Intensity-Modulated Radiotherapy versus 3-Dimensional Conformal Radiotherapy Strategies for Locally Advanced Non-Small-Cell Lung Cancer

The Therapeutic Potential of DNA Damage Repair Pathways and Genomic Stability in Lung Cancer

Despite advances in our understanding of the molecular biology of the disease and improved therapeutics, lung cancer remains the most common cause of cancer-related deaths worldwide. Therefore, an unmet need remains for improved treatments, especially in advanced stage disease. Genomic instability is a universal hallmark of all cancers. Many of the most commonly prescribed chemotherapeutics, including platinum-based compounds such as cisplatin, target the characteristic genomic instability of tumors by directly damaging the DNA. Chemotherapies are designed to selectively target rapidly dividing cells, where they cause critical DNA damage and subsequent cell death (1, 2). Despite the initial efficacy of these drugs, the development of chemotherapy resistant tumors remains the primary concern for treatment of all lung cancer patients. The correct functioning of the DNA damage repair machinery is essential to ensure the maintenance of normal cycling cells. Dysregulation of these pathways promotes the accumulation of mutations which increase the potential of malignancy. Following the development of the initial malignancy, the continued disruption of the DNA repair machinery may result in the further progression of metastatic disease. Lung cancer is recognized as one of the most genomically unstable cancers (3). In this review, we present an overview of the DNA damage repair pathways and their contributions to lung cancer disease occurrence and progression. We conclude with an overview of current targeted lung cancer treatments and their evolution toward combination therapies, including chemotherapy with immunotherapies and antibody-drug conjugates and the mechanisms by which they target DNA damage repair pathways.

Challenges of radical chemoradiation planning in Stage III non-small-cell lung cancer: Can volumetric modulated arc radiotherapy overcome an unfavourable location?

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Subset of Stage III Non-Small Cell Lung Cancer patients are not fit for upfront chemoradiotherapy.

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Spatial location of disease burden hinders radiotherapy treatment planning due to organs at risk.

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Prediction based on disease location requiring VMAT to circumvent this problem necessary.

Background and purpose

Radiotherapy treatment planning of radical doses for concurrent chemoradiation in Stage III non-small-cell lung cancer (NSCLC) presents many challenges. This dosimetric study aimed to analyse the impact of spatial location of tumour and nodal burden in limiting the achievement of normal organ constraints and the use of appropriate radiotherapy technique to address it.

Materials and methods

Fifteen Stage III NSCLC patients underwent ¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET)/computed tomography (CT) based treatment planning. VMAT (Volumetric Modulated Arc Radiotherapy) plans were made for all patients treated by 3D-CRT (3-Dimensional Conformal Radiotherapy). A binomial logistic regression was performed to ascertain the tumour and nodal characteristics that decreased the likelihood of being planned to 60 Gy.

Results

Inability to achieve normal tissue constraints, particularly spinal cord dose to less than 50 Gy, during initial planning by the assigned treatment technique was the primary dose limiting factor in four patients (p = 0.02). Alternate VMAT plans could achieve the dose constraints where 3D-CRT was unsuccessful in patients with bulky central disease in two patients. This technique fell short when there was gross vertebral body erosion.

Conclusions

For tumours with bulky central disease, VMAT should be preferred. With gross vertebral body erosion, even VMAT falls short if the planning target volume includes the spinal cord. In a subset of Stage III NSCLC upfront chemoradiation to radical doses may not be feasible.

Chemoradiation and granulocyte-colony or granulocyte macrophage-colony stimulating factors (G-CSF or GM-CSF): time to think out of the box?

Concerns have been raised about potential toxic interactions when colony-stimulating factors (CSFs) and chemoradiation are concurrently performed. In 2006, the ASCO guidelines advised against their concomitant use. Nevertheless, with the development of modern radiotherapy techniques and supportive care, the therapeutic index of combined chemotherapy, radiotherapy, and CSFs is worth reassessing. Recent clinical trials testing chemoradiation in lung cancer let investigators free to decide the use of concomitant CSFs or not. No abnormal infield event was reported after the use of modern radiotherapy techniques and concomitant chemotherapy regimens. These elements call for further investigation to set new recommendations in favour of the association of chemoradiation and CSFs. Moreover, radiotherapy could induce anticancer systemic effects mediated by the immune system in vitro and in vivo. With combined CSFs, this effect was reinforced in preclinical and clinical trials introducing innovative radioimmunotherapy models. So far, the association of radiation with CSFs has not been combined with immunotherapy. However, it might play a major role in triggering an immune response against cancer cells, leading to abscopal effects. The present article reassesses the therapeutic index of the combination CSFs-chemoradiation through an updated review on its safety and efficacy. It also provides a special focus on radioimmunotherapy.

