Local treatment of mixed osteolytic/osteoblastic spinal metastases: is photodynamic therapy effective?

Progress of Phototherapy Applications in the Treatment of Bone Cancer

Bone cancer including primary bone cancer and metastatic bone cancer, remains a challenge claiming millions of lives and affecting the life quality of survivors. Conventional treatments of bone cancer include wide surgical resection, radiotherapy, and chemotherapy. However, some bone cancer cells may remain or recur in the local area after resection, some are highly resistant to chemotherapy, and some are insensitive to radiotherapy. Phototherapy (PT) including photodynamic therapy (PDT) and photothermal therapy (PTT), is a clinically approved, minimally invasive, and highly selective treatment, and has been widely reported for cancer therapy. Under the irradiation of light of a specific wavelength, the photosensitizer (PS) in PDT can cause the increase of intracellular ROS and the photothermal agent (PTA) in PTT can induce photothermal conversion, leading to the tumoricidal effects. In this review, the progress of PT applications in the treatment of bone cancer has been outlined and summarized, and some envisioned challenges and future perspectives have been mentioned. This review provides the current state of the art regarding PDT and PTT in bone cancer and inspiration for future studies on PT.

Assessment of 5-Aminolevulinic Acid-Mediated Photodynamic Therapy on Bone Metastases: An in Vitro Study

Simple Summary

Bone metastases are typically associated with a short-term prognosis. Photodynamic therapy (PDT) emerges as a promising alternative treatment for targeting metastatic lesions. In this study we investigated the effect of 5-aminolevulinic acid-mediated PDT treatment on both primary and human bone metastatic cancer cell lines. We found that human cell lines have different sensitivity to the same doses and exposure of 5-ALA PDT resulting in two different cell fates, apoptosis or senescence, depending on the extent of the cellular damage. As such, PDT has potential applicability in bone metastases of invasive ductal carcinoma.

Abstract

Bone is a frequent site of metastases, being typically associated with a short-term prognosis in affected patients. Photodynamic therapy (PDT) emerges as a promising alternative treatment for controlling malignant disease that can directly target interstitial metastatic lesions. The aim of this study was to assess the effect induced by PDT treatment on both primary (giant cell bone tumor) and human bone metastatic cancer cell lines (derived from a primary invasive ductal breast carcinoma and renal carcinoma). After 24 h post light delivery (blue light-wavelength 436 nm) with 5-aminolevulinic acid, the effect on cellular migration, viability, apoptosis, and senescence were assessed. Our results showed that bone metastasis derived from breast cancer reacted with an inhibition of cell migration coupled with reduced viability and signs of apoptosis such as nuclei fragmentation following PDT exposure. A limited effect in terms of cellular viability inhibition was observed for the cells of giant cell bone tumors. In contrast, bone metastasis derived from renal carcinoma followed a different fate—cells were characterized by senescent features, without a notable effect on cell migration or viability. Collectively, our study illustrates that PDT could act as a successful therapy concept for local tumor control in some entities of bone metastases.

Photodynamic therapy outcome modelling for patients with spinal metastases: a simulation-based study

Spinal metastases often occur in the advanced stages of breast, lung or prostate cancer, resulting in a significant impact on the patient's quality of life. Current treatment modalities for spinal metastases include both systemic and localized treatments that aim to decrease pain, improve mobility and structural stability, and control tumour growth. With the development of non-toxic photosensitizer drugs, photodynamic therapy (PDT) has shown promise as a minimally invasive non-thermal alternative in oncology, including for spinal metastases. To apply PDT to spinal metastases, predictive algorithms that optimize tumour treatment and minimize the risk of spinal cord damage are needed to assess the feasibility of the treatment and encourage a broad acceptance of PDT in clinical trials. This work presents a framework for PDT modelling and planning, and simulates the feasibility of using a BPD-MA mediated PDT to treat bone metastases at two different wavelengths (690 nm and 565 nm). An open-source software for PDT planning, PDT-SPACE, is used to evaluate different configurations of light diffusers (cut-end and cylindrical) fibres with optimized power allocation in order to minimize the damage to spinal cord or maximize tumour destruction. The work is simulated on three CT images of metastatically involved vertebrae acquired from three patients with spinal metastases secondary to colorectal or lung cancer. Simulation results show that PDT at a 565 nm wavelength has the ability to treat 90% of the metastatic lesion with less than 17% damage to the spinal cord. However, the energy required, and hence treatment time, to achieve this outcome with the 565 nm is infeasible. The energy required and treatment time for the longer wavelength of 690 nm is feasible ([Formula: see text] min), but treatment aimed at 90% of the metastatic lesion would severely damage the proximal spinal cord. PDT-SPACE provides a simulation platform that can be used to optimize PDT delivery in the metastatic spine. While this work serves as a prospective methodology to analyze the feasibility of PDT for tumour ablation in the spine, preclinical studies in an animal model are ongoing to elucidate the spinal cord damage extent as a function of PDT dose, and the resulting short and long term functional impairments. These will be required before there can be any consideration of clinical trials.

