Impact of dose hot spots on spinal cord tolerance following stereotactic body radiotherapy: a generalized biological effective dose analysis

The purpose of this study was to investigate the effects of high-dose inhomogeneous irradiation to small volumes of spinal cord with a new generalized biological effective dose (gBED) analysis for spine stereotactic body radiotherapy (SBRT). The gBED was applied to spinal cord dosimetric data (contoured per the thecal sac) at specified volumes for a cohort of five patients with radiation-induced myelopathy (RM) and compared to nineteen patients without RM post-SBRT. The spinal cord gBED was calculated and normalized to a conventional 2-Gy equivalent dose fraction scheme (α/β = 2 Gy for late toxicity). Differences between the conventional BED and those gBED calculations by accounting for small-volume dosing within the spinal cord was observed. Statistically significant differences in the mean gBED between the RM group and the non-RM group was observed both at the maximum point volume (gBED of 66 Gy vs. 37 Gy (p = 0.01), respectively) and at the 0.1 cm(3) volume (gBED of 53 Gy vs. 28 Gy (p = 0.01), respectively). No significant difference at the 0.1 cm(3) volume was observed based on the mean BED comparisons. No significant differences were observed at the larger 1 cm(3), 2 cm(3) or 5 cm(3) volumes for either BED or gBED comparisons. We conclude that differences in dose hot spots characteristics within small inhomogenously irradiated volumes of spinal cord can affect spinal cord tolerance following SBRT treatments.

Use of Von-Hippel Lindau (VHL) mutation status to predict objective response to vascular endothelial growth factor (VEGF) -targeted therapy in metastatic renal cell carcinoma (RCC)

5012

Background: The clinical response to VEGF-targeted therapy in metastatic RCC is robust, yet variability in outcome exists. VHL is often mutated in RCC, but the relation to therapeutic outcome is unclear. Identification of tumor molecular characteristics associated with outcome would aid in patient selection and interpretation of clinical trials. Materials and Methods: Patients with metastatic, clear-cell RCC with available baseline frozen or paraffin-embedded tumor samples who received VEGF-targeted monotherapy with sunitinb, sorafenib, axitinib or bevacizumab at Cleveland Clinic or University of California San Francisco, were included. Patient characteristics, VHL gene status (mutated or not mutated) and objective response rate (ORR) were documented. ORR was investigator-assessed per RECIST criteria. Fisher’s exact test and logistic regression models were used to assess ORR in univariate and multivariate analyses, respectively. Results: One-hundred twenty-three patients were evaluable. The ORR was 36.5% for the entire cohort. VHL mutation was found in 48% of patients and was seen across all three exons. Patients with VHL mutation had an ORR of 46% versus 28% for pts without a mutated VHL gene (p=0.06). In multivariate analysis, presence of a VHL mutation remained an independent prognostic factor associated with improved ORR (p=.02) when multiple clinical prognostic factors (ECOG PS, hemoglobin, corrected calcium, LDH, prior radiation, prior therapy and number of metastatic sites) were also considered. Conclusion: This is the first large study testing the impact of VHL mutation on response to VEGF-targeted agents in metastatic RCC. Although objective responses were more likely among patients with mutated VHL gene, lack of VHL mutation did not preclude a response. Additional tissue analysis and identification of biomarkers relevant to response to VEGF-targeted agents in metastatic RCC are warranted.

[Table: see text]

Combination immunotherapy with GM-CSF and CTLA-4 blockade for hormone refractory prostate cancer: Balancing the expansion of activated effector and regulatory T cells

