The role of postmastectomy radiotherapy in women with pathologic T3N0M0 breast cancer: PMRT in Patients With pT3N0M0 Breast Cancer

Nomogram-Based Risk Stratification to Identify Patients with T3N0M0 Breast Cancer with Survival Benefit from Postmastectomy Radiotherapy

BACKGROUND

The survival benefit of postmastectomy radiotherapy (PMRT) for patients with T3N0M0 breast cancer remains controversial. This study aimed to identify patients with a survival benefit from PMRT by developing a novel risk stratification model.

PATIENTS AND METHODS

The study recruited 2062 patients with pT3N0M0 breast cancer from the Surveillance, Epidemiology, and End Results (SEER) database who underwent mastectomy between 2010 and 2019. Overall survival (OS) and breast-cancer-specific survival (BCSS) prognostic nomograms based on multivariate Cox regression were constructed to quantify the survival risk and classify patients into low- and high-risk groups. Subgroup analyses were undertaken to assess the role of PMRT according to age and risk stratification.

RESULTS

In the overall cohort, PMRT was beneficial in improving OS in patients with pT3N0 breast cancer (5-year OS, non-PMRT versus PMRT: 76.6% vs. 84.2%, P < 0.001), while the benefit on BCSS was not significant (P = 0.084). On the basis of the risk stratification nomogram, in the high-risk group, PMRT improved OS in young patients by 10.1%, OS in elderly patients by 12.4%, and BCSS by 10.2% (P < 0.05), but the use of PMRT in the low-risk group did not improve OS and BCSS in all patients (P > 0.05).

CONCLUSIONS

We presented a new method for quantifying risk using the nomogram to identify patients with high risk of pT3N0M0 breast cancer. This study found that older patients in the newly constructed high-risk group benefited from OS and BCSS benefits from PMRT, while for younger high-risk patients, there was only a benefit in terms of OS.

American Radium Society Appropriate Use Criteria Postmastectomy Radiation Therapy: Executive Summary of Clinical Topics

PURPOSE

To conduct an appropriate use criteria expert panel update on clinical topics relevant to current clinical practice regarding postmastectomy radiation therapy (PMRT).

METHODS AND MATERIALS

An analysis of the medical literature from peer-reviewed journals was conducted from May 4, 2010 to May 4, 2022 using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines to search the PubMed database to retrieve a comprehensive set of relevant articles. A well-established methodology (modified Delphi) was used by the expert panel to rate the appropriate use of procedures.

RESULTS

Evidence for key questions in PMRT regarding benefit in special populations and technical considerations for delivery was examined and described. Risk factors for local-regional recurrence in patients with intermediate-risk disease that indicate benefit of PMRT include molecular subtype, age, clinical stage, and pathologic response to neoadjuvant chemotherapy. Use of hypofractionated radiation in PMRT has been examined in several recent randomized trials and is under investigation for patients with breast reconstruction. The use of bolus varies significantly by practice region and has limited evidence for routine use. Adverse effects occurred with both PMRT preimplant and postimplant exchange in 2-staged breast reconstruction.

CONCLUSIONS

Most patients with even limited nodal involvement will likely benefit from PMRT with significant reduction in local-regional recurrence and potential survival. Patients with initial clinical stage III disease and/or any residual disease after neoadjuvant chemotherapy should be strongly considered for PMRT. Growing evidence supports the use of hypofractionated radiation for PMRT with equivalent efficacy and decreased acute side effects, but additional evidence is needed for special populations. There is limited evidence to support routine use of bolus in all patients. Timing of PMRT regarding completion of 2-staged breast reconstruction requires a discussion of increased risks with radiation postimplant exchange compared with increased risk of failure of reconstruction or surgical complications with radiation preimplant exchange.

Variation in Rates of Post-Mastectomy Radiotherapy Among Women with Early Invasive Breast Cancer in England and Wales: A Population-Based Cohort Study

AIMS

This study examined whether patterns of post-mastectomy radiotherapy (PMRT) among women with early invasive breast cancer (EIBC) varied within England and Wales and explored the role of different patient factors in explaining any variation.

