Intrinsic radiosensitivity of human cell lines is correlated with radioresponsiveness of human tumors: analysis of 101 published survival curves

Radiosurgery for melanoma brain metastases in the ipilimumab era and the possibility of longer survival

OBJECT

A prospectively collected cohort of 77 patients who underwent definitive radiosurgery between 2002 and 2010 for melanoma brain metastases was retrospectively reviewed to assess the impact of ipilimumab use and other clinical variables on survival.

METHODS

The authors conducted an institutional review board-approved chart review to assess patient age at the time of brain metastasis diagnosis, sex, primary disease location, initial radiosurgery date, number of metastases treated, performance status, systemic therapy and ipilimumab history, whole-brain radiation therapy (WBRT) use, follow-up duration, and survival at the last follow-up. The Diagnosis-Specific Graded Prognostic Assessment (DSGPA) score was calculated for each patient based on performance status and the number of brain metastases treated.

RESULTS

Thirty-five percent of the patients received ipilimumab. The median survival in this group was 21.3 months, as compared with 4.9 months in patients who did not receive ipilimumab. The 2-year survival rate was 47.2% in the ipilimumab group compared with 19.7% in the nonipilimumab group. The DS-GPA score was the most significant predictor of overall survival, and ipilimumab therapy was also independently associated with an improvement in the hazard for death (p = 0.03).

CONCLUSIONS

The survival of patients with melanoma brain metastases managed with ipilimumab and definitive radiosurgery can exceed the commonly anticipated 4-6 months. Using ipilimumab in a supportive treatment paradigm of radiosurgery for brain oligometastases was associated with an increased median survival from 4.9 to 21.3 months, with a 2-year survival rate of 19.7% versus 47.2%. This association between ipilimumab and prolonged survival remains significant even after adjustment for performance status without an increased need for salvage WBRT.

Hemoglobin level significantly impacts the tumor cell survival fraction in humans after internal radiotherapy

Background

Anemia is usually not taken into account in internal radiotherapy. We investigated whether the hemoglobin (Hb) level could have an impact on the tumor response, as observed in external beam radiotherapy (EBRT).

Methods

Absorbed doses of 25 hepatic metastatic sites in eight patients who underwent a liver selective internal radiotherapy (SIRT) were computed by a 3D convolution of a dose deposition kernel with the ⁹⁰Y time-of-flight positron emission tomography (TOF-PET) images acquired following therapy. Early tumor response was assessed by comparing a follow-up FDG TOF-PET scan with a baseline scan. Hb level was measured on the day of the SIRT procedure.

Results

All patients displayed early tumor response increasing with the tumor-absorbed dose. Significant differences between patients were noted, the response slope correlating with the Hb level. After applying a global fit on all metastases using a tumor radiosensitivity modulated by a Hb enhancement factor (HEF) linearly dependent on the Hb level, a strong correlation (R = 0.96) was observed between the early response and the absorbed dose. Hb level had a major impact on tumor response by modulating HEF by a factor 6.

Conclusions

These results prove the significant impact of Hb level on the tumor response and support the study of methods for correcting tumor hypoxia, such as intensively performed in EBRT. The quantitative analysis of the relationship between tumor doses and early response has the power to allow fast screening of such correction methods in limited patient series. Internal radiotherapy could be more efficient if performed earlier in the therapy line, when the disease- and treatment-related anemia remains limited.

Monte Carlo role in radiobiological modelling of radiotherapy outcomes

Radiobiological models are essential components of modern radiotherapy. They are increasingly applied to optimize and evaluate the quality of different treatment planning modalities. They are frequently used in designing new radiotherapy clinical trials by estimating the expected therapeutic ratio of new protocols. In radiobiology, the therapeutic ratio is estimated from the expected gain in tumour control probability (TCP) to the risk of normal tissue complication probability (NTCP). However, estimates of TCP/NTCP are currently based on the deterministic and simplistic linear-quadratic formalism with limited prediction power when applied prospectively. Given the complex and stochastic nature of the physical, chemical and biological interactions associated with spatial and temporal radiation induced effects in living tissues, it is conjectured that methods based on Monte Carlo (MC) analysis may provide better estimates of TCP/NTCP for radiotherapy treatment planning and trial design. Indeed, over the past few decades, methods based on MC have demonstrated superior performance for accurate simulation of radiation transport, tumour growth and particle track structures; however, successful application of modelling radiobiological response and outcomes in radiotherapy is still hampered with several challenges. In this review, we provide an overview of some of the main techniques used in radiobiological modelling for radiotherapy, with focus on the MC role as a promising computational vehicle. We highlight the current challenges, issues and future potentials of the MC approach towards a comprehensive systems-based framework in radiobiological modelling for radiotherapy.

Differential mechanisms of x-ray-induced cell death in human endothelial progenitor cells isolated from cord blood and adults

Endothelial colony-forming cells (ECFCs) are endothelial progenitor cells that circulate at low concentration in human umbilical cord and adult peripheral blood and are largely resident in blood vessels. ECFCs not only appear to be critical for normal vascular homeostasis and repair but may also contribute to tumor angiogenesis and response to therapy. To begin to characterize the potential role of ECFCs during the treatment of tumors in children and adults with radiation, we characterized the X-ray sensitivity of cord and adult blood-derived ECFCs. We found both cord blood and adult ECFCs to be highly radiation sensitive (3 Gy resulted in >90% killing without induction of apoptosis). The X-ray survival curves suggested reduced potential for repair capacity, but X-ray fractionation studies demonstrated that all the ECFCs exhibited repair when the radiation was fractionated. Finally, the mechanisms of X-ray-induced cell death for cord blood and adult ECFCs were different at low and high dose. At low dose, all ECFCs appear to die by mitotic death/catastrophe. However, at high radiation doses (≥ 10 Gy) cord blood ECFCs underwent p53 stabilization and Bax-dependent apoptosis as well as p21-dependent G₁ and G₂/M cell cycle checkpoints. By contrast, after 10 Gy adult ECFCs undergo only large-scale radiation-induced senescence, which is a cellular phenotype linked to premature development of atherosclerosis and vasculopathies. These data demonstrate that the ECFC response to radiation is dose-dependent and developmentally regulated and may provide potential mechanistic insight into their role in tumor and normal tissue response after ionizing radiation treatment.

