Role of photodynamic therapy in unresectable esophageal and lung cancer

Utilization and Outcomes of Radiation in Stage IV Esophageal Cancer

Introduction

For patients with stage IV esophageal cancer, esophageal radiation may be used selectively for local control and palliation. We aimed to understand patterns of radiation administration among patients with stage IV esophageal cancer and any potential survival associations.

Methods

In this retrospective cohort study, the National Cancer Database was queried for patients with metastatic stage IV esophageal cancer diagnosed between 2016 and 2019. Patterns of radiation use were identified. Survival was determined through Kaplan-Meier analysis of propensity score-matched pairs of patients who did and did not receive radiotherapy and time-to-event models.

Results

Overall, 12,088 patients with stage IV esophageal cancer were identified, including 32.7% who received esophageal radiation. The median age was 65 (interquartile range [IQR]: 58-73) years, and 82.6% were male. Among the irradiated patients, the median total radiation dose was 35 (IQR: 30-50) Gy administered in a median of 14 (IQR: 10-25) fractions given in 22 (IQR: 14-39) days. Overall, esophageal radiation was not associated with better survival (log-rank p = 0.41). When stratified by radiation dose, a survival advantage (over no radiation) was found in the 1144 patients (29% of the irradiated patients) who received 45 to 59.9 Gy (time ratio = 1.28, 95% confidence interval: 1.20-1.37, p < 0.001) and the 88 patients (2.2%) who received 60 to 80 Gy (time ratio = 1.37, 95% confidence interval: 1.11-1.69, p = 0.003).

Conclusions

One-third of the patients with metastatic stage IV esophageal cancer in the National Cancer Database received esophageal radiation. Most received a radiation dose that, although consistent with palliative regimens, was not associated with a survival advantage. Further study is warranted to understand the indications for radiation in stage IV esophageal cancer and potentially reevaluate the most appropriate radiation dose for palliation.

Immunoproteasome Inhibitor-Doxorubicin Conjugates Target Multiple Myeloma Cells and Release Doxorubicin upon Low-Dose Photon Irradiation

Proteasome inhibitors are established therapeutic agents for the treatment of hematological cancers, as are anthracyclines such as doxorubicin. We here present a new drug targeting approach that combines both drug classes into a single molecule. Doxorubicin was conjugated to an immunoproteasome-selective inhibitor via light-cleavable linkers, yielding peptide epoxyketone–doxorubicin prodrugs that remained selective and active toward immunoproteasomes. Upon cellular uptake and immunoproteasome inhibition, doxorubicin is released from the immunoproteasome inhibitor through photoirradiation. Multiple myeloma cells in this way take a double hit: immunoproteasome inhibition and doxorubicin-induced toxicity. Our strategy, which entails targeting of a cytotoxic agent, through a covalent enzyme inhibitor that is detrimental to tumor tissue in its own right, may find use in the search for improved anticancer drugs.

Photodynamic activity of new photosensitizers obtained from 5,10,15,20-tetrapentafluorophenylporphyrin

The commercially available tetrapentafluorophenylporphyrin has been used as parent compounds for the synthesis of six new tetraarylporphyrins. These new porphyrins were obtained following aromatic nucleophilic substitution of the para-position fluorine atoms by means of molecules bearing an oxygen or sulphur anion, providing either tri- or tetra-substituted derivatives which were isolated as pure compounds after a single step of column chromatography purification. These new porphyrins, first analyzed to determine the photobleaching stability and the octanol/water repartition values, were studied as photosensitizers against the HCT116 cancer cell line with irradiation by a blue LED device. The intrinsic toxicity of these compounds was negligible, whereas the photodynamic efficacy was found to be directly related to the cellular uptake of the photosensitizer that was correlated with the hydrophilicity of the substituent. In fact, the PSs lacking of any polar groups were found to be poorly efficient while the photosensitizer bearing four hydroxyl groups showed the greatest photodynamic activity, thus confirming the importance of the presence of polar appendixes to properly interact with the cells, thus exerting the desired photo-killing effect.