MATERIALS AND METHODS

The study used national cancer data on women aged ≥50 years diagnosed with EIBC (stage I-IIIa) in England and Wales between January 2014 and December 2018 who had a mastectomy within 12 months of diagnosis. A multilevel mixed-effects logistic regression model was used to calculate risk-adjusted rates of PMRT for geographical regions and National Health Service acute care organisations. The study examined the variation in these rates within subgroups of women with different risks of recurrence (low: T1-2N0; intermediate: T3N0/T1-2N1; high: T1-2N2/T3N1-2) and investigated whether the variation was linked to patient case-mix within regions and organisations.

RESULTS

Among 26 228 women, use of PMRT increased with greater recurrence risk (low: 15.0%; intermediate: 59.4%; high: 85.1%). In all risk groups, use of PMRT was more common among women who had received chemotherapy and decreased among women aged ≥80 years. There was weak or no evidence of an association between use of PMRT and comorbidity or frailty, for each risk group. In women with an intermediate risk, unadjusted rates of PMRT varied substantially between geographical regions (range 40.3-77.3%), but varied less for the high-risk (range 77.1-91.6%) and low-risk groups (range 4.1-32.9%). Adjusting for patient case-mix reduced the variation in regional and organisational PMRT rates to a small degree.

CONCLUSIONS

Rates of PMRT are consistently high across England and Wales among women with high-risk EIBC, but variation exists across regions and organisations for women with intermediate-risk EIBC. Effort is required to reduce unwarranted variation in practice for intermediate-risk EIBC.

The Association Between Survival and Receipt of Post-mastectomy Radiotherapy According to Age at Diagnosis Among Women With Early Invasive Breast Cancer: A Population-Based Cohort Study

AIMS

Clinical trials of post-mastectomy radiotherapy (PMRT) for early invasive breast cancer (EIBC) have included few older women. This study examined whether the association between overall survival or breast cancer-specific survival (BCSS) and receipt of PMRT for EIBC altered with age.

MATERIALS AND METHODS

The study used patient-level linked cancer registration, routine hospital and radiotherapy data for England and Wales. It included 31 243 women aged ≥50 years diagnosed between 2014 and 2018 with low- (T1-2N0), intermediate- (T3N0/T1-2N1) or high-risk (T1-2N2/T3N1-2) EIBC who received a mastectomy within 12 months from diagnosis. Patterns of survival were analysed using a landmark approach. Associations between overall survival/BCSS and PMRT in each risk group were analysed with flexible parametric survival models, which included patient and tumour factors; whether the association between PMRT and overall survival/BCSS varied by age was assessed using interaction terms.

RESULTS

Among 4711 women with high-risk EIBC, 86% had PMRT. Five-year overall survival was 70.5% and BCSS was 79.3%. Receipt of PMRT was associated with improved overall survival [adjusted hazard ratio (aHR) 0.75, 95% confidence interval 0.64-0.87] and BCSS (aHR 0.78, 95% confidence interval 0.65-0.95) compared with women who did not have PMRT; associations did not vary by age (overall survival, P-value for interaction term = 0.141; BCSS, P = 0.077). Among 10 814 women with intermediate-risk EIBC, 59% had PMRT; 5-year overall survival was 78.4% and BCSS was 88.0%. No association was found between overall survival (aHR 1.01, 95% confidence interval 0.92-1.11) or BCSS (aHR 1.16, 95% confidence interval 1.01-1.32) and PMRT. There was statistical evidence of a small change in the association with age for overall survival (P = 0.007), although differences in relative survival were minimal, but not for BCSS (P = 0.362).

CONCLUSIONS

The association between PMRT and overall survival/BCSS does not appear to be modified by age among women with high- or intermediate-risk EIBC and, thus, treatment recommendations should not be modified on the basis of age alone.

