The generalisability of randomised clinical trials: an interim external validity analysis of the ongoing SENOMAC trial in sentinel lymph node-positive breast cancer

Quality assessment of radiotherapy in the prospective randomized SENOMAC trial

BACKGROUND AND PURPOSE

Recommendations for regional radiotherapy (RT) of sentinel lymph node (SLN)-positive breast cancer are debated. We here report a RT quality assessment of the SENOMAC trial.

MATERIALS AND METHODS

The SENOMAC trial randomized clinically node-negative breast cancer patients with 1-2 SLN macrometastases to completion axillary lymph node dissection (cALND) or SLN biopsy only between 2015-2021. Adjuvant RT followed national guidelines. RT plans for patients included in Sweden and Denmark until June 2019 were collected (N = 1176) and compared to case report forms (CRF). Dose to level I (N = 270) and the humeral head (N = 321) was analyzed in detail.

RESULTS

CRF-data and RT plans agreed in 99.3 % (breast/chest wall) and in 96.6 % of patients (regional RT). Congruence for whether level I was an intended RT target was lower (78 %). In accordance with Danish national guidelines, level I was more often an intended target in the SLN biopsy only arm (N = 334/611, 55 %,) than in the cALND arm (N = 174/565, 31 %,). When an intended target, level I received prescribed dose to 100 % (IQR 98-100 %) of the volume. However, even when not an intended target, full dose was delivered to > 80 % of level I (IQR 75-90 %). The intentional inclusion of level I in the target volume more than doubled the dose received by ≥ 50 % of the humeral head.

CONCLUSION

Congruence between CRF data and RT plans was excellent. Level I received a high dose coverage even when not intentionally included in the target. Including level I in target significantly increased dose to the humeral head.

De-escalation of axillary treatment in the event of a positive sentinel lymph node biopsy in cT1-2 N0 breast cancer treated with mastectomy: nationwide registry study (BOOG 2013-07)

BACKGROUND

Trials have demonstrated the safety of omitting completion axillary lymph node dissection in patients with cT1-2 N0 breast cancer operated with breast-conserving surgery who have limited metastatic burden in the sentinel lymph node. The aim of this registry study was to provide insight into the oncological safety of omitting completion axillary treatment in patients operated with mastectomy who have limited-volume sentinel lymph node metastasis.

METHODS

Women diagnosed in 2013-2014 with unilateral cT1-2 N0 breast cancer treated with mastectomy, with one to three sentinel lymph node metastases (pN1mi-pN1a), were identified from the Netherlands Cancer Registry, and classified by axillary treatment: no completion axillary treatment, completion axillary lymph node dissection, regional radiotherapy, or completion axillary lymph node dissection followed by regional radiotherapy. The primary endpoint was 5-year regional recurrence rate. Secondary endpoints included recurrence-free interval and overall survival, among others.

RESULTS

In total, 1090 patients were included (no completion axillary treatment, 219 (20.1%); completion axillary lymph node dissection, 437 (40.1%); regional radiotherapy, 327 (30.0%); completion axillary lymph node dissection and regional radiotherapy, 107 (9.8%)). Patients in the group without completion axillary treatment had more favourable tumour characteristics and were older. The overall 5-year regional recurrence rate was 1.3%, and did not differ significantly between the groups. The recurrence-free interval was also comparable among groups. The group of patients who did not undergo completion axillary treatment had statistically significantly worse 5-year overall survival, owing to a higher percentage of non-cancer deaths.

CONCLUSION

In this registry study of patients with cT1-2 N0 breast cancer treated with mastectomy, with low-volume sentinel lymph node metastasis, the 5-year regional recurrence rate was low and comparable between patients with and without completion axillary treatment.

Quality assurance of radiation therapy after breast-conserving surgery among patients in the BOOG 2013-08 trial

BACKGROUND AND PURPOSE

In the BOOG 2013-08 trial (NCT02271828), cT1-2N0 breast cancer patients were randomized between breast conserving surgery with or without sentinel lymph node biopsy (SLNB) followed by whole breast radiotherapy (WBRT). While awaiting primary endpoint results (axillary recurrence rate), this study aims to perform a quality assurance analysis on protocol adherence and (incidental) axillary radiation therapy (RT) dose.

MATERIALS AND METHODS

Patients were enrolled between 2015 and 2022. Data on prescribed RT and (in 25% of included patients) planning target volumes (PTV) parameters were recorded for axillary levels I-IV and compared between treatment arms. Multivariable linear regression analysis was performed to determine prognostic variables for incidental axillary RT dose.

