Feasibility and toxicity of hypofractionated image guided radiation therapy for large volume limited metastatic disease

Stereotactic body radiation therapy for adrenal gland metastases: A multi-institutional outcome analysis

Aim

The adrenal gland is a common site of metastasis with a rate of up to 27% in autopsy series. The incidence of these metastases is increasing due to greater use of Positron Emission Tomography scans and improved overall survival of patients with metastatic cancers. Stereotactic body radiation therapy (SBRT) is a non-invasive treatment option for metastasis. The aim of this study is to assess prognostic factors influencing local control, progression-free and overall survival in oligometastatic patients treated with SBRT for an adrenal metastasis.

Methods

In this multicentric retrospective study, we included patients with adrenal metastases treated with SBRT between 2010 and 2021 in eleven french centers. All primary tumors were included.

Results

A total of 110 patients treated for 121 adrenal lesions were included. Non-small-cell lung cancer was the predominant histologic type (55.4 %). Eighty-two percent of patients had at least 2 metastatic sites. The median Planning Target Volume was 70 cm3 with a median prescription dose of 40 Gray (Gy). The mean Biologically Effective Dose (BED) 10 dose was 74.2 Gy. Local control at 1 and 2 years was 85.9 % and 72.5 % respectively. The median overall survival and progression-free survival were 31.6 and 8.5 months respectively. Local control was significantly improved by systemic treatment one month before or after SBRT (p = 0.009) and by a BED10 greater than or equal to 50 Gy (p = 0.003).In multivariate analysis, oligometastatic presentation (p = 0.009) and a metachronous metastatic presentation (p = 0.008) were independent factors for progression-free survival.Tolerance was excellent, no grade 3 and 4 toxicities were described due to SBRT.

Conclusion

Stereotactic radiotherapy of adrenal metastases makes possible a local control of more than 85% at one year and was well tolerated. The factors influencing survival in oligometastatic patients still need to be found in order to better select those who benefit the most from this type of treatment.

Phase 2 Trial of Stereotactic Ablative Radiotherapy for Patients with Primary Renal Cancer

BACKGROUND

Most renal cell carcinomas (RCCs) are localized and managed by active surveillance, surgery, or minimally invasive techniques. Stereotactic ablative radiation (SAbR) may provide an innovative non-invasive alternative although prospective data are limited.

OBJECTIVE

To investigate whether SAbR is effective in the management of primary RCCs.

DESIGN, SETTING, AND PARTICIPANTS

Patients with biopsy-confirmed radiographically enlarging primary RCC (≤5 cm) were enrolled. SAbR was delivered in either three (12 Gy) or five (8 Gy) fractions.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was local control (LC) defined as a reduction in tumor growth rate (compared with a benchmark of 4 mm/yr on active surveillance) and pathologic evidence of tumor response at 1 yr. Secondary endpoints included LC by the Response Evaluation Criteria in Solid Tumors (RECIST 1.1), safety, and preservation of kidney function. Exploratory tumor cell-enriched spatial protein and gene expression analysis were conducted on pre- and post-treatment biopsy samples.

RESULTS AND LIMITATIONS

Target accrual was reached with the enrollment of 16 ethnically diverse patients. Radiographic LC at 1 yr was observed in 94% of patients (15/16; 95% confidence interval: 70, 100), and this was accompanied by pathologic evidence of tumor response (hyalinization, necrosis, and reduced tumor cellularity) in all patients. By RECIST, 100% of the sites remained without progression at 1 yr. The median pretreatment growth rate was 0.8 cm/yr (interquartile range [IQR]: 0.3, 1.4), and the median post-treatment growth rate was 0.0 cm/yr (IQR: -0.4, 0.1, p < 0.002). Tumor cell viability decreased from 4.6% to 0.7% at 1 yr (p = 0.004). With a median follow-up of 36 mo for censored patients, the disease control rate was 94%. SAbR was well tolerated with no grade ≥2 (acute or late) toxicities. The average glomerular filtration rate declined from a baseline of 65.6 to 55.4 ml/min at 1 yr (p = 0.003). Spatial protein and gene expression analyses were consistent with the induction of cellular senescence by radiation.