Knockdown of TRIM66 inhibits malignant behavior and epithelial-mesenchymal transition in non-small cell lung cancer

OBJECTIVE

The tripartite motif 66(TRIM66) is an important member of the TRIM protein superfamily, which can participate in the expression of multiple proteins, and is closely associated with the behaviors of non-small cell lung cancer (NSCLC). In this study, we aimed to explore the effect of TRIM66 in this process in vitro using NSCLC cell lines, and the role of TRIM66 in regulating epithelial-mesenchymal transition(EMT) in NSCLC.

METHODS

Western blotting was used to detect the TRIM66 protein expression levels in NSCLC cell lines and normal lung epithelial cells BEAS-2B. We silenced its expression in A549 cells by transient siRNA transfection to ascertain the function of TRIM66 in NSCLC cells. Western blotting was used to detect the expression of EMT-related proteins.

RESULTS

TRIM66 protein content was highest in NSCLC cell line A549, compared with BEAS-2B, it showed that the TRIM66-siRNA group lung cancer cell proliferation was significantly reduced after knockdown of TRIM66, and knockdown of TRIM66 also suppressed invasion, migration and clonogenic ability of A549 cells. Finally, we found that siRNA-mediated TRIM66 silencing suppressed EMT by downregulating expression of N-cadherin and vimentin and upregulating that of E-cadherin in NSCLC cells, which could effectively reduce the invasive, migratory, and proliferative capacities of lung cancer cells.

CONCLUSION

Silence TRIM66 expression suppressed NSCLC cell proliferation, invasion, and migration. The siRNA-mediated TRIM66 silencing could block the occurrence of EMT. TRIM66 could be a promising novel target for future NSCLC treatments.

A Dosimetric Comparison of Dose Escalation with Simultaneous Integrated Boost for Locally Advanced Non-Small-Cell Lung Cancer

Background

Many studies have demonstrated that a higher radiotherapy dose is associated with improved outcomes in non-small-cell lung cancer (NSCLC). We performed a dosimetric planning study to assess the dosimetric feasibility of intensity-modulated radiation therapy (IMRT) with a simultaneous integrated boost (SIB) in locally advanced NSCLC.

Methods

We enrolled twenty patients. Five different dose plans were generated for each patient. All plans were prescribed a dose of 60 Gy to the planning tumor volume (PTV). In the three SIB groups, the prescribed dose was 69 Gy, 75 Gy, and 81 Gy in 30 fractions to the internal gross tumor volume (iGTV).

Results

The SIB-IMRT plans were associated with a significant increase in the iGTV dose (P < 0.05), without increased normal tissue exposure or prolonged overall treatment time. Significant differences were not observed in the dose to the normal lung in terms of the V5 and V20 among the four IMRT plans. The maximum dose (Dmax) in the esophagus moderately increased along with the prescribed dose (P < 0.05).

Conclusions

Our results indicated that escalating the dose by SIB-IMRT is dosimetrically feasible; however, systematic evaluations via clinical trials are still warranted. We have designed a further clinical study (which is registered with ClinicalTrials.gov, number NCT02841228).

Superior sulcus non-small cell lung carcinoma: A comparison of IMRT and 3D-RT dosimetry

AIM

A dosimetric study comparing intensity modulated radiotherapy (IMRT) by TomoTherapy to conformational 3D radiotherapy (3D-RT) in patients with superior sulcus non-small cell lung cancer (NSCLC).

BACKGROUND

IMRT became the main technique in modern radiotherapy. However it was not currently used for lung cancers. Because of the need to increase the dose to control lung cancers but because of the critical organs surrounding the tumors, the gains obtainable with IMRT is not still demonstrated.

MATERIAL AND METHODS

A dosimetric comparison of the planned target and organs at risk parameters between IMRT and 3D-RT in eight patients who received preoperative or curative intent irradiation.

RESULTS

In the patients who received at least 66 Gy, the mean V95% was significantly better with IMRT than 3D-RT (p = 0.043). IMRT delivered a lower D2% compared to 3D-RT (p = 0.043). The IH was significantly better with IMRT (p = 0.043). The lung V 5 Gy and V 13 Gy were significantly higher in IMRT than 3D-RT (p = 0.043), while the maximal dose (D max) to the spinal cord was significantly lower in IMRT (p = 0.043). The brachial plexus D max was significantly lower in IMRT than 3D-RT (p = 0.048). For patients treated with 46 Gy, no significant differences were found.

CONCLUSION

Our study showed that IMRT is relevant for SS-NSCLC. In patients treated with a curative dose, it led to a reduction of the exposure of critical organs, allowing a better dose distribution in the tumor. For the patients treated with a preoperative schedule, our results provide a basis for future controlled trials to improve the histological complete response by increasing the radiation dose.