RESULTS

1,439/1,461 included patients (98.5%) were treated according to protocol and 87 patients (5.9%) received regional RT (SLNB 10.9%, no-SLNB 1.5 %). In 326 patients included in the subgroup analysis, the mean incidental PTV dose at axilla level I was 59.5% of the prescribed breast RT dose. In 5 patients (1.5%) the mean PTV dose at level I was ≥95% of the prescribed breast dose. No statistically or clinically significant differences regarding incidental axillary RT dose were found between treatment arms. Tumour bed boost (yes/no) was associated with a higher incidental mean dose in level I (R2 = 0.035, F(6, 263) = 1.532, p 0.168).

CONCLUSION

The results indicate that RT-protocol adherence was high, and that incidental axillary RT dose was low in the BOOG 2013-08 trial. Potential differences between treatmentarms regarding the primary endpoint can thus not be attributed to different axillary radiation doses.

Protocol for the T-REX-trial: tailored regional external beam radiotherapy in clinically node-negative breast cancer patients with 1-2 sentinel node macrometastases - an open, multicentre, randomised non-inferiority phase 3 trial

INTRODUCTION

Modern systemic treatment has reduced incidence of regional recurrences and improved survival in breast cancer (BC). It is thus questionable whether regional radiotherapy (RT) is still beneficial in patients with sentinel lymph node (SLN) macrometastasis. Postoperative regional RT is associated with an increased risk of arm morbidity, pneumonitis, cardiac disease and secondary cancer. Therefore, there is a need to individualise regional RT in relation to the risk of recurrence.

METHODS AND ANALYSIS

In this multicentre, prospective randomised trial, clinically node-negative patients with oestrogen receptor-positive, HER2-negative BC and 1-2 SLN macrometastases are eligible. Participants are randomly assigned to receive regional RT (standard arm) or not (intervention arm). Regional RT includes the axilla level I-III, the supraclavicular fossa and in selected patients the internal mammary nodes. Both groups receive RT to the remaining breast. Chest-wall RT after mastectomy is given in the standard arm, but in the intervention arm only in cases of widespread multifocality according to national guidelines. RT quality assurance is an integral part of the trial.The trial aims to include 1350 patients between March 2023 and December 2028 in Sweden and Norway. Primary outcome is recurrence-free survival (RFS) at 5 years. Non-inferiority will be declared if outcome in the de-escalation arm is not >4.5 percentage units below that with regional RT, corresponding to an HR of 1.41 assuming 88% 5-year RFS with standard treatment. Secondary outcomes include locoregional recurrence, overall survival, patient-reported arm morbidity and health-related quality of life. Gene expression analysis and tumour tissue-based studies to identify prognostic and predictive markers for benefit of regional RT are included.

ETHICS AND DISSEMINATION

The trial protocol is approved by the Swedish Ethics Authority (Dnr-2022-02178-01, 2022-05093-02, 2023-00826-02, 2023-03035-02). Results will be presented at scientific conferences and in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05634889.

Uncertainties and controversies in axillary management of patients with breast cancer

The aims of this Oncoplastic Breast Consortium and European Breast Cancer Research Association of Surgical Trialists initiative were to identify uncertainties and controversies in axillary management of early breast cancer and to recommend appropriate strategies to address them. By use of Delphi methods, 15 questions were prioritized by more than 250 breast surgeons, patient advocates and radiation oncologists from 60 countries. Subsequently, a global virtual consensus panel considered available data, ongoing studies and resource utilization. It agreed that research should no longer be prioritized for standardization of axillary imaging, de-escalation of axillary surgery in node-positive cancer and risk evaluation of modern surgery and radiotherapy. Instead, expert consensus recommendations for clinical practice should be based on current evidence and updated once results from ongoing studies become available. Research on de-escalation of radiotherapy and identification of the most relevant endpoints in axillary management should encompass a meta-analysis to identify knowledge gaps, followed by a Delphi process to prioritize and a consensus conference to refine recommendations for specific trial designs. Finally, treatment of residual nodal disease after surgery was recommended to be assessed in a prospective register.

Omission of sentinel node biopsy for breast cancer: Historical context and future perspectives on a modern controversy