Low-power and low-drug-dose photodynamic chemotherapy via the breakdown of tumor-targeted micelles by reactive oxygen species

Tumor-targeted delivery of anticancer agents using nanocarriers has been explored to increase the therapeutic index of cancer chemotherapy. However, only a few nanocarriers are clinically available because the physiological complexity often compromises their ability to target, penetrate, and control the release of drugs. Here, we report a method which dramatically increases in vivo therapeutic drug efficacy levels through the photodynamic degradation of tumor-targeted nanocarriers. Folate-decorated poly(ethylene glycol)-polythioketal micelles are prepared to encapsulate paclitaxel and porphyrins. Photo-excitation generates reactive oxygen species within the micelles to cleave the polythioketal backbone efficiently and facilitate drug release only at the illuminated tumor site. Intravenous injection of a murine xenograft model with a low dose of paclitaxel within the micelles, one-milligram drug per kg (mouse), corresponding to an amount less than that of Taxol by one order of magnitude, induces dramatic tumor regression without any acute systemic inflammation responses or organ toxicity under low-power irradiation (55 mW cm^-2) at 650 nm.

Glycol porphyrin derivatives and temoporfin elicit resistance to photodynamic therapy by different mechanisms

The development of drug resistance is a major problem which often occurs during anticancer chemotherapies. Photodynamic therapy (PDT) has been studied as an alternative treatment modality for drug-resistant tumors, however the question of resistance to PDT and potential cross-resistance with chemotherapy has yet to be fully answered. To investigate the mechanism of resistance to PDT, we developed an in vitro experimental model system in a mouse mammary carcinoma cell line 4T1. We used two ethylene glycol derivatives of tetraphenylporphyrin, and tetraphenylchlorin derivative, temoporfin, as photosensitizers (PS). PDT-resistant clones were obtained by exposure to a set concentration of PS followed by irradiation with increasing light doses. PDT resistance to soluble glycol porphyrins was mediated mainly by increased drug efflux through ABCB1 (P-glycoprotein) as we demonstrated by specific ABCB1 knockdown experiments, which in turn rescued the sensitivity of resistant cells to PDT. In contrast, resistance raised to temoporfin, which is generally more lipophilic than glycol porphyrins, elicited mechanism based on sequestration of the drug to lysosomes. The resistance that is acquired from a particular PS could be overcome by using a different PS, which is not susceptible to the same mechanism(s) of resistance. Elucidation of the underlying mechanisms in various types of resistance might facilitate improvements in PDT treatment design.

Photodynamic Therapy of Non-Small Cell Lung Cancer. Narrative Review and Future Directions

Photodynamic therapy (PDT) is an established treatment modality for non-small cell lung cancer. Phototoxicity, the primary adverse event, is expected to be minimized with the introduction of new photosensitizers that have shown promising results in phase I and II clinical studies. Early-stage and superficial endobronchial lesions less than 1 cm in thickness can be effectively treated with external light sources. Thicker lesions and peripheral lesions may be amenable to interstitial PDT, where the light is delivered intratumorally. The addition of PDT to standard-of-care surgery and chemotherapy can improve survival and outcomes in patients with pleural disease. Intraoperative PDT has shown promise in the treatment of non-small cell lung cancer with pleural spread. Recent preclinical and clinical data suggest that PDT can increase antitumor immunity. Crosslinking of signal transducer and activator of transcription-3 molecules is a reliable biomarker to quantify the photoreaction induced by PDT. Randomized studies are required to test the prognosis value of this biomarker, obtain approval for the new photosensitizers, and test the potential efficacy of interstitial and intraoperative PDT in the treatment of patients with non-small cell lung cancer.

The effect of photodynamic therapy on cisterna chyli patency in rats

OBJECTIVE

To radiographically and histologically evaluate the effects of photodynamic therapy on the cisterna chyli in rats.

STUDY DESIGN

Experimental study.

ANIMALS

Adult male Sprague-Dawley rats (n = 60).

METHODS

Cecal lymph nodes were injected with the photodynamic compound verteporfin. A 690 nm, 500 mW diode laser was then directed at the area of the cisterna chyli for either 0, 1.5, or 3 minutes. Cisterna chyli patency was evaluated using lymphography, and histologic changes were evaluated on postoperative Days 1, 3, 5, 7, and 14.

