Biological basis of radiation therapy for cancer

Future Treatment Strategies for Cancer Patients Combining Targeted Alpha Therapy with Pillars of Cancer Treatment: External Beam Radiation Therapy, Checkpoint Inhibition Immunotherapy, Cytostatic Chemotherapy, and Brachytherapy

Cancer is one of the most complex and challenging human diseases, with rising incidences and cancer-related deaths despite improved diagnosis and personalized treatment options. Targeted alpha therapy (TαT) offers an exciting strategy emerging for cancer treatment which has proven effective even in patients with advanced metastatic disease that has become resistant to other treatments. Yet, in many cases, more sophisticated strategies are needed to stall disease progression and overcome resistance to TαT. The combination of two or more therapies which have historically been used as stand-alone treatments is an approach that has been pursued in recent years. This review aims to provide an overview on TαT and the four main pillars of therapeutic strategies in cancer management, namely external beam radiation therapy (EBRT), immunotherapy with checkpoint inhibitors (ICI), cytostatic chemotherapy (CCT), and brachytherapy (BT), and to discuss their potential use in combination with TαT. A brief description of each therapy is followed by a review of known biological aspects and state-of-the-art treatment practices. The emphasis, however, is given to the motivation for combination with TαT as well as the pre-clinical and clinical studies conducted to date.

Combining Pr3+-Doped Nanoradiosensitizers and Endogenous Protoporphyrin IX for X-ray-Mediated Photodynamic Therapy of Glioblastoma Cells

Glioblastoma multiforme is an aggressive type of brain cancer with high recurrence rates due to the presence of radioresistant cells remaining after tumor resection. Here, we report the development of an X-ray-mediated photodynamic therapy (X-PDT) system using NaLuF₄:25% Pr³⁺ radioluminescent nanoparticles in conjunction with protoporphyrin IX (PPIX), an endogenous photosensitizer that accumulates selectively in cancer cells. Conveniently, 5-aminolevulinic acid (5-ALA), the prodrug that is administered for PDT, is the only drug approved for fluorescence-guided resection of glioblastoma, enabling dual detection and treatment of malignant cells. NaLuF₄:Pr³⁺ nanoparticles were synthesized and spectroscopically evaluated at a range of Pr³⁺ concentrations. This generated radioluminescent nanoparticles with strong emissions from the ¹S₀ excited state of Pr³⁺, which overlaps with the Soret band of PPIX to perform photodynamic therapy. The spectral overlap between the nanoparticles and PPIX improved treatment outcomes for U251 cells, which were used as a model for the thin tumor margin. In addition to sensitizing PPIX to induce X-PDT, our nanoparticles exhibit strong radiosensitizing properties through a radiation dose-enhancement effect. We evaluate the effects of the nanoparticles alone and in combination with PPIX on viability, death, stress, senescence, and proliferation. Collectively, our results demonstrate this as a strong proof of concept for nanomedicine.

The role of radiation therapy in the management of cutaneous malignancies. Part I: Diagnostic modalities and applications

Radiation therapy offers distinct advantages over other currently available treatments for cutaneous malignancies in certain circumstances. Dermatologists and dermatologic surgeons should be familiar with the available radiation therapy techniques as well as their value and potential limitations in a variety of clinical scenarios. The first article in this 2-part continuing medical education series highlights the mechanisms, modalities, and applications of the most commonly used radiotherapy treatments as they relate to cutaneous oncology. We review the current indications for the use of radiation in the treatment of various cutaneous malignancies, the techniques commonly employed in modern radiotherapy, and the associated complications.

Organoids as Complex In Vitro Models for Studying Radiation-Induced Cell Recruitment

Patients with triple negative breast cancer (TNBC) typically receive chemotherapy, surgery, and radiation therapy. Although this treatment improves prognosis for most patients, some patients continue to experience recurrence within 5 years. Preclinical studies have shown that immune cell infiltration at the irradiated site may play a significant role in tumor cell recruitment; however, little is known about the mechanisms that govern this process. This lack of knowledge highlights the need to evaluate radiation-induced cell infiltration with models that have controllable variables and maintain biological integrity. Mammary organoids are multicellular three-dimensional (3D) in vitro models, and they have been used to examine many aspects of mammary development and tumorigenesis. Organoids are also emerging as a powerful tool to investigate normal tissue radiation damage. In this review, we evaluate recent advances in mammary organoid technology, consider the advantages of using organoids to study radiation response, and discuss future directions for the applications of this technique.

Durable therapeutic gain despite competing mortality in long-term follow-up of a randomized hyperfractionated radiotherapy trial for locally advanced head and neck cancer

Purpose/objectives

To examine the therapeutic ratio and mortality profile over time in a radiotherapy randomized trial in stage III-IV larynx/pharynx cancer with long-term follow-up.

Materials/methods

From 1988 to 1995, 331 cases were randomized to either hyperfractionated (HF) (58 Gy/40 fractions, twice daily) or conventional (CF) (51 Gy/20 fractions, once daily) radiotherapy. Overall survival (OS), locoregional (LRC), distant control (DC), ≥Grade 3 late toxicity (LT), and relative mortality risk profile over time were compared between both arms.

Results

Median follow-up was 13.6 years. HF had a 10% improved OS at 5-years (40% vs 30%, p = 0.04), but the benefit diminished to 3% at 10-years (21% vs 18%). A trend towards higher LRC with HF remained (5-year: 49% vs 40%; 10-year: 49% vs 39%, p = 0.05). DC rates were unchanged (5-year: 87% vs 85%; 10-year: 87 vs 84%, p = 0.56). LT rates were similar (HF vs CF: 5-year: 9% vs 12%; 10-year: 11% vs 14%, p = 0.27). Multivariable analysis confirmed that HF reduced mortality risk by 31% [HR 0.69 (0.55-0.88), p < 0.01] and locoregional failure risk by 35% [HR 0.65 (0.48-0.89), p < 0.01]. Index cancer mortality (5-year: 46% vs 51%; 10-year: 49% vs 55%) was lower in the HF arm. Competing mortality (mostly smoking-related) was also numerically lower with HF at 5-years (14% vs 19%) but became similar at 10-years (30% vs 28%).

