Inconsistent selection and definition of local and regional endpoints in breast cancer research

The use of bolus in postmastectomy radiation therapy for breast cancer: A systematic review

PURPOSE

Post mastectomy radiation therapy (PMRT) reduces locoregional recurrence (LRR) and breast cancer mortality for selected patients. Bolus overcomes the skin-sparing effect of external-beam radiotherapy, ensuring adequate dose to superficial regions at risk of local recurrence (LR). This systematic review summarizes the current evidence regarding the impact of bolus on LR and acute toxicity in the setting of PMRT.

RESULTS

27 studies were included. The use of bolus led to higher rates of acute grade 3 radiation dermatitis (pooled rates of 9.6% with bolus vs. 1.2% without). Pooled crude LR rates from thirteen studies (n = 3756) were similar with (3.5%) and without (3.6%) bolus.

CONCLUSIONS

Bolus may be indicated in cases with a high risk of LR in the skin, but seems not to be necessary for all patients. Further work is needed to define the role of bolus in PMRT.

Repeat breast-conserving therapy for ipsilateral breast cancer recurrence: A systematic review

The standard of care for patients with an ipsilateral breast tumour recurrence (IBTR) after breast-conserving therapy (BCT) is a salvage mastectomy. However, there is growing interest in the feasibility of repeat BCT for these patients. This systematic review contains the latest insights on BCT options for patients with an IBTR after initial BCT. A PubMed literature search was performed for articles on BCT options for IBTR after primary lumpectomy followed by radiotherapy. Weighted estimates were calculated for 5- and 10-year local control, distant metastasis-free and overall survival rates. Secondary outcomes were toxicity, cosmesis and quality of life. In total, 34 studies were eligible for analysis, of which 5 reported on repeat breast-conserving surgery (BCS) alone, 10 with mixed populations (BCS ± RT and/or mastectomy), 18 on repeat BCS followed by re-irradiation (whole-breast or partial) and one on quality of life. The weighted estimates for 5-year overall survival for repeat BCS and repeat BCS followed by reirradiation were 77% and 87%, respectively. Five-year local control was 76% for repeat BCS alone and 89% for repeat BCS followed by re-irradiation. Grade III-IV toxicity rates after re-irradiation varied from 0 to 21%, whereas the cosmesis was excellent-good in 29-100% of patients and unacceptable in 0-18%. Repeat BCS followed by re-irradiation, with either whole breast or partial breast re-irradiation, seems a feasible alternative to mastectomy in case of IBTR, in selected patients. Toxicity rates are low and the cosmetic outcome is good, but the size and follow-up of the published patient series is limited.

Is Mastectomy Oncologically Safer than Breast-Conserving Treatment in Early Breast Cancer?

AIM

To describe and discuss the evidence for oncological safety of different procedures in oncological breast surgery, i.e. breast-conserving treatment versus mastectomy.

METHODS

Literature review and discussion.

RESULTS

Oncological safety in breast cancer surgery has many dimensions. Breast-conserving treatment has been established as the standard surgical procedure for primary breast cancer and fits to the preferences of most breast cancer patients concerning oncological safety and aesthetic outcome.

CONCLUSIONS

Breast-conserving treatment is safe. Nonetheless, the preferences of the individual patients in their consideration of breast conservation versus mastectomy should be integrated into routine treatment decisions.

Clinically node negative breast cancer patients undergoing breast conserving therapy, sentinel lymph node procedure versus follow-up: a Dutch randomized controlled multicentre trial (BOOG 2013-08)

BACKGROUND

Studies showed that axillary lymph node dissection can be safely omitted in presence of positive sentinel lymph node(s) in breast cancer patients treated with breast conserving therapy. Since the outcome of the sentinel lymph node biopsy has no clinical consequence, the value of the procedure itself is being questioned. The aim of the BOOG 2013-08 trial is to investigate whether the sentinel lymph node biopsy can be safely omitted in clinically node negative breast cancer patients treated with breast conserving therapy.

METHODS

The BOOG 2013-08 is a Dutch prospective non-inferiority randomized multicentre trial. Women with pathologically confirmed clinically node negative T1-2 invasive breast cancer undergoing breast conserving therapy will be randomized for sentinel lymph node biopsy versus no sentinel lymph node biopsy. Endpoints include regional recurrence after 5 (primary endpoint) and 10 years of follow-up, distant-disease free and overall survival, quality of life, morbidity and cost-effectiveness. Previous data indicate a 5-year regional recurrence free survival rate of 99% for the control arm and 96% for the study arm. In combination with a non-inferiority limit of 5% and probability of 0.8, this result in a sample size of 1.644 patients including a lost to follow-up rate of 10%. Primary and secondary endpoints will be reported after 5 and 10 years of follow-up.

DISCUSSION

If the sentinel lymph node biopsy can be safely omitted in clinically node negative breast cancer patients undergoing breast conserving therapy, this study will cost-effectively lead to a decreased axillary morbidity rate and thereby improved quality of life with non-inferior regional control, distant-disease free survival and overall survival.

TRIAL REGISTRATION

The BOOG 2013-08 study is registered in ClinicalTrials.gov since October 20, 2014, Identifier: NCT02271828. https://clinicaltrials.gov/ct2/show/NCT02271828.

