/T2 vs. T3). Changes between the prognostically significant T1/T2 versus T3 categories occurred in < or =25%. This accounted for the similarity in NED outcome for DRE and TRUS T categories. However, TRUS categories did not discriminate significantly for metastatic recurrence between T1/T2 and T3 categories, whereas DRE categories did. Upstaging or downstaging by TRUS relative to DRE did not alter the DRE prognostic groupings substantially. CONCLUSIONS: There was no clinically meaningful superiority of TRUS over DRE in the definition of prognostically useful T categories. Moreover, the addition of TRUS to DRE did not enhance the prognostic value of DRE findings in any meaningful way. Despite its subjectivity and inaccuracy, DRE provides prognostic information at least equivalent to TRUS and is preferable because of its low cost.

Relationship of ultrasound staging and bilateral biopsy positivity to outcome in stage T1c prostate cancer treated with radiotherapy.

OBJECTIVES: The strict definition of Stage T1c prostate cancer is that the tumor is not palpable on digital rectal examination (DRE) or seen on imaging studies such as ultrasound. The inclusion of ultrasound imaging was brought about without an understanding of the relationship between ultrasound upstaging and prognosis. We have also noticed that in clinical practice, treatment decisions are made on the basis of the finding of bilateral versus unilateral biopsy positivity. The objectives in this study were to determine the prognostic significance of upstaging by transrectal ultrasound (TRUS) to uT2 or uT3, and unilateral versus bilateral biopsy positivity in patients with Stage T1c cancer as determined by DRE (DRE-Stage T1c patients). METHODS: Between 1987 and 1995 there were 643 patients with DRE-Stage T1-T2 prostate cancer treated with external beam radiotherapy; 24 had T1a, 76 had T1b, 183 had T1c, 133 had T2a, 168 had T2b, and 59 had T2c. Of these, 135 DRE-Stage T1c patients underwent ultrasound staging and 122 underwent bilateral prostate biopsies. All had pretreatment prostate-specific antigen values (PSAs) available and no patient received adjuvant androgen ablation. The median pretreatment PSA was 9.1 ng/mL, median radiotherapy dose was 66.0 Gy, and median follow-up was 41 months. Post-treatment failure was defined as disease recurrence and/or two elevations in PSA on consecutive follow-up visits. RESULTS: The 5-year freedom from failure rate for DRE-Stage T1c patients (71%) was not significantly different from that of DRE-Stage T1b (65%) or DRE-Stage T2a (71%) patients. There was a trend (P = 0.1) toward a worse outcome for DRE-Stage T2b/T2c patients compared with DRE-Stage T1b/T1c/T2a patients. The distribution of DRE-Stage T1c patients by ultrasound staging was 29 with uT1c, 88 with uT2, and 18 with uT3 findings. Twenty percent of patients had bilateral positive biopsy specimens. In univariate and multivariate analyses, the only correlates of patient outcome were pretreatment PSA (P < or = 0.002) and isocenter dose (P = 0.03). TRUS upstaging had no effect on freedom from failure; uT1c patients had about the same risk of relapse or a rising PSA as uT2 or uT3 patients. Patients with bilateral positive prostate biopsy specimens had about the same prognosis as those with unilateral positive biopsy specimens. CONCLUSIONS: For patients with DRE-Stage T1c prostate cancer, the data indicate that ultrasound staging and bilateral biopsy positivity are not predictive of outcome for patients treated with external beam radiotherapy and treatment decisions should not be based on these parameters.

Prostate-specific antigen cancer volume: a significant prognostic factor in prostate cancer patients at intermediate risk of failing radiotherapy.

PURPOSE: Although the pretreatment serum prostate-specific antigen level (PSAL) is the single-most significant predictor of local and biochemical control in prostate cancer patients treated with radiotherapy, it is relatively insensitive for patients with a PSAL in the intermediate range (4-20 ng/ml). PSA density (PSAD) has been shown to be slightly more predictive of outcome than PSAL for this intermediate risk group; however, this improvement is small and of little use clinically. PSA cancer volume (PSACV), an estimate of cancer volume based on PSA, has recently been described and has been purported to be more significant than PSAL in predicting early biochemical failure after radiotherapy. We report a detailed comparison between this new prognostic factor, PSAL, and PSAD. METHODS AND MATERIALS: The records of 356 patients treated with definitive external beam radiotherapy for regionally localized (T1-4,Nx,M0) adenocarcinoma of the prostate were reviewed. Each patient had a PSAL, biopsy Gleason score, and pretreatment prostate volume by transrectal ultrasonography. The median PSAL was 9.3 ng/ml and 66% had Gleason scores in the 2-6 range. The median radiation dose was 66.0 Gy and the median follow-up for those living was 27 months. PSACV was calculated using a formula which takes into account PSAL, pretreatment prostate ultrasound volume, and Gleason score. The median PSACV was 1.43 cc. Biochemical failure was defined as increases in two consecutive follow-up PSA levels, one increase by a factor > 1.5, or an absolute increase of > 1 ng/ml. Local failure was defined as a cancer-positive prostate biopsy, obtained for evidence of tumor progression. RESULTS: The distributions of PSACV and PSAL were similar and, when normalized by log transformation, were highly correlated (p < 0.0001, linear regression). There was a statistically significant relationship between PSACV and several potential prognostic factors including PSAL, PSAD, stage, Gleason score, and pretreatment prostatic acid phosphatase (PAP). In univariate analyses, PSACV, PSAL, and PSAD proved to be the most significant predictors of both biochemical and local control. In multivariate analyses using Cox proportional hazards models with PSAL, PSAD, PSACV, and PAP as continuous variables, PSAL, PSACV, and Gleason score were significant in predicting biochemical control. Only PSAL was significantly correlated with local control. However, when these analyses were restricted to patients with intermediate PSALs (4-20 ng/ml), only PSACV was significant for predicting both biochemical and local control. CONCLUSION: PSACV was highly correlated with actuarial local and biochemical control and was superior to both PSAL and PSAD in predicting these outcomes in patients with PSALs between 4 and 20 ng/ml.