RESULTS

Histologically, minimal to marked injury to the cisternal and/or pericisternal tissues was present in all treated rats at all time periods. Radiographically, 8/20 cisternae were occluded in the 1.5-minute treatment group (including 1/4 on Day 1, 2/4 on Day 3, 3/4 on Day 5, 0/4 on Day 7, and 2/4 on Day 14), and 9/20 cisternae were occluded in the 3-minute treatment group (including 0/4 on Day 1, 1/4 on Day 3, 3/4 on Day 5, 3/4 on Day 7, and 2/4 on Day 14). There was minimal to no histologic evidence of tissue injury in control rats. All control cisternae were radiographically open.

CONCLUSIONS

Further investigations into the timing of laser application and light dose, or alternative photodynamic agents are required to limit injury to adjacent tissues and to improve the effectiveness of cisternal photoablation.

Ten-year experience of esophageal self-expanding metal stent insertion at a single institution

Palliation of malignant dysphagia can be achieved using self-expanding metal stents (SEMS). This study was conceived to confirm that the insertion of SEMS improved patient symptoms without serious complications and to allow comparison with recent national data. Retrospective case note review of all patients receiving SEMS over a 10-year period between March 1999 and February 2009 was used in this study. There were 138 consecutive patients (50 female), median age of 75 (range 46-90) years, 122 (88.5%) had primary malignant disease of the esophagus or gastroesophageal junction. In total, 250 endoscopic examinations were carried out, with 200 interventional procedures, including the insertion of 156 SEMS. Before stenting, 74.2% of patients had a dysphagia score of 2-3. Following stent insertion, dysphagia scores improved to 0-1 in 90.3% of patients (P < 0.0001, Wilcoxon signed ranks). No complications were encountered in 61 (44%) patients. Chest pain was the most frequent difficulty, encountered in 50 (36%) patients. Tumor overgrowth occurred in 17 (12.3%) patients and food bolus obstruction was seen in 7% of patients. There were no esophageal perforations attributable to SEMS insertion. Overall 30-day mortality for those with esophago-gastric malignancy was 11.6% (16 patients), although the SEMS-related mortality was 2.2% (3 patients). Median survival from SEMS insertion was 3 (IQR 1.5-7) months. Patients requiring re-intervention for tumor overgrowth had a significantly longer median survival of 9.2 months (P= 0.001, log rank). SEMS were well tolerated with overall mortality and complication rates comparable to national data. For the longer survivors, re-intervention for recurrent dysphagia was not unusual.

Cancer cells uptake porphyrinsviaheme carrier protein 1

Although exogenous porphyrin accumulation in cancer cells is important for the success of photodynamic therapies, the mechanism is not clear. We hypothesized that a newly reported transporter, heme carrier protein 1 (HCP1), is highly expressed in cancer cells, and transports porphyrins into the cells. We investigated the following three unknowns: whether cancer cells take up hematoporphyrin derivative via HCP1, whether HCP1 is involved in photodynamic therapies, and whether cancer cells highly express HCP1. First, when HCP1-overexpressed cells were treated with hematoporphyrin derivative and then exposed to an eximer laser beam, they emitted a significantly higher intensity of hematoporphyrin derivative fluorescence and became more susceptible to the laser beam than control. Second, when three other types of cancer cells with silenced HCP1 were treated with hematoporphyrin derivative and then exposed to the laser beam, they emitted a significantly lower intensity of hematoporphyrin derivative fluorescence. Third, non-cancer cells slightly expressed HCP1; on the other hand, the three other types of cancer cells clearly expressed HCP1. These results indicated that cancer cells uptake hematoporphyrin derivative via HCP1 and over-expression of HCP1 increases the efficacy of photodynamic therapies by increasing porphyrin accumulation in the cells. This is the first report about a transporter of porphyrin in cancer cells.

Patient-related independent clinical risk factors for early complications following Nd: YAG laser resection of lung cancer

INTRODUCTION

Neodymium:yttrium aluminum garnet (Nd:YAG) laser resection is one of the most established interventional pulmonology techniques for immediate debulking of malignant central airway obstruction (CAO). The major aim of this study was to investigate the complication rate and identify clinical risk factors for complications in patients with advanced lung cancer.