Evolving role of minimally invasive techniques in the management of symptomatic bone metastases

PURPOSE OF REVIEW

Bone metastases are responsible for considerable morbidity, which can significantly limit a patient's quality of life. This article aims to review minimally invasive, image-guided locoregional treatments for symptomatic bone metastases as an adjunct to conventional treatment modalities.

RECENT FINDINGS

Conservative therapy and radiation therapy (RT) can be effective at addressing pain, however, they require time to achieve optimal efficacy and do not address the instability and progressive collapse of pathological fractures. Vertebral and pelvic augmentation with cement enhances structural stability and can prevent progressive collapse and deformity. Ablative therapies, including radiofrequency ablation (RFA), cryoablation, and photodynamic therapy (PDT), induce cellular destruction of tumor tissue. RFA and PDT can be combined with cement augmentation in a single sitting.

SUMMARY

Minimally invasive image-guided treatments can provide rapid pain relief, enhance mechanical stability, and improve quality of life. These treatments are associated with low complication rates and are suitable for frail patients. They can be used as companion procedures to conventional treatments, or function as an alternative for patients with radioresistant biologies or those with dose limitations from prior RT sessions.

Functionalizing NaGdF4:Yb,Er Upconverting Nanoparticles with Bone-Targeting Phosphonate Ligands: Imaging and In Vivo Biodistribution

Lanthanide-doped upconverting nanoparticles (UCNPs) transform near infrared light (NIR) into higher-energy UV and visible light by multiphotonic processes. Owing to such unique feature, UCNPs have found application in optical imaging and have been investigated for the NIR light activation of prodrugs, including transition metal complexes of interest in photochemotherapy. Besides, UCNPs also function as magnetic resonance imaging (MRI) contrast agents and positron emission tomography (PET) probes when labelled with radionuclides such as 18F. In this contribution, we report on a new series of phosphonate-functionalized NaGdF4:Yb,Er UCNPs that show affinity for hydroxyapatite (inorganic constituent of bones), and we discuss their potential as bone targeting multimodal (MRI/PET) imaging agents. In vivo biodistribution studies of 18F-labelled NaGdF4:Yb,Er UCNPs in rats indicate that surface functionalization with phosphonates favours the accumulation of nanoparticles in bones over time. PET results reveal leakage of 18F− for phosphonate-functionalized NaGdF4:Yb,Er and control nanomaterials. However, Gd was detected in the femur for phosphonate-capped UCNPs by ex vivo analysis using ICP-MS, corresponding to 6–7% of the injected dose.

Photodynamic therapy in spinal metastases: a qualitative analysis of published results

The current study was to perform qualitative comparison of photodynamic therapy (PDT), based on previously published articles on spinal disease distribution status before and after treatment. Spinal metastasis, the migration of primary cancer cells and establishment of secondary tumors in the spine. We electronically searched CENTRAL (The Cochrane Library 2012), MEDLINE, EMBASE, CINAHL and AMED (from their beginning to December 31, 2012) to identify published studies assessing the effectiveness of PDT in spinal metastases. Our inclusion criteria resulted in only 4 articles, all in mice models. Due to study limitations and sparse data, the quality of evidence for all outcomes was low. Our analyses shows that effects on stereological and mechanical properties observed at the 1-week time point post-PDT are maintained at a longer 6-week time point, with combined PDT + bisphosphonate treatment being the most beneficial in terms of bone enhancement. Additionally, the combination of PDT + radiation therapy also demonstrated significant increases in stereological parameters, suggesting that previous radiation therapy treatment does not preclude the bone-enhancing effects of PDT and in fact may be synergistic in the longer term. The bone-enhancing effects of PDT in combination with conventional treatments, and its ability to destroy metastatic human breast cancer cells within bone, present PDT as an attractive novel treatment for spinal metastasis. The positive results from these preclinical studies might motivate future clinical translation of PDT for spinal metastasis.

Antitumor activity of photodynamic therapy performed with nanospheres containing zinc-phthalocyanine

BACKGROUND

The increasing incidence of cancer and the search for more effective therapies with minimal collateral effects have prompted studies to find alternative new treatments. Among these, photodynamic therapy (PDT) has been proposed as a very promising new modality in cancer treatment with the lowest rates of side effects, revealing itself to be particularly successful when the photosensitizer is associated with nanoscaled carriers. This study aimed to design and develop a new formulation based on albumin nanospheres containing zinc-phthalocyanine tetrasulfonate (ZnPcS4-AN) for use in the PDT protocol and to investigate its antitumor activity in Swiss albino mice using the Ehrlich solid tumor as an experimental model for breast cancer.

