Associated Factors and Survival Outcomes for Breast Conserving Surgery versus Mastectomy among New Zealand Women with Early-Stage Breast Cancer

Ethnic inequities in use of breast conserving surgery and radiation therapy in Aotearoa/New Zealand: which factors contribute?

PURPOSE

Aotearoa/New Zealand (NZ) faces ethnic inequities with respect to breast cancer survival and treatment. This study establishes if there are ethnic differences in (i) type of surgery and (ii) receipt of radiotherapy (RT) following breast conserving surgery (BCS), among women with early-stage breast cancer in NZ.

METHODS

This analysis used Te Rēhita Mata Ūtaetae (Breast Cancer Foundation National Register), a prospectively maintained database of breast cancers from 2000 to 2020. Logistic regression models evaluated ethnic differences in type of surgery (mastectomy or BCS) and receipt of RT with sequential adjustment for potential contributing factors. Subgroup analyses by treatment facility type were undertaken.

RESULTS

Of the 16,228 women included, 74% were NZ European (NZE), 10.3% were Māori, 9.4% were Asian and 6.2% were Pacific. Over one-third of women with BCS-eligible tumours received mastectomy. Asian women were more likely to receive mastectomy than NZE (OR 1.62; 95% CI 1.39, 1.90) as were wāhine Māori in the public system (OR 1.21; 95% CI 1.02, 1.44) but not in the private system (OR 0.78; 95% CI 0.51, 1.21). In women undergoing BCS, compared to NZE, Pacific women overall and wāhine Māori in the private system were, respectively, 36 and 38% less likely to receive RT (respective OR 0.64; 95% CI 0.50, 0.83 and 0.62; 95% CI 0.39, 0.98).

CONCLUSION

A significant proportion of women with early-stage breast cancer underwent mastectomy and significant ethnic inequities exist. Recently developed NZ Quality Performance Indicators strongly encourage breast conservation and should facilitate more standardized and equitable surgical management of early-stage breast cancer.

Receipt of mastectomy and adjuvant radiotherapy following breast conserving surgery (BCS) in New Zealand women with BCS-eligible breast cancer, 2010-2015: an observational study focusing on ethnic differences

BACKGROUND

Women with early breast cancer who meet guideline-based criteria should be offered breast conserving surgery (BCS) with adjuvant radiotherapy as an alternative to mastectomy. New Zealand (NZ) has documented ethnic disparities in screening access and in breast cancer treatment pathways. This study aimed to determine whether, among BCS-eligible women, rates of receipt of mastectomy or radiotherapy differed by ethnicity and other factors.

METHODS

The study assessed management of women with early breast cancer (ductal carcinoma in situ [DCIS] and invasive stages I-IIIA) registered between 2010 and 2015, extracted from the recently consolidated New Zealand Breast Cancer Registry (now Te Rēhita Mate Ūtaetae NZBCF National Breast Cancer Register). Specific criteria were applied to determine women eligible for BCS. Uni- and multivariable analyses were undertaken to examine differences by demographic and clinicopathological factors with a primary focus on ethnicity (Māori, Pacific, Asian, and Other; the latter is defined as NZ European, Other European, and Middle Eastern Latin American and African).

RESULTS

Overall 22.2% of 5520 BCS-eligible women were treated with mastectomy, and 91.1% of 3807 women who undertook BCS received adjuvant radiotherapy (93.5% for invasive cancer, and 78.3% for DCIS). Asian ethnicity was associated with a higher mastectomy rate in the invasive cancer group (OR 2.18; 95%CI 1.72-2.75), compared to Other ethnicity, along with older age, symptomatic diagnosis, advanced stage, larger tumour, HER2-positive, and hormone receptor-negative groups. Pacific ethnicity was associated with a lower adjuvant radiotherapy rate, compared to Other ethnicity, in both invasive and DCIS groups, along with older age, symptomatic diagnosis, and lower grade tumour in the invasive group. Both mastectomy and adjuvant radiotherapy rates decreased over time. For those who did not receive radiotherapy, non-referral by a clinician was the most common documented reason (8%), followed by patient decline after being referred (5%).

