Understanding age and race disparities in the application of sentinel lymph node biopsy in breast cancer

Discussion

In our cross-sectional study of 479 women with clinically node-negative, early-stage breast cancer, SLNB was performed in 90% of the patients. Women 80 years and older had significantly lower odds of receiving SLNB compared to women younger than 65 years. However, there was no difference in receipt of SLNB between black and white women. Detailed chart review found that there was an appropriate medical reason for why all but two women did not receive SLNB. These findings suggest that, in our population, lack of SLNB did not represent a disparity but rather reflected appropriate clinical decision-making.

In nearly all cases, patients who did not receive SLNB did so for a reason that was based on clinical judgment. Reasons found for the deferrals include advanced age, breast cancer recurrences with previous axillary node dissections, comorbid conditions or patient declining the procedure. While previous surgery and comorbidity are often available from administrative claims data, the level of detail may not be adequate to know which patients are not receiving SLNB for a medically appropriate reason; further, patient decision-making is not captured in claims data. The results suggest that using SLNB as a quality indicator solely using administrative claims data may be inappropriate. If SLNB is used as a quality indicator, it will be necessary to have strict exclusion criteria to avoid unwarranted penalization; patient preferences (especially among older and sicker women) and provider medical decision-making (which should be rooted in the best available evidence) must be incorporated into criteria evaluating adherence with quality guidelines.

Similar to previous findings, we found differences in SLNB receipt based on insurance status and age. The most recent ASCO clinical guidelines for SLNB specifically state that age should not be a determining factor for SLNB (or axillary lymph node dissection) consideration, citing insufficient evidence showing difference in outcomes by age.13 Similar disparities were previously seen with axillary lymph node dissection, as older women were less likely to undergo the procedure.14 ,15 In these studies, reasons given by surgeons for not offering axillary lymph node dissections in their older patients included the belief that lymph nodal status would not alter subsequent treatment decisions and the potential morbidity outweighing the potential benefits.14 It is likely that surgeons hold similar beliefs with SLNB utilization in the older patient population, judging it to not be clinically appropriate, accounting for the observed differences.

In contrast to prior studies, we did not observe a racial disparity in the receipt of SLNB within our single institution. Many of the previous studies demonstrating racial differences in the use of SLNB use older data.9–12 Since the rate of SLNB has grown dramatically over time,9–11 disparities in access to SLNB may have decreased over time. An overlapping explanation is that racial disparities in the receipt of SLNB may be driven, at least in part, by where patients receive care.16–19 Prior research has found that black and white patients tend to receive care from different primary care providers who have different access to specialty resources.20–22 In cancer care, racial differences in the receipt of prostatectomy for localized prostate cancer are due, in part, to where patients receive care. In particular, patients treated at hospitals with a larger proportion of non-white patients were significantly less likely to receive surgery.23 Lending credence to this explanation in the case of SLNB is a prior work finding that institutional features, such as NCI Cancer Center affiliation, are associated with the receipt of SLNB.9 ,11 ,12 Disaggregating the observed disparities in SLNB into those that exist between institutions versus those that occur within institutions is an important next step. If disparities are indeed due to different sites of care, then it is critical to examine what factors drive patients to receive care from different surgeons and institutions.

There are limitations to our study. Data were obtained only from single healthcare system, using a relatively small sample, which limits the generalizability of the findings. The smaller sample size, however, allowed us to conduct an extensive chart review to identify why patients did not receive SLNB. Although a priori power analyses did validate the size, some differences that could be clinically meaningful may have not have reached statistical significance. Lastly, we relied on the accuracy of chart documentation to obtain reasons for SLNB deferral.

In our study population of patients with early-stage breast cancer within a single institution, we found that women 80 years of age and older had the lowest rate of receiving SLNB. Importantly, most patients who did not receive SLNB had a clinically justified reason for deferral. Advanced age was the reason most commonly documented by physicians for not receiving SLNB in the medical record. Although large registry-based data may be useful in identifying issues such as age and racial disparities in SLNB, lack of detailed clinical reasoning makes it difficult to evaluate potential reasons for differences and use as the sole source for determining compliance with quality metrics associated with breast center accreditation.