CONCLUSIONS

This clinical trial adds to the growing body of evidence suggesting that SAbR is effective for primary RCC supporting its evaluation in comparative phase 3 clinical trials.

PATIENT SUMMARY

In this clinical trial, we investigated a noninvasive treatment option of stereotactic radiation therapy for the treatment of primary kidney cancer and found that it was safe and effective.

Stereotactic ablative radiotherapy for pulmonary oligometastases from primary hepatocellular carcinoma: a multicenter and retrospective analysis (KROG 17-08)

OBJECTIVE

Hypofractionated radiotherapy has recently been applied to treat pulmonary metastases of hepatocellular carcinoma. However, there is no definite evidence on its safety and efficacy. We evaluate the clinical outcomes of hypofractionated radiotherapy for oligo pulmonary metastases of hepatocellular carcinoma in the multicenter and retrospective study.

METHODS

From March 2011 to February 2018, 58 patients with fewer than five pulmonary metastases of hepatocellular carcinoma who underwent hypofractionated radiotherapy in nine tertiary university hospitals were analyzed retrospectively. The primary endpoint was the local control rate. The secondary endpoints were overall survival, progression-free survival, prognostic factors affecting the treatment outcomes and treatment-related side effects.

RESULTS

The local tumor response rate including complete and partial response was 77.6% at 3 months after hypofractionated radiotherapy. The median survival and progression-free survival times were 20.9 and 5.3 months, respectively. The 1-year overall survival and progression-free survival rates were 65.5 and 22.4%, respectively. The good treatment response after hypofractionated radiotherapy (P = 0.001), the absence of intrahepatic tumor (P = 0.004) and Child-Pugh class A (P = 0.010) were revealed as significant prognostic factors for overall survival in the multivariate analysis. A progression-free interval of <6 months (P = 0.009) was a negative prognostic factor for overall survival in the multivariate analysis. Of 58 patients, five (8.6%) had grade 2 or higher radiation pneumonitis after hypofractionated radiotherapy.

CONCLUSIONS

The favorable local control rate and acceptable toxicity indicate the clinical usefulness of hypofractionated radiotherapy for hepatocellular carcinoma patients who have less than five pulmonary metastases.

Evaluation of Safety of Stereotactic Body Radiotherapy for the Treatment of Patients With Multiple Metastases: Findings From the NRG-BR001 Phase 1 Trial

IMPORTANCE

Stereotactic body radiotherapy (SBRT) for oligometastases is hypothesized to improve survival and is increasingly used. Little evidence supports its safe use to treat patients with multiple metastases.

OBJECTIVE

To establish safety of SBRT dose schedules in patients with 3 to 4 metastases or 2 metastases in close proximity to each other.

DESIGN, SETTING, AND PARTICIPANTS

This phase 1 trial opened on August 4, 2014, and closed to accrual on March 20, 2018. Metastases to 7 anatomic locations were included: bone/osseous (BO), spinal/paraspinal (SP), peripheral lung (PL), central lung (CL), abdominal-pelvic (AP), mediastinal/cervical lymph node (MC), and liver (L). Six patients could be enrolled per anatomic site. The setting was a consortium of North American academic and community practice cancer centers participating in NRG Oncology trials. Patients with breast, prostate, or non-small cell lung cancer with 3 to 4 metastases or 2 metastases in close proximity (≤5 cm) amenable to SBRT were eligible for this phase 1 study. Statistical analyses were performed from December 31, 2017, to September 19, 2019.

INTERVENTIONS

The starting dose was 50 Gy in 5 fractions (CL, MC), 45 Gy in 3 fractions (PL, AP, L), and 30 Gy in 3 fractions (BO, SP).

MAIN OUTCOMES AND MEASURES

The primary end point was dose-limiting toxicity (DLT) defined by the Common Terminology Criteria for Adverse Events, version 4.0, as specific adverse events (AEs) of grades 3 to 5 (definite or probable per the protocol DLT definition) related to SBRT within 180 days of treatment. Dose levels were considered safe if DLTs were observed in no more than 1 of 6 patients per location; otherwise, the dose at that location would be de-escalated.