METHODS

In the period from January 2006 to January 2011, data sufficient for analysis were identified in 464 patients. Nd:YAG laser resection due to malignant CAO was performed in all patients. The procedure was carried out in general anesthesia. Complications after laser resection were defined as severe hypoxemia, global respiratory failure, arrhythmia requiring treatment, hemoptysis, pneumothorax, pneumomediastinum, pulmonary edema, tracheoesophageal fistulae, and death. Risk factors were defined as acute myocardial infarction within 6 months before treatment, hypertension, chronic arrhythmia, chronic obstructive pulmonary disease (COPD), stabilized cardiomyopathy, previous external beam radiotherapy, previous chemotherapy, and previous interventional pulmonology treatment.

RESULTS

There was 76.1% male and 23.9% female patients in the study, 76.5% were current smokers, 17.2% former smokers, and 6.3% of nonsmokers. The majority of patients had squamous cell lung cancer (70%), small cell lung cancer was identified in 18.3%, adenocarcinoma in 3.4%, and metastases from lung primary in 8.2%. The overall complication rate was 8.4%. Statistically significant risk factors were age (P = 0.001), current smoking status (P = 0.012), arterial hypertension (P < 0.0001), chronic arrhythmia (P = 0.034), COPD (P < 0.0001), and stabilized cardiomyopathy (P < 0.0001). Independent clinical risk factors were age over 60 years (P = 0.026), arterial hypertension (P < 0.0001), and COPD (P < 0.0001).

CONCLUSION

Closer monitoring of patients with identified risk factors is advisable prior and immediately after laser resection. In order to avoid or minimize complications, special attention should be directed toward patients who are current smokers, over 60 years of age, with arterial hypertension or COPD.

Effect and mechanism of 5-aminolevulinic acid-mediated photodynamic therapy in esophageal cancer

5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) provides a novel and promising treatment for esophageal cancer. However, its specific mechanism has not been fully elucidated and its efficacy is remarkably varied. This study investigated the effect of ALA-PDT on esophageal squamous carcinoma cell line Eca-109 in vitro and vivo to explore optimal parameters, and evaluated the significance of cell apoptosis, cell cycle, ALA-protoporphyrin IX (ALA-PpIX) subcellular localization, and expression of Bcl-2 and Bax mRNA in cells to understand the mechanism of ALA-PDT for esophageal cancer. How ALA concentration, incubation time, and laser irradiation dose influenced the cell proliferation was determined by MTT assay. ALA-PpIX subcellular localization was analyzed by confocal microscopy. The mRNA changes were detected by quantitative real-time polymerase chain reaction (QRT-PCR). Tumor models transplanted with Eca-109 cells in nude mice were established (n = 10) and killed (n = 4) at 24 h post-PDT for malondialdehyde (MDA) detection and histological study. The remaining mice were measured the tumor size for 3 weeks after treatment. Our data show that ALA-PDT significantly inhibits cell proliferation (p < 0.05), the PDT efficacy depends on the saturation of ALA concentration, incubation time, and laser irradiation dose, and the best effect in tumor destruction is at 7-14 days post-PDT. ALA-PpIX is localized in mitochondria and cytoplasm. ALA-PDT induces cell apoptosis and arrests cell cycle at G0/G1 phase. Bcl-2 is significantly down-regulated while Bax is up-regulated (p < 0.05). The results of this study provide references in choosing clinical optimal PDT parameters and help in better understanding the PDT mechanism for esophageal cancer.

Esophageal cancer: an update

Esophageal cancer continues to be a lethal disease with the majority of patients presenting at an advanced stage. The incidence of adenocarcinoma is rising. Although Barrett's esophagus has been well characterized, specific pathways to the development of adenocarcinoma remain undefined. Current treatments for locoregional esophageal cancer include surgery, chemotherapy, radiation therapy, or a combination of these modalities. Optimal surgical treatment strategies include appropriate patient selection, accurate staging and risk assessment, selection of an appropriate surgical approach, and the use of multimodality treatment. This article provides an update on the myriad of options for managing esophageal cancer and outlines the surgical technique for minimally invasive esophagectomy used at our center.

Stenting of the upper gastrointestinal tract: current status

Minimally invasive image-guided insertion of self-expanding metal stents in the upper gastrointestinal tract is the current treatment of choice for palliation of malignant esophageal or gastroduodenal outlet obstructions. A concise review is presented of contemporary stenting practice of the upper gastrointestinal tract, and the procedures in terms of appropriate patient evaluation, indications, and contraindications for treatment are analyzed, along with available stent designs, procedural steps, clinical outcomes, inadvertent complications, and future technology. Latest developments include biodegradable polymeric stents for benign disease and radioactive or drug-eluting stents for malignant obstructions.