Conclusions

This trial confirms that HF with augmented total dose has a durable 10% effect size on LRC with comparable LT. OS benefit is evident at 5-years (10%) but relative mortality risk profile changes in longer follow-up.

Biological characteristics of gene expression features in pancreatic cancer cells induced by proton and X-ray irradiation

BACKGROUND

Radiation therapy is an important alternative treatment for advanced cancer. The aim of the current study was to disclose distinct alterations of the biological characteristics of gene expression features in pancreatic cancer cells, MIAPaCa-2, following proton and X-ray irradiation.

MATERIALS AND METHODS

Using cDNA microarray, we examined the gene expression alterations of MIAPaCa-2 cells following proton or X-ray irradiation. We also isolated the surviving MIAPaCa-2 cells after irradiation and analyzed their gene expression profiles.

RESULTS

Although the cytocidal effects of both types of irradiation were similar at sufficient doses in vitro and in vivo, the affected gene expression profile alterations of MIAPaCa-2 cells irradiated with protons were distinct from those irradiated with X-ray. Interestingly, clustering analysis of gene expression of the surviving MIAPaCa-2 cells was also completely discernible between the two types of irradiation. However, a similar cytocidal effect was still observed in the proton- and X-ray-irradiated surviving cells after re-irradiation, commonly showing biological effects related to apoptosis and cell cycle processes.

CONCLUSIONS

Proton irradiation treatment for pancreatic cancer provides the distinct biological effect of steady gene expression alterations compared to X-ray irradiation; however, surviving cells from both types of irradiation were still susceptible to the cytocidal effects induced by proton re-irradiation treatment.

Integrating nanomedicine into clinical radiotherapy regimens

While the advancement of clinical radiotherapy was driven by technological innovations throughout the 20th century, continued improvement relies on rational combination therapies derived from biological insights. In this review, we highlight the importance of combination radiotherapy in the era of precision medicine. Specifically, we survey and summarize the areas of research where improved understanding in cancer biology will propel the field of radiotherapy forward by allowing integration of novel nanotechnology-based treatments.

Chemoradiotherapy screening in a novel biomimetic polymer based pancreatic cancer model

Pancreatic Ductal Adenocarcinoma (PDAC) is a deadly and aggressive disease with a very low survival rate. This is partly due to the resistance of the disease to currently available treatment options. Herein, we report for the first time the use of a novel polyurethane scaffold based PDAC model for screening the short and relatively long term (1 and 17 days post-treatment) responses of chemotherapy, radiotherapy and their combination. We show a dose dependent cell viability reduction and apoptosis induction for both chemotherapy and radiotherapy. Furthermore, we observe a change in the impact of the treatment depending on the time-frame, especially for radiation for which the PDAC scaffolds showed resistance after 1 day but responded more 17 days post-treatment. This is the first study to report a viable PDAC culture in a scaffold for more than 2 months and the first to perform long-term (17 days) post-treatment observations in vitro. This is particularly important as a longer time-frame is much closer to animal studies and to patient treatment regimes, highlighting that our scaffold system has great potential to be used as an animal free model for screening of PDAC.

Poly-urethane scaffold based 3D pancreatic cancer model enables realistic long term chemotherapy and radiotherapy screening. This model can be used for personalised treatment screening.

[Hypofractionated radiotherapy for glioblastoma: changing the radiation treatment paradigm]

Hypofractionation has the dual advantage of increased cell death with a higher dose per fraction and a reduced effect of accelerated tumor cell repopulation due to a shorter overall treatment time. However, the potential advantage may be offset by increased toxicity in the late-responding neural tissues. Recently, investigators have attempted delivering radical doses of HFRT by escalating the dose in the immediate vicinity of the enhancing tumor and postoperative surgical cavity and reported reasonable outcomes with acceptable toxicity levels. Three different studies of high-dose HFRT have reported on the paradoxical phenomenon of improved survival in patients developing radiation necrosis at the primary tumor site. The toxicity criteria of RTOG and EORTC have defined clinically or radiographically suspected radionecrosis as Grade 4 toxicity. However, most patients diagnosed with radiation necrosis in the above studies remained asymptomatic. Furthermore, the probable association with improved survival would strongly argue against adopting a blind approach for classifying radiation necrosis as Grade 4 toxicity. The data emerging from the above studies is encouraging and strongly argues for further research. However, the majority of these studies are predominantly retrospective or relatively small single-arm prospective series that add little to the overall quality of evidence. Notwithstanding the above limitations, HFRT appears to be a safe and feasible strategy for glioblastoma patients.

Proton Beam Radiotherapy of Uveal Melanoma: Italian Patients Treated in Nice, France

Purpose

To evaluate the results of 15 years of experience with proton beam radiotherapy in the treatment of intraocular melanoma, and to determine univariate and multivariate risk factors for local failure, eye retention, and survival.

Methods

A total of 368 cases of intraocular melanoma were treated with proton beam radiotherapy at Centre Lacassagne Cyclotron Biomedical of Nice, France, between 1991 and 2006. Actuarial methods were used to evaluate rate of local tumor control, eye retention, and survival after proton beam radiotherapy. Cox regression models were extracted to evaluate univariate risk factors, while regularized least squares algorithm was used to have a multivariate classification model to better discriminate risk factors.

Results

Tumor relapse occurred in 8.4% of the eyes, with a median recurrence time of 46 months. Enucleation was performed on 11.7% of the eyes after a median time of 49 months following proton beam; out of these, 29 eyes were enucleated due to relapse and 16 due to other causes. The univariate regression analysis identified tumor height and diameter as primary risk factors for enucleation. Regularized least squares analysis demonstrated the higher effectiveness of a multivariate model of five risk factors (macula distance, optic disc distance, tumor height, maximum diameter, and age) in discriminating relapsed vs nonrelapsed patients.

Conclusions

This data set, which is the largest in Italy with relatively long-term follow-up, demonstrates that a high rate of tumor control, survival, and eye retention were achieved after proton beam irradiation, as in other series.