Established and new horizons in radiotherapy for breast cancer

Modern advances in diagnostics, surgery, systemic therapies, and radiotherapy (RT) have drastically revolutionized treatment strategies for breast cancer. This review outlines current and evolving treatment paradigms for RT in the breast-conserving therapy and post-mastectomy setting. In early-stage breast cancer, there is active investigation in expanding eligibility for omission of RT in women with more biologically favorable tumors and growing options to effectively irradiate less breast tissue and shorten RT treatment courses. For locally advanced breast cancer, we discuss several patient cohorts in which the necessity of post-mastectomy RT (PMRT) is commonly debated. Ongoing efforts to better refine indications for PMRT and evaluate the feasibility of hypofractionated PMRT are being studied. Metastasis-directed therapy with ablative RT is an emerging topic of interest in many cancers, including its role and impact in oligometastatic breast cancer. In this review, we will discuss the rationale for current standard of care and address in greater detail the aforementioned concepts.

Treatment of Breast Cancer in Young Adults

Although breast cancer is rare and understudied in adults age 40 and younger, recent epidemiologic data show an increasing incidence of breast cancer among young women in the United States and ongoing inferior long-term outcomes. Given breast cancers arising at a young age are more likely to present at advanced stages and to have aggressive biology, multimodal treatments are often indicated. Elevated local recurrence risks and greater propensity for germline cancer predisposition mutations can impact local therapy choices. Recently, escalated systemic therapy regimens for triple-negative breast cancer incorporating immunotherapy, de-escalated anti-HER2 therapy, and emerging targeted agents, including CDK4/6 inhibitors and PARP inhibitors, for early-stage disease may be employed in younger and older patients alike, with some special considerations. Prognostic genomic signatures can spare low-risk young women with hormone receptor-positive breast cancer adjuvant chemotherapy, but management of intermediate-risk patients remains controversial. Ovarian function suppression and extended endocrine therapy are improving outcomes in hormone receptor-positive breast cancer, but treatment adherence is a particular problem for young patients. Young women may also face greater challenges in long-term survivorship, including impaired fertility, difficulties in psychosocial adjustment, and other treatment-related comorbidities. Consideration of these age-specific issues through dedicated multidisciplinary strategies is necessary for optimal care of young women with breast cancer.

Effects of postmastectomy radiotherapy on survival in different age groups for patients with T3N0M0 breast cancer

BACKGROUND

Postmastectomy radiotherapy (PMRT), as an important regional treatment, improves the survival rate of patients with T3N0M0 breast cancers. However, the therapeutic effect of PMRT on T3N0M0 patients in different age groups is unclear.

METHODS

Using Surveillance, Epidemiology, and End Results database, we identified 4840 T3N0M0 patients between 2000 and 2015. The primary and secondary outcomes were overall survival (OS) and breast cancer-specific survival (BCSS). Survival outcomes were compared using Kaplan-Meier survival test, COX regression analysis, propensity score matching and forest plot, which present the relationship between age and PMRT.

RESULTS

Survival analysis demonstrated that for young patients (aged 18-45 and 46-55), there was no significant difference in OS between with and without PMRT. However, for patients older than 65 years, PMRT could significantly improve survival time (P < 0.001). Multivariate Cox analysis of OS showed older patients with PMRT had a lower hazard ratio (HR) than those without PMRT (aged 56-65: HR = 0.67, P = 0.014; aged >65: HR = 0.60, P < 0.001), and little benefit for young patients. The consistent results were also observed in 1:1 matched cohort. Subgroup analysis revealed the survival HRs of with versus without PMRT for patients older than 65 years were significant in most subgroups.

CONCLUSION

The effect of PMRT in T3N0M0 patients is related to the age. PMRT is associated with improved survival in older patients with T3N0M0 breast cancer, especially those older than 65 years. While the benefit of PMRT is limited in T3N0M0 patients of young age. The observation suggests the importance of age for T3N0M0 patients when individualized treatment is made.