Photodynamic therapy as an innovative treatment for malignant pleural mesothelioma

Photodynamic therapy (PDT) of the pleura is an experimental treatment aimed at eradicating residual microscopic disease after macroscopic complete resection of malignant pleural mesothelioma (MPM) by means of intracavitary administration. A light-based treatment, PDT consists of 3 components: a nontoxic photosensitizing compound, oxygen, and visible light. The treatment is FDA-approved for several oncological targets, but remains experimental for MPM. PDT can be combined with lung-sparing pleurectomy and decortication and does not preclude other treatments such as adjuvant chemotherapy and/or radiation therapy. Additionally, PDT appears to bolster an immunologic effect by rendering the cancer cells that have been destroyed by the light-activated photosensitizer more presentable to the immune system. Local control and survival rates have been sufficiently rewarding to merit ongoing development of this combination of surgical technique and PDT.

A single-institutional brachytherapy experience in the management of esophageal cancer

PURPOSE

The aim of this work was to analyze the efficacy of high-dose-rate brachytherapy in the management of patients with esophageal cancer.

METHODS AND MATERIALS

Between 2001 and 2008, 104 patients (88 males and 16 females) received a brachytherapy treatment as a part of a personalized multimodal approach. The median age was 72 years, and the median Karnofsky performance status was 60. Brachytherapy was used in different situations: to complete a primary treatment with radical intent in patients not suitable for surgery; to control local recurrences; or to obtain a rapid and durable palliation of dysphagia in patients with metastases or in poor general condition. In selected cases, endoscopic ultrasound images were integrated in treatment planning procedure to obtain a more accurate volume definition. Efficacy in controlling dysphagia was assessed 1 month after brachytherapy.

RESULTS

Fifty-one patients received a radical treatment, and 53 patients were treated to relieve the symptoms. The median overall survival was 20.8 months. Lymph node involvement was found to be a significant prognostic factor for overall survival and dysphagia. Dysphagia was controlled in 88 patients (84.6%), and the median dysphagia-free interval was 17.5 months. Early and late adverse events were generally mild to moderate. The most severe effects were esophagotracheal fistulas, observed in 3 patients.

CONCLUSIONS

Brachytherapy has an important role in the management of esophageal cancer with a low rate of complications. endoscopic ultrasound-assisted treatment planning can be useful for a better individualization of curative treatments.

Stage-specific therapy for cancer of the oesophagus: a new 'cancer of the elderly'

Oesophageal and gastric cancers are amongst the most frequent and lethal of cancers worldwide. In the US alone, some 13 000 individuals are affected each year, and mortality is particularly high in elderly patients with advanced stage disease and multiple co-morbidities. Patients usually do not present until later in the disease when symptoms occur, once the tumour is sufficiently large to cause obstruction or invasion of adjacent structures. Oesophageal cancer can metastasize to almost any organ, and widespread distant metastases are almost always present at the time of death. Overall mortality from this cancer is around 80-90%. Curative treatment of oesophageal cancer must achieve local control of the primary lesion as well as control and/or prevention of metastases. These are important contributors to overall results when therapy is undertaken in elderly patients, as are the significant risks of adverse effects such as morbidity from chemoradiation and the morbidity and mortality of oesophagectomy. Surgical resection affords the best chance for local control and the best means of palliation of dysphagia for most patients with localized disease, although both local and systemic recurrence of disease are common when surgery is used alone. Because of the low cure rates associated with the use of surgery alone, other modalities have been added to the treatment regimen. Elderly patients with significant cardiac and pulmonary co-morbidity are candidates for nonoperative therapy, even at an early disease stage. There are few data to support a survival advantage from adjuvant radiotherapy or chemotherapy following complete resection, in the absence of documented metastatic disease. Chemotherapy and radiotherapy have both been reported to improve survival when administered preoperatively in patients with oesophageal cancer, while current data using trimodal therapy show a trend towards increased treatment-related mortality with only a slight increase in overall survival. There is currently no completely reliable preoperative method for restaging patients following neoadjuvant chemoradiation in order to assess pathological complete response. Novel restaging techniques are therefore required, in addition to further study of the risks and benefits of neoadjuvant chemoradiotherapy for this disease.