In vitro effects of imatinib mesylate on radiosensitivity and chemosensitivity of breast cancer cells

Background

Breast cancer treatment is based on a combination of adjuvant chemotherapy followed by radiotherapy effecting intracellular signal transduction. With the tyrosine kinase inhibitors new targeted drugs are available. Imatinib mesylate is a selective inhibitor of bcr-abl, PRGFR alpha, beta and c-kit. The purpose of this study was to determine whether Imatinib has an influence on the effectiveness of radiotherapy in breast cancer cell lines and if a combination of imatinib with standard chemotherapy could lead to increased cytoreduction.

Methods

Colony-forming tests of MCF 7 and MDA MB 231 were used to study differences in cell proliferation under incubation with imatinib and radiation. Changes in expression and phosphorylation of target receptors were detected using western blot. Cell proliferation, migration and apoptosis assays were performed combining imatinib with doxorubicin.

Results

The combination of imatinib and radiotherapy showed a significantly stronger inhibition of cell proliferation compared to single radiotherapy. Differences in PDGFR expression could not be detected, but receptor phosphorylation was significantly inhibited when treated with imatinib. Combination of imatinib with standard chemotherapy lead to an additive effect on cell growth inhibition compared to single treatment.

Conclusions

Imatinib treatment combined with radiotherapy leads in breast cancer cell lines to a significant benefit which might be influenced through inhibition of PDGFR phosphorylation. Combining imatinib with chemotherapy enhances cytoreductive effects. Further in vivo studies are needed to evaluate the benefit of Imatinib in combination with radiotherapy and chemotherapy on the treatment of breast cancer.

p53-dependent G(1) arrest in 1st or 2nd cell cycle may protect human cancer cells from cell death after treatment with ionizing radiation and Chk1 inhibitors

OBJECTIVES

This study was performed to explore the strategy of combining Chk1 inhibitors with ionizing radiation (IR) to selectively target p53-deficient cancer cells.

MATERIALS AND METHODS

Survival and cell cycle progression were measured in response to IR and the Chk1 inhibitors, UCN-01 and CEP-3891, in colon carcinoma HCT116 p53+/+ and p53-/- cells, and in osteosarcoma U2OS-VP16 cells with conditional expression of dominant-negative p53 (p53DD).

RESULTS

Clonogenic survival was selectively reduced in HCT116 p53-/- compared to p53+/+ cells after treatment with UCN-01 and IR, and HCT116 p53+/+ cells also displayed strong p53-dependent G(1) arrest in the 1st cell cycle after IR. In contrast, clonogenic survival was affected similarly in U2OS-VP16 cells with and without expression of p53DD. However, death of U2OS-VP16 cells was p53 dependent as assessed by cell viability assay at 72 h, and this was associated with p53-dependent G(1) arrest in the 2nd cell cycle after treatment. Notably, HCT116 cells were overall more resistant than U2OS cells to cytotoxic effects of Chk1 inhibitors.

CONCLUSION

Our results suggest that p53-dependent G(1) arrest in both 1st and 2nd cell cycles may protect human cancer cells from cell death after treatment with IR and Chk1 inhibitors. However, a challenge for future clinical use will be that different cancers display different intrinsic sensitivity to such inhibitors.

Dose escalation for metastatic spinal cord compression in patients with relatively radioresistant tumors

PURPOSE

Radiotherapy alone is the most common treatment for metastatic spinal cord compression (MSCC) from relatively radioresistant tumors such as renal cell carcinoma, colorectal cancer, and malignant melanoma. However, the results of the "standard" regimen 30 Gy/10 fractions need to be improved with respect to functional outcome. This study investigated whether a dose escalation beyond 30 Gy can improve treatment outcomes.

METHODS AND MATERIALS

A total of 91 patients receiving 30 Gy/10 fractions were retrospectively compared to 115 patients receiving higher doses (37.5 Gy/15 fractions, 40 Gy/20 fractions) for motor function and local control of MSCC. Ten further potential prognostic factors were evaluated: age, gender, tumor type, performance status, number of involved vertebrae, visceral or other bone metastases, interval from tumor diagnosis to radiotherapy, pretreatment ambulatory status, and time developing motor deficits before radiotherapy.

RESULTS

Motor function improved in 18% of patients after 30 Gy and in 22% after higher doses (p = 0.81). On multivariate analysis, functional outcome was associated with visceral metastases (p = 0.030), interval from tumor diagnosis to radiotherapy (p = 0.010), and time developing motor deficits (p < 0.001). The 1-year local control rates were 76% after 30 Gy and 80% after higher doses, respectively (p = 0.64). On multivariate analysis, local control was significantly associated with visceral metastases (p = 0.029) and number of involved vertebrae (p = 0.043).

CONCLUSIONS

Given the limitations of a retrospective study, escalation of the radiation dose beyond 30 Gy/10 fractions did not significantly improve motor function and local control of MSCC in patients with relatively radioresistant tumors.

The alternative end-joining pathway for repair of DNA double-strand breaks requires PARP1 but is not dependent upon microhomologies

Non-homologous end-joining (NHEJ), the major repair pathway for DNA double-strand breaks (DSB) in mammalian cells, employs a repertoire of core proteins, the recruitment of which to DSB-ends is Ku-dependent. Lack of either of the core components invariably leads to a repair deficiency. There has been evidence that an alternative end-joining operates in the absence of the core components. We used chromosomal reporter substrates to specifically monitor NHEJ of single I-SceI-induced-DSB for detailed comparison of classical and alternative end-joining. We show that rapid repair of both compatible and non-compatible ends require Ku-protein. In the absence of Ku, cells use a slow but efficient repair mode which experiences increasing sequence-loss with time after DSB induction. Chemical inhibition and PARP1-depletion demonstrated that the alternative end-joining in vivo is completely dependent upon functional PARP1. Furthermore, we show that the requirement for PARP1 depends on the absence of Ku but not on DNA-dependent protein kinase (DNA-PKcs). Extensive sequencing of repair junctions revealed that the alternative rejoining does not require long microhomologies. Together, we show that mammalian cells need Ku for rapid and conservative NHEJ. PARP1-dependent alternative route may partially rescue the deficient repair phenotype presumably at the expense of an enhanced mutation rate.