RESULTS

A total of 42 patients enrolled, 39 were eligible, and 35 (mean [SD] age, 63.1 [14.2] years; 20 men [57.1%]; 30 White patients [85.7%]) were evaluable for DLT. Twelve patients (34.3%) had breast cancer, 10 (28.6%) had non-small cell lung cancer, and 13 (37.1%) had prostate cancer; there was a median of 3 metastases treated per patient. Median survival was not reached. No protocol-defined DLTs were observed. When examining all AEs, 8 instances of grade 3 AEs, most likely related to protocol therapy, occurred approximately 125 to 556 days from SBRT initiation in 7 patients.

CONCLUSIONS AND RELEVANCE

This phase 1 trial demonstrated the safety of SBRT for patients with 3 to 4 metastases or 2 metastases in close proximity. There were no treatment-related deaths. Late grade 3 AEs demonstrate the need for extended follow-up in long-surviving patients with oligometastatic disease. Treatment with SBRT for multiple metastases has been expanded into multiple ongoing randomized phase 2/3 National Cancer Institute-sponsored trials (NRG-BR002, NRG-LU002).

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02206334.

Local Treatment in Addition to Endocrine Therapy in Hormone Receptor-Positive and HER2-Negative Oligometastatic Breast Cancer Patients: A Retrospective Multicenter Analysis

BACKGROUND

Recent trials have provided robust evidence demonstrating that endocrine therapy with/without targeted therapy, such as cyclin-dependent kinase 4/6 inhibitors or mTOR (mammalian target of rapamycin) inhibitors, effectively halts disease progression in hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer. We investigated the survival impact of local treatment of metastases as a first-line treatment after metastasis in HR-positive and HER2-negative breast cancer patients with a very low metastatic volume.

MATERIALS AND METHODS

From a retrospectively constructed database for three institutes, we identified HR-positive and HER2-negative breast cancer patients with recurrent distant oligometastatic disease after initially curative treatment. De novo stage 4 patients were excluded, and only those with recurrent metastatic disease were included. Oligometastatic disease was defined as follows: (1) ≤2 metastatic lesions in a single organ, (2) a maximal diameter ≤3 cm, and (3) organ involvement, including the lung, liver, adrenal gland, bone, or distant lymph nodes. Local treatment comprised surgery or radiotherapy. Progression-free survival (PFS) and overall survival (OS) were investigated.

RESULTS

Forty-nine patients were included; 33 underwent local treatment. Of these 33 patients, 5 underwent surgical resection and 27 received radiotherapy. One patient underwent both surgical resection and radiotherapy. Median PFS was significantly longer among the patients with local treatment than among the patients without local treatment (30.0 vs. 18.0 months, p = 0.049). In multivariate analysis, local treatment was shown to prolong PFS. However, median OS after metastasis did not differ with regard to local treatment (72.3 vs. 91.0 months, p = 0.272).

CONCLUSION

We showed that local treatment could positively affect disease progression in HR-positive and HER2-negative oligometastatic breast cancer.

Radiation Therapy for Patients with Advanced Renal Cell Carcinoma

Stereotactic radiosurgery and stereotactic body radiation therapy (SBRT) have led to a resurgence of the use of radiotherapy in the management of advanced renal cell carcinoma (RCC). These techniques provide excellent local control and palliation of metastatic sites of disease with minimal toxicity. Additionally, SBRT to the primary tumor may be efficacious and well tolerated in select patients that are not surgical candidates. Emerging data suggest that SBRT may potentiate the immune response, and current and future study will evaluate if SBRT can improve survival outcomes in patients with metastatic RCC.

The Yin and Yang of Cytoreductive SBRT in Oligometastases and Beyond

Background: Oligometastatic disease has emerged as a possibly distinct metastatic phenotype in numerous cancer histologies. With the advancement in treatment modalities including stereotactic body radiation therapy (SBRT), certain patients may derive benefits from local ablative therapy. SBRT alone has already shown to have potential benefits in certain oligometastatic disease types. However, more understanding of the immunologic modulation and microenvironment is needed to guide which patients may benefit from SBRT alone or with combination therapy, if at all. Purpose: The purpose of this review is to offer an update on the emerging data testing SBRT combined with immunotherapy, review the pro-inflammatory and immunosuppressive effects of the tumor microenvironment, discuss novel molecular targets used to augment the immune response, and review potential methods used to decrease toxicity in order to improve the therapeutic ratio.