Local Recurrence and Breast Oncological Surgery in Young Women With Breast Cancer: The POSH Observational Cohort Study

OBJECTIVE

To assess clinical and surgical factors affecting local recurrence and survival in young breast cancer patients in the Prospective study of Outcomes in Sporadic versus Hereditary breast cancer (POSH).

BACKGROUND

Emerging data suggest young age is a predictor of increased local recurrence.

METHODS

POSH is a prospective cohort of 3024 women of 18 to 40 years with breast cancer. Cohort characteristics were grouped by mastectomy or BCS. Endpoints were local-recurrence interval (LRI), distant disease-free interval (DDFI), and overall survival (OS); described using cumulative-hazard and Kaplan-Meier plots and multivariable analyses by Flexible Parametric and Cox regression models.

RESULTS

Mastectomy was performed in 1464 patients and breast-conserving surgery (BCS) in 1395. Patients undergoing mastectomy had larger tumors and higher proportions of positive family history, estrogen receptor+, progesterone receptor+, and/or human epidermal growth factor receptor 2+ tumors. Local events accounted for 15% of recurrences. LRI by surgical type varied over time with LRI similar at 18 months (1.0% vs 1.0%, P = 0.348) but higher for BCS at 5 and 10 years (5.3% vs 2.6%, P < 0.001; and 11.7% vs 4.9%, P < 0.001, respectively). Similar results were found in the adjusted model. Conversely, distant-metastases and deaths were lower for BCS but not after adjusting for prognostic factors. After mastectomy chest-wall radiotherapy was associated with improved LRI (hazard ratio, HR = 0.46, P = 0.015). Positive surgical margins, and development of local recurrence predicted for reduced DDFI (HR = 0.50, P < 0.001; and HR = 0.29, P = 0.001, respectively).

CONCLUSIONS

Surgical extent appears less important for DDFI than completeness of excision or, where appropriate, chest-wall radiotherapy. Despite higher local-recurrence rates for BCS, surgical type does not influence DDFI or OS after adjusting for known prognostic factors in young breast cancer patients.

Challenges in translating endpoints from trials to observational cohort studies in oncology

Clinical trials are considered the gold standard for examining drug efficacy and for approval of new drugs. Medical databases and population surveillance registries are valuable resources for post-approval observational research, which are increasingly used in studies of benefits and risk of new cancer drugs. Here, we address the challenges in translating endpoints from oncology trials to observational studies. Registry-based cohort studies can investigate real-world safety issues – including previously unrecognized concerns – by examining rare endpoints or multiple endpoints at once. In contrast to clinical trials, observational cohort studies typically do not exclude real-world patients from clinical practice, such as old and frail patients with comorbidity. The observational cohort study complements the clinical trial by examining the effectiveness of interventions applied in clinical practice and by providing evidence on long-term clinical outcomes, which are often not feasible to study in a clinical trial. Various endpoints can be included in clinical trials, such as hard endpoints, soft endpoints, surrogate endpoints, and patient-reported endpoints. Each endpoint has it strengths and limitations for use in research studies. Endpoints used in oncology trials are often not applicable in observational cohort studies which are limited by the setting of standard clinical practice and by non-standardized endpoint determination. Observational studies can be more helpful moving research forward if they restrict focus to appropriate and valid endpoints.

The value of completion axillary treatment in sentinel node positive breast cancer patients undergoing a mastectomy: a Dutch randomized controlled multicentre trial (BOOG 2013-07)

BACKGROUND

Trials failed to demonstrate additional value of completion axillary lymph node dissection in case of limited sentinel lymph node metastases in breast cancer patients undergoing breast conserving therapy. It has been suggested that the low regional recurrence rates in these trials might partially be ascribed to accidental irradiation of part of the axilla by whole breast radiation therapy, which precludes extrapolation of results to mastectomy patients. The aim of the randomized controlled BOOG 2013-07 trial is therefore to investigate whether completion axillary treatment can be safely omitted in sentinel lymph node positive breast cancer patients treated with mastectomy.

DESIGN

This study is designed as a non-inferiority randomized controlled multicentre trial. Women aged 18 years or older diagnosed with unilateral invasive clinically T1-2 N0 breast cancer who are treated with mastectomy, and who have a maximum of three axillary sentinel lymph nodes containing micro- and/or macrometastases, will be randomized for completion axillary treatment versus no completion axillary treatment. Completion axillary treatment can consist of completion axillary lymph node dissection or axillary radiation therapy. Primary endpoint is regional recurrence rate at 5 years. Based on a 5-year regional recurrence free survival rate of 98 % among controls and 96 % for study subjects, the sample size amounts 439 per arm (including 10 % lost to follow-up), to be able to reject the null hypothesis that the rate for study and control subjects is inferior by at least 5 % with a probability of 0.8. Results will be reported after 5 and 10 years of follow-up.

DISCUSSION

We hypothesize that completion axillary treatment can be safely omitted in sentinel node positive breast cancer patients undergoing mastectomy. If confirmed, this study will significantly decrease the number of breast cancer patients receiving extensive treatment of the axilla, thereby diminishing the risk of morbidity and improving quality of life, while maintaining excellent regional control and without affecting survival.

TRIAL REGISTRATION

The BOOG 2013-07 study is registered in the register of ClinicalTrials.gov since April 10, 2014, Identifier: NCT02112682 .