Postmastectomy Radiation Therapy for Node-Negative Breast Cancer of 5cm or Larger Tumors: A Multicenter Retrospective Analysis (KROG 20-03)

Purpose

This study aimed to evaluate the role of postmastectomy radiation therapy (PMRT) in patients with node-negative breast cancer of 5cm or larger tumors undergoing mastectomy.

Materials and Methods

Medical records of 274 patients from 18 institutions treated with mastectomy between January 2000 and December 2016 were retrospectively reviewed. Among these, 202 patients underwent PMRT, while 72 did not. Two hundred and forty-one patients (88.0%) received systemic chemotherapy, and 172 (62.8%) received hormonal therapy. Patients receiving PMRT were younger, more likely to have progesterone receptor-positive tumors, and received adjuvant chemotherapy more frequently compared with those without PMRT (p < 0.001, p=0.018, and p < 0.001, respectively). Other characteristics were not significantly different between the two groups.

Results

With a median follow-up of 95 months (range, 1 to 249 months), there were nine locoregional recurrences, and 20 distant metastases. The 8-year locoregional recurrence-free survival rates were 98.0% with PMRT and 91.3% without PMRT (p=0.133), and the 8-year disease-free survival (DFS) rates were 91.8% with PMRT and 73.9% without PMRT (p=0.008). On multivariate analysis incorporating age, histologic grade, lymphovascular invasion, hormonal therapy, chemotherapy, and PMRT, the absence of lymphovascular invasion and the receipt of PMRT were associated with improved DFS (p=0.025 and p=0.009, respectively).

Conclusion

Locoregional recurrence rate was very low in node-negative breast cancer of 5 cm or larger tumors treated with mastectomy regardless of the receipt of PMRT. However, PMRT was significantly associated with improved DFS. Further investigation is needed to confirm these findings.

The Survival Effect of Chest Wall With or Without Regional Lymphatic Radiotherapy for Breast Cancer Patients With T3~4N0M0

Background

Peripheral lymphatic radiotherapy in patients with pT3N0M0 and pT4N0M0 breast cancer has been a matter of considerable debate among radiation oncologists. This is the first report in a non-Caucasian population.

Patients and Methods

The study included 165 pT3N0M0 and pT4N0M0 patients. Univariate, multivariate, propensity score matching (PSM), and Kaplan-Meier analyses were conducted to evaluate the survival of patients. We also review all the literature about regional lymph nodes radiation in T3-4N0M0 patients and summarize them with tables to compare with the present study.

Results

The median follow-up duration was 58.7 months. Multivariate analyses showed that advance T stage and grade were dependent poor prognostic factors for OS, DMFS, LRFS, and DFS between group A (chest wall radiation) and group B (chest wall and regional lymph nodes radiation). The overall survival (OS), disease-free survival (DFS), local relapse-free survival (LRFS), and distant metastasis-free survival (DMFS) rates were not significantly different between group A and group B. The 5-year OS rate was 92.3% vs 89.7% for group A and group B, respectively (P=0.819). The 5-year LRFS rate was 94.9% vs 94.3% for group A and group B, respectively (P=0.852). Fifty-four pairs of patients were selected after propensity score matching (PSM) analysis was conducted. There was also no significant difference between group A and group B in regard to the OS, DFS, LRFS, and DMFS rates after PSM. The patients included in previous studies were all Caucasians, and our study was focused on non-Caucasians. The cases of previous studies were 10 to 20 years ago, but our study has more recent cases. The radiotherapy techniques of previous studies were conventional, and the techniques used in our study were three-dimensional conformal radiotherapy (3DCRT) or intensity modulated radiotherapy (IMRT).

Conclusion

Both our study and previous studies suggested that regional lymph nodes radiation cannot improve the survival rate for breast cancer patients with T3-4N0M0 in non-Caucasian population. Advance T stage and grade were the dependent poor prognostic factors for T3-4N0M0 patients.