Mathematical Modeling of the Effects of Tumor Heterogeneity on the Efficiency of Radiation Treatment Schedule

Radiotherapy uses high doses of energy to eradicate cancer cells and control tumors. Various treatment schedules have been developed and tried in clinical trials, yet significant obstacles remain to improving the radiotherapy fractionation. Genetic and non-genetic cellular diversity within tumors can lead to different radiosensitivity among cancer cells that can affect radiation treatment outcome. We propose a minimal mathematical model to study the effect of tumor heterogeneity and repair in different radiation treatment schedules. We perform stochastic and deterministic simulations to estimate model parameters using available experimental data. Our results suggest that gross tumor volume reduction is insufficient to control the disease if a fraction of radioresistant cells survives therapy. If cure cannot be achieved, protocols should balance volume reduction with minimal selection for radioresistant cells. We show that the most efficient treatment schedule is dependent on biology and model parameter values and, therefore, emphasize the need for careful tumor-specific model calibration before clinically actionable conclusions can be drawn.

Optimal treatment and stochastic modeling of heterogeneous tumors

In this work we review past articles that have mathematically studied cancer heterogeneity and the impact of this heterogeneity on the structure of optimal therapy. We look at past works on modeling how heterogeneous tumors respond to radiotherapy, and take a particularly close look at how the optimal radiotherapy schedule is modified by the presence of heterogeneity. In addition, we review past works on the study of optimal chemotherapy when dealing with heterogeneous tumors.

REVIEWERS

This article was reviewed by Thomas McDonald, David Axelrod, and Leonid Hanin.

Bilateral Isolated Coronary Ostial Stenosis following Mediastinal Irradiation

Isolated coronary ostial narrowing is rare and may represent a separate disease entity from atherosclerotic coronary artery disease. The case of a 41-year-old female with no coronary risk factors who developed severe bilateral isolated coronary ostial stenosis following mantle radiotherapy for Hodgkin's disease is described. She underwent urgent coronary artery bypass grafting and has remained well for 3 years.

Treatment of Breast and Prostate Cancer by Hypofractionated Radiotherapy: Potential Risks and Benefits

Breast cancer and prostate cancer are the most common cancers diagnosed in women and men, respectively, in the UK, and radiotherapy is used extensively in the treatment of both. In vitro data suggest that tumours in the breast and prostate have unique properties that make a hypofractionated radiotherapy treatment schedule advantageous in terms of therapeutic index. Many clinical trials of hypofractionated radiotherapy treatment schedules have been completed to establish the extent to which hypofractionation can improve patient outcome. Here we present a concise description of hypofractionation, the mathematical description of converting between conventional and hypofractionated schedules, and the motivation for using hypofractionation in the treatment of breast and prostate cancer. Furthermore, we summarise the results of important recent hypofractionation trials and highlight the limitations of a hypofractionated treatment regimen.

Biologically effective dose and breast cancer conservative treatment: is duration of radiation therapy really important?

To evaluate if biologically effective dose (BED), and in particular the duration of radiation treatment, has an effect on local relapse risk. Between January 2000 and December 2008 a total of 762 patients with T1-2 N0/+ breast cancer was treated with breast-conserving surgery and radiotherapy, with and without hormone therapy and chemotherapy. Adjuvant radiation therapy was administered to a total dose of 60-66 Gy in 30-33 fractions. The computed BEDs were divided in four groups: <43.1, 43.1-44.9, 45.0-46.1, and >46.1 Gy (A-D, respectively). Kaplan-Meier method was used to calculate local relapse rates. Cox regression method was used to identify prognostic factors of local relapse. Evaluated variables were age, tumor histology, tumor size, surgical margin status, axillary nodal status, tumor grading, adjuvant therapies, adjuvant chemotherapy alone, adjuvant hormone therapy alone, adjuvant anthracyclines, and BEDs values. 8-year local relapse rates were 18.0% for group A, 8.5% for group B, 4.6% for group C, and 2.7% for group D (P=0.008). Multivariate Cox regression analysis showed that BEDs values were associated with higher local relapse risk (P=0.001). In our study, a prolongation of radiotherapy treatment, intended as a lower BED value, after breast-conserving surgery is associated with an increased risk of local relapse. Considering the wide range of results published in other studies, hypofractionation for breast cancer should be considered, at the moment, feasible in selected patients.

Language disorders in children with central nervous system injury

Children with injury to the central nervous system (CNS) exhibit a variety of language disorders that have been described by members of different disciplines, in different journals, using different descriptors and taxonomies. This paper is an overview of language deficits in children with CNS injury, whether congenital or acquired after a period of normal development. It first reviews the principal CNS conditions associated with language disorders in childhood. It then describes a functional taxonomy of language, with examples of the phenomenology and neurobiology of clinical deficits in children with CNS insults. Finally, it attempts to situate language in the broader realm of cognition and in current theoretical accounts of embodied cognition.

Effect of stereotactic radiosurgery on lipids and proteins of normal and hypoperfused rat brain homogenates: A Fourier transform infrared spectroscopy study

PURPOSE

The effect of stereotactic radiosurgery on lipids and proteins of normal and hypoperfused rat brain was investigated to see if hypoxic areas are really more resistant to radiation effects or not.

MATERIALS AND METHODS

Rat brain samples from control, stereotactically irradiated and chronically hypoperfused plus stereotactically irradiated groups were homogenized separately with saline phosphate buffer, and centrifuged at 125,000 g for 15 min. Membrane rich parts (pellet) of these homogenates were used for Fourier Transform Infrared (FTIR) spectroscopy studies. Mann-Whitney U tests were performed on the groups, two by two, to test the significance of the differences between the control group and stereotactically irradiated group as well as the control group and chronically hypoperfused plus stereotactically irradiated group.

RESULTS

After a single high dose of X-rays to healthy rat brain, the lipid concentration increased slightly, protein content decreased significantly (p < 0.05) and protein-to-lipid ratio decreased slightly. The secondary structure of the proteins was altered in the irradiated brain samples such that the content of a-helical structure decreased significantly (p < 0.01) and random coil increased dramatically (p < 0.05). The effect of radiation on the content of a-helical structure was not found to be significant in the hypoperfused group, but the decrease in the content of random coil was significant (p < 0.01).

