Les thérapeutiques ciblées en association avec la radiothérapie dans le cancer bronchique

[Targeted therapies and radiation therapy in non-small cell lung cancer]

Lung cancer is the leading cause of cancer-related death. Between 80-85% of lung cancers are non-small cell lung carcinomas. One third of the patients are diagnosed with locally advanced stage. In this condition, concomitant radio-chemotherapy is the standard treatment for patients with good performance status. Despite important improvements in the last years, non-small cell lung carcinoma prognosis remains poor, with high rates of both local recurrences and metastases. The heterogeneity of molecular characteristics of non-small cell lung carcinoma cells and a better knowledge of potential targets offer promising developments for new pharmacologic agents. Hereafter we will review the currently most studied pathways and the most promising ones for the treatment of locally advanced unresectable non-small cell lung carcinoma. Two of the most attractive pathways where new agents have been developed and assessed in combination with thoracic radiotherapy or radiochemotherapy are the EGFR pathway (either with the use of monoclonal antibodies or tyrosine kinase inhibitors) and the angiogenesis inhibition. The development of targeted agents could lead to individualized therapeutic combinations taking into account the intrinsic characteristics of tumor cells. Pharmacological modulation of tumour cells radiosensitivity by targeted therapies is only starting, but yet offers promising perspectives.

新型分子靶向药物联合放疗在肺癌中的应用

非小细胞肺癌（non-small cell lung cancer, NSCLC）约占肺癌总病例数的80%-85%，对于Ⅲ期患者来说，NSCLC约占肺癌总病例数的40%。不可切除Ⅲ期NSCLC的治疗为以铂类为基础的化疗联合胸部放疗。本文将综述正在研发中且有可能用于联合治疗的新型靶向制剂。其中最具前景的策略之一为表皮生长因子受体（epidermal growth factor receptor, EGFR）通路的抑制。放疗可激活EGFR信号，通过诱导细胞增殖并增强DNA修复而导致放疗抵抗。几项临床前模型研究表明西妥昔单抗与放疗联合具有协同效应。几项Ⅱ期试验评估了西妥昔单抗与放疗同步使用的安全性与疗效，结果喜人。吉非替尼对多种细胞系具有放疗增敏作用，其与放疗的联合已被试验用于不可切除Ⅲ期NSCLC的治疗。然而，放化疗后使用吉非替尼作为维持治疗的结果不容乐观。一项Ⅰ期试验评估了厄洛替尼与放化疗联合的疗效。放疗可通过损伤细胞膜、DNA以及微血管内皮细胞而诱导肿瘤死亡，而这反过来可增加促血管生成生长因子的产生。抗血管生长制剂可降低血管密度，但可改善肿瘤的含氧量。应用血管内皮生长因子受体（vascular endothelial growth factor receptor, VEGFR）抑制剂可通过阻断亚致死量辐射损伤的修复而增强放疗对人NSCLC的疗效。厄洛替尼、贝伐珠单抗与胸部放疗联合试验正在进行中。该三种药物联合治疗的新策略尚需制订。由于放疗可增强HSP90分子伴侣的功能从而引起肺癌细胞的放疗抵抗，此通路的阻断剂可通过抑制HIF-1α和VEGF的表达进而抑制肺癌细胞的生存和血管生成，因而可能用于减少放疗抵抗。在NSCLC和间皮瘤的临床前模型中，Aurora激酶抑制剂似乎对放疗具有增效作用。

New molecular targeted therapies integrated with radiation therapy in lung cancer

Non-small-cell lung cancer (NSCLC) accounts for approximately 80%-85% of all cases of lung cancer; for patients with stage III disease, it accounts for approximately 40% of all cases. The treatment for unresectable stage III NSCLC is the combination of platinum-based chemotherapy and thoracic radiation. In this article, new targeted agents under investigation for possible integration into the combined therapy are reviewed. One of the most promising strategies is the inhibition of the epidermal growth factor receptor (EGFR) pathway. Radiation activates EGFR signaling, leading to radio-resistance by inducing cell proliferation and enhanced DNA repair. Several preclinical models have shown synergistic activity when cetuximab was combined with radiation therapy. Some phase II trials have evaluated the safety and efficacy of synchronous cetuximab and radiation therapy with promising results. Gefitinib has a radiosensitizing effect on cell lines and has been investigated in combination with radiation therapy for unresectable stage III NSCLC. However, disappointing results were observed in the maintenance treatment with gefitinib after chemoradiation therapy. Erlotinib has been tested in a phase I trial with chemoradiation therapy. Radiation induces tumor death by damaging cell membranes, DNA, and microvascular endothelial cells, which in response increase proangiogenic growth factors. Antiangiogenic agents reduce vascular density but improve tumor oxygenation. Use of vascular endothelial growth factor receptor (VEGFR) inhibitors enhances the therapeutic efficacy of irradiation in human NSCLC by hindering the repair of sublethal radiation damage. Trials combining erlotinib and bevacizumab with thoracic radiation are ongoing. New strategies must be developed for the integration of this triple-combination treatment. As radiation therapy enhances HSP90 chaperone function, causing radio-resistant lung cancer cells, therapeutic agents that block this path are likely candidates for decreasing radio-resistance by suppressing HIF-1alpha and VEGF expression and thus inhibiting the survival and angiogenic potential of lung cancer cells. Aurora kinase inhibitors with radiation therapy seem to have an additive effect in preclinical models in NSCLC and mesothelioma.