Outcomes in Patients with pT3N0M0 Breast Cancer with and without Postmastectomy Radiotherapy

Purpose

The role of adjuvant postmastectomy radiotherapy (PMRT) remains controversial for patients with pT3N0M0 breast cancer, especially when patients are treated with the updated adjuvant chemotherapy. Our study aimed to compare locoregional recurrence-free survival (LRFS), disease-free survival (DFS), and breast cancer-specific survival (BCSS) in pT3N0M0 patients with and without postmastectomy radiotherapy.

Patients and Methods

Between October 2000 and 8 September 2016, the database of the Breast Cancer Center of Shanghai yielded 114 patients with node-negative non-metastatic breast cancer larger than 5 cm. Univariate and multivariate analyses were performed to assess the risk factors for survivals. Differences between the two groups were compared using the Log rank test.

Results

Fifty-nine (51.8%) of the patients received adjuvant PMRT. The median follow-up was 62.3 months. Five-year LRFS was 100% in the PMRT group vs 98.1% in the non-PMRT group (P=0.17); 5-year DFS was 97.1% for the entire cohort, 98.0% for the PMRT group vs 96.2% for the non-PMRT group (P=0.18). Univariate analysis identified that family history of malignant tumors, lymphovascular invasion (LVI), or triple-negative breast cancer (TNBC) molecular subtype were associated with higher locoregional recurrence (LRR) (P<0.05). No PMRT was the only risk factor independently associated with poorer DFS (P=0.048) on multivariate analysis. No difference in BCSS was observed between the two groups.

Conclusion

The present study demonstrated a low LRR rate and good survival for node-negative breast cancer >5 cm. Patients with family history of malignant tumors, TNBC subtype, LVI positivity, or grade 3 disease are at high risk for LRR and might benefit from PMRT.

Postmastectomy Radiotherapy: Barriers to Implementation in a Disparate Population

Appalachian Kentucky (AK) has a disproportionally high breast cancer mortality rate. Postmastectomy radiotherapy (PMRT) in N2/N3 nodal disease improves survival and locoregional recurrence. We evaluated Kentucky patient compliance to the quality measure of PMRT received within one year of diagnosis. A population-based retrospective review of patients who received mastectomy with N2/N3 nodal disease from 2006 to 2015 was obtained through the Kentucky Cancer Registry. A total of 1489 patients met the inclusion criteria. Of these, 1104 (66.6%) received PMRT. AK patients were less likely to receive PMRT (58.3%) than non-AK patients (70%, P < 0.001). After adjusting for significant factors, private insurance, education level, treatment center, and receipt of adjuvant chemotherapy were independently associated with PMRT compliance. Patients who received PMRT had improved overall survival (OS, P < 0.0001) and disease-free survival (DFS, P < 0.0001). Appalachian status was not a major factor in OS ( P = 0.1929) or DFS ( P = 0.5840). Nearly two decades after the recommendation of PMRT, compliance remains poor in Kentucky. PMRT continues to be a major factor in survival and recurrence in this population. Interventions focusing on improving insurance coverage, education level, and guideline adherence in nonacademic centers are needed to improve compliance.

Breast cancer in the young patient: review of therapy and treatment considerations

In 2019, 13,050 young women were diagnosed with pre-invasive or invasive breast cancer in the USA and 1070 women died of their disease. Young women are underrepresented in clinical trials, and treatment for these women less than 40 years old is extrapolated from studies of older women. Young women face unique challenges such as decreased fertility, psychosocial issues and an extended survivorship period that impacts quality of life. Herein, we review breast cancer treatment options in the young patient (women <40 years old). We explore the biologic differences between breast cancer in young versus older patients, review surgical and systemic therapy options and highlight special considerations that are unique in these young patients.

