Optimizing patient selection for dose escalation techniques using the prostate-specific antigen level, biopsy gleason score, and clinical T-stage

Immune Modulation by Androgen Deprivation and Radiation Therapy: Implications for Prostate Cancer Immunotherapy

Prostate cancer patients often receive androgen deprivation therapy (ADT) in combination with radiation therapy (RT). Recent evidence suggests that both ADT and RT have immune modulatory properties. First, ADT can cause infiltration of lymphocytes into the prostate, although it remains unclear whether the influx of lymphocytes is beneficial, particularly with the advent of new classes of androgen blockers. Second, in rare cases, radiation can elicit immune responses that mediate regression of metastatic lesions lying outside the field of radiation, a phenomenon known as the abscopal response. In light of these findings, there is emerging interest in exploiting any potential synergy between ADT, RT, and immunotherapy. Here, we provide a comprehensive review of the rationale behind combining immunotherapy with ADT and RT for the treatment of prostate cancer, including an examination of the current clinical trials that employ this combination. The reported outcomes of several trials demonstrate the promise of this combination strategy; however, further scrutiny is needed to elucidate how these standard therapies interact with immune modulators. In addition, we discuss the importance of synchronizing immune modulation relative to ADT and RT, and provide insight into elements that may impact the ability to achieve maximum synergy between these treatments.

Synergistic action of image-guided radiotherapy and androgen deprivation therapy

The combined use of androgen deprivation therapy (ADT) and image-guided radiotherapy (IGRT) can improve overall survival in aggressive, localized prostate cancer. However, owing to the adverse effects of prolonged ADT, it is imperative to identify the patients who would benefit from this combined-modality therapy relative to the use of IGRT alone. Opportunities exist for more personalized approaches in treating aggressive, locally advanced prostate cancer. Biomarkers--such as disseminated tumour cells, circulating tumour cells, genomic signatures and molecular imaging techniques--could identify the patients who are at greatest risk for systemic metastases and who would benefit from the addition of systemic ADT. By contrast, when biomarkers of systemic disease are not present, treatment could proceed using local IGRT alone. The choice of drug, treatment duration and timing of ADT relative to IGRT could be predicated on these personalized approaches to prostate cancer medicine. These novel treatment intensification and reduction strategies could result in improved prostate-cancer-specific survival and overall survival, without incurring the added expense of metabolic syndrome and other adverse effects of ADT in all patients.

Copy number alterations of c-MYC and PTEN are prognostic factors for relapse after prostate cancer radiotherapy

Despite the use of PSA, Gleason score, and T-category as prognosticators in intermediate-risk prostate cancer, 20-40% of patients will fail local therapy. In order to optimize treatment approaches for intermediate-risk patients, additional genetic prognosticators are needed. Previous reports using array comparative genomic hybridization (aCGH) in radical prostatectomy cohorts suggested a combination of allelic loss of the PTEN gene on 10q and allelic gain of the c-MYC gene on 8q were associated with metastatic disease. We tested whether copy number alterations (CNAs) in PTEN (allelic loss) and c-MYC (allelic gain) were associated with biochemical relapse following modern-era, image-guided radiotherapy (mean dose 76.4 Gy). We used aCGH analyses validated by fluorescence in-situ hybridization (FISH) of DNA was derived from frozen, pre-treatment biopsies in 126 intermediate-risk prostate cancer patients. Patients whose tumors had CNAs in both PTEN and c-MYC had significantly increased genetic instability (percent genome alteration; PGA) compared to tumors with normal PTEN and c-MYC status (p < 0.0001). We demonstrate that c-MYC gain alone, or combined c-MYC gain and PTEN loss, were increasingly prognostic for relapse on multivariable analyses (hazard ratios (HR) of 2.58/p = 0.005 and 3.21/p = 0.0004; respectively). Triaging patients by the use of CNAs within pre-treatment biopsies may allow for better use of systemic therapies to target sub-clinical metastases or locally recurrent disease and improve clinical outcomes.

NKX3.1 haploinsufficiency is prognostic for prostate cancer relapse following surgery or image-guided radiotherapy

BACKGROUND

Despite the use of prostate specific antigen (PSA), Gleason-score, and T-category as prognostic factors, up to 40% of patients with intermediate-risk prostate cancer will fail radical prostatectomy or precision image-guided radiotherapy (IGRT). Additional genetic prognosticators are needed to triage these patients toward intensified combination therapy with novel targeted therapeutics. We tested the role of the NKX3.1 gene as a determinant of treatment outcome given its reported roles in tumor initiating cell (TIC) renewal, the DNA damage response, and cooperation with c-MYC during prostate cancer progression.

METHODS

Using high-resolution array comparative genomic hybridization (aCGH), we profiled the copy number alterations in TIC genes using tumor DNA from frozen needle biopsies derived from 126 intermediate-risk patients who underwent IGRT. These data were correlated to biochemical relapse-free rate (bRFR) by the Kaplan-Meier method and Cox proportional hazards models.

