Radiation survival of vascular smooth muscle cells as a function of age

Managing an Older Adult with Cancer: Considerations for Radiation Oncologists

Older adults with cancer present a unique set of management complexities for oncologists and radiation oncologists. Prognosis and resilience to cancer treatments are notably dependent on the presence or risk of "geriatric syndromes," in addition to cancer stage and histology. Recognition, proper evaluation, and management of these conditions in conjunction with management of the cancer itself are critical and can be accomplished by utilization of various geriatric assessment tools. Here we review principles of the geriatric assessment, common geriatric syndromes, and application of these concepts to multidisciplinary oncologic treatment. Older patients may experience toxicities related to treatments that impact treatment effectiveness, quality of life, treatment-related mortality, and treatment compliance. Treatment-related burdens from radiotherapy are increasingly important considerations and include procedural demands, travel, costs, and temporary or permanent loss of functional independence. An overall approach to delivering radiotherapy to an older cancer patient requires a comprehensive assessment of both physical and nonphysical factors that may impact treatment outcome. Patient and family-centered communication is also an important part of developing a shared understanding of illness and reasonable expectations of treatment.

Stereotactic ablative body radiation therapy for tumors in the lung in octogenarians: a retrospective single institution study

Background

Treatment of cancer in the lung in octogenarians is limited by their health and functional status. Stereotactic ablative radiotherapy is an established noninvasive treatment option for medically inoperable patients, with a toxicity profile that may be more tolerable in elderly patients.

Methods

Patients more than 80 years old treated with stereotactic ablative radiotherapy for malignant tumors in the lung between January 2007 and August 2012 at a single institution were identified and retrospectively analyzed for toxicity and survival.

Results

Thirty patients were identified with a total of 32 lesions treated. Patients ranged in age from 80.8 to 90.7 years old (median 84.9) at the time of treatment. Twenty patients had ECOG performance status 0–1, and 10 had performance status 2–3. Stage distribution at treatment was: stage I (20 patients), stage III (1), stage IV (1), and 8 recurrent tumors. Patients were treated to a median total dose of 54 Gy in 3 fractions (range 20–60 Gy in 1 to 5 fractions). Median follow up was 13 months (range 2–60 months). Fifteen patients were still living at last review. There was one failure in field and one failure in the same lobe that was treated. One patient died with progressive regional disease, and four died of progressive metastatic disease. Three patients had late grade 3 pulmonary dyspnea with no grade 4 or 5 toxicities. One patient had late grade 2 pneumonitis, and 3 patients had late grade 1 pneumonitis. Three patients had grade 1 chest wall pain.

Conclusions

Octogenarians tolerated ablative treatment with minimal toxicity. Stereotactic ablative body radiotherapy is an option to consider in treatment of elderly patients.

Vein graft failure

After the creation of an autogenous lower extremity bypass graft, the vein must undergo a series of dynamic structural changes to stabilize the arterial hemodynamic forces. These changes, which are commonly referred to as remodeling, include an inflammatory response, the development of a neointima, matrix turnover, and cellular proliferation and apoptosis. The sum total of these processes results in dramatic alterations in the physical and biomechanical attributes of the arterialized vein. The most clinically obvious and easily measured of these is lumen remodeling of the graft. However, although somewhat less precise, wall thickness, matrix composition, and endothelial changes can be measured in vivo within the healing vein graft. Recent translational work has demonstrated the clinical relevance of remodeling as it relates to vein graft patency and the systemic factors influencing it. By correlating histologic and molecular changes in the vein, insights into potential therapeutic strategies to prevent bypass failure and areas for future investigation are explored.

Radiation therapy in the elderly: more side effects and complications?

Aging is associated with physiological changes and comorbid illnesses, which may affect an individual's tolerance to radiation. There is the belief that a relationship exists between age and radiation toxicity and therefore non-curative schemes are offered to older patients. Preclinical studies show that normal tissue radiation-induced toxicity differs little with age. In the clinical setting, retrospective and some prospective studies have reported that elderly patients treated with radical radiotherapy alone or in combination with chemotherapy, who do not have comorbidities and retain a good performance status, show a benefit in treatment outcomes. However, an increase in acute effects or a lowered functional tolerance has also been reported. To select candidates for radical treatments, a specific geriatric assessment should be used to stratify elderly patients as a function of the physiological status. Only specifically designed prospective studies can define the role of radiation treatment in elderly patients with different physiological status.