The 2018 assisi think tank meeting on breast cancer: International expert panel white paper

We report on the second Assisi Think Tank Meeting (ATTM) on breast cancer which was held under the auspices of the European Society for RadioTherapy & Oncology (ESTRO). In discussing in-depth current evidence and practice it was designed to identify grey areas in diverse forms of the disease. It aimed at addressing uncertainties and proposing future trials to improve patient care. Before the meeting, three key topics were selected: 1) primary systemic therapy, mastectomy, breast reconstruction and post-mastectomy radiation therapy, 2) therapeutic options in ductal carcinoma in situ, and 3) therapy de-escalation in early stage breast cancer. Clinical practice in these areas was investigated by means of an online questionnaire. The time lapse period between the survey and the meeting was used to review the literature and on-going clinical trials. At the ATTM both were discussed in depth and research protocols were proposed.

Post-mastectomy radiotherapy is associated with improved overall survival in T3N0 patients who do not receive chemotherapy

BACKGROUND AND PURPOSE

There is limited retrospective evidence addressing the utility of post-mastectomy radiotherapy (PMRT) in patients with T3N0 breast cancer. We performed a retrospective analysis of the National Cancer Database (NCDB) comparing overall survival (OS) in T3N0 patients treated with mastectomy alone (MTX) or with PMRT.

MATERIALS AND METHODS

We performed a matched-cohort analysis of NCDB breast cancer patients with pT3N0 disease who did not receive NAC, or cT3N0 patients who received NAC treated between 2006 and 2014. Patients were matched for all available baseline characteristics using propensity scores with inverse probability of treatment weighting (IPTW) with stabilized weights.

RESULTS

We identified 13,901 eligible patients. In the pT3N0 cohort, median follow-up was 47 months for the MTX group and 50 months for the PMRT group. In the cT3N0 cohort, median follow-up was 44 months for the MTX group and 46 months for the PMRT group. OS was higher in pT3N0 patients treated with PMRT compared to MTX: 7-year OS of 74% vs. 65% (P < 0.001). Doubly robust multivariable analysis showed an association between PMRT and improved OS (HR 0.78, 95% CI 0.68-0.89, P < 0.001). There was no benefit to PMRT in patients who received adjuvant chemotherapy (AC). In the NAC cohort, PMRT did not change OS, with 7-year OS of 78% with MTX and 79% with PMRT. There was a trend of improved OS with PMRT in patients with residual disease in the breast and lymph nodes (HR 0.70, 95% CI 0.46-1.07).

CONCLUSION

PMRT improves OS in patients with pT3N0 disease, but the benefit appears limited to those who do not receive AC. PMRT does not improve OS in patients with cT3N0 disease who receive NAC, but there might be a benefit in patients with a poor response to chemotherapy. However, longer follow-up may be needed to make a definitive conclusion about the benefit of PMRT in patients who receive chemotherapy.

Prognostic validation and therapeutic decision-making of the AJCC eighth pathological prognostic staging for T3N0 breast cancer after mastectomy

BACKGROUND

T3N0 breast cancer might be a distinct clinical and biological entity, with higher heterogeneity and presenting diverse responses to locoregional and systemic therapy. The aim of the current study was to validate the prognostic effect and assess the treatment decision-making of the American Joint Committee on Cancer (AJCC) eighth pathological prognostic staging in T3N0 breast cancer after mastectomy.

METHODS

We retrospectively included 2465 patients with stage T3N0 breast cancer who had undergone mastectomy between 2010 and 2014 using the data from Surveillance, Epidemiology, and End Results program. The primary endpoint of this study was breast cancer-specific survival (BCSS).

RESULTS

Of the entire cohort, 76.0% of patients in the seventh AJCC staging system were restaged to the eighth AJCC pathological prognostic staging system. A total of 1431 (58.1%) and 1175 (47.7%) of them received chemotherapy and postmastectomy radiotherapy (PMRT), respectively. Pathological staging was an independent prognostic factor for BCSS. Using pathological prognostic stage IA as the reference, BCSS gradually became worse with increased hazard ratios. The 5-years BCSS was 96.9%, 95.5%, 91.1%, 85.6%, and 75.5% in pathological prognostic stage IA, IB, IIA, IIB, and IIIA breast cancers, respectively (P < .001). In pathological prognostic stage IA, IB, and IIA breast cancers, the receipt of PMRT or chemotherapy was not correlated with better BCSS. However, PMRT was correlated with better BCSS in pathological prognostic stage IIB disease (P = .006), but not in pathological prognostic IIIA disease. Moreover, chemotherapy was correlated with better BCSS in pathological prognostic stage IIIA disease (P = .006), but not in pathological prognostic stage IIB disease.