CONCLUSION

Stereotactic radiosurgery of the brain increased the lipid concentration, decreased the protein concentration and consequently resulted in a decrease in the protein to lipid ratio compared to un-irradiated brain. Radiation also altered the secondary structure of protein. The variations in lipid and protein content and the resulting lipid to protein ratio imply that chronically hypoperfused brain is more vulnerable to radiation than non-hypoperfused brain and suggests chronic hypoperfusion does not prevent cerebral damage caused by irradiation. However, irradiation of hypoperfused brain resulted in less alteration in protein structure than in non-hyperfused brain, suggesting higher resistance to irradiation using this endpoint.

Long-term neuromotor speech deficits in survivors of childhood posterior fossa tumors: effects of tumor type, radiation, age at diagnosis, and survival years

The cerebellum is important for the coordination of fluent speech. The authors studied how childhood cerebellar tumors affect long-term neuromotor speech outcomes, including the relation between outcome and tumor type, radiation, age at diagnosis, and survival years. Videotaped speech samples of child and adult long-term survivors of childhood cerebellar astrocytoma (nonradiated) and medulloblastoma (radiated) tumors and healthy controls were analyzed by 2 speech pathologists for ataxic dysarthria, dysfluency, and speech rate. Ataxia varied with tumor type/radiation. Medulloblastoma survivors had significantly more ataxic dysarthric features than either survivors of astrocytomas or controls, who did not differ from each other. Dysfluency varied with a history of a posterior fossa tumor. Medulloblastoma and astrocytoma survivors were each significantly more dysfluent than controls but did not differ from each other. Speech rate varied with age and tumor type. Adult controls were significantly faster than child controls, although adult tumor survivors were comparable to their child counterparts. Adult controls had significantly faster speech rates than adult survivors of medulloblastoma tumors. Ataxic dysarthric speech characteristics are more frequent in radiated survivors of medulloblastoma tumors than nonradiated survivors of astrocytoma tumors. Dysfluent and slow speech occur in cerebellar tumor survivors, regardless of tumor type and radiation history. Cerebellar tumors in childhood limit speech rate in adulthood.

Late effects from hadron therapy

Successful cancer patient survival and local tumor control from hadron radiotherapy warrant a discussion of potential secondary late effects from the radiation. The study of late-appearing clinical effects from particle beams of protons, carbon, or heavier ions is a relatively new field with few data. However, new clinical information is available from pioneer hadron radiotherapy programs in the USA, Japan, Germany and Switzerland. This paper will review available data on late tissue effects from particle radiation exposures, and discuss its importance to the future of hadron therapy. Potential late radiation effects are associated with irradiated normal tissue volumes at risk that in many cases can be reduced with hadron therapy. However, normal tissues present within hadron treatment volumes can demonstrate enhanced responses compared to conventional modes of therapy. Late endpoints of concern include induction of secondary cancers, cataract, fibrosis, neurodegeneration, vascular damage, and immunological, endocrine and hereditary effects. Low-dose tissue effects at tumor margins need further study, and there is need for more acute molecular studies underlying late effects of hadron therapy.

Chronomics: circadian and circaseptan timing of radiotherapy, drugs, calories, perhaps nutriceuticals and beyond

We suggest a putative benefit from timing nutriceuticals (substances that are both nutrients and pharmaceuticals) such as antioxidants for preventive or curative health care, based on the proven merits of timing nutrients, drugs, and other treatments, as documented, i.a., in India. The necessity of timing melatonin, a major antioxidant, is noted. A protocol to extend the scope of chronoradiotherapy awaits testing. Imaging in time by mapping rhythms and broader time structures, chronomes, for earliest diagnoses, for example detection of vascular disease risk, is recommended. The study of rhythms and broader chronomes leads to a dynamic functional genomics, guided by imaging in time of free radicals and antioxidants, amongst many other variables.

Investigating the effect of cell repopulation on the tumor response to fractionated external radiotherapy

In this work we study the descriptive power of the main tumor control probability (TCP) models based on the linear quadratic (LQ) mechanism of cell damage with cell recovery. The Poisson, binomial, and a dynamic TCP model, developed recently by Zaider and Minerbo are considered. The Zaider-Minerbo model takes cell repopulation into account. It is shown that the Poisson approximation incorporating cell repopulation is conceptually incorrect. Based on the Zaider-Minerbo model, an expression for the TCP for fractionated treatments with varying intervals between two consecutive fractions and with cell survival probability that changes from fraction to fraction is derived. The models are fitted to an experimental data set consisting of dose response curves that correspond to different fractionation regimes. The binomial TCP model based on the LQ mechanism of cell damage solely was unable to fit the fractionated response data. It was found that the Zaider-Minerbo model, which takes tumor cell repopulation into account, best fits the data.

Influence of the delay of adjuvant postoperative radiation therapy on relapse and survival in oropharyngeal and hypopharyngeal cancers

PURPOSE

To determine whether the delay between surgery and the beginning of radiation therapy influences survival or the risk of local-regional relapse in oropharyngeal or hypopharyngeal squamous cell carcinomas.

METHODS AND MATERIALS

From 2052 patients referred to the Henri Becquerel Center for the radiation therapy of an oropharyngeal or hypopharyngeal cancer between January 1, 1981 and December 31, 1992, 420 were included in a retrospective study. Exclusion criteria were another cancer, metastasis, incomplete resection, lack of homolateral lymph node resection, or previous chemotherapy. Radiation therapy delivered 45 to 75 Gy on initial location and lymph node. Follow-up was performed until December 31, 1997. A Cox proportional hazard regression analysis was used to evaluate the prognostic factors.

RESULTS

The delay between surgery and radiation therapy was not found to be a significant prognostic factor for survival or risk of local-regional relapse. The only parameters found to influence local-regional and survival control were margins' pathologic state (respectively p < 0.0001 and p = 0.015) and T (p < 0.0001) and N (respectively p < 0.0001 and p = 0.0004) stages. In terms of local-regional relapse only, age was a prognostic factor (p = 0.048), and a trend was noted for tumor emboli in vessels or nerves (p = 0.061).

CONCLUSION

In patients with oropharyngeal or hypopharyngeal squamous cell carcinoma, the delay between surgical procedure and radiation therapy does not influence survival or risk of local-regional relapse. Radiation therapy might be subjected to complete healing in these patients.