Radiation therapy in the elderly

The purpose of this review is to highlight aspects of radiation oncology specifically related to aging and caring for the older patient with cancer. Particular emphasis is placed on the preclinical and clinical studies focusing on the efficacy and toxicity of RT in this population. Special techniques are also reviewed that have particular relevance to the treatment of the elderly.

Vascularization in the transition area between free grafted soft tissues and pre-irradiated graft bed tissues following preoperative radiotherapy in the head and neck region

BACKGROUND

The healing of free vascular grafts in a pre-irradiated graft bed is characterized by an increased risk of wound healing disorders. For that reason, the aim of this study was to examine quantitative vascularization pattern between free vascular grafts and the pre-irradiated graft bed as a function of the preoperative irradiation dose.

METHODS

A total of 217 free microvascular hard and soft tissue grafts were used within 199 patients in the head and neck region to cover defects after ablative tumor surgery. Seventy-six patients (group 1) had no prior radiation (RT), 50 patients (group 2) were treated with preoperative radiochemotherapy using 40 to 50 Gy and 5-FU/cisplatin, and 73 patients (group 3) had prior RT (60-70 Gy) between 1 and 7 years before surgery. After healing of the grafts, samples were taken from 42 patients from the graft, the irradiated graft bed, and the transition area between graft and irradiated graft bed. Samples were analyzed as follows: capillary sprouting, structural changes, and distribution patterns were analyzed by immunohistochemical staining (CD34 labeling of capillary endothelium). Three histological sections (2-4 microm) per sample were examined histomorphometrically (ratio capillary area/total area, capillary lumen, and the number of capillaries) by (National Institute of Health) NIH-image-digitized measurements. A statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney test (two-tailed p <.05).

RESULTS

The success rate of vascular grafts in group 1 (0 Gy) was 94%, in group 2 (40-50 Gy/5-FU/cisplatin) 90%, in group 3 (60-70 Gy) 84%. In contrast to groups 1 and 2, group 3 showed qualitatively reduced and more irregular capillary distribution with more marked pericapillary fibrosis in the irradiated tissue. Quantitatively, the ratio capillary area/total area, as a marker of improved capillarization, was significantly reduced in group 3 (median 0.01; IQR 0.02) compared with group 1 (median 0.53; IQR 0.32) and group 2 (median 0.44; IQR 1.40) (p <.001).

CONCLUSION

After preoperative RT, vascularization of the graft bed decreased continuously as a function of the total dose and time after RT. The results strongly advocate the use of a primary reconstruction after a time interval between 4 and 6 weeks following preoperative RT and suggest the use of a total radiation dose of 40 to 50 Gy.

Inhibition of rat smooth muscle proliferation by radiation after arterial injury: temporal characteristics in vivo and in vitro

Although several studies have suggested that inhibition of arterial narrowing by radiation after angioplasty is dependent on both time and dose, little is known regarding the temporal aspects of this effect and the mechanisms by which radiation affects the response of smooth muscle cells to injury. To determine the time course of inhibition of intimal hyperplasia by radiation, 135 rats were given single-fraction external gamma irradiation (1-10 Gy) to one carotid artery at intervals from 5 days before to 5 days after bilateral carotid artery balloon catheter injury, and intimal cross-sectional area was determined from histological sections at 20 days after injury. There was a prominent time- and dose-dependent inhibition of intimal hyperplasia by radiation when it was administered before or after balloon injury, with the greatest effect noted within 24 h before or after injury. To investigate the effect of radiation on smooth muscle cell growth (by cell counting) and proliferation, cell cycle kinetics (by BrdU incorporation), and cell killing (by clonogenic assay), smooth muscle cell cultures derived from rat aortic explants were seeded in equine plasma to induce quiescence, and radiation (2.5-10 Gy) was administered at various intervals before or after synchronous growth stimulation by 10% whole blood serum. A similar time and dose dependence was noted in growth kinetics, BrdU incorporation and cell killing for smooth muscle cells irradiated in vitro; in each case, the effect was most prominent for radiation administered in temporal proximity to stimulation with whole blood serum. By Western blot analysis, cultured smooth muscle cells showed a rapid time-dependent increase in Cdkn1a (formerly known as p21) protein expression, followed by a delayed increase in Tp53 (formerly known as p53) expression after irradiation. Activation of intracellular caspases, manifest by proteolytic poly(ADP-ribose) polymerase (PARP) cleavage, was not detected in smooth muscle cell cultures after irradiation. These observations suggest that radiation limits intimal hyperplasia in vivo by a transient, reversible process. Although apparent cytotoxic injury occurs in vitro, apoptosis of smooth muscle cells is not apparent. Both inhibition of proliferation of smooth muscle cells and cell cycle delay may contribute to inhibition of intimal hyperplasia in vivo by radiation.