Radiotherapy for regionally localized hormone refractory prostate cancer.

PURPOSE: Patients with regionally localized hormone refractory adenocarcinoma of the prostate are often referred for radiotherapy to relieve local symptoms, prevent further local progression, or prevent impending urinary tract obstruction. However, the merits of radiotherapy for this patient population have not been documented. In this retrospective series, the results of 29 such patients treated at our institution between 1987-1992 are reviewed. METHODS AND MATERIALS: Prior to androgen ablation, the majority of these patients (79%) had Stage D0 or D1 disease. After androgen ablation, radiotherapy was given to 16 (55%) for progressive symptoms (mostly urinary obstructive), 11 (38%) for palpable local progression in the absence of symptoms, and 2 for a rising prostate specific antigen (PSA) profile without palpable disease. None of the patients had distant metastasis at the time of radiotherapy. The median dose to the prostate was 66 Gy and the median follow-up after radiotherapy was 43 months. RESULTS: Following local-regional radiotherapy, the actuarial rate of local failure at 4 years was only 39%. However, 80% had disease progression or a rising PSA in this time period. The actuarial survival at 4 years following radiotherapy was 39%. Univariate analyses of potential prognostic factors revealed that preandrogen ablation Gleason score, preradiotherapy PSA, and preradiotherapy prostatic acid phosphatase (PAP) were predictive of patient outcome. Most importantly, doses above 60 Gy to the prostate at standard fractionation were associated with symptom-free local control in 90% of patients at 3 years. The majority of the patients were treated using limited fields (n = 20). CONCLUSIONS: The regionally localized hormone refractory prostate cancer patients described benefited from high dose, continuous course, local radiotherapy in that excellent local control rates were obtained for an extended period. Because the majority of these patients fail with distant metastasis within 4 years, this treatment represents an aggressive approach to palliation that is justified by the maintenance of freedom from local symptoms.

Potential effects of age-specific reference ranges for serum prostate-specific antigen.

Age-specific reference ranges for serum prostate-specific antigen (PSA) may improve this test for detecting prostate cancer. We have analyzed PSA levels from 10,024 men to determine the potential effects of these reference ranges. PSA levels (ng/ml) were grouped by patient age for comparison between standard (all ages: PSA < or = 4.0) and age-specific (< or = 49 years: PSA < or = 2.5; 50-59 years: PSA < or = 3.5; 60-69 years: PSA < or = 4.5; > or = 70 years: PSA < or = 6.5) reference ranges. Serum PSA correlated significantly with age (r = 0.33; p < 0.001). Fewer men > or = 60 years had elevated levels when age-specific reference ranges were applied (1,373 vs. 1,967; p < 0.001). Prostate biopsies and prebiopsy PSA levels from 865 men were reviewed. Sensitivities and specificities were calculated using both reference ranges. A significant increase in specificity with the age-specific reference ranges was seen for men > or = 70 years (58.6 vs. 34.2%; p < 0.001). There was, however, a concomitant decrease in sensitivity (77.6 vs. 91.7%; p < 0.001). We conclude serum PSA increases with age and we support the concept of age-specific reference ranges. However, the specificity of this test remains low, illustrating its limitations for prostate cancer detection.

Transmembrane domain length affects charge-mediated retention and degradation of proteins within the endoplasmic reticulum.

Previous studies have shown that the presence of potentially charged amino acid residues within the transmembrane domains of type I integral membrane proteins can result in protein retention and, in some cases, degradation within the endoplasmic reticulum (ER). An apparent exception to this observation is the CD3-epsilon chain of the T-cell antigen receptor complex, which is relatively stable in spite of having a transmembrane aspartic acid residue. A chimeric protein (T epsilon T) made by replacing the transmembrane domain of the Tac antigen with that of CD3-epsilon was normally transported to the cell surface, indicating that the transmembrane domain of CD3-epsilon was essentially unable to confer the phenotype of ER retention and degradation to another protein. Progressive shortening of the T epsilon T transmembrane domain, however, resulted in increasing retention and degradation of the mutant proteins in the ER. Conversely, a mutant Tac protein containing a single aspartic acid residue in its transmembrane domain was found to be retained and degraded in the ER, but when the transmembrane domain was lengthened, ER retention and degradation of the protein were abrogated. The aspartic acid residue in the transmembrane domain of all of these mutant proteins could mediate assembly with another protein having an arginine residue in its transmembrane domain, independent of the length of the transmembrane sequence. These findings demonstrate that the length of the hydrophobic transmembrane sequence has a critical influence on the ability of potentially charged transmembrane residues to cause protein retention and degradation in the ER.