Evading tumor evasion: current concepts and perspectives of anti-angiogenic cancer therapy

Within three decades, anti-angiogenic therapy has rapidly evolved into an integral component of current standard anti-cancer treatment. Anti-angiogenic therapy has fulfilled a number of its earlier proposed promises. The universality of this approach is demonstrated by the broad spectrum of malignant and benign tumor entities, as well as non-neoplastic diseases, that are currently treated with anti-angiogenic agents. In contrast to tumor cell targeting therapies, the development of acquired drug resistance (e.g., via mutations in growth factor receptor signaling genes) has not been described yet for the principal target of anti-angiogenic therapy--the tumor endothelium. Moreover, the tumor endothelium has emerged as a critical target of conventional cancer therapies, such as chemotherapy and radiotherapy. The presumption that tumor growth and metastasis are angiogenesis-dependent implies that the number of potential targets of an anti-cancer therapy could be reduced to those that stimulate the angiogenesis process. Therefore, the set of endogenous angiogenesis stimulants might constitute an "Achilles heel" of cancer. Direct targeting of tumor endothelium via, e.g., endogenous angiogenesis inhibitors poses another promising but clinically less explored therapeutic strategy. Indeed, the majority of current anti-angiogenic approaches block the activity of a single or at most a few pro-angiogenic proteins secreted by tumor cells or the tumor stroma. Based on our systems biology work on the angiogenic switch, we predicted that the redundancy of angiogenic signals might limit the efficacy of anti-angiogenic monotherapies. In support of this hypothesis, emerging experimental evidence suggests that tumors may become refractory or even evade the inhibition of a single pro-angiogenic pathway via compensatory upregulation of alternative angiogenic factors. Here, we discuss current concepts and propose novel strategies to overcome tumor evasion of anti-angiogenic therapy. We believe that early detection of tumors, prediction of tumor evasive mechanisms and rational design of anti-angiogenic combinations will direct anti-angiogenic therapy towards its ultimate goal--the conversion of cancer to a dormant, chronic, manageable disease.

Systems biology modeling of the radiation sensitivity network: a biomarker discovery platform

PURPOSE

The discovery of effective biomarkers is a fundamental goal of molecular medicine. Developing a systems-biology understanding of radiosensitivity can enhance our ability of identifying radiation-specific biomarkers.

METHODS AND MATERIALS

Radiosensitivity, as represented by the survival fraction at 2 Gy was modeled in 48 human cancer cell lines. We applied a linear regression algorithm that integrates gene expression with biological variables, including ras status (mut/wt), tissue of origin and p53 status (mut/wt).

RESULTS

The biomarker discovery platform is a network representation of the top 500 genes identified by linear regression analysis. This network was reduced to a 10-hub network that includes c-Jun, HDAC1, RELA (p65 subunit of NFKB), PKC-beta, SUMO-1, c-Abl, STAT1, AR, CDK1, and IRF1. Nine targets associated with radiosensitization drugs are linked to the network, demonstrating clinical relevance. Furthermore, the model identified four significant radiosensitivity clusters of terms and genes. Ras was a dominant variable in the analysis, as was the tissue of origin, and their interaction with gene expression but not p53. Overrepresented biological pathways differed between clusters but included DNA repair, cell cycle, apoptosis, and metabolism. The c-Jun network hub was validated using a knockdown approach in 8 human cell lines representing lung, colon, and breast cancers.

CONCLUSION

We have developed a novel radiation-biomarker discovery platform using a systems biology modeling approach. We believe this platform will play a central role in the integration of biology into clinical radiation oncology practice.

Treatment modelling: the influence of micro-environmental conditions

The interest in theoretical modelling of radiation response has grown steadily from a fast method to estimate the gain of new treatment strategies to an individualisation tool that may be used as part of the treatment planning algorithms. While the advantages of biological optimisation of plans are obvious, accurate theoretical models and realistic information about the micro-environmental conditions in tissues are needed. This paper aimed to investigate the clinical implications of taking into consideration the details of the tumour microenvironmental conditions. The focus was on the availability of oxygen and other nutrients to tumour cells and the relationship between cellular energy reserves and DNA repair ability as this is thought to influence the response of the various hypoxic cells. The choice of the theoretical models for predicting the response (the linear quadratic model or the inducible repair model) was also addressed. The modelling performed in this project has shown that the postulated radiobiological differences between acute and chronic hypoxia have some important clinical implications which may help to understand the mechanism behind the current success rates of radiotherapy. The results also suggested that it is important to distinguish between the two types of hypoxia in predictive assays and other treatment simulations.

Intrinsic Radiosensitivity and PLD Repair in Osteosarcoma Cell Lines

The response to radiation of seven osteosarcoma cell lines was analysed by in vitro colony-forming assay and compared with that of eight human fibroblast strains. The values of D0, the surviving fraction after 2 Gy (S2Gy), and the mean inactivation dose (D) of osteosarcoma cells in log-phase culture were significantly higher than those of fibroblast strains (p less than 0.01). PLD (potentially lethal damage) repair of osteosarcoma cells evaluated in the plateau phase of growth showed great variation for enhancement of survival, although all of the values were maximized within 12 h after irradiation. In the osteosarcoma, intrinsic radiosensitivity in vitro reflected the clinical response to radiation. However, the capacity for PLD repair might not be a good indicator for predicting the results of radiation therapy.

The Intrinsic α/β Ratio for Human Tumour Cells: Is It a Constant?

The radiation response of 15 mammalian cell lines comprising 11 human tumour, two human fibroblast and two murine lymphoma cell lines, has been analysed using the linear-quadratic equation. As well as using conventional analysis of acute dose-survival curves to derive values for alpha and beta (termed alpha ac and beta ac), low dose-rate and split-dose experiments have been used to derive independent values of alpha and beta (alpha 1dr and beta RR), respectively. alpha 1dr provides a measure of irrecoverable damage, the magnitude of which agreed well with the initial slope of the acute survival curve for most cell lines. beta RR derived from split-dose experiments represents a unique measure of recovery for each cell line. Large differences were found between individual values of beta ac and beta RR, especially in the radiosensitive cell lines. Since beta RR is a functional measure of recovery we suggest that this is the more relevant parameter in studies of dose sparing. The most striking result of this analysis was found in considering the alpha/beta ratios. No relationship was observed between alpha ac and beta ac resulting in values of alpha ac/beta ac ranging from 1 to 175. In contrast a positive correlation was observed between alpha 1dr beta RR in the 11 tumour cell lines, giving an alpha/beta ratio of 9.4 +/- 1.8 Gy. This observation of the relative constancy of the ratio for human tumour cells leads to an hypothesis about the role of initial damage as a determinant of radiosensitivity.

Radiobiological analysis of human melanoma cells on the 62 MeV CATANA proton beam

PURPOSE

To measure the ability of protons and gamma-rays to effect cell viability and cell survival of human HTB140 melanoma cells.