3001

Background: CTLA-4 is a costimulatory molecule expressed on activated T cells that delivers an inhibitory signal to these T cells. CTLA4 blockade with antibody treatment has been shown to augment T cell responses and anti-tumor immunity in animal models. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a bone marrow growth factor for antigen presenting cells, which has also been shown to enhance anti-tumor immune responses. Methods: A phase I trial in patients with metastatic, hormone refractory prostate cancer (HRPC) was undertaken to combine these immunotherapies. Sequential cohorts of 3–6 patients were treated with escalating doses (0.5, 1.5 or 3 mg/kg) of ipilimumab, a fully human anti-CTLA-4 antibody, given IV on day 1 of each 28-day cycle × 4 cycles. Patients also received GM-CSF 250 mg/m2/d SC on days 1–14 of the 28-day cycles. Patients were monitored for toxicity as well as for T cell activation. PSA and radiographic tests were performed at baseline and through therapy to evaluate for clinical response. Results: 24 patients have been treated. Of 6 patients treated on the highest dose level (3 mg/kg ×4), 3 (50%) had confirmed PSA declines of >50%, and one of these patients had a partial response in hepatic metastases. Immune-related adverse events associated with ipilimumab treatment consisted of a grade 3 rash in 1 patient at 1.5 mg/kg, a grade 3 rash and panhypopituitarism in 1 patient at 3.0 mg/kg, and a grade 3 colitis in one patient at 3.0 mg/kg. All events were successfully managed. A dose-response relationship was seen between ipilimumab dose and effector T cell activation. Expansion of circulating CD4+ FoxP3+ regulatory T cells was also seen with treatment. Conclusions: CTLA-4 blockade combined with GM-CSF treatment induces clinical responses in HRPC. Treatment induces both the expansion of activated effector and regulatory T cells in vivo in cancer patients. Finally, CD4 and CD8 T cell activation, adverse events, and clinical responses appear to be dose-dependant. Supported by NIH SPORE P50 CA89520.

No significant financial relationships to disclose.

Intermittent androgen deprivation therapy (IADT) for patients with non-metastatic prostate cancer: A retrospective review

15635

Background: IADT is a therapeutic option frequently utilized in men with progressive non-castrate prostate cancer (PCa) which, compared to continuous ADT, may result in an improvement in quality of life while potentially prolonging time to androgen independence (AI). Methods: The records of 43 consecutive men with non-metastatic progressive non-castrate PCa treated with IADT were analyzed. 21 men had received no prior primary treatment (tx), and 22 had developed recurrent disease after previous local therapy. Therapy for this cohort of patients (pts) consisted of combined androgen blockade for 32 pts and a leutenizing hormone-releasing hormone agonist alone for 11. Pts were allowed to come off androgen deprivation (AD) when (a) PSA became undetectable, (b) after 9 to 12 months (mos) of receiving AD, (c) or per patient request. AD was re-initiated when (a) serum PSA reached 50% or greater of the pre-tx level, (b) at physician discretion, or (c) at patient's request. A tx cycle was defined as the number of months on tx plus the number of months off tx until the reinstitution of AD. Progressive disease and AI were defined by consensus criteria (climbing PSA despite AD). Results: Follow up ranged from 18 to 153 mos (median 68.2 mos) from the start of tx. Pts received from 1 to 10 cycles (median 4), with a median cycle length of 19 mos. The median pre-tx PSA value was 8.9, and the median nadir serum PSA level with ADT was 0.09 and was reached within an average of 6.4 mos (range 2–25) after beginning tx. Pts spent an average of 50.7% of time on hormones and 49.3% off hormones. Eleven pts developed AI progressive disease, with a median time to progression of 47 mos. When examining for potential characteristics that contributed to AI, such as duration of ADT, PSA at start of therapy, nadir PSA, stage, or Gleason score, no consistent patterns of failure emerged. Conclusions: IADT appears to be a viable tx option for men with non-metastatic progressive non-castrate PCa, resulting in prolonged duration of response. However, with a median follow up of nearly 6 years, AI still develops in over a quarter of pts, at a median of 47 months from starting ADT.

No significant financial relationships to disclose.

Beta-lapachone inhibits proliferation and induces apoptosis in retinoblastoma cell lines

AIMS

To investigate the cytotoxicity of beta-lapachone, a potent agent that may selectively target tumour cells, in retinoblastoma (RB) cell lines.

METHODS

Growth inhibitory effects of beta-lapachone were evaluated in Y79, WERI-RB1, and RBM human retinoblastoma cell lines. Pro-apoptotic effects of beta-lapachone were evaluated in Y79 cells by detection of caspase 3/7 activity, by enzyme-linked immunosorbent assay for nucleosome fragments, and by cellular morphological analysis.

RESULTS

Beta-lapachone induced significant dose-dependent growth inhibitory effects in all three retinoblastoma cell lines. The 50% growth inhibitory concentration (IC(50)) of this agent was 1.9 microM in Y79 cells, 1.3 microM in WERI-RB1 cells, and 0.9 microM in RBM cells. Beta-lapachone also induced proapoptotic effects in RB cells. Treatment of Y79 cells with 1.9 microM beta-lapachone (IC(50)) resulted in a peak, fourfold induction of caspase 3/7 activity at 72 h post-treatment; a peak, 5.6-fold increase in nucleosome fragments at 96 h post-treatment; and a peak, 1.7-fold increase in the frequency of apoptotic cells at 48 h post-treatment, relative to vehicle-treated controls.