RESULTS

A screen of the aCGH-IGRT data for TIC genes showed frequent copy number alterations for NKX3.1, PSCA, and c-MYC. NKX3.1 haploinsufficiency was associated with increased genomic instability independent of PSA, T-category, and Gleason-score. After adjusting for clinical factors in a multivariate model, NKX3.1 haploinsufficiency was associated with bRFR when tested alone (HR = 3.05, 95% CI: 1.46-6.39, P = 0.0030) or when combined with c-MYC gain (HR = 3.88, 95% CI: 1.78-8.49, P = 0.00067). A similar association was observed for patients following radical prostatectomy with a public aCGH database. NKX3.1 status was associated with positive biopsies post-IGRT and increased clonogen radioresistance in vitro.

CONCLUSIONS

Our results support the use of genomic predictors, such as NKX3.1 status, in needle biopsies for personalized approaches to prostate cancer management.

Favorable clinical outcomes of three-dimensional computer-optimized high-dose-rate prostate brachytherapy in the management of localized prostate cancer

PURPOSE

To report PSA relapse-free survival and toxicity outcomes of prostate cancer patients who have undergone three-dimensional computer-optimized high-dose-rate (HDR) brachytherapy with external beam radiotherapy as definitive treatment.

METHODS AND MATERIALS

One hundred five patients consecutively treated between 1998 and 2004 are reported. All patients were treated with HDR boost with lr 192 (5.5-7.0 Gy), based upon postimplant CT three-dimensional treatment planning using an in-house treatment plan optimization algorithm. Three-dimensional conformal external beam radiotherapy (45-50.4 Gy) was also administered 3 weeks after the HDR procedure. Toxicity was measured using National Cancer Institutes Common Toxicity Criteria and International Prostate Symptom Score indices.

RESULTS

With a median followup of 44 months (8-79 months), the 5-year PSA relapse-free survival outcomes for low, intermediate and high-risk patients were 100%, 98%, and 92%, respectively, Median urinary toxicity, and 93% of patients denied rectal problems at the time of last followup. Erectile dysfunction was noted in 47% patients at the time of last followup, but overall 80% were able to achieve vaginal penetration when those who responded to sildenafil were included.

CONCLUSION

Computer-optimized three-dimensional HDR prostate brachytherapy provides excellent disease control for even high risk localized prostate cancer. Significant toxicity has been minimal.

Dose escalation for localized prostate cancer: substantial benefit observed with 3D conformal therapy

PURPOSE

To determine the effect of radiation dose escalation on biochemical and/or disease failure in patients with localized prostate cancer treated with three-dimensional conformal radiotherapy (3D-CRT).

METHODS AND MATERIALS

Between May 1987 and December 2000, 1473 patients were assessed after treatment with 3D-CRT. The mean patient age was 70.4 +/- 6.8 years, 1316 patients had T1-T2 disease, and 1150 had Gleason score <or=7. The median pretreatment prostate-specific antigen (PSA) level was 8.9 ng/mL. The mean dose was 71.7 +/- 4.3 Gy (range 60.0-80.4). Failure was defined as the first event of any of the following: biochemical failure, local recurrence or metastasis, postirradiation hormonal therapy, or death from disease.

RESULTS

At a median follow-up of 35.2 months, 395 failures (26.8%) had occurred. Adjusting for dose as a continuous variable, the hazard ratio for failure was 2.03 (p < 0.0001) for 569 intermediate-risk patients (stage T1-T2 and Gleason score 7 or PSA 10-20 ng/mL) and 5.16 (p < 0.0001) for 456 high-risk patients (stage T3-T4 or PSA >20 ng/mL or Gleason score >or=8) compared with 448 low-risk patients (stage T1-T2 and Gleason score <or=6 and PSA <10 ng/mL). For intermediate-risk patients, each 1-Gy increment in total radiation dose was associated with a highly significant 8% reduction in the probability of failure (hazard ratio = 0.92, p = 0.005).

CONCLUSION

Dose escalation using 3D-CRT significantly reduces the risk of biochemical/disease failure among intermediate-risk prostate cancer patients.

Evidence-based estimate of appropriate radiotherapy utilization rate for prostate cancer

PURPOSE

Current estimates of the proportion of cancer patients who will require radiotherapy (RT) are based almost entirely on expert opinion. The objective of this study was to use an evidence-based approach to estimate the proportion of incident cases of prostate cancer that should receive RT at any point in the evolution of the illness.

METHODS AND MATERIALS

A systematic review of the literature was undertaken to identify indications for RT for prostate cancer and to ascertain the level of evidence that supported each indication. An epidemiologic approach was then used to estimate the incidence of each indication for RT in a typical North American population of prostate cancer patients. The effect of sampling error on the estimated appropriate rate of RT was calculated mathematically, and the effect of systematic error using alternative sources of information was estimated by sensitivity analysis.