Effects of radiation on cerebral vasculature: a review

Radiation therapy plays a critical role in the treatment of central nervous system neoplasms and cerebral arteriovenous malformations. The deleterious effects of radiation on cerebral arteries may be the primary limitation to these treatment methods, as radiation may cause a variety of cerebrovascular injuries and hemodynamic changes. Radiation-induced changes in the cerebral arterial wall are determined by a number of cellular processes in endothelium and smooth muscle cells that modulate differences in radiosensitivity and phenotypic expression. The histopathological findings in arterial radiation injury include vessel wall thickening, thrombosis, luminal occlusion, and occasional telangiectases. Mechanisms for radiation injury to blood vessels include phenotypic changes in normal vessel wall cells (especially endothelium) manifested by the expression or suppression of specific gene and protein products that affect cell cycle progression or cellular proliferation or demise via cytotoxic injury or apoptosis. This review describes the molecular and cellular events involved in the systemic and cerebral vascular response to radiation and the potential means by which these responses may be influenced to augment the therapeutic effects of radiation while minimizing the untoward consequences.

Gamma irradiation inhibits neointimal hyperplasia in rats after arterial injury

BACKGROUND AND PURPOSE

Restenosis complicates a significant proportion of endovascular and open vascular procedures such as carotid endarterectomy. In contrast to the primary atheroma, restenosis is characterized by intimal hyperplasia of vascular smooth muscle cells. We hypothesized that gamma radiation would reduce restenosis by limiting intimal hyperplasia after arterial injury.

METHODS

To demonstrate the effect of gamma radiation on smooth muscle hyperplasia in vivo, a standardized bilateral carotid balloon catheter arterial injury was produced in 37 rats. A single dose of 750, 1500, or 2250 cGy (1cGy = 1 rad) gamma radiation was delivered to the right carotid artery at either 1 or 2 days after injury; the shielded contralateral carotid artery served as matched control. At 21 days after injury, vessels were perfusion-fixed in situ, and cross-sectional area of neointima was determined from axial sections using image analysis.

RESULTS

Marked reductions in neointimal cross-sectional area were demonstrated in vessels subjected to 1500- and 2250-cGy radiation at both 1 and 2 days after injury. A less prominent effect was noted for 750 cGy, reaching statistical significance only at 2 days after injury. By two-way ANOVA, radiation dose (P = .0002), timing of radiation delivery (P = .003), and an interaction between timing and dose (P = .0278) were significantly associated with reduction in neointimal cross-sectional area. At 1500 cGy, delivery of radiation 1 day after injury inhibited neointimal hyperplasia more prominently than the same dose 2 days after injury; a dose-response relation was evident at 1 day.

CONCLUSIONS

Radiation may be an important adjunctive therapy for reducing the incidence of restenosis after angioplasty or endarterectomy.

Survival and repair of potentially lethal radiation damage in confluent vascular smooth muscle cell cultures

Confluent cultures of rat aortic smooth muscle cells demonstrated dose-dependent potentially lethal damage repair (PLDR), with an average repair factor of 4 for a 10 Gy dose. PLDR occurred with a half-time of 2 hours and was nearly maximal by 8 h. Among other factors, PLDR may contribute to the radioresistance of large blood vessels.