Predictive factors for survival of oligometastatic colorectal cancer treated with Stereotactic body radiation therapy

BACKGROUND AND PURPOSE

Colorectal cancer (CRC) represents one of the major leading causes of death from cancer. Aim of the present study was to analyze outcome of oligometastatic CRC patients treated with stereotactic body radiation therapy (SBRT), and to evaluate predictive factors of survival.

MATERIALS AND METHODS

We included patients with maximum 5 metastases. Previous/concomitant systemic treatments were allowed. End points of the present study were the outcome in terms of Local control of treated metastases (LC), progression free survival (PFS), and overall survival (OS).

RESULTS

437 metastases were treated in 270 patients. Lung was site of metastases in 48.5% of cases, followed by liver (36.4%). Systemic treatment was administered before SBRT in 199 patients (73.7%). Median follow-up time was 23 months (3-98.7). Rates of LC at 1, 3 and 5 years were 95%, 73% and 73%, respectively. Time from diagnosis of metastases to SBRT was the only factor predictive of LC (HR 1.62, p = 0.023). Median PFS was 8.6 months. Rates of OS at 1, 3 and 5 years were 88.5%, 56.6%, and 37.2%, respectively. Lesion greater than 30 mm (HR 1.82, p = 0.030), presence of non-lung metastases (HR 1.67, p = 0.020), the use of systemic treatment before SBRT (HR 1.82, p = 0.023), and progression of treated metastases (HR 1.80, p = 0.007), were all predictive of worse OS.

CONCLUSIONS

Stereotactic body radiation therapy represents an effective approach in the management of oligometastatic CRC. Control of treated oligometastases seems to be a strong positive predictive factor for both PFS and OS.

Stereotactic Body Radiation Therapy for Oligometastatic Ovarian Cancer: A Step Toward a Drug Holiday

PURPOSE

To evaluate stereotactic body radiation therapy (SBRT) for metachronous oligometastatic ovarian cancer patients in terms of local control, delay of systemic treatment, survival outcomes, and toxicity.

METHODS AND MATERIALS

Retrospective data collection from a single institution was performed. The inclusion criteria were as follows: (1) oligorecurrent or oligoprogressive disease in ovarian cancer patients during or after systemic therapy; (2) surgery or other local therapies not feasible; and (3) relative contraindication to systemic therapy for reasons such as unavailability of additional chemotherapy lines or refusal of the patient. Tumor response and toxicity were evaluated using the Response Evaluation Criteria in Solid Tumors and the Common Terminology Criteria for Adverse Events version 4.03, respectively. A new systemic therapy regimen was started after an SBRT treatment course in 57 of 109 cases (52.3%). Local progression-free survival, progression-free survival, and overall survival were calculated via the Kaplan-Meier method. The systemic treatment-free interval was calculated in cases without concomitant systemic therapy.

RESULTS

Between May 2012 and December 2016, 82 patients (156 lesions) underwent SBRT with a median dose of 24 Gy in 3 fractions. The median follow-up period was 17.4 months. Patients received a median of 3 systemic therapy regimens prior to SBRT. Concomitant systemic therapy was performed for 29 lesions (18.6%). Among 152 evaluable lesions, a complete radiologic response, partial response, stabilization, and progressive disease were observed in 91 (60%), 26 (17%), 24 (16%), and 11 (7%), respectively. No grade 3 or 4 acute or late toxicities were observed. The median systemic treatment-free interval after SBRT was 7.4 months, and 1 of 3 patients was disease free at 1 year after SBRT. The actuarial 2-year local progression-free survival, progression-free survival, and overall survival rates were 68%, 18%, and 71%, respectively. The pattern of failure was predominantly out of field.

CONCLUSIONS

SBRT for oligometastatic ovarian cancer showed good local control and a good toxicity profile. It might be an appealing alternative to other invasive local therapies to delay systemic therapy in the case of chemorefractory disease or intolerance to systemic agents.

