Breast cancer treatment patterns by age and time since last pregnancy in the Carolina Breast Cancer Study-Phase III

PurposeTo describe breast cancer treatment patterns among premenopausal women by age and time since last pregnancy. MethodsData were analyzed from 1,179 women diagnosed with premenopausal breast cancer in the Carolina Breast Cancer Study. Of these, 160 had a recent pregnancy (within 5 years of cancer diagnosis). Relative frequency differences (RFDs) and 95% confidence intervals (CIs) were used to compare cancer stage, treatment modality received, treatment initiation delay (>30 days), and prolonged treatment duration (>2 to >8 months depending on the treatment received) by age and recency of pregnancy. ResultsRecently postpartum women were significantly more likely to have stage III disease [RFD (95% CI): 12.2% (3.6%, 20.8%)] and to receive more aggressive treatment compared to nulliparous women. After adjustment for age, race and standard clinical tumor characteristics, recently postpartum women were significantly less likely to have delayed treatment initiation [RFD (95% CI): -11.2% (-21.4%, -1.0%)] and prolonged treatment duration [RFD (95% CI): -17.5% (-28.0%, -7.1%)], and were more likely to have mastectomy [RFD (95% CI): 14.9% (4.8%, 25.0%)] compared to nulliparous. Similarly, younger women (<40 years of age) were significantly less likely to experience prolonged treatment duration [RFD (95% CI): -5.6% (11.1%, -0.0%)] and more likely to undergo mastectomy [RFD (95% CI): 10.6% (5.2%, 16.0%)] compared to older women (≥40 years of age). ConclusionThese results suggest that recently postpartum and younger women often received prompt and aggressive breast cancer treatment. Higher mortality and recurrence among recently pregnant women are unlikely to be related to under-treatment.

Inherited predisposition to breast cancer in the Carolina Breast Cancer Study

The Carolina Breast Cancer Study (CBCS) phases I–II was a case-control study of biological and social risk factors for invasive breast cancer that enrolled cases and controls between 1993 and 1999. Case selection was population-based and stratified by ancestry and age at diagnosis. Controls were matched to cases by age, self-identified race, and neighborhood of residence. Sequencing genomic DNA from 1370 cases and 1635 controls yielded odds ratios (with 95% confidence limits) for breast cancer of all subtypes of 26.7 (3.59, 189.1) for BRCA1, 8.8 (3.44, 22.48) for BRCA2, and 9.0 (2.06, 39.60) for PALB2; and for triple-negative breast cancer (TNBC) of 55.0 (7.01, 431.4) for BRCA1, 12.1 (4.18, 35.12) for BRCA2, and 10.8 (1.97, 59.11) for PALB2. Overall, 5.6% of patients carried a pathogenic variant in BRCA1, BRCA2, PALB2, or TP53, the four most highly penetrant breast cancer genes. Analysis of cases by tumor subtype revealed the expected association of TNBC versus other tumor subtypes with BRCA1, and suggested a significant association between TNBC versus other tumor subtypes with BRCA2 or PALB2 among African-American (AA) patients [2.95 (1.18, 7.37)], but not among European-American (EA) patients [0.62 (0.18, 2.09)]. AA patients with pathogenic variants in BRCA2 or PALB2 were 11 times more likely to be diagnosed with TNBC versus another tumor subtype than were EA patients with pathogenic variants in either of these genes (P = 0.001). If this pattern is confirmed in other comparisons of similarly ascertained AA and EA breast cancer patients, it could in part explain the higher prevalence of TNBC among AA breast cancer patients.