MATERIALS AND METHODS

Exponentially growing HTB140 cells were irradiated close to the Bragg peak maximum of the 62 MeV protons or with 60Co gamma-rays with single doses, ranging from 8 - 24 Gy. Cell viability using the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay was evaluated at 6 h, 24 h, 48 h or 7 days after irradiation and clonogenic survival was assessed at 7 days after irradiation. Cell cycle phase redistribution and the level of apoptosis were evaluated at 6 h and 48 h after irradiation.

RESULTS

The study of cell viability as a function of time (cell survival progression) and cell survival, using a clonal assay, demonstrated the considerably stronger inactivation effect of protons compared to gamma-rays with a relative biological effectiveness (RBE) of approximately 1.64. Cell cycle phase distribution and apoptosis levels with time enabled us to investigate the development and the character of the damage induced by irradiation. Due to the high radio-resistance of HTB140 cells, cell cycle phase redistribution exhibited only a modest cell accumulation in G2/M phase. Protons but not gamma-rays induced apoptosis.

CONCLUSIONS

It appears that protons reduce the number of HTB140 cells by apoptosis as well as by severe DNA damage, while gamma-rays eliminate viable cells primarily by the production of irreparable DNA damage. Protons have an increased RBE relative to gamma-rays.

Role of cell cycle in epidermal growth factor receptor inhibitor-mediated radiosensitization

Epidermal growth factor receptor (EGFR) inhibitors are increasingly used in combination with radiotherapy in the treatment of various EGFR-overexpressing cancers. However, little is known about the effects of cell cycle status on EGFR inhibitor-mediated radiosensitization. Using EGFR-overexpressing A431 and UMSCC-1 cells in culture, we found that radiation activated the EGFR and extracellular signal-regulated kinase pathways in quiescent cells, leading to progression of cells from G(1) to S, but this activation and progression did not occur in proliferating cells. Inhibition of this activation blocked S-phase progression and protected quiescent cells from radiation-induced death. To determine if these effects were caused by EGFR expression, we transfected Chinese hamster ovary (CHO) cells, which lack EGFR expression, with EGFR expression vector. EGFR expressed in CHO cells also became activated in quiescent cells but not in proliferating cells after irradiation. Moreover, quiescent cells expressing EGFR underwent increased radiation-induced clonogenic death compared with both proliferating CHO cells expressing EGFR and quiescent wild-type CHO cells. Our data show that radiation-induced enhancement of cell death in quiescent cells involves activation of the EGFR and extracellular signal-regulated kinase pathways. Furthermore, they suggest that EGFR inhibitors may protect quiescent tumor cells, whereas radiosensitization of proliferating cells may be caused by downstream effects such as cell cycle redistribution. These findings emphasize the need for careful scheduling of treatment with the combination of EGFR inhibitors and radiation and suggest that EGFR inhibitors might best be given after radiation in order to optimize clinical outcome.

Peptide receptor therapies in neuroendocrine tumors

Neuroendocrine tumors (NETs) are relatively rare tumors, mainly originating from the digestive system, able to produce bioactive amines and hormones. NETs tend to be slow growing and are often diagnosed when metastatic. The localization of a NETs and the assessment of the extent of disease are crucial for management. Commonly used diagnostic techniques include morphological imaging (ultrasound, computerized tomography, magnetic resonance), and functional imaging (somatostatin receptor scintigraphy, positron emission tomography techniques). Treatment is multidisciplinary and should be individualized according to the tumor type, burden, and symptoms. Therapeutic tools include surgery, interventional radiology, and medical treatments such as somatostatin analogues, interferon, chemotherapy, new targeted drugs and peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogues. NETs usually over-express somatostatin receptors, thus enabling the therapeutic use of somatostatin analogues, one of the basic tools, able to reduce signs and symptoms of hormone hypersecretion, improve quality of life, and slow tumor growth. PRRT with somatostatin analogues 90Y-DOTATOC and 177Lu-DOTATATE has been explored in NETs for more than a decade. Present knowledge and clinical studies indicate that it is possible to deliver high-absorbed doses to tumors expressing sst2 receptors, with partial and complete objective responses in up to 30% of patients. Side effects, involving the kidney and the bone marrow, are mild if adequate renal protection is used. Moreover, a consistent survival benefit is reported. As NETs may also express cholecystokinin 2, bombesin, neuropeptide Y or vasoactive intestinal peptide receptors even simultaneously, the potential availability and biological stability of radio-analogues will improve the multireceptor targeting of NETs.

Rapid improvement in pain and functional level in a patient with metastatic renal cell carcinoma: a case report and review of the literature

Renal cell carcinoma (RCC) represents approximately 3% of all adult cancers and is more common in males. Systemic treatment for RCC has improved following the introduction of sunitinib. Bone metastases are present in up to 50% of RCC patients. We report a case of rapid improvement in metastatic bone lesions, recorded by nuclear bone scan, in a male patient receiving localized palliative radiotherapy in addition to systemic sunitinib and zoledronic acid. Concurrently, quality of life and performance status improved dramatically. Although we are unsure of the exact mechanism for such rapid improvement in metastatic bone lesions, the swiftness this improvement deserves reporting.

Overview of radiosensitivity of human tumor cells to low-dose-rate irradiation

PURPOSE

We compared clonogenic survival in 27 human tumor cell lines that vary in genotype after low-dose-rate (LDR) or high-dose rate (HDR) irradiation. We measured susceptibility to LDR-induced redistribution in the cell cycle in eight of these cell lines.

METHODS AND MATERIALS

We measured clonogenic survival after up to 96 hours of LDR (0.25 Gy/h) irradiation. We compared these with clonogenic survival after HDR irradiation (50 Gy/h). Using flow cytometry, we measured LDR-induced redistribution as a function of time during LDR irradiation in eight of these cell lines.

RESULTS

Coefficients that describe clonogenic survival after both LDR and HDR irradiation segregate into four radiosensitivity groups that associate with cell genotype: mutant (mut)ATM, wild-type TP53, mutTP53, and an unidentified gene in radioresistant glioma cells. The LDR and HDR radiosensitivity correlates at lower doses ( approximately 2 Gy HDR, approximately 6 Gy LDR), but not at higher doses (HDR > 4 Gy; LDR > 6 Gy). The rate of LDR-induced loss of clonogenic survival changes at approximately 24 hours; wild-type TP53 cells become more resistant and mutTP53 cells become more sensitive. Redistribution induced by LDR irradiation also changes at approximately 24 hours.