CONCLUSIONS

The eighth AJCC pathological prognostic staging system provides more risk stratification of T3N0 breast cancers after mastectomy and might affect individualized decision-making for chemotherapy and PMRT in this patient subset.

Partial chest wall radiation therapy for positive or close surgical margins after modified radical mastectomy for breast cancer without lymph node metastasis

Aim

Whole‐breast radiation therapy after breast‐conserving surgery can control local recurrence with a long‐term survival rate equivalent to that of radical mastectomy for patients with early breast cancer. However, the significance of radiation therapy for patients with positive/close margins after mastectomy remains controversial. Following radical mastectomy, no residual breast parenchyma remains, and thus radiation therapy of the entire chest wall may represent overtreatment in the patients, especially those without lymph node metastasis (N0). We therefore implemented partial chest wall radiation therapy for patients with N0 breast cancer and positive and/or close margins after mastectomy.

Methods

A total of 22 patients with N0 status but positive/close margins underwent partial chest wall radiation therapy to irradiate the predetermined clinical target volume, which had margins of at least 2 cm medial, lateral, superior, and inferior to the primary tumor bed. With reference to chest wall thickness, 4‐10‐MV photons or 5‐8‐MeV electrons with/without a bolus were delivered. The total dose was 50‐66 Gy. We compared the results with those from 18 nonradiation therapy patients using Pearson's χ² test.

Results

All patients in the partial chest wall radiation therapy group achieved good local control despite having a significantly higher proportion of positive margins (77.3%) compared with the nonradiation therapy group (27.8%) (P = 0.002). Both groups showed 100% recurrence‐ and disease‐free survival.

Conclusion

Partial chest wall radiation therapy may offer recurrence‐ and disease‐free survival without local recurrence in N0 mastectomy patients with positive/close surgical margins.

Immortal Time Bias in National Cancer Database Studies

PURPOSE

In studies evaluating the benefit of adjuvant therapies, immortal time bias (ITB) can affect the results by incorrectly reporting a survival advantage. It does so by including all deceased patients who may have been planned to receive adjuvant therapy within the observation cohort. Given the increase in National Cancer Database (NCDB) analyses evaluating postoperative radiation therapy (PORT) as an adjuvant therapy, we sought to examine how often such studies accounted and adjusted for ITB.

METHODS AND MATERIALS

A systematic review was undertaken to search MEDLINE and EMBASE from January 2014 until May 2019 for NCDB studies evaluating PORT. After appropriate exclusion criteria were applied, 60 peer-reviewed manuscripts in which PORT was compared with postoperative observation or maintenance therapy were reviewed. The manuscripts were reviewed to evaluate whether ITB was accounted for, the method with which it was adjusted for, impact factor, year of publication, and whether PORT was beneficial.

RESULTS

Of the 60 publications reviewed, 23 studies (38.3%) did not include an adjustment for ITB. Most studies that did adjust for ITB employed a single landmark (LM) time (n = 31), 4 used a sequential landmark analyses, and 2 used a time-dependent Cox model. In 23 of 31 studies (74.2%) that did adjust for ITB via a single LM time, the rationale behind why the specified LM time was chosen was not clearly explained. There was no relationship between adjusting for ITB and year of publication (P = .074) or whether the study was published in a high-impact journal (P = .55).

CONCLUSIONS

Studies assessing adjuvant radiation therapy by analyzing the NCDB are susceptible to ITB, which overestimates the effect size of adjuvant therapies and can provide misleading results. Adjusting for this bias is essential for accurate data representation and to better quantify the impact of adjuvant therapies such as PORT.