Long-term risk of second malignancies in women after breast conservation therapy for ductal carcinoma in situ or early-stage breast cancer

Risk of second primary cancer among breast cancer patients: A systematic review and meta-analysis

Objectives

The aim of this study was to estimate the extra risk of second primary cancer among breast cancer patients.

Methods and materials

This is a systematic review. A comprehensive search of literature was performed in PubMed, Web of Science, Cochrane library, and Scopus. The search included all published studies up to October 2022. This systematic review included studies published in the English language that reported the risk of second primary non-breast cancer [i.e., standardized incidence ratio (SIR)] among breast cancer patients older than 15 years. After evaluating the methodological quality of the selected studies, SIRs were pooled with consideration of heterogeneity among studies. The estimates were pooled by age and time since the diagnosis of primary breast cancer for both sexes (male and female). Age was categorized based on before 50 years and after 50 years, and time was categorized as duration of less than and more than 10 years, respectively.

Results

From 2,484 articles, 30 articles were eligible for inclusion in the systematic review and meta-analysis. The studies varied in terms of population, number of cases, study design, setting, and year of implementation of the research. The estimated SIR for men and women was 1.28 (95% CI: 1.18, 1.38) and 1.27 (95% CI: 1.15, 1.39), respectively. Women diagnosed with breast cancer before menopause [SIR: 1.52 (95% CI: 1.34, 1.71) vs. 1.21 (95% CI: 1.08, 1.34)] as well as women after 10 years since their breast cancer diagnosis [1.33 (95% CI: 1.22, 1.431) vs. 1.24 (95% CI: 1.10, 1.37)] were at a higher risk of developing second primary cancer. Among men, while there were no differences in risk based on age, with the increase of time, the risk of second primary cancer was reduced [SIR: 1.22 (95% CI: 1.12, 1.33) vs. 1.00 (95% CI: 0.79, 1.22)].

Conclusion

There is an extra risk of second primary cancer among breast cancer patients. The extra risk should be considered for further screening and preventive measures among this population.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=336062, identifier (CRD42022336062).

Risk of hematologic malignancies after breast ductal carcinoma in situ treatment with ionizing radiation

The increased incidence of secondary hematologic malignancies (SHM) is a well-known, potentially fatal, complication after cancer treatment. It is unknown if patients with ductal carcinoma in situ (DCIS) of the breast treated with external beam radiotherapy (RT) and who survive long-term have increased risks of secondary hematologic malignancies (SHM), especially for low/intermediate-risk subsets with limited benefits from RT. DCIS patients in Surveillance, Epidemiology, and End Results (SEER) registries (1975-2016) were identified. Relative risks (RR), hazard ratio (HR), and standardized incidence ratios (SIR) were calculated to assess the SHM risk and subsequent survival times. SHM development, defined as a nonsynchronous SHM occurring ≥1 year after DCIS diagnosis, was our primary endpoint. Of 184,363 eligible patients with DCIS, 77,927 (42.3%) in the RT group, and 106,436 (57.7%) in the non-RT group, 1289 developed SHMs a median of 6.4 years (interquartile range, 3.5 to 10.3 years) after their DCIS diagnosis. Compared with DCIS patients in the non-RT group, RT was associated with increased early risk of developing acute lymphoblastic leukemia (ALL; hazard ratio, 3.15; 95% CI, 1.21 to 8.17; P = 0.02), and a delayed risk of non-Hodgkin lymphoma (NHL; hazard ratio, 1.33; 95% CI, 1.09 to 1.62; P < 0.001). This increased risk of ALL and NHL after RT was also observed in subgroup analyses restricted to low/intermediate-risk DCIS. In summary, our data suggest that RT after breast conserving surgery for DCIS patients should be cautiously tailored, especially for low and intermediate-risk patients. Long-term SHM surveillance after DCIS diagnosis is warranted.