CONCLUSIONS

Radiosensitivity of human tumor cells to both LDR and HDR irradiation is genotype dependent. Analysis of coefficients that describe cellular radiosensitivity segregates 27 cell lines into four statistically distinct groups, each associating with specific genotypes. Changes in cellular radiosensitivity and redistribution in the cell cycle are strongly time dependent. Our data establish a genotype-dependent time-dependent model that predicts clonogenic survival, explains the inverse dose-rate effect, and suggests possible clinical applications.

Hypofractionated high-dose intensity-modulated radiotherapy (60 Gy at 2.5 Gy per fraction) for recurrent renal cell carcinoma: a case report

A patient with renal cell carcinoma (RCC) developed synchronous bone metastasis with metachronous relapses to the bone and renal fossa. The primary lesion was initially removed surgically, and the metastatic bone lesions and locally recurrent tumours were treated by a high-fractional dose and high-total-dose intensity-modulated radiotherapy (IMRT, 60 Gy at 2.5 Gy per fraction) without significant side effects. All the grossly relapsed tumors underwent complete remission (CR) within a short time after IMRT. To date, CR has been maintained for more than two years. This case study reports the successful treatment of radioresistant RCC using a new scheme that involves a fractionation regimen with a high precision radiotherapy.

Characterization of structurally distinct, isoform-selective phosphoinositide 3'-kinase inhibitors in combination with radiation in the treatment of glioblastoma

The phosphoinositide 3'-kinase (PI3K)-mediated signaling pathway plays a key role in fundamental cellular functions important in normal cellular homeostasis and malignant transformation. Deregulated signaling through this pathway contributes to development of gliomas and their resistance to radiation and chemotherapy. Targeting the PI3K signaling pathway has thus emerged as a promising approach to successful treatment of gliomas. We assessed the radiosensitizing potential of four small-molecule inhibitors that differ in their activities against specific isoforms of the PI3K 110-kDa catalytic subunit (p110). p110alpha inhibitors blocked phosphorylation of both protein kinase B/Akt and S6 in all cell lines examined, effectively decreased cellular proliferation, and produced additive cytotoxic effects in combination with radiation therapy. The p110beta inhibitor exhibited limited biochemical effects and failed to decrease cellular proliferation or viability as either a single agent or in combination with radiation or rapamycin. In vivo studies examining the effects of the p110alpha inhibitor in combination with radiation indicated a significant reduction in tumor growth rate induced by the combined treatment compared with each treatment modality alone. This translated into a trend toward prolonged time-to-failure for mice in the combination treatment group. In conclusion, PI3K inhibitors are promising agents in the treatment of glioblastomas, especially when used in combination with ionizing radiation.

A quantitative overview of radiosensitivity of human tumor cells across histological type and TP53 status

PURPOSE

We have previously shown in a limited number of tumor cell lines derived from only two histological types that clonogenic survival patterns fall into radiosensitivity groups, each group associating with a specific genotype. We now establish a global, quantitative description of human tumor cells based on genotype-dependent radiosensitivity across histological types.

METHODS

We measure clonogenic radiosensitivity in 39 human tumor cell lines that vary in histological type (colorectal, glioblastoma, prostate, bladder, teratoma, breast, melanoma and liver) and expression of several genes purported to influence radiosensitivity: ATM (ataxia telangiectasia mutated), TP53 (tumor protein 53), CDKN1A (cyclin-dependent kinase N1A), 14-3-3sigma (an isoform of the 14-3-3 gene) and DNA mismatch repair genes . For each survival curve we use the linear-quadratic model and a linear-linear model to extract multiple coefficients and seek correlation across histological types.

RESULTS

Under one-parameter analysis, survival rate at circa 2 Gy, cell lines segregate into two major, statistically-significant groups that correlate with TP53 status (wildtype versus mutant). Under two-parameter analysis, cell lines segregate into four radiosensitivity groups based on correlations between response at lower doses (ca. 2 Gy) and a component of response to higher doses (>4 Gy).

CONCLUSIONS

Intrinsic radiosensitivity of 39 human tumor cell lines segregate into distinct genotype-dependent radiosensitivity groups that associate with mutATM, wtTP53, mutTP53, and an unidentified factor in some glioblastoma cells. Genotype-dependent radiosensitivity underlies histology-dependent variation in radiosensitivity. Our analysis establishes a quantitative overview of radiosensitivity that can predict possible response of human tumors to radiotherapy protocols.

Radioresistance in a tumour cell line correlates with radiation inducible Ku 70/80 end-binding activity

PURPOSE

The aims of the present study were to better understand the role of Ku 80, which is involved in double-strand break repair in mammalian cells in the mechanism of radiation resistance and to verify the possibility of increasing cell radiosensitivity by targeted inhibition of Ku autoantigen 80 (Ku 80).

MATERIALS AND METHODS

Western blot and electrophoretic mobility shift assay (EMSA) were performed on the human bladder carcinoma cell line RT112 (radioresistant) and on the human colorectal carcinoma cell line SW48 (radiosensitive) to assess the expression levels of DNA-dependent protein kinase (DNA-PK) components and the DNA-binding activity of the Ku 70/80 heterodimer after exposure to radiation, respectively. Ku 80 silencing was carried out with the use of small interfering RNA (siRNA).

RESULTS

Greater differences in the DNA-binding activity of Ku 70/80 and Ku 80 phosphorylation level were observed in RT112 as compared to SW48 after X-ray treatment. There is no correlation between Ku expression and DNA-binding activity at lower doses. A significant increase in nuclear Ku 80 expression was observed one hour after the exposure, only at the higher doses, while the DNA-PK catalytic subunits (DNA-PKcs) and Ku 70 levels did not change significantly. Inhibition of Ku 80 expression by siRNA induced radiosensitivity in the RT112 cell line.

CONCLUSIONS

Our data demonstrate that in a bladder tumour cell line up-regulation of Ku end-binding activity without any marked change in Ku expression underlie radiation resistance.

DNA double-strand break repair defects in syndromes associated with acute radiation response: at least two different assays to predict intrinsic radiosensitivity?

PURPOSE

Human diseases associated with acute radiation responses are rare genetic disorders with common clinical and biological features including radiosensitivity, genomic instability, chromosomal aberrations, and frequently immunodeficiency. To determine what molecular assays are predictive of cellular radiosensitivity whatever the genes mutations, the existence of a quantitative correlation between cellular radiosensitivity and unrepaired DNA double-strand breaks (DSB) repair defects was examined in a collection of 40 human fibroblasts representing 8 different syndromes.

MATERIALS AND METHODS

A number of techniques such as pulsed-field gel electrophoresis, plasmid assay and immunofluorescence with antibodies against MRE11, MDC1, 53BP1 and phosphorylated forms of H2AX, DNA-PK were applied systematically.

