Indication and perspectives of radiation therapy in the setting of de-novo metastatic prostate cancer

Prostate cancer is the most common cancer and the third leading cause of cancer mortality in men. Each year, approximately 10% of prostate cancers are diagnosed metastatic at initial presentation. The standard treatment option for de-novo metastatic prostate cancer is androgen deprivation therapy with novel hormonal agent or with chemotherapy. Recently, PEACE-1 trial highlighted the benefit of triplet therapy resulting in the combination of androgen deprivation therapy combined with docetaxel and abiraterone. Radiotherapy can be proposed in a curative intent or to treat local symptomatic disease. Nowadays, radiotherapy of the primary disease is only recommended for de novo low-burden/low-volume metastatic prostate cancer, as defined in the CHAARTED criteria. However, studies on stereotactic radiotherapy on oligometastases have shown that this therapeutic approach is feasible and well tolerated. Prospective research currently focuses on the benefit of intensification by combining treatment of the metastatic sites and the primary all together. The contribution of metabolic imaging to better define the target volumes and specify the oligometastatic character allows a better selection of patients. This article aims to define indications of radiotherapy and perspectives of this therapeutic option for de-novo metastatic prostate cancer.

Radiation therapy of the primary tumour and/or metastases of digestive metastatic cancers

Metastatic gastrointestinal cancer is not an uncommon situation, especially for pancreatic, gastric, and colorectal cancers. In this setting, few data are available on the impact of the treatment of the primary tumour. Oligometastatic disease is associated with longer survival in comparison with more advanced disease. Metastasis-directed therapy, such as stereotactic body radiotherapy, seems related to better outcomes, but the level of evidence is low. In most tumour locations, prospective data are very scarce and inclusion in ongoing trials is strongly recommended.

The role of radiation therapy for de novo metastatic bladder and renal cancers

Metastatic bladder and renal cancers account respectively for 2.1% and 1.8% of cancer deaths worldwide. The advent of immune checkpoint inhibitors has revolutionized the management of metastatic disease, by demonstrating considerable improvements in overall survival. However, despite initial sensitivity to immune checkpoint inhibitors for most patients, both bladder and renal cancer are associated with short progression-free survival and overall survival, raising the need for further strategies to improve their efficacy. Combining systemic therapies with local approaches is a longstanding concept in urological oncology, in clinical settings including both oligometastatic and polymetastatic disease. Radiation therapy has been increasingly studied with either cytoreductive, consolidative, ablative or immune boosting purposes, but the long-term impact of this strategy remains unclear. This review intends to address the impact of radiation therapy with either curative or palliative intent, for synchronous de novo metastatic bladder and renal cancers.

Radiotherapy in the management of lung oligometastases

In recent years, the development of both medical imaging and new systemic agents (targeted therapy and immunotherapy) have revolutionized the field of oncology, leading to a new entity: oligometastatic disease. Adding local treatment of oligometastases to systemic treatment could lead to prolonged survival with no significant impact on quality of life. Given the high prevalence of lung oligometastases and the new systemic agents coming with increased pulmonary toxicity, this article provides a comprehensive review of the current state-of-art for radiotherapy of lung oligometastases. After reviewing pretreatment workup, the authors define several radiotherapy regimen based on the localization and size of the oligometastases. A comment on the synergistic combination of medical treatment and radiotherapy is also made, projecting on future steps in this specific clinical setting.

Management of head and neck carcinomas with synchronous or metachronous oligometastatic disease: Role of locoregional radiotherapy and metastasis-directed radiotherapy

Head and neck carcinomas are initially metastatic in about 15% of cases. Radiotherapy is a cornerstone in the multimodal strategy at the locoregional phase. In patients with head and neck cancer, often heavily pretreated and with comorbidities, who relapse locoregionally or at distant sites, radiotherapy has also become increasingly important at the metastatic phase. Data on the optimal sequence of systemic treatments and metastasis-directed treatments including stereotactic irradiation are still lacking. Several randomized head and neck trials have been initiated that should provide important answers, including one recent GORTEC trial.

[Radiotherapy for oligometastatic non-small cell lung cancer patients]

The oligometastatic disease concept suggests that patients with a limited number of metastases have a favorable prognosis. Radical local treatment of oligometastatic patients has then increased given developments in imaging (mainly positron emission tomography and brain magnetic resonance imaging) and access to effective and better tolerated treatments. Stereotactic radiotherapy has the advantage of being noninvasive, allowing a good rate of local control and a limited number of side effects. A better definition of oligometastatic disease, particularly for non-small cell lung cancer (NSCLC), has recently been published. For patients with NSCLC, two randomized phase II trials also suggested that the addition of a radical local treatment results in encouraging survival data, with a good safety profile. A single-arm phase II finally showed a benefit when combining a radical local treatment with an anti-PD1 immunotherapy. This review describes the definitions of oligometastatic disease, the main prospective findings including radiation therapy, and prospects for oligometastatic NSCLC patients.

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OLIGOMETASTASIS AND OLIGOPROGRESSION

Oligometastic progression (or solitary metastases) can justify ablative treatment for metastatic treatment. When such a strategy is discussed, it is important to notice that definition of oligometastases is not consensual both in terms of clinical presentation than on the biological basis. Does a specific biological background truly exist and are there markers that could predict for additional occult disease and its oligo or polymetastatic profile in individuals with demonstrated oligometastasis. This article provides a summary of the state of the art in this field and highlights some current areas of controversies.

[Stereotactic body radiation therapy and oligometastases]

In stage IV cancers, locoregional management of primitive tumours as surgery and/or radiotherapy improved both progression-free survival and overall survival. Among metastatic cancer patients, some of them are considered as oligometastatic stage as they present few metastatic sites associated with low tumor aggressiveness. For those patients, metastatic local control, and therefore prolonged time to progression should be reached through local treatments as surgery and/or radiofrequency ablation and/or stereotactic radiotherapy. Here we propose a review of oligometastatic stage and results from extracranial stereotactic radiotherapy in terms of efficacy and tolerance.