Expectations and quality of life of cancer patients undergoing radiotherapy

Expectations, real or false, affect the way patients respond to their illnesses. We assessed therapy-related expectations in relation to global quality of life in 55 cancer patients before and after radiotherapy. Factor analysis indicated that therapy-related expectations come into three broad categories--pain/emotional control, healing and tumour/symptom control. 35 patients expected 'healing' even though curative treatment was intended in only 19 and all patients had been fully informed. The expectation of healing was associated with high quality of life, and the same was true of perception of healing after radiotherapy. In the group as a whole, quality of life was little altered by radiotherapy, but it became substantially worse in those patients who had expected healing but perceived that this had failed, even though physician-assessed Karnofsky status did not change. These findings indicate that the expectation of healing, in cancer patients, is a component of a good global quality of life, whereas more limited expectations (pain control, tumour control) relate to lower quality of life. Patients' expectations deserve further study as a novel approach to improving care.

Dynamic optimization of a linear-quadratic model with incomplete repair and volume-dependent sensitivity and repopulation

PURPOSE

The linear-quadratic model typically assumes that tumor sensitivity and repopulation are constant over the time course of radiotherapy. However, evidence suggests that the growth fraction increases and the cell-loss factor decreases as the tumor shrinks. We investigate whether this evolution in tumor geometry, as well as the irregular time intervals between fractions in conventional hyperfractionation schemes, can be exploited by fractionation schedules that employ time-varying fraction sizes.

METHODS

We construct a mathematical model of a spherical tumor with a hypoxic core and a viable rim, which is most appropriate for a prevascular tumor, and is only a caricature of a vascularized tumor. This model is embedded into the traditional linear-quadratic model by assuming instantaneous reoxygenation. Dynamic programming is used to numerically compute the fractionation regimen that maximizes the tumor-control probability (TCP) subject to constraints on the biologically effective dose of the early and late tissues.

RESULTS

In several numerical examples that employ five or 10 fractions per week on a 1-cm or 5-cm diameter tumor, optimally varying the fraction sizes increases the TCP significantly. The optimal regimen incorporates large Friday (afternoon, if 10 fractions per week) fractions that are escalated throughout the course of treatment, and larger afternoon fractions than morning fractions.

CONCLUSION

Numerical results suggest that a significant increase in tumor cure can be achieved by allowing the fraction sizes to vary throughout the course of treatment. Several strategies deserve further investigation: using larger fractions before overnight and weekend breaks, and escalating the dose (particularly on Friday afternoons) throughout the course of treatment.

Hyperfractionated accelerated radiotherapy (HART) for inoperable, nonmetastatic non-small cell lung carcinoma of the lung (NSCLC): results of a phase II study for patients ineligible for combination radiochemotherapy

PURPOSE

To evaluate a hyperfractionated and accelerated radiotherapy (HART) protocol in patients with inoperable non-small cell lung carcinoma (NSCLC) who were ineligible for combination radiochemotherapy studies.

METHODS AND MATERIALS

From February 1989 through August 1994, 23 patients ineligible for available combined modality protocols in our institution were enrolled and treated with HART, consisting of 63 Gy given in 42 fractions of 1.5 Gy each, twice daily, with a minimum time interval of 6 h between fractions, 5 days a week, over an elapsed time of 4.2 weeks, or 29 days. There was no planned interruption.

RESULTS

The 1-, 2-, and 3-year survival rates were 61%, 39%, and 19%, respectively, with a median survival of 16.8 months. At the time of analysis, 4 patients are alive and 19 have died, 16 from NSCLC and 3 from cardiac disease. Overall response rate was 48%, with 22% of patients achieving a complete response and 26% a partial response. Correlation between acute response rate and survival was poor. First site of relapse was local-regional in 8 patients (35%), distant in 6 patients (26%), and local-regional and distant in 4 (17%) patients. One patient had Grade IV and 2 had Grade III esophagitis. One patient presented with chronic Grade III lung toxicity. There were no treatment-related deaths.

CONCLUSION

In this group of 23 patients ineligible for radiochemotherapy, this HART regime was quite feasible and was followed by little toxicity. Results in this particularly poor prognosis NSCLC patient category should be compared to series with a similar patient profile; however, median survival is at least similar to that obtained in recent series of combination radiochemotherapy.

Influence of dose-rate on inflammatory damage and adhesion molecule expression after abdominal radiation in the rat

PURPOSE

The goal of this study was to assess the effects of two clinically relevant radiation dose-rates on endothelial adhesion molecule expression, inflammatory response, and microvascular dysfunction.

METHODS AND MATERIALS

Rats were irradiated with 10 Gy at low (0.9 Gy/min) or high (3 Gy/min) dose-rates. Control animals received sham irradiation. Leukocyte rolling, adhesion, emigration, and microvascular permeability were assessed in mesenteric venules by intravital microscopy 6 hours after irradiation. P-selectin and intercellular adhesion molecule-1 (ICAM-1) expression were measured using radiolabeled monoclonal antibodies.

RESULTS

Low dose-rate (LDR) abdominal irradiation increased leukocyte adhesion compared with sham-irradiated animals, whereas high dose-rate (HDR) irradiation resulted in enhanced leukocyte rolling, adhesion, and emigration, compared with the LDR or with sham-irradiated rats. Both dose-rates increased microvascular permeability, although this effect was significantly greater after radiation with the high (8-fold) than the low (5-fold) dose-rate. HDR radiation induced significantly larger increments in P-selectin expression in splanchnic organs than LDR, whereas in most organs ICAM-1 expression was only upregulated by the HDR. Blockade of ICAM-1, but not P-selectin, abrogated leukocyte adhesion at both dose-rates.

CONCLUSIONS

The magnitude of upregulation of endothelial adhesion molecules, leukocyte recruitment, and endothelial barrier dysfunction elicited by radiation therapy is dependent on the dose-rate at which the radiation is delivered.

Randomized study of CODE versus alternating CAV/EP for extensive-stage small-cell lung cancer: an Intergroup Study of the National Cancer Institute of Canada Clinical Trials Group and the Southwest Oncology Group

PURPOSE

To determine whether an intensive weekly chemotherapy regimen plus thoracic irradiation is superior to standard chemotherapy in the treatment of extensive-stage small-cell lung cancer (ESCLC).