CONCLUSION

Beta-lapachone induced potent cytotoxic effects in RB cell lines at low micromolar concentrations, suggesting this agent could be useful in the clinical management of RB.

Defining High Risk Prostate Cancer With Risk Groups and Nomograms: Implications for Designing Clinical Trials

PURPOSE

Death from prostate cancer is usually preceded by metastases and it usually occurs in men with high risk disease who experienced biochemical failure with a short prostate specific antigen doubling time. We developed a model for determining disease specific survival in prostate cancer.

MATERIALS AND METHODS

We used the model for defining high risk prostate cancer that was developed by the Radiation Therapy Oncology Group and combined it with the Kattan nomogram for predicting the risk of metastases. We selected 414 Radiation Therapy Oncology Group intermediate and high risk patients who were treated with external beam radiotherapy alone. Excluded were patients with low risk disease. The Kaplan-Meier product limit method was used to estimate the probability of freedom from biochemical failure, overall survival and disease specific survival.

RESULTS

A significant difference was observed in freedom from biochemical failure, disease specific survival and overall survival among the 3 tertiles created by the nomogram using the cutoff points less than 8.5%, 8.5% to 15% and greater than 15% (p <0.001, 0.0002 and 0.0003, respectively). Only the risk of metastases using the categorized nomogram score (less than 8.5% and 8.5% to 15% vs greater than 15%), not preradiotherapy prostate specific antigen or Radiation Therapy Oncology Group risk (Radiation Therapy Oncology Group 2 vs 3), was a significant predictor of disease specific and overall survival for intermediate/high risk patients and intermediate/high risk with 15% or less risk for metastases.

CONCLUSIONS

We combined a risk group stratification scheme for disease specific survival with a nomogram predicting the risk of metastases and created a model that may be useful for designing phase III trials with metastases and disease specific survival as study end points.

A phase I trial of combination immunotherapy with CTLA-4 blockade and GM-CSF in hormone-refractory prostate cancer

2508

Background: CTLA-4 is an costimulatory molecule expressed on activated T cells that delivers an inhibitory signal to these T cells. CTLA-4 blockade with antibody treatment augments T cell responses and anti-tumor immunity in animal models. Clinical trials with anti-CTLA-4 antibody treatment have demonstrated clinical responses in different malignancies including melanoma and hormone-refractory prostate cancer (HRPC). We have also shown that administration of granulocyte-macrophage colony-stimulating factor (GM-CSF) can also induce PSA declines in HRPC patients, presumably through enhancing presentation of endogenous antigens. The current study examines whether combining systemic GM-CSF to CTLA-4 blockade can augment immune and/or clinical responses in HRPC patients. Methods: In a phase I trial of patients with metastatic HRPC, sequential cohorts of 3–6 patients received GM-CSF (sargramostim, Berlex) 250 mg/m2/d SC on days 1–14 of a 28-day cycle with escalating doses (0.5, 1.5 or 3 mg/kg) of ipilimumab (MDX-010), a fully human anti-CTLA antibody (Medarex/BMS), given IV on day 1 of each cycle x 4 cycles. Patients were monitored for toxicity as well as for T cell activation. PSA and radiographic tests were performed at baseline and through therapy to evaluate for clinical response. Results: 18 patients were accrued. Ipilimumab-related dose-limiting toxicity was limited to one patient with grade 3 rash at the 3 mg/kg priming dose level. Seven patients had <50% declines in their serum PSA levels. A dose response relationship was seen between ipilimumab dose and activation of both CD4 and CD8 T cells in the blood. These effects were increased compared to effects seen with ipilimumab treatment alone in prior studies. Interferon-gamma production and lytic activity were also enhanced in circulating antigen-specific CD8+ T cells by the combination. Conclusions: GM-CSF may enhance T cell activation induced by CTLA-4 blockade. With increasing doses of anti-CTLA-4, both CD4 and CD8 T cell activation can be detected in the blood, consistent with a dose-response relationship. Supported by the UCSF Prostate SPORE NIH P50 CA89520.

No significant financial relationships to disclose.