Lung metastases treated with stereotactic body radiotherapy: the RSSearch® patient Registry's experience

Objectives

To report overall survival and local control for patients identified in the RSSearch® Patient Registry with metastatic cancer to the lung treated with SBRT.

Methods

Seven hundred two patients were identified with lung metastases in the RSSearch® Registry. Of these patients, 577 patients had SBRT dose and fractionation information available. Patients were excluded if they received prior surgery, radiation, or radiofrequency ablation to the SBRT treated area. Between April 2004-July 2015, 447 patients treated with SBRT at 30 academic and community-based centers were evaluable for overall survival (OS). Three hundred four patients with 327 lesions were evaluable for local control (LC). All doses were converted to Monte Carlo equivalents and subsequent BED Gy₁₀ for dose response analysis.

Results

Median age was 69 years (range, 18–93 years). Median Karnofsky performance status (KPS) was 90 (range 25/75% 80–100). 49.2% of patients had prior systemic therapy. Median metastasis volume was 10.58 cc (range 25/75% 3.7–25.54 cc). Site of primary tumor included colorectal (25.7%), lung (16.6%), head and neck (11.4%), breast (9.2%), kidney (8.1%), skin (6.5%) and other (22.1%). Median dose was 50 Gy (range 25/75% 48–54) delivered in 3 fractions (range 25/75% 3–5) with a median BED of 100Gy₁₀ (range 25/75% 81–136).

Median OS for the entire group was 26 months, with actuarial 1-, 3-, and 5-year OS of 74.1%, 33.3, and 21.8%, respectively. Patients with head and neck and breast cancers had longer median OS of 37 and 32 months respectively, compared to colorectal (30 months) and lung (26 months) which corresponded to 3-year actuarial OS of 51.8 and 47.9% for head and neck and breast respectively, compared to 35.8% for colorectal and 31.2% for lung.

The median LC for all patients was 53 months, with actuarial 1-, 3-, and 5-year LC rates of 80.4, 58.9, and 46.3%, respectively. There was no difference in LC by primary histologic type (p = 0.49). Improved LC was observed for lung metastases that received SBRT doses of BED ≥100Gy₁₀ with 3-year LC rate of 77.1% compared to 45% for lung metastases treated with BED < 100Gy₁₀ (p = 0.01). Smaller tumor volumes (<11 cc) had improved LC compared to tumor volumes > 11 cc. (p = 0.005) Two-year LC rates for tumor volumes < 11 cc, 11–27 cc and > 27 cc were 72.9, 64.2 and 45.6%, respectively. This correlated with improved OS with 2-year OS rates of 62.4, 60.9 and 46.2% for tumor volumes < 11 cc, 11–27 cc and > 27 cc, respectively (p = 0.0023). In a subset of patients who received BED ≥100Gy₁₀, 2-year LC rates for tumor volumes < 11 cc, 11–27 cc and > 27 cc were 82.8, 58.9 and 68.6%, respectively (p = 0.0244), and 2-year OS rates were 66.0, 58.8 and 28.5%, respectively (p = 0.0081).

Conclusion

Excellent OS and LC is achievable with SBRT utilizing BED ≥100Gy₁₀ for lung metastases according to the RSSearch® Registry data. Patients with small lung metastases (volumes < 11 cc) had better LC and OS when using SBRT doses of BED ≥100Gy₁₀. Further studies to evaluate a difference, if any, between various tumor types will require a larger number of patients.

The expanding role of stereotactic body radiation therapy in oligometastatic solid tumors: What do we know and where are we going?

The spectrum hypothesis posits that there are distinct clinical states of metastatic progression. Early data suggest that aggressive treatment of more biologically indolent metastatic disease, characterized by metastases limited in number and destination organ, may offer an opportunity to alter the disease course, potentially allowing for longer survival, delay of systemic therapy, or even cure. The development of stereotactic body radiation therapy (SBRT) has opened new avenues for the treatment of oligometastatic disease. Early data support the use of SBRT for treating oligometastases in a number of organs, with promising rates of treated metastasis control and overall survival. Ongoing investigation is required to definitively establish benefit, determine the appropriate treatment regimen, refine patient selection, and incorporate SBRT with systemic therapies.