CONCLUSION

Rates of radiotherapy use are high by international standards. Further research is required to understand differences by ethnicity in both rates of mastectomy and lower rates of radiotherapy after BCS for Pacific women, and the reasons for non-referral by clinicians.

Breast-Conserving Surgery or Mastectomy?: Impact on Survival

The early randomized controlled trials revealed no differences in survival between breast-conserving surgery (BCS) and mastectomy. However, breast cancer treatment has undergone changes, and the results of recent population-based registry studies suggest superior long-term survival after BCS. To explore the current evidence, a systematic review and meta-ana lysis of population-based observational studies from 2010 and onward was conducted.

Methods

A literature search was conducted in the PubMed, Embase, and Cochrane databases to identify relevant literature. Keywords included "mastectomy," "breast conserving surgery," and "survival." The identified studies were narratively reviewed and effect sizes (hazard ratios [HRs]) for overall (OS) and breast cancer-specific survival (BCSS) were combined with random-effects models.

Results

A total of 30 reports were included in the review, and results from 25 studies were included in the meta-analyses. Compared with mastectomy, BCS was associated with better OS (HR = 1.34 [1.20-1.51]; N = 1,311,600) and BCSS (HR = 1.38 [1.29-1.47]; N = 494,267). Selected subgroups of patients, based on lymph node status, age (<50 years/≥50 years), and radiation therapy after mastectomy (±), all showed better overall survival after BCS. The number (range 4-12) and type of prognostic variables adjusted for in the survival analyses of the studies did not statistically significantly moderate the differences in survival between BCS and mastectomy.

Conclusions

The combined findings from large population-based studies indicate that BCS is associated with survival benefit compared with mastectomy, suggesting that BCS be the recommended treatment of early breast cancer (T1-2N0-1M0) if a radical lumpectomy can be performed.

Survival outcomes for breast conserving surgery versus mastectomy among elderly women with breast cancer

PURPOSE

Elderly patients have different physical condition and tumor biology of breast cancer. Surgical choices for older patients are complicated and several studies have reported that breast conserving surgery (BCS) had better survival than mastectomy in different patient population. The major objective of this study was to compare the efficacy of BCS and mastectomy in the whole elderly cohort in SEER database.

METHODS

Female patients aged over 70 years old and diagnosed with breast cancer between 2010 and 2015 were included from SEER database. Propensity score matching (PSM) was used to establish a cohort composing of similar characteristics. We compared the overall survival (OS) among patients undergoing BCS and mastectomy. Kaplan-Meier analysis and Cox proportional regression model were used to evaluate the associated factors of survival outcome.

RESULTS

Of 44,755 eligible patients, 30,375 (67.9%) patients underwent BCS and 14,380 (32.1%) patients underwent mastectomy. After PSM, 7222 patients in each group were analyzed and there was no significant difference between BCS and mastectomy in terms of the OS rate (85.8% in BCS group and 85.0% in mastectomy group, p = 0.135). Multivariable analysis also indicated that no significant difference between two surgical procedures after adjusting for covariates in matched cohort (HR 1.062, 95% CI 0.997-1.132, p = 0.063). Subgroup analysis demonstrated that postoperative radiotherapy and chemotherapy contributed to the survival benefit of BCS compared to mastectomy (p < 0.05).

CONCLUSION

For elderly breast cancer patients, BCS and mastectomy appeared to be comparable in terms of OS after being matched by clinicopathologic features. While our findings suggested that there was statistically survival benefit of BCS in some subsets of patients, including radiotherapy, chemotherapy, and 80-84 year-old subgroups, these results were likely to be related to selection bias and should be interpreted with caution. Thus, for this elderly patient population, BCS should be considered as an equivalent and less aggressive alternative to mastectomy.