PATIENTS AND METHODS

Patients with ESCLC were considered eligible for the study if they were younger than 68 years, had a performance status of 0 to 2, and were free of brain metastases. Patients were randomized to receive cisplatin, vincristine, doxorubicin, and etoposide (CODE) or alternating cyclophosphamide, doxorubicin, vincristine/etoposide and cisplatin (CAV/EP). Consolidative thoracic irradiation and prophylactic cranial irradiation were given to patients responding to CODE and according to investigator discretion on the CAV/EP arm.

RESULTS

The fidelity of drug delivery on both drug regimens was equal, and more than 70% of all patients received the intended protocol chemotherapy. Although rates of neutropenic fever were similar, nine (8.2%) of 110 patients on the CODE arm died during chemotherapy, whereas one (0.9%) of 109 patients died on the CAV/EP arm. Response rates after chemotherapy were higher (P =.006) with CODE (87%) than with CAV/EP (70%). However, progression-free survival (median of 0.66 years on both arms) and overall survival (median, 0.98 years for CODE and 0. 91 years for CAV/EP) were not statistically different.

CONCLUSION

The CODE regimen increased two-fold the received dose-intensity of four of the most active drugs in small-cell lung cancer compared with the standard CAV/EP regimen while maintaining an approximately equal total dose. Despite supportive care (but not routine prophylactic use of granulocyte colony-stimulating factor), there was excessive toxic mortality with the CODE regimen. The response rate with CODE was higher than that of CAV/EP, but progression-free and overall survival were not significantly improved. In view of increased toxicity and similar efficacy, the CODE chemotherapy regimen is not recommended for treatment of ESCLC.

Molecular genetic alterations in radiation-induced astrocytomas

Astrocytic tumors occasionally arise in the central nervous system following radiotherapy. It is not clear if these gliomas represent a unique molecular genetic subset. We identified nine cases in which an astrocytoma arose within ports of previous radiation therapy, with total doses ranging from 2400 to 5500 cGy. Irradiated primary lesions included craniopharyngioma, pituitary adenoma, Hodgkin's lymphoma, ependymoma, pineal neoplasm, rhabdomyosarcoma, and three cases of lymphoblastic malignancies. Patients ranged from 9 to 60 years of age and developed secondary tumors 5 to 23 years after radiotherapy. The 9 postradiation neoplasms presented as either anaplastic astrocytoma (3 cases) or glioblastoma multiforme (6 cases). Two of the latter contained malignant mesenchymal components. We performed DNA sequence analysis, differential polymerase chain reaction (PCR), and quantitative PCR on DNA from formalin-fixed, paraffin-embedded tumors to evaluate possible alterations of p53, PTEN, K-ras, EGFR, MTAP, and p16 (MTS1/CDKN2) genes. By quantitative PCR, we found EGFR gene amplification in 2 of 8 tumors. One of these demonstrated strong immunoreactivity for EGFR. Quantitative PCR showed chromosome 9p deletions including p16 tumor suppressor gene (2 of 7 tumors) and MTAP gene (3 of 7). Five of 9 tumors demonstrated diffuse nuclear immunoreactivity for p53 protein. Sequencing of the p53 gene in these 9 cases revealed a mutation in only one of these cases, a G-to-A substitution in codon 285 (exon 8). Somewhat unexpectedly, no mutations were identified in PTEN, a commonly altered tumor suppressor gene in de novo glioblastoma multiformes. Unlike some radiation-induced tumors, no activating point mutations of the K-ras proto-oncogene or base pair deletions of tumor suppressor genes were noted. These radiation-induced tumors are distinctive in their high histological grade at clinical presentation. The spectrum of molecular genetic alterations appears to be similar to that described in spontaneous high grade astrocytomas, especially those of the de novo type.

Radiation therapy in tumors of the central nervous system

OBJECTIVES

To review the role of radiation therapy in the management of primary tumors of the central nervous system (CNS).

DATA SOURCES

Book chapters, review articles, and research studies.

CONCLUSIONS

Radiation therapy plays an important role in the management of primary and metastatic tumors of the CNS. Radiation and surgery are combined with curative intent for low-grade tumors. Cranial radiation may be used to prevent brain metastases, and palliative radiation may be used to alleviate symptoms.

IMPLICATIONS FOR NURSING PRACTICE

Helping patients with tumors of the CNS and their family members understand the anticipated side effects of the disease and the therapeutic goals of radiation therapy may help to alleviate anxiety and maintain an optimal quality of life during therapy.

Randomised multicentre trials of CHART vs conventional radiotherapy in head and neck and non-small-cell lung cancer: an interim report. CHART Steering Committee

While radiotherapy is proceeding, tumour cells may proliferate. The use of small individual doses reduces late morbidity. Continuous hyperfractionated accelerated radiation therapy (CHART), which reduces overall treatment from 6-7 weeks to 12 days and gives 36 small fractions, has now been tested in multicentre randomised controlled clinical trials. The trial in non-small-cell lung cancer included 563 patients and showed improvement in survival; 30% of the CHART patients were alive at 2 years compared with 20% in the control group (P = 0.006). In the 918 head and neck cases, there was only a small, non-significant improvement in the disease-free interval. In this interim analysis there was a trend for those with more advanced disease (T3 and T4) to show advantage; this will be subject to further analysis when the data are more mature. The early mucosal reactions appeared sooner and were more troublesome with CHART, however they quickly settled; so far no difference in long-term morbidity has emerged. These results support the hypothesis that tumour cell repopulation can occur during a conventional course of radiotherapy and be a cause of treatment failure.