Cancer stem cell related markers of radioresistance in head and neck squamous cell carcinoma

Despite recent advances in understanding of the molecular pathogenesis and improvement of treatment techniques, locally advanced head and neck squamous cell carcinoma (HNSCC) remains associated with an unfavorable prognosis. Compelling evidence suggests that cancer stem cells (CSC) may cause tumor recurrence if they are not eradicated by current therapies as radiotherapy or radio-chemotherapy. Recent in vitro studies have demonstrated that CSCs may be protected from treatment-induced death by multiple intrinsic and extrinsic mechanisms. Therefore, early determination of CSC abundance in tumor biopsies prior-treatment and development of therapeutics, which specifically target CSCs, are promising strategies to optimize treatment. Here we provide evidence that aldehyde dehydrogenase (ALDH) activity is indicative for radioresistant HNSCC CSCs. Our study suggests that ALDH⁺ cells comprise a population that maintains its tumorigenic properties in vivo after irradiation and may provide tumor regrowth after therapy. We found that ALDH activity in HNSCC cells can be attributed, at least in part, to the ALDH1A3 isoform and inhibition of the ALDH1A3 expression by small interfering RNA (siRNA) decreases tumor cell radioresistance. The expression dynamic of ALDH1A3 upon irradiation by either induction or selection of the ALDH1A3 positive population correlates to in vivo curability, suggesting that changes in protein expression during radiotherapy are indicative for tumor radioresistance. Our data indicate that ALDH1A3⁺ HNSCC cells may contribute to tumor relapse after irradiation, and inhibition of this cell population might improve therapeutic response to radiotherapy.

Ablative Approaches for Pulmonary Metastases

Pulmonary metastases are common in patients with cancer for which surgery is considered a standard approach in appropriately selected patients. A number of patients are not candidates for surgery due to a medical comorbidities or the extent of surgery required. For these patients, noninvasive or minimally invasive approaches to ablate pulmonary metastases are potential treatment strategies. This article summarizes the rationale and outcomes for non-surgical treatment approaches, including radiotherapy, radiofrequency and microwave ablation, for pulmonary metastases.

Prospective evaluation of radiation-induced skin toxicity in a race/ethnically diverse breast cancer population

We evaluated predictors of radiation‐induced skin toxicity in a prospective study of a tri‐racial/ethnic breast cancer population. We evaluated patient demographics, tumor characteristics, and treatment variables in the first 392 patients in a prospective study assessing radiation‐induced skin toxicity. Logistic regression analyses were conducted to evaluate potential predictors of skin toxicity. The study consists of 59 non‐Hispanic whites (NHW; 15%), 241 Hispanic Whites (HW; 62%), 79 black or African Americans (AA; 20%), and 13 others (3%). Overall, 48% developed grade 0–1 skin toxicity, 49.8% grade 2, and 2.2% grade 3 by the National Cancer Institute's Common Toxicity Criteria for Adverse Events (CTCAE) scale. Twenty‐one percent developed moist desquamation. In multivariate analysis, higher body mass index (BMI; OR = 2.09; 95%CI = 1.15, 3.82), higher disease stage (OR = 1.82; 95%CI = 1.06, 3.11), ER‐positive/PR‐negative status (OR = 2.74; 95%CI = 1.26, 5.98), and conventionally fractionated regimens (OR = 3.25; 95%CI = 1.76, 6.01) were significantly associated with higher skin toxicity grade after adjustment for age, race, ethnicity, ER status, and breast volume. BMI specifically predicted for moist desquamation, but not degree of erythema. In this racially and ethnically diverse cohort of breast cancer patients receiving radiation to the intact breast, risk factors including BMI, disease stage, and conventionally fractionated radiation predicted for higher skin toxicity grade, whereas age, race, ethnicity, and breast volume did not. BMI specifically predicted for moist desquamation, suggesting that preventive measures to address this particular outcome should be investigated.