RESULTS AND CONCLUSIONS

Survival fraction at 2 Gy was found to be inversely proportional to the amount of unrepaired DSB, whatever the genes mutations and the assay applied. However, no single assay discriminates the full range of human radiosensitivity. Particularly, nuclear foci formed by the phosphorylation of H2AX do not predict well moderate radiosensitivities. Our findings suggest the existence of an ATM-dependent interplay between the activation of DNA-PK and MRE11. A classification of diseases according their cellular radiosensitivity, their molecular response to radiation and the functional assays permitting their evaluation is proposed.

Estimate of radiobiologic parameters from clinical data for biologically based treatment planning for liver irradiation

PURPOSE

The Radiation Therapy Oncology Group (RTOG) is initiating a few new hypofractionation regimens (RTOG 0438) to treat liver cancer patients. To evaluate the radiobiologic equivalence between different regimens requires reliable radiobiologic parameters. The purpose of this work is to estimate a plausible set of such parameters for liver tumors and to design new optimized dose fractionation schemes to increase patient survival.

METHODS AND MATERIALS

A model was developed to fit clinical survival data from irradiation of a series of primary liver patients. The model consists of six parameters including radiosensitivity parameters alpha and alpha/beta, potential doubling time T(d). Using this model together with the Lyman model for calculations of the normal tissue complication probability, we designed a series of hypofractionated treatment strategies for liver irradiation.

RESULTS

The radiobiologic parameters for liver tumors were estimated to be: alpha/beta = 15.0 +/- 2.0 Gy, alpha = 0.010 +/- 0.001 Gy (-1), T(d) = 128 +/- 12 day. By calculating the biologically effective dose using the obtained parameters, it is found that for liver patients with an effective liver volume of approximately 45% the dose fractionation regimens suggested in RTOG 0438 can be escalated to higher dose for improved patient survival ( approximately 80% at 1 year) while keeping the normal tissue complication probability to less than 10%.

CONCLUSIONS

A plausible set of radiobiologic parameters has been obtained based on clinical data. These parameters may be used for radiation treatment planning of liver tumors, in particular, for the design of new treatment regimens aimed at dose escalation.

Karyoanomalic frequency during radiation therapy

AIM

To identify the relationship between the radiosensitivity of oral cancers and to evaluate the dose-dependent relationship of nuclear abnormalities by serial cytology during fractionated radiotherapy in head and neck cancer patients.

MATERIALS AND METHODS

30 patients with histologically proven cases of squamous cell carcinoma were included in the study. Serial scrape smear were taken from the tumor before and during radiotherapy (0 to 24 Gy), and stained with Giemsa and May Grunwald's stain and frequency of micronucleated, binucleated and multinucleated cells were evaluated with the help of light microscope. The counts were expressed per 1000 uninucleated cells.

RESULTS

Each parameter showed a statistical increase with increase dose. Before treatment, the mean values of micronucleated cells, binucleated cells and multinucleated cells were 3.5, 10.1 and 4.2. At 4 Gy these were 7.7, 12.0 and 6.2 which further increased with radiation dose; and the mean values were 8.8, 16.2 and 14.9 at 14 Gy and 12.8, 18.5 and 15.1 at 24 Gy. After analysis of p-value, all such abnormal cells showed significant difference (p < 0.0001) with respect to normal subjects.

CONCLUSION

Our study results that micronucleus assay is a very useful tool in the assessment of biological damage that can help to identify tumor radiosensitivity.

Tumor cell radiosensitivity is a major determinant of tumor response to radiation

Substantial evidence suggests that the radiosensitivity of the tumor cells is the primary determinant of tumor response to radiation. More recent studies suggest that tumor stroma radiosensitivity is the principle determinant of response. To assess the relationship between intrinsic tumor cell radiosensitivity and tumor response, we altered the intrinsic radiosensitivity of a cloned tumor cell line and analyzed the effect of this alteration on tumor response. A cloned tumor cell line derived from DNA double-strand break repair--deficient severe combined immunodeficient mice was transfected with the double-strand break repair gene DNA-PKcs. The intrinsic radiosensitivity of the transfected tumor line was decreased by a factor of approximately 1.5. The isogenic lines were used to initiate tumors in NCr-nu/nu mice. When transplanted in the same strain of mice and exposed to the same dose of radiation, the isogenic tumors may be expected to exhibit a similar response to radiation if radiation damage to host stroma is the principle determinant of response. This was not observed. Over the dose range of 20 Gy in four 5-Gy fractions to a single dose of 30 Gy, the 1.5-fold increase in intrinsic tumor cell radioresistance conferred by the introduction of DNA-PKcs caused a 1.5-fold decrease in tumor growth delay. The results show that the intrinsic radiosensitivity of tumor cells is a major determinant of tumor response to radiation.

Photodynamic therapy resistant human colon carcinoma HT29 cells show cross-resistance to UVA but not UVC light

The isolation of photodynamic therapy (PDT)-resistant HT29 human colon adenocarcinoma cells has been reported previously. These PDT-resistant variants show increased expression of the Hsp27 and BNip3 proteins and a decreased expression of mutant p53 protein compared with parental HT29 cells. Because mutant p53 and increased expression of Hsp27 have been associated with resistance to various chemotherapeutic agents, whereas BNip3 is a potent inducer of apoptosis, we were interested in determining whether these PDT-resistant cells were cross-resistant to other cytotoxic agents. In the present report, we examined the colony survival of the PDT-resistant HT29 variants and several other clonal variants of HT29 cells to ultraviolet light (UV) treatment. The HT29 PDT-resistant variants showed cross-resistance to long-wavelength UVA (320-400 nm) but not to short-wavelength UVC (200-280 nm) light. Cell sensitivity to UVA or UVC was then correlated with Hsp27, BNip3 and mutant p53 protein levels in the PDT-resistant variants as well as in several clonal variants of HT29 cells that express different levels of Hsp27, BNip3 and mutant p53. We show that increased expression of Hsp27 and BNip3 and decreased expression of mutant p53 correlated with increased resistance to UVA. In contrast, increased expression of Hsp27 and BNip3 correlated with increased sensitivity to UVC, whereas increased expression of mutant p53 showed no significant correlation with sensitivity to UVC. These results suggest that the PDT-resistant HT29 cell variants are differentially sensitized to UVA compared with UVC due, in part at least, through the altered expression levels of BNip3, Hsp27 and mutant p53.