Treatment planning using tailored and standard cylindrical light diffusers for photodynamic therapy of the prostate

Interstitial photodynamic therapy (PDT) has seen a rebirth, partially prompted by the development of photosensitizers with longer absorption wavelengths that enable the treatment of larger tissue volumes. Here, we study whether using diffusers with customizable longitudinal emission profiles, rather than conventional ones with flat emission profiles, improves our ability to conform the light dose to the prostate. We present a modified Cimmino linear feasibility algorithm to solve the treatment planning problem, which improves upon previous algorithms by (1) correctly minimizing the cost function that penalizes deviations from the prescribed light dose, and (2) regularizing the inverse problem. Based on this algorithm, treatment plans were obtained under a variety of light delivery scenarios using 5-15 standard or tailored diffusers. The sensitivity of the resulting light dose distributions to uncertainties in the optical properties, and the placement of diffusers was also studied. We find that tailored diffusers only marginally outperform conventional ones in terms of prostate coverage and rectal sparing. Furthermore, it is shown that small perturbations in optical properties can lead to large changes in the light dose distribution, but that those changes can be largely corrected with a simple light dose re-normalization. Finally, we find that prostate coverage is only minimally affected by small changes in diffuser placement. Our results suggest that prostate PDT is not likely to benefit from the use of tailored diffusers. Other locations with more complex geometries might see a better improvement.

Photodynamic therapy: basic principles and potential uses for the veterinary ophthalmologist

Photodynamic therapy (PDT) involves the use of photochemical reactions mediated through the interaction of photosensitizing agents, light and oxygen. PDT, while now commonly used in physician ophthalmology and oncology, is uncommonly used for the veterinary ophthalmic patient. It is an emerging new therapy in veterinary ophthalmology for the treatment of periocular tumors. This article reviews the basic principles of PDT to provide the veterinary ophthalmologic community with a succinct reference for this emerging treatment modality in our field.

Palliation of thoracic malignancies

The sequelae of advanced malignancies of the chest, whether primary or metastatic, can be severely debilitating. In this review, we discuss the advances in palliative treatment for several intrathoracic complications of malignancy. The treatment of malignant pleural and pericardial effusions now includes a range of chemical sclerosants and percutaneous or surgical interventions. A new generation of promising stent and ablation technologies allows for the treatment of intrinsic or extrinsic airway obstruction. Similar techniques are being explored for esophageal obstruction, while the possible benefit of palliative radiation and chemotherapy continues to be investigated. Although their symptoms are often severe, patients with advanced thoracic malignancies have a growing number and variety of palliative treatment options to improve their quality of life.

Photodynamic therapy for lung cancers based on novel photodynamic diagnosis using talaporfin sodium (NPe6) and autofluorescence bronchoscopy

BACKGROUND

We had previously developed the possibility of use of a photodynamic diagnosis (PDD) system using a tumor-selective photosensitizer and laser irradiation for the early detection and photodynamic therapy (PDT) for centrally located early lung cancers. Recently, we established the autofluorescence diagnosis system integrated into a videoendoscope (SAFE-3000) as a very useful technique for the early diagnosis of lung cancer.

PATIENTS AND METHODS

Twenty-nine patients (38 lesions) with centrally located early lung cancer received PDD and PDT using the second-generation photosensitizer, talaporfin sodium (NPe6). Just before the PDT, we defined the tumor margin accurately using the novel PDD system SAFE-3000 with NPe6 and a diode laser (408nm).

RESULTS

Red fluorescence emitted from the tumor by excitation of the photosensitizer by the diode laser (408nm) from SAFE-3000 allowed accurate determination of the tumor margin just before the PDT. The complete remission (CR) rate following NPe6-PDT in the cases with early lung cancer was 92.1% (35/38 lesions). We also confirmed the loss of red fluorescence from the tumors immediately after the PDT using SAFE-3000. We confirmed that all the NPe6 in the tumor had been excited and photobleached by the laser irradiation (664nm) and that no additional laser irradiation was needed for curative treatment.

CONCLUSIONS

This novel PDD system using SAFE-3000 and NPe6 improved the quality and efficacy of PDT and avoided misjudgement of the dose of the photosensitizer or laser irradiation in PDT. PDT using NPe6 will become a standard option of treatments for centrally located early lung cancer.