For older patients with clinically lymph node-negative breast cancer who have estrogen receptor-positive tumors and are treated with tamoxifen, randomized trials comparing axillary lymph node dissection (ALND) versus no ALND show that the omission of ALND improves patient quality of life and has no adverse effects on mortality. These results have served to justify sentinel node biopsy (SNB) omission in selected older patients with breast cancer. More recently, clinical trials were launched to assess SNB omission in younger patients, with recurrence and survival as the primary outcomes of interest. Three important considerations serve as the basis for these ongoing trials. First, it is assumed that SNB omission will improve patient quality of life, although, to date, there is no level I evidence to support this assumption. Second, axillary surgery has never been shown to reduce breast cancer mortality, but it does reduce the risk of axillary recurrences, although adjuvant systemic therapy and radiotherapy also reduce these recurrence risks. Finally, nodal status is losing importance as a guide for adjuvant systemic therapy decision making because these decisions are now increasingly predicated on tumor biomarkers and gene profiling, but it is gaining importance for adjuvant radiotherapy decision making. Because quality-of-life considerations are the primary motivation for abandoning SNB, there is a need for randomized trials comparing SNB versus no SNB/no axillary surgery, with quality of life as the primary end point (level I evidence). Moreover, suitable alternatives to guide adjuvant radiotherapy decision making will require validation before SNB omission can be justified for patients of all ages who have clinically node-negative breast cancer. LAY SUMMARY: In this review article, the authors provide a brief historical overview of the role of axillary surgery in breast cancer management and discuss additional studies and ramifications that should be considered before abandoning the sentinel node biopsy (SNB) procedure. Specifically, there is a need for level I evidence demonstrating that omission of the SNB procedure will improve patient quality of life and a need to validate suitable alternatives to SNB as a guide for adjuvant radiotherapy decision making.

Axillary Ultrasound Evaluation in Breast Cancer Patients: A Multidisciplinary Viewpoint and Middle Ground

Over the past decade, there has been a trend toward de-escalation of axillary surgery. Certain patients may now forego axillary lymph node dissection even in the setting of a positive sentinel lymph node biopsy (SLNB), and some patients may not even undergo a SLNB. However, there is wide variability in the imaging approach to assessing axillary lymph nodes in patients with breast cancer. Approaches range from performing axillary US in all patients with newly diagnosed breast cancer to omitting axillary imaging evaluation in all patients. This article provides a multidisciplinary middle ground approach for axillary nodal evaluation. The clinical impact and rationale for appropriate axillary nodal imaging are discussed and an imaging algorithm is proposed.

Are morbidity and mortality estimates from randomized controlled trials externally valid? A comparison of outcomes among infants enrolled into an RCT or a cohort study in Botswana

Background

The external validity of the randomized controlled trial (RCT) refers to the extent to which the results of the RCT apply to the relevant, non-trial population and is impacted by its eligibility criteria, its organization, and its delivery of the intervention. Here, we compared the outcomes of mortality and hospitalization between an RCT and a cohort study that concurrently enrolled HIV-exposed uninfected (HEU) newborns in Botswana.

Methods

The Mpepu Study (the RCT) was a clinical trial which determined that co-trimoxazole (CTX) provided no survival benefit for HEUs, allowing both arms of the RCT to be used. The Maikaelelo study (the cohort study) was a prospective observational study that enrolled HEU newborns with telephone follow-up and no in-person visits. Rates of death and hospitalization in the pooled population, were modeled using cox-proportional hazards models for time to death or time to first hospitalization, with study setting (RCT vs. cohort study) as an independent variable. The causal effect of study setting on morbidity and mortality was obtained through a treatment effects approach.

Results

In total, 4,010 infants were included; 1,306 were enrolled into the cohort study and 2,704 were enrolled into the RCT. No significant differences in mortality were observed between the two study settings (HR: 1.28, 95% CI: 0.76, 2.13), but RCT participants had a lower risk of hospitalization (HR: 0.72, 95% CI: 0.58, 0.89) that decreased with age. However, RCT participants had a higher risk of hospitalization within the first six months of life. The causal risk difference in hospitalizations attributable to the RCT setting was -0.03 (95% CI: -0.05, -0.01).

Conclusions

Children in an RCT with rigorous application of national standard of care guidelines experienced a significantly lower risk of hospitalization than children participating in a cohort study that did not alter clinical care. Future research is needed to further investigate outcome disparities when real-world results fail to mirror those achieved in a clinical trial.

Trial registration

The Mpepu Trial was funded by the U.S. National Institutes of Health (No. NCT01229761) and the Maikaelelo Study was funded primarily by the U.S. Centers for Disease Control and Prevention (32AI007433-21).

Axillary surgery in node-positive breast cancer

Long-term follow-up data from multicenter phase III non-inferiority trials confirmed the safety of omission of axillary dissection in selected patients with clinically node-negative, sentinel node-positive breast cancer. Several ongoing trials investigate extended eligibility of the Z0011 protocol in the adjuvant setting. De-escalation of axillary surgery in patients with clinically node-positive breast cancer is currently limited to the neoadjuvant setting, where the sentinel procedure is used to determine nodal pathological complete response. Targeted axillary dissection lowers the false-negative rate of the sentinel procedure, which, however, is consistently associated with a very low risk of axillary recurrence in several recent single-center series. Axillary dissection remains standard care in patients with residual disease after neoadjuvant chemotherapy while the results of Alliance A011202 are pending. The TAXIS trial investigates the role of tailored axillary surgery in patients with clinically node-positive breast cancer, a novel concept designed to selectively remove positive nodes in the adjuvant and neoadjuvant setting.