Conferring drug resistance by MDR1 gene transfection increases susceptibility to irradiation and lipid peroxidation in 3T3 cell line

This study was performed to test the hypothesis that conferring multiple drug resistance reduces cell susceptibility to irradiation and iron-stimulated lipid peroxidation. Multidrug resistant (PN1A) and parental drug sensitive (PSI-2) cell lines were exposed to ADP-Fe or Ascorbate-Fe complexes at 37 degrees C and to irradiation. Lipid peroxidation was estimated by the TBA test, whereas x-ray effect was estimated by clonogenic assay. Cell glutathione-S-transferase (GST), total and Se-dependent glutathione peroxidase (GSH-Px) activities, and glutathione and vitamin E were measured. PN1A produced more peroxides than PSI-2 after exposure to iron complexes and formed fewer colonies after irradiation. Higher activities of GST and total and Se-GSH-Px were observed in PN1A. Vitamin E and total glutathione did not differ in the two cell subclones. These data show that the induction of the mdr1 phenotype by transfection of mdr1 gene in 3T3 cells increases susceptibility to irradiation and iron stimulated lipid peroxidation.

Evaluation of response to radiotherapy in head and neck cancer by positron emission tomography and [11C]methionine

PURPOSE

To evaluate the usefulness of positron emission tomography (PET) and L-[methyl-11C]methionine in assessing treatment response to radiotherapy in head and neck cancer.

METHODS AND MATERIALS

Fifteen patients with head and neck cancer (13 with squamous cell carcinoma, 1 with adenocystic carcinoma, and 1 with paranasal plasmocytoma) underwent a PET study with [11C]-methionine both before and after preoperative radiotherapy to the total tumor dose of 61-73 Gy. Twelve primary and 12 metastatic tumor sites were within the field of view. Nineteen of the 24 tumor sites were surgically explored after radiotherapy, and the tumor standardized uptake values (SUVs) of [11C]methionine were compared with histological findings.

RESULTS

All 24 malignant lesions were detectable in the pretreatment study. In all but one case, the tumor SUV decreased after radiotherapy. The median SUV of the tumor site was smaller (1.9, range, 1.3-3.1, n = 7) in cases with histologically verified complete response than in cases with persistent cancer (median 4.1, range, 2.8-7.6, n = 12, p = 0.0008). A complete histological response was verified in none of the 9 cases with a postirradiation SUV larger than the median (3.1), whereas 7 of the 10 cases with a SUV of 3.1 or smaller had complete response (p = 0.003). The preirradiation uptake of [11C]methionine in tumors did not have significant association with histological response (p = 0.45). The PET findings correlated well with follow-up data in five cases with unoperated tumor sites. The [11C]methionine uptake of the submandibular salivary glands decreased after radiotherapy (p = 0.04).

CONCLUSION

PET with [11C]methionine as a tracer may be useful in assessing response to radiotherapy in head and neck cancer. High uptake of [11C]methionine in the postirradiation scan suggests the presence of persistent disease.

Ionizing radiation damage to cells: effects of cell cycle redistribution

If a population of cycling cells is exposed to a fixed dose of ionizing radiation delivered over time T, it is sometimes observed that increasing T increases the amount of cell killing. This is essentially because at first the radiation preferentially kills cells in a sensitive portion of the cycle and the surviving, more resistant cells then have time to reach more sensitive stages. We refer to this effect as population resensitization, caused by redistribution within the cell cycle. We investigate the effect theoretically by employing the McKendrick-von Foerster equation for age-structured proliferating cell populations, generalized by introducing a radiation damage term. Within our formalism, we show that population resensitization occurs whenever: (a) prior to irradiation the cell population has the stable age-distribution approached asymptotically by an unirradiated population, and (b) T is sufficiently small. Examples and other cases are outlined. The methods of Volterra integral equations, renewal theory, and positive semigroup theory are applied. The effect of varying T is evaluated by considering the ultimate amplitude of the stable age-distribution population at times much greater than both the irradiation duration and the average cell-cycle time. The main biological limitations of the formalism are the following: considering only radiation damage which is not subject to enzymatic repair or quadratic misrepair, using an overly naive method of ensuring loss of cell cycle synchrony, neglecting nonlinear effects such as density inhibition of growth, and neglecting radiatively induced perturbations of the cell cycle. Possible methods for removing these limitations are briefly discussed.

Lens changes after proton beam irradiation for uveal melanoma

PURPOSE

Because limited data exist on the incidence of lens changes after therapeutic intraocular irradiation, we studied a group of patients who underwent proton irradiation for uveal melanoma, in order to estimate cumulative rates of radiation-induced posterior subcapsular opacities and age-related lens changes at specific time points. after irradiation.

METHODS

Cumulative rates for each type of opacity were estimated from among the 383 patients, treated between 1987 and 1989, who had clear lenses or minimal lens changes before irradiation. Cox's proportional hazards model was used to evaluate the independent effects of tumor and treatment-related characteristics on the development of posterior subcapsular opacities in these patients. Risk factors for posterior subcapsular opacities were evaluated.

RESULTS

By three years after irradiation, posterior subcapsular opacities had developed in 42% of the patients, and rates increased significantly with lens dose and with tumor height. The risk of posterior subcapsular opacities was over three times higher when the lens received a substantial dose of irradiation (adjusted relative risk, 3.25; 95% confidence interval, 1.60-6.59), as compared with minimal dose, and was three times higher when the tumor was highly elevated (adjusted relative risk, 3.05; 95% confidence interval, 1.45-6.40) as compared with minimally elevated lesions. Opacities in the other segments of the lens were age related.

CONCLUSIONS

These data show that patients receiving therapeutic intraocular irradiation have a high risk of developing posterior subcapsular opacities. As expected, the leading risk determinant of posterior subcapsular change is the amount of irradiation received by the lens.

Development of clinical radiotherapy since 1896

From the discovery of x-rays in November 1895 and the first publication in December 1985 it did not take long for the first x-ray therapy of cancer in January 1896. The first 25 years in the history of radiotherapy was not a very flattering period for the discipline. During the following 25 years, however, important developments in clinical radiotherapy occurred and in some countries the speciality of radiotherapy was established in the 1930s. In the last 50 years gradual changes have taken place and now modern radiotherapy is an established curative method in the treatment of cancer. The scientific background of radiotherapy is solid, and the understanding of cancer biology and radiobiology has improved drastically. The radiotherapists of today are cancer specialists, oncologists. The technical development has been enormous. The future of radiation oncology looks very promising, with local cancer treatment being shown to be most effective.