Outcome of patients with non-metastatic versus metastatic hormone refractory prostate cancer (HRPC) treated with second-line hormonal therapy consisting of ketoconazole (keto) plus granulocyte macrophage colony stimulating factor (GM-CSF)

4626

Background: Second line hormonal manipulations are frequently used in pts with HRPC. It is unknown if these manipulations are more effective in patients without clinical metastases. The efficacy of a second-line hormonal manipulation (keto plus GM-CSF) was prospectively evaluated in a cohort of HRPC patients with and without metastases. Methods: Eligible pts had progressive HRPC by consensus criteria, no prior immunotherapy, chemotherapy or keto. Pts received keto 400 mg po tid and hydrocortisone 20 mg po qAM and 10 mg po qPM. GM-CSF 250 mcg/m2 was administered SQ on days 15–28 of each 28-day cycle. Results: Forty-two of 48 planned pts have been enrolled, 30 with clinical metastases, 12 with PSA-only disease and are evaluable for PSA response, using consensus criteria. The median age is 68 years (range: 53–84), and median PSA 23.1 ng/mL (range: 5.4–306.5). The median treatment duration is 5.1 months (range: 0.3–22+). Overall, 30 of 43 patients (69%) have experienced a ≥ 50% reduction in PSA. The PSA response proportion in the non-metastatic patients is 8/12 (66%) while the response proportion in those with metastases is 16/30 (53%, chi squared p = 0.41). Twenty-three patients have discontinued therapy after a median of three cycles. Progressive disease has occurred in 17 patients, 3 of 12 patients with non-metastatic disease and in 14 of 30 patients with metastatic disease (25% vs. 47%, chi squared p=0.20). Six patients have discontinued due to toxicity or patient choice. The primary endpoint of the study, overall time to progression, has not been reached at a median follow up of 7 months. Conclusions: There was no significant difference in response proportion and progressive disease rate in HRPC patients with and without metastatic disease treated with keto/GM-CSF. While these data require prospective confirmation in a larger group of patients, they suggest that secondary hormonal manipulations are warranted in either patient group.

No significant financial relationships to disclose.

Preliminary evaluation of prostate cancer metastatic risk biomarkers

Prostate cancer patients at high risk of metastasis need to be identified as early as possible since metastasis is invariably fatal. Treatment could be tailored to risk. Recent array comparative genomic hybridization (aCGH) studies of primary and metastatic prostate tumors identified 39 BAC clones capable of detecting genomic signatures of metastasis. We termed these loci the genomic evaluators of metastatic CaP (GEMCaP). Risk assessments were made on a set of men who were managed with radical prostatectomy. We compared the utility of GEMCaP loci and the Kattan nomogram, a common risk assessment tool, in relation to biochemical outcome. This preliminary evaluation experiment suggests we can use aCGH to detect genomic signatures of metastasis in primary tumors with an accuracy of 78%. The classification accuracy for the Kattan nomogram was 75%. Therefore, validation of GEMCaP is warranted in a larger, appropriately designed cohort.

Discordance between beliefs and recommendations of gynecologic oncologists in ovarian cancer management

PURPOSE

The purpose of this study was to determine how physician experts make decisions for clinical scenarios in ovarian cancer and describe a profile of factors reported to influence treatment decisions.

METHODS

A questionnaire was sent to Full Members of the Society of Gynecologic Oncologists regarding surgery and chemotherapy for scenarios of primary and recurrent ovarian cancer.

RESULTS

In a scenario of primary presentation, 94% of respondents chose a treatment of tumor resection over chemotherapy. Despite the preference for surgery in a clinical scenario, 50% agreed with a statement that neoadjuvant chemotherapy is equivalent to primary surgery. In a scenario of recurrent disease, a comparable number of respondents chose a treatment of secondary cytoreductive surgery (45%) versus direct retreatment with chemotherapy (49%). Those choosing surgery responded that they believed in extensive surgery to achieve optimal cytoreduction. Most (62%) respondents described themselves as collaborative in treatment planning, yet only 24% reported that patient preference strongly influences their decision making.

CONCLUSIONS

Although a plan for primary cytoreduction is favored, in specific scenarios, views were divided for the role of neoadjuvant chemotherapy. For a recurrent disease scenario, support was divided between secondary cytoreductive surgery and direct retreatment with chemotherapy. Further clinical research is necessary to minimize the discordance between physician beliefs and recommendations.