Changes in cytochrome oxidation in outer and inner stripes of outer medulla.

To examine regional cytochrome oxidation in the outer medulla, we developed fiber optic probes that allowed us to obtain localized reflectance measurements from the outer and inner stripes of the outer medulla. We measured directional changes in cytochrome oxidation in these two regions. In the outer stripe furosemide surprisingly caused a significant decrease in cytochrome oxidation. The decrease occurred concomitantly with a fall in outer medullary blood flow as measured by laser-Doppler flowmetry. Saralasin, an antagonist of angiotensin II caused a significant increase in cytochrome oxidation in the outer stripe. In the inner stripe furosemide tended to increase cytochrome oxidation, and saralasin had no effect. These results indicate that the two regions of the outer medulla may be affected differently by the same agent. They suggest that cytochrome oxidation in the outer stripe is predominantly influenced by outer medullary blood flow, whereas the inner stripe is predominantly influenced by the rate of oxygen consumption. The advantages and limitations of this methodology are discussed.

Renal tubular actions of ANF.

Many of the earliest investigations of the renal effects of atrial natriuretic factor (ANF) pointed to the glomerulus as a major site of the peptide's action. More recently, there have been many reports showing various effects of ANF on renal tubular epithelia, including collecting ducts, thick ascending limbs of Henle's loop, thin limbs of Henle's loops, and proximal tubules. The purpose of this review is to summarize the evidence for renal tubular actions of ANF and analyze it from the perspective of the specialized functions of the individual nephron segments, addressing the question: can renal tubule effects of ANF play a significant role in the precise day-to-day regulation of renal NaCl and water excretion? Based on these considerations, we propose that long-term renal tubular action of ANF may be distinct from its short-term natriuretic effect. The short-term action of ANF to accelerate salt and water excretion may play a role in the overall response to acute volume overload. This action of ANF appears to be largely due to an ANF-mediated increase in glomerular filtration rate accompanied by a blunting of the tubuloglomerular feedback mechanism, perhaps with some contribution from ANF-mediated inhibition of fluid absorption in the proximal tubule. In contrast, contributions of ANF to the precise day-to-day regulation of salt and water excretion are likely to be chiefly due to ANF-mediated inhibition of NaCl and water absorption in collecting ducts, but may also involve actions of ANF on the loop of Henle.

Regulation of collecting duct water permeability independent of cAMP-mediated AVP response.

We have used the isolated perfused tubule technique, measurements of adenosine 3',5'-cyclic monophosphate (cAMP) content in single tubules, and freeze-fracture electron microscopy to study the basis of high vasopressin-independent (basal) osmotic water permeability (Pf) in the terminal inner medullary collecting duct (IMCD) of the rat. The results confirmed the observation that the basal Pf of the terminal IMCD is considerably higher than that of the initial IMCD. They also showed that the basal Pf of the terminal IMCD is regulated by in vivo factors related to water intake, such that a very high vasopressin-independent Pf can be induced in isolated tubules by prior in vivo thirsting. Tubules from thirsted rats did not display elevated urea permeabilities, nor did they exhibit measurable cAMP levels in the absence of exogenous vasopressin, indicating that the high basal Pf was not due to residual binding of vasopressin to its receptors. Freeze-fracture studies in thirsted rats demonstrated the presence of intramembrane particle (IMP) clusters in both initial and terminal IMCD, with more in the latter. Water loading of the rats suppressed the incidence of clusters almost entirely but did not fully suppress the basal Pf in the terminal IMCD, raising the possibility that a component of transepithelial water transport may occur independently of the vasopressin-regulated IMP clusters. On the basis of these results, we conclude that the vasopressin-independent Pf in the terminal IMCD can be stably elevated to very high levels in response to in vivo thirsting. This elevation appears to be due to a chronic conditioning effect mediated by unknown in vivo factors and is not due to the short-term cAMP-mediated regulatory effect of vasopressin.

Membrane protein association by potential intramembrane charge pairs.

The transmembrane domain of the alpha chain of the T-cell receptor is responsible both for its assembly with the CD3 delta chain and for rapid degradation of the unassembled chain within the endoplasmic reticulum. The determinant for both assembly and degradation is located in a segment of eight residues containing two basic amino acids. We show here that placement of a single basic residue in the transmembrane domain of the Tac antigen can induce interaction with the CD3 chain, through its transmembrane acidic residue. This interaction is most favoured when the interacting residues are located at the same level in the membrane. The ability to induce protein-protein interaction by placing charge pairs within transmembrane domains suggests an approach to producing artificial dimers.