Influence of tumor cell and stroma sensitivity on tumor response to radiation

In this study, we evaluated the role of tumor cell and tumor stroma sensitivity as determinants of radiation-induced tumor growth delay. A DNA double-strand break repair-defective DNA-PKcs(-/-) tumor cell line and its radioresistant DNA-PKcs(+/+)-transfected counterpart were used to initiate tumors in nude and hypersensitive severe combined immunodeficient (SCID) mice. Insertion of the human DNA-PKcs(+/+) gene substantially increased the intrinsic radioresistance of the DNA-PKcs(-/-) tumor cells and substantially decreased tumor response to radiation in both nude and hypersensitive SCID mice. Tumor cell radiosensitivity was the major determinant of tumor response in nude mice. In SCID mice, both tumor cell sensitivity and radiation-induced stromal damage contributed to response. The relative contribution of host and tumor cell sensitivity on tumor response was unchanged for single doses of 1 x 15 and 6 x 3 Gy-fractionated dose irradiation.

A novel study investigating the therapeutic outcome of patients with lytic, mixed and sclerotic bone metastases treated with combined radiotherapy and ibandronate

PURPOSE

To investigate the therapeutic response of patients with different types of bone metastases treated with combined radiotherapy and bisphosphonates.

PATIENTS AND METHODS

By using computed tomography 52 patients were grouped into groups of lytic, mixed and sclerotic bone lesions. All patients were treated with concomitant radiotherapy and ibandronate (10 monthly cycles) and underwent clinical and radiological evaluations prior to therapy and at 3, 6 and 10 months of follow up.

RESULTS

At baseline there were statistically significant differences between the three groups for all the evaluated parameters. From 3 months onwards differences were leveled out. Statistically significant improvements were noted at all time points of evaluation for all groups in parameters such as pain (0-10), quality of life (QOL-physical functioning, 0-100) and Karnofsky performance status (KPS). The average pain score for the lytic group was reduced from 8.1 to 1.5 points at 3 months. The corresponding reductions for the mixed and sclerotic groups were from 6.2 to 0.5 and from 4.4 to 0.3 points respectively. Complete pain responses were >76.4% at all time points for all groups. Opioid consumption was also markedly reduced. Overall, the highest clinical response was noted for the lytic group, even though the mean values of pain, QOL and KPS were worse than those of the two other groups at all time points (apart from pain score at 10 months). The percentage of patients of the lytic group experiencing a complete pain response was the least of the three groups during follow up. At 10 months bone density was almost tripled for the lytic and almost doubled for the mixed group.

CONCLUSIONS

Even though the therapeutic outcome for the three groups was similar, the degree of clinical response and reossification differed.

Combination ibandronate and radiotherapy for the treatment of bone metastases: Clinical evaluation and radiologic assessment

PURPOSE

Ibandronate is a single-nitrogen, noncyclic bisphosphonate with proven efficacy for reducing metastatic bone pain. In this study, we assessed the palliative effects of combined ibandronate and radiotherapy.

METHODS AND MATERIALS

Forty-five patients with bone metastases from various solid tumors received external-beam radiotherapy, 30-40 Gy over 3-4.5, weeks combined with 10 cycles of monthly intravenous ibandronate, 6 mg.

RESULTS

After combined therapy, mean bone pain scores (graded from 0 to 10) were reduced from 6.3 at baseline to 0.8 after 3 months, with further reductions at later time points (all p < 0.001). Opioid use decreased from 84% of patients at baseline (38/45) to 24% (11/45) at 3 months, with further subsequent reductions (all p < 0.001). Mean performance status and functioning scores also significantly improved. Bone density (assessed by computed tomography scan) increased by 20% vs. baseline at 3 months, 46% at 6 months, and 73% at 10 months (all p < 0.001). Lesion improvement was also demonstrated by magnetic resonance imaging. Treatment was well tolerated with no renal toxicity.

CONCLUSIONS

In this pilot study, combined radiotherapy and ibandronate provided substantial bone pain relief and increased bone density. Computed tomography-based or magnetic resonance imaging-based evaluations offer objective methods for assessing therapeutic outcomes.

Peroxiredoxin V is essential for protection against apoptosis in human lung carcinoma cells

Sensitivity of tumor cells to treatment with anticancer drugs depends on expression and function of antiapoptotic and antioxidant proteins. The goal of our study was to determine the functional role of the novel antioxidant protein Peroxiredoxin V (PrxV), in protection of human lung carcinoma cell lines against apoptosis. Analysis of expression of PrxV in multiple lung carcinoma cell lines revealed a positive correlation between the expression of PrxV and radioresistance in vitro. Clones of the lung carcinoma cells U1810 with down-regulated expression of PrxV, or with its impaired enzymatic function (expression of redox-negative PrxV), demonstrated increased sensitivity to treatment with anticancer drugs etoposide and adriamycin. Pre-treatment of these clones with antioxidant N-acetyl-cysteine did not change their sensitivity to adriamycin, suggesting the involvement of a non-redox activity of PrxV. Expression of the redox-negative PrxV mainly affected the mitochondrial pathway of apoptosis, as assessed by cytochrome c release assay. Impairment of the PrxV enzymatic function also affected transmembrane potential and calcium loading capacity of mitochondria, as well as mitochondrial morphology. Altogether, these findings suggest that PrxV is a multifunctional protein, which is essential for protection against apoptosis induced by anticancer drugs.

Radiation-Induced Caspase-8 Mediates p53-Independent Apoptosis in Glioma Cells

Malignant gliomas are almost uniformly fatal and display exquisite radiation resistance. Glioma cells lacking wild-type (WT) p53 function are more susceptible to radiation-induced apoptosis than their isogenic counterparts expressing WT p53. We explored the mechanisms of such apoptosis and found that, in the absence of WT p53, radiation increases caspase-8 expression and activity. Inhibition of caspase-8 expression using caspase-8 antisense or small interfering RNA (siRNA) oligonucleotides partially blocks radiation-induced apoptosis. In contrast, inhibition of the mitochondrial death pathway by expression of Bcl-2 has no effect on radiation-induced caspase-8 activity or apoptosis. Our data indicate that, in contrast to commonly accepted models of p53-dependent radiation-induced apoptosis, in our cell system, radiation relies on caspase-8 activity to help mediate p53-independent cell death. In a system of inducible E2F1 activity, E2F1 activated caspase-8 and, accordingly, decreased cellular viability, effects that were abolished by caspase-8 siRNA. In this model, in the absence of WT p53, p21Cip1 is not induced, and E2F1 activity is sustained and allows transcription and activation of caspase-8. This model may explain why p53 mutations in adult gliomas paradoxically correlate with improved survival and enhanced response to radiation.