METHODS

Ehrlich tumor's volume, histopathology and morphometry were used to assess the efficacy of intratumoral injection of ZnPcS4-AN in containing tumor aggressiveness and promoting its regression, while the toxicity of possible treatments was assessed by animal weight, morphological analysis of the liver and kidneys, hemogram, and serum levels of total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (GGT), alkaline phosphatase, creatinine and urea. In order to evaluate the efficacy of PDT, groups of animals treated with intratumoral injection of doxorubicin (Dox) were also investigated.

RESULTS

Intratumoral injection of ZnPcS4-AN was found to be efficient in mediating PDT to refrain tumor aggressiveness and to induce its regression. Although tumor volume reduction was not significant, PDT induced a remarkable increase in the necrosis area seen in the tumor's central region, as in other experimental groups, including tumor and Dox treated groups, but also in the tumor's peripheral region. Further, PDT showed minimal adverse effects. Indeed, the use of ZnPcS4-AN in mediating PDT revealed anti-neoplastic activity similar to that obtained while using intratumoral Dox therapy.

CONCLUSIONS

PDT mediated by the new formulation ZnPcS4-AN enhanced the inhibition of tumor growth while producing practically no adverse effects and thus emerges as a very promising nanotechnology-based strategy for solid cancer treatment.

The benefits of photodynamic therapy on vertebral bone are maintained and enhanced by combination treatment with bisphosphonates and radiation therapy

Photodynamic therapy (PDT) has been shown to ablate tumors within vertebral bone and yield short-term improvements in vertebral architecture and biomechanical strength, in particular when combined with bisphosphonate (BP) treatment. Longer-term outcomes of PDT combined with current treatments for skeletal metastases are essential to understand its therapeutic potential. The objective of this study is to evaluate the response of vertebrae to PDT after a longer (6-week) time period, alone and combined with previous BP or radiation treatment (RT). Sixty-three female rnu/rnu rats were randomized to six treatment groups: untreated control, BP-only, RT-only, PDT-only, combined BP + PDT and combined RT + PDT. L2 vertebrae were structurally analyzed through µCT-based analysis, axial compressive load-to-failure testing and histological analysis of morphology, osteoid formation and osteoclast activity. Combined BP + PDT treatment yielded the largest improvements in bone architecture with combined RT + PDT treatment yielding similar findings, but of a lesser magnitude. Mechanically, ultimate force and stress were correlated to stereological parameters that demonstrated a positive structural effect from combinatory treatment. Increased osteoid formation was observed in both combination therapies without any significant differences in osteoclast activity. Overall, multimodality treatment demonstrated a sustained positive effect on vertebral structural integrity, motivating PDT as a minimally-invasive adjuvant treatment for spinal metastases.

Beyond radiation therapy: photodynamic therapy maintains structural integrity of irradiated healthy and metastatically involved vertebrae in a pre-clinical in vivo model

Spinal metastasis commonly occurs in advanced breast cancer. Treatment is often multimodal including radiation therapy (RT), bisphosphonates (BPs), and surgery, yet alternative minimally invasive local treatments are needed. Photodynamic therapy (PDT) has been shown to ablate tumor cells and enhance bone formation secondary to metastatic breast cancer, demonstrating potential as a treatment for spinal metastasis. Combined with previous BP treatment, bone formation was further enhanced by PDT. This study aimed to determine the effects of PDT in combination with previous RT on healthy and metastatically involved vertebrae. Forty-six athymic rats underwent RT (4 Gy on day-7), twenty-three of them were inoculated with MT-1 human breast cancer cells on day 0. Thirteen healthy and ten metastatically involved rats underwent PDT treatment on day 14. All rats were sacrificed on day 21. L2 vertebrae were analyzed using μCT imaging, mechanical testing, and histological methods. In healthy vertebrae, while modest increases in trabecular structure were found in RT + PDT compared to RT only, mechanical stability was negatively affected. The 4 Gy RT dose was found to ablate all tumor cells and prevent further vertebral metastasis. As such, in metastatically involved rats, no differences in stereological or mechanical properties were detected. RT + PDT and RT-only treatment resulted in greatly improved vertebral structural and mechanical properties versus untreated or PDT-only treatment in metastatically involved rats, due to early tumor destruction in RT-treated groups. Increased amounts of woven bone and osteoid volume were found in PDT-treated vertebrae. Further investigation is needed to understand if structural improvements seen in RT + PDT treatment can translate into longer-term improvements in strength to support the potential of PDT as a viable adjuvant treatment for spinal metastasis postradiation.