Surgery or ablative radiotherapy for breast cancer oligometastases

Precisely focused radiation or surgical resection of limited metastases resulted in long-term disease control and survival in multiple studies of patients with oligometastatic breast cancer. The integration of these ablative techniques into standard systemic therapy regimens has the potential to be paradigm shifting, leaving many patients without evidence of disease. Although an attractive treatment option, the utility of these therapies have not been proven in controlled studies, and improved outcomes may be because of patient selection or favorable biology alone. Ongoing studies continue to refine radiation techniques and determine the role for ablative therapies in the management of patients with metastatic breast cancer (MBC). Additionally, patient selection for metastasis-directed therapies is based on clinical criteria, with many not benefiting from therapies that may have substantial toxicities. Recent reports are beginning to uncover the biology of oligometastatic cancer, but much work is needed. Current and developing trials that integrate both clinical and translational endpoints have the potential to transform management strategies in women with limited MBC.

The role of surgery and ablative radiotherapy in oligometastatic breast cancer

The ability to deliver precise focused radiation, combined with improved surgical techniques, has led to multiple reports of long-term survivors in patients with oligometastatic breast cancer. The removal or ablation of known metastases, often present after systemic therapy regimens has the potential to be paradigm shifting rendering many patients without evidence of disease. However, the utility of these therapies has not been proven in phase III studies. Additionally, patient selection for metastasis-directed therapies is based on clinical criteria, with many patients not benefiting from these therapies. Refinements of radiation techniques are continuing, and discoveries are uncovering the biology of breast cancer in the oligometastatic state among patients. Integrated into ongoing studies, and those in development, they have the potential to alter standard management strategies in oligometastatic patients.

Radical irradiation of extracranial oligometastases

Advances in radiotherapy planning and delivery have been used to treat patients with limited metastatic disease. With these techniques, high rates of treated metastasis control and low toxicity have been reported. Some patients have long disease-free intervals after radiotherapy similar to those seen after surgical resection. Ongoing studies will determine the benefit of these irradiation techniques to treat limited metastases, identify appropriate candidates, and assist in integrating these treatments into management strategies for specific diseases.

The oligometastatic state - separating truth from wishful thinking

The oligometastatic paradigm implies that patients who develop a small number of metastatic lesions might achieve long-term survival if all these lesions are ablated with surgery or stereotactic radiotherapy. Clinical data indicate that the number of patients with oligometastatic disease receiving aggressive treatment is increasing rapidly. We examine the key evidence supporting or refuting the existence of an oligometastatic state. Numerous single-arm studies suggest that long-term survival is 'better-than-expected' after ablative treatment. However, the few studies with adequate controls raise the possibility that this long-term survival might not be due to the treatments themselves, but rather to the selection of patients based on favourable inclusion criteria. Furthermore, ablative treatments carry a risk of harming healthy tissue, yet the risk-benefit ratio cannot be quantified if the benefits are unmeasured. If the strategy of treating oligometastases is to gain widespread acceptance as routine clinical practice, there should be stronger evidence supporting its efficacy.

Stereotactic body radiotherapy treatment of extracranial metastases

Radiotherapy is an integral treatment for patients with metastatic cancer, although it is usually reserved for palliation of pain, dyspnoea, oedema, bleeding and neurological symptoms. However, the administration of high-precision radiotherapy, termed stereotactic body radiotherapy (SBRT), has the potential to significantly affect the disease course for some patients with metastatic cancer by delivering high doses of radiation to the secondary tumours with limited high-dose delivery to adjacent healthy tissues. Indeed, such accurate delivery has been firmly established as a therapy for medically inoperable early-stage non-small-cell lung cancer. To date, the technique has demonstrated improvements in controlling metastasis and, in some cases, improved palliation compared with conventionally fractionated radiotherapy. Active areas of research in SBRT include patient selection for curative intent, optimization of SBRT planning techniques, dosing schema and integration of SBRT into systemic therapies. Given the improvements in cytotoxic and targeted therapies over the past decade, studies testing the careful integration of SBRT into standard systemic therapy regimens are needed. Further investigations are also needed to understand the basic biological mechanisms underlying SBRT because they are likely to be different to those mechanisms in conventional radiotherapy.