RESULTS

It was estimated that 61.2% +/- 5.6% of prostate cancer cases develop one or more indications for RT at some point in the course of the illness. The plausible range for this rate was 57.3%-69.8% on sensitivity analysis. Of all prostate cancer patients, 32.2% +/- 3.8% should receive RT in their initial treatment and 29.0% +/- 4.1% later for recurrence or progression. The proportion of cases that ever require RT is risk grouping dependent; 43.9% +/- 2.2% in low-risk disease, 68.7% +/- 3.5% in intermediate-risk disease; and 79.0% +/- 3.8% in high-risk locoregional disease. For metastatic disease, the predicted rate was 66.4% +/- 0.3%.

CONCLUSION

This method provides a rational starting point for the long-term planning of radiation services and for the audit of access to RT at the population level. By completing such evaluations in major cancer sites, it will be possible to estimate the appropriate RT rate for the cancer population as a whole.

The rush to judgment: Does the evidence support the enthusiasm over three-dimensional conformal radiation therapy and dose escalation in the treatment of prostate cancer?

PURPOSE

To discuss the assumptions behind and current clinical evidence on three-dimensional conformal radiation therapy (3D-CRT) and dose escalation in the treatment of prostate cancer.

METHODS

We first define 3D-CRT in comparison to standard radiation therapy and discuss the assumptions on which the technology of 3D-CRT and dose escalation are based. We then examine the evidence on the benefits and limitations from the current most commonly cited studies on dose-escalation trials to treat prostate cancer.

RESULTS

The assumption that 3D-CRT can provide a tighter margin around the tumor area to allow for dose escalation is not yet proven by studies that show continual difficulty in defining the planning treatment volume because of extrinsic and intrinsic difficulties, such as imaging variabilities and patient and organ movement. Current short-term dose-escalation studies on the use of 3D-CRT to treat prostate cancer are limited in their ability to prove that increasing dose improves survival and does not incur potential long-term complications to normal tissue.

CONCLUSION

Although 3D-CRT is a promising technology that many radiation oncologists and clinics are quickly adopting to treat such tumors as prostate cancer, the long-term evidence on the benefits and limitations of this technology is still lacking. Until we have solid long-term evidence on the true clinical potential of this new technology, let us not rush to judgment, but exercise caution, diligence, and thoughtfulness in using this new technology to treat our patients.

Molecular staging of surgical margins after radical prostatectomy by detection of telomerase activity

BACKGROUND

The further course of prostate cancer (PC) after radical prostatectomy (RPX) is decisively influenced by the local tumor stage. Although it is thus far possible to assess the risk of local recurrence from the pathohistology, precise predictions cannot be made. A more precise evaluation would be desirable, mainly for early planning of adjuvant therapy. Other authors have shown that telomerase activity may be a marker for malignant potential. We assessed the detection of telomerase activity using the telomeric repeat amplification protocol (TRAP) in surgical margins compared to conventional histopathological examination.

METHODS

Ninety-two patients with local PC who underwent RPX were examined. After RPX biopsies were obtained from four defined areas of the prostatic fossa and processed by TRAP assay for telomerase activity using a standard protocol.

RESULTS

In 5 of 48 patients (10.4%) with organ-confined prostate carcinoma (pT2) telomerase activity could be detected. Seven of 47 patients (14.9%) with locally advanced PC (> pT2) had at least one positive specimen.

CONCLUSIONS

The results obtained in our study indicate that detection of telomerase activity by TRAP assay may be a suitable parameter for molecular staging of surgical margins, because of the high tumor-specificity. Further follow-up must clarify whether patients with positive molecular detection have an increased risk of local recurrence.

Reverse transcriptase-polymerase chain reaction for prostate-specific antigen in the molecular staging of pelvic surgical margins after radical prostatectomy

OBJECTIVES

To examine the application of reverse transcriptase-polymerase chain reaction (RT-PCR) to assist in prostate-specific antigen (PSA) detection in the surgical margins after radical prostatectomy (RP). The risk of local recurrence increases considerably in the presence of extracapsular tumor growth and/or positive surgical margins at RP. Although this makes it possible to identify patients with an increased risk of local recurrence, precise predictions cannot be made. A more precise assessment is desirable mainly for early planning of adjuvant therapy.

METHODS

Ninety-five patients with clinically organ-confined prostate cancer (CaP) underwent RP. After removing the gland, biopsies were obtained from four defined areas of the prostatic fossa and processed for RT-PCR for PSA detection. Sixteen patients with muscle-invasive bladder carcinoma who underwent radical cystoprostatectomy served as controls.

RESULTS

Thirty-two of 95 patients with CaP (35%) had at least one positive molecular margin indicating an expression for PSA; 19 of 48 (39%) of these had an organ-confined tumor stage according to conventional histology and 13 of 47 (28%) had tumor growth beyond the prostate. A statistically significant correlation between the frequency of positive molecular margins and clinical data was only observed in the group with disease greater than Stage pT2. All controls had negative molecular margins (P = 0.012).

CONCLUSIONS

On the basis of the results obtained, molecular diagnostic RT-PCR for PSA detection in the surgical margins after RP seems to be an interesting supplementary tool for monitoring the course and establishing the prognosis. Long-term follow-up of these patients is needed to demonstrate the clinical value of molecular diagnostics of surgical margins during RP.