Basic Principles of Radiobiology Applied to Radiotherapy of Benign Intracranial Tumors

The use of ionizing radiation in the treatment of benign intracranial tumors may involve one of several types of ionizing radiation given as single-fraction radiosurgery or fractionated radiotherapy. An understanding of the biophysical and radiobiologic principles involved in these treatments is essential to the design and delivery of safe and efficacious treatment. This article discusses the basic radiobiologic principles applicable to radiotherapy of benign brain tumors.

Butyric acid prodrugs are histone deacetylase inhibitors that show antineoplastic activity and radiosensitizing capacity in the treatment of malignant gliomas

Histone modification has emerged as a promising approach to cancer therapy. We explored the efficacy of a novel class of histone deacetylase inhibitors in the treatment of malignant gliomas. Treatment of glioma cell lines with two butyric acid derivatives, pivaloylomethyl butyrate (AN-9) and butyroyloxymethyl butyrate (AN-1), induced hyperacetylation, increased p21(Cip1) expression, inhibited proliferation, and enhanced apoptosis. Histone deacetylase inhibitor-induced apoptosis was mediated primarily by caspase-8. Treatment of cells with AN-1 or AN-9 for 24 hours before exposure to gamma-irradiation potentiated further caspase-8 activity and resultant apoptosis. Clonogenic survival curves revealed marked reductions in cell renewal capacity of U251 MG cells exposed to combinations of AN-1 and radiation. Preliminary in vivo experiments using human glioma cell lines grown as xenografts in mouse flanks suggest in vivo efficacy of AN-9. The data suggest that novel butyric acid prodrugs provide a promising treatment strategy for malignant gliomas as single agents and in combination with radiation therapy.

Short-course radiotherapy is not optimal for spinal cord compression due to myeloma

PURPOSE

To investigate the suitability of short-course radiotherapy (RT) for spinal cord compression (SCC) in myeloma patients.

METHODS AND MATERIALS

Data for 172 myeloma patients irradiated between January 1994 and December 2004 for SCC were retrospectively evaluated. Short-course RT (1 x 8 Gy, 5 x 4 Gy, n = 61) and long-course RT (10 x 3 Gy, 15 x 2.5 Gy, 20 x 2 Gy, n = 111) were compared for functional outcome up to 24 months after RT. In addition, 10 potential prognostic factors were investigated.

RESULTS

Improvement of motor function occurred in 90 patients (52%). Forty-seven percent of nonambulatory patients regained the ability to walk. Functional outcome was significantly influenced by the time of developing motor deficits before RT. Improvement of motor function was more frequent after long-course RT than after short-course RT: 59% vs. 39% (p = 0.10) at 1 month, 67% vs. 43% (p = 0.043) at 6 months, 76% vs. 40% (p = 0.003) at 12 months, 78% vs. 43% (p = 0.07) at 18 months, and 83% v 54% (p = 0.33) at 24 months. A subgroup analysis of the long-course RT group demonstrated a similar functional outcome for 10 x 3 Gy when compared with 15 x 2.5 Gy and 20 x 2 Gy.

CONCLUSIONS

Long-course RT is preferable for SCC in myeloma patients because it resulted in better functional outcome than short-course RT. Treatment with 10 x 3 Gy can be considered appropriate.

Safety and efficacy of external beam radiation therapy for non-Hodgkin lymphoma in patients with prior90Y-ibritumomab tiuxetan radioimmunotherapy

BACKGROUND

Non-Hodgkin lymphomas (NHL) are radiosensitive tumors. Recent trials have demonstrated the effectiveness of beta irradiation delivered by monoclonal antibodies conjugated to radioisotopes such as yttrium-90 or iodine-131. Many patients eventually relapse after radioimmunotherapy (RIT) and require additional treatment. The goal of this study was to determine the safety and efficacy of external beam radiation therapy (EBRT) delivered after RIT.

METHODS

We reviewed the records of 135 patients with relapsed B-cell NHL who had received RIT with 90Y-ibritumomab tiuxetan to identify patients who subsequently received EBRT. The response rates and radiation-induced toxicity from the EBRT were assessed.

RESULTS

Nineteen of 135 (14%) patients received EBRT to a total of 39 tumor sites. Complete radiation therapy records were available for 16 patients (36 tumor sites), which formed the basis for this analysis. The median EBRT dose was 28.5 Gy (range, 10-40 Gy), with a median fraction size of 2 Gy (range, 1-5 Gy). Response data were available for 29 treated sites. The overall response rate was 90% (26/29) with 12 complete responses (41%), 7 complete clinical responses (24%), 7 partial responses (24%), and 3 stable (10%). Toxicities were generally transient, reversible, and corresponded to the anatomic regions irradiated.

CONCLUSIONS

EBRT can produce tumor responses at sites of NHL that relapse after RIT with acceptable toxicity.

A phase II trial of palliative radiotherapy for metastatic renal cell carcinoma

BACKGROUND

Renal cell carcinoma (RCC) has previously been described as being less responsive to radiotherapy (RT) than other tumor types. The authors conducted a prospective study to assess the effect of RT on symptoms and quality of life (QOL) in patients with metastatic RCC.

METHODS

Between 1996 and 2002, patients with symptomatic metastatic RCC were entered into a prospective study in two cancer centers. Symptomatic sites of disease were treated with 30 grays (Gy) in 10 fractions. Patients reported pain, analgesic use, symptoms, and QOL using validated questionnaires before RT, 1 month and 3 months after treatment, and every 3 months to 1 year thereafter.

RESULTS

Thirty-one patients (19 males and 12 females) were entered into the trial. The median age of the patients was 61 years (range, 35-81 yrs). The most common indication for RT was bone pain (n = 24). The median duration of follow-up was 4.3 months (range, 1-15 mos). Of 23 evaluable patients treated for pain, 83% (n = 19) experienced site-specific pain relief after RT, and 48% (n = 11) did not have an associated increase in analgesic medication use. The median duration of site-specific pain response was 3 months (range, 1-15 mos). The global pain response rate was only 15% (n = 3) because many patients developed other painful metastases. Global QOL was found to improve in 33% (n = 8) of the evaluable patients.

CONCLUSIONS

A palliative radiotherapy dose of 30 Gy in 10 fractions can result in a significant response rate and the relief of local symptoms in patients with bone metastases from RCC. Improvements in global pain and QOL appear to be limited by the effects of progressive systemic disease.