Influence of time-dependent stochastic heterogeneity on the radiation response of a cell population

A solid tumor is a cell population with extensive cellular heterogeneity, which severely complicates tumor treatment by therapeutic agents such as ionizing radiation. We model the response to ionizing radiation of a multicellular population whose cells have time-dependent stochastic radiosensitivity. A reaction-diffusion equation, obtained by assuming a random process with the radiation response of a cell partly determined by competition between repair and binary misrepair of DNA double-strand breaks, is used. By a suitable transformation, the equation is reduced to that of an Ornstein-Uhlenbeck process so explicit analytic solutions are available. Three consequences of the model's assumptions are that (1) response diversity within a population increases resistance to radiation, that is, the population surviving is greater than that anticipated from considering an average cell; (2) resistant cell subpopulations preferentially spared by the first part of a prolonged radiation protocol are driven biologically into more radiosensitive states as time increases, that is, resensitization occurs; (3) an inverse dose-rate effect, that is, an increase in cell killing as overall irradiation time is increased, occurs in those situations where resensitization dominates effects due to binary misrepair of repairable damage. The results are consistent with the classic results of Elkind and coworkers on extra cell killing attributed to cell-cycle redistribution and are in agreement with some recent results on in vitro and in vivo population radiosensitivity. They also generalize the therapeutic paradigm that low dose rate or fractionated radiation can help overcome hypoxic radioresistance in tumors.

Radiotherapy for painful bone metastases

Bone metastases are a frequent cause of morbidity in patients with malignant disease. Pain is the commonest symptom; it can be treated successfully in the majority of patients by local external beam irradiation. Controversy exists over which regimen should be used, with a single dose necessitating only one treatment visit to the radiotherapy department, or a fractionated course requiring several visits. Many radiotherapists continue to use fractionated regimens despite the current evidence that single fractions are as effective. Many reasons exist for this, including departmental policy and training, fears of recurrence, problems with retreatment of previously treated areas, fears of increased early and late morbidity, and attempts at promoting recalcification. The majority of these reasons are theoretical and have yet to be substantiated. In many patients, symptomatic bone metastases are widespread, and hemibody irradiation, although more toxic, should be considered in order to avoid the need for repeated courses of local treatment.

Radiation injuries of the colon and rectum

Approximately 5% to 10% of patients receiving abdominopelvic radiation therapy will develop a colon or rectal injury. Thorough evaluation of the patient to determine the extent of the injury and the presence of concomitant lesions and to rule out recurrent malignancy is urged. Many radiation complications can be managed with medical regimens. Although colostomy remains a valuable and frequently utilized mode of treatment, it is by no means the sole alternative when surgical intervention is required. Rectal resection with colorectal or coloanal anastomosis can be performed safely for some injuries involving the distal rectum. Surgery for irradiated bowel should be focused on minimizing dissection to minimize injuries and on providing healthy non-irradiated tissues to provide adequate blood supply to promote healing. Patients who have received abdominopelvic radiation are at greater risk of developing colorectal cancer, and cancer surveillance should be commenced 5 years after completion of therapy.

Severe coronary artery disease after radiation therapy of the chest and mediastinum: clinical presentation and treatment

OBJECTIVE

To define the clinical and angiographic features and the therapeutic problems in patients with coronary artery disease after therapeutic irradiation of the chest.

DESIGN

An observational retrospective study.

SETTING

The cardiac catheterisation laboratory, university medical school.

PATIENTS

15 subjects (8 men and 7 women, aged 25-56 years, mean 44) examined in the cardiac catheterisation laboratory, who had significant coronary artery disease years after having radiation treatment to the chest and anterior mediastinum. In the early stages of the study angiography was performed because of typical symptoms of ischaemic heart disease. Later on it was performed because of a high index of suspicion in people with signs of extensive radiation heart damage.

MAIN OUTCOME MEASURES

Clinical and electrocardiographic evidence of ischaemic heart disease; echocardiographic signs of pericardial, myocardial or valvar involvement; angiographic evidence of coronary arterial stenosis, with special attention to the ostia; haemodynamic and angiographic signs of pericardial, myocardial, and valvar disease. Survival and symptomatic and functional status were ascertained after medical or surgical treatment.

RESULTS

The patients were relatively young and had no risk factors. Seven patients had no signs or symptoms of ischaemic heart disease. Ten patients had ostial stenosis, which was associated with extensive involvement of other cardiac structures in nine of them. Seven required surgical treatment for coronary artery disease. Two died, one at surgery and the other one six months later. Five patients had complications associated with irradiation.

CONCLUSIONS

Coronary arterial disease can be reasonably ascribed to the effects of chest irradiation when the patients are young and free from risk factors, especially if the obstructions are ostial and there is important damage to other cardiac structures. In patients with damage to other cardiac structures angina and infarction are often absent and coronary angiography seems to be mandatory. Patients often require surgical treatment and postoperative complications are common.

Cancer in the elderly

This article reviews geriatric oncology and assesses options for treatment and care of the elderly patient with cancer. The size of the population over 65 years old is defined, with particular reference to the continuing growth of this subsection of the community. The high incidence of many cancers and their associated mortality rates in the elderly are identified and the epidemiology of such diseases in the geriatric population is addressed. Given the discrepancies in incidence and survival rates between patients younger and older than 65 years, the association between tumorigenesis and the aging process is explored. Specific aspects of tumor growth in the elderly are considered. General considerations of therapy for elderly patients with cancer are discussed, including the pharmacokinetics and pharmacodynamics of chemotherapy in those over 65 years old, surgical options, the use of radiotherapy, and overall patient assessment. Next, treatment options for individual cancer states are reviewed, with particular emphasis on newer treatment options designed specifically for the elderly. Sections on cancer screening and supportive care are also included, the latter dealing with aspects of symptom control, quality of life assessment, and the physical and psychologic rehabilitation of the elderly patient with cancer who is undergoing treatment. Conclusions are then drawn as to the extent of the oncological process in those over 65 years old, with particular emphasis on the underdiagnosis and undertreatment of many malignancies in the past. The challenge created by the growing elderly population is underscored and necessary plans of action for oncologists in the future are defined. Such proposals are necessary if inroads are to be made into the unacceptable morbidity and mortality rates borne by our elderly patients with cancer.