HBOC study (2000–2016)
Among the 751 evaluated families, residents of Navarra, with clinical and family history that suggested HBOC, 233 were classified as low-risk families, with no further analysis, and 518 others as high-risk families, for which mutational analysis was performed in the index affected member (Table 1).. The number of cases included in the study is represented in Figure 1, showing a remarkable increase of BRCA1/2 testing and diagnosis over time.
From the high-risk group, 84 unrelated families (16.2%), 228 individuals, were found carrying pathogenic mutations: 31 (37%) in BRCA1 and 53 (63%) in BRCA2. Of them, 39% of the transmitting parents or grandparents were originally from Navarra (33 families), 18% came from the neighbouring communities (15 families) and the remaining families (42%) had ancestors from other communities (34 families) or countries (2 families) (Figure 2).. Frequency of mutations in BRCA2 gene was higher than in BRCA1 in all geographic groups, and more so in families of local ancestors, in which two thirds (67%) of them were BRCA2 positive.
BRCA1 families (n = 31) carried a total of 23 different mutations (Table 2);; two were recurrent mutations and 21 were unique mutations. The most frequent mutation was c.5123C>A, present in eight apparently unrelated families, followed by c.211A>G, identified in two families, representing a 26%, and 7%, respectively, of the total families with BRCA1 mutations.
Among BRCA2 positive families (n = 53), 29 different mutations were observed (Table 3).. Eight were recurrent mutations and 21 unique mutations. Variant c.2806_2809delAAAC was highly represented (11 unrelated families). The five most frequent pathogenic variants accounted for 50% of BRCA2 mutations.
Four novel, unreported, pathogenic mutations, responsible for early-onset BC and OC were identified.
- BRCA1 c.4343delG (exon 13)
This deletion, located in exon 13, results in a frame shift variant that originates a stop codon in position 1455. The index patient in this family was a male, diagnosed of PC at age 67 with family history of BC and OC on the mother’s side. BCs were diagnosed at ages 90 (mother) and 55 (maternal aunt) and OC at age 42 (maternal aunt).
- BRCA1 exon 5–7 duplication
This variant was found in a 54 year old woman diagnosed with invasive ductal carcinoma. Her mother died of BC at 46. Two additional family members (a maternal cousin and her daughter), carriers of the same mutation, suffered from BC at ages 33 and 34, respectively.
- BRCA2 c.4132_4133delAC (exon 11)
This alteration triggers a frame shift variant resulting in a stop codon in position 1380. The index patient, who inherited the mutation from her father, was diagnosed with invasive ductal carcinoma at 40 years old and a few months after she also developed cervix cancer. Two of her paternal aunts died of BC.
- BRCA2 c.5216_5218insAAA (exon 11)
This insertion originates a nonsense mutation with a stop codon in position 1739. The index patient was a woman that developed BC at 28 years old, whose mother, carrier of the mutation, had OC at the age of 60.
Clinical data from the Navarra Cancer Registry
Of all the 1246 individuals in the HBOC study, 593 were included in the Navarra Cancer Registry with a total of 693 tumor entries. Twenty four (4%) patients were males and 9 (37.5%) of them carried a BRCA deleterious mutation.
The frequency of multiple tumors was significantly higher among BRCA1/2 carriers (21.6%) than in individuals of the low-risk families (11.5%), with an OR of 2.11 (95% CI = 1.04 to 4.33, p = 0.038) (Table 4).. The difference did not reach statistical significance when compared with the high risk BRCA-negative group (HR-BRCA-negative). BRCA1 and BRCA2 mutations were associated with a different range of tumors. Cancer affecting breast, ovary, skin (SC), endometrium (EC), pancreas (PC) and prostate (PrC) accounted for 91.2% of all tumors registered in BRCA1/2 patients and 93.7% among HR-BRCA-negative and low risk cases. BRCA1 carriers had a higher frequency of OC (24.1%), SC (11.1%) and PC (3.7%) than individuals in the other three groups (9.3%, 5.3% and 0%, respectively). BC (70.7%) and PrC (2.7%), however, were overrepresented in BRCA2 carriers compared to BRCA1-positives (55.6% and 0%, respectively).
Among men, there were 3 BRCA1 mutation carriers who developed PC (1) and SC (2), and 6 BRCA2 positive cases, presenting with a wide variety of tumors: breast (4), prostate gland (2), lung (1), colon (1), fossa piriform (1) and thyroid gland (1). Three of the 9 males BRCA1/2 mutation carriers, developed multiple tumors, all associated with BRCA2.
To further study severity of the disease we analysed laterality, stage of the tumor, age at diagnosis and overall survival (OS) in patients of the HBOC study in comparison with a cohort sample of BC (n = 4384) and OC (n = 561) in the general population. As shown in Table 5, all four risk groups of the HBOC study showed a higher incidence of bilateral BC compared to the general population, although only in the group of BRCA2 positives the difference reached statistical significance (7.6% vs 1.8%; p = 0.021, OR = 4.3; 95% CI = 1.3 to 11.4). For OC, BRCA1 carriers had a much higher frequency of bilateral tumors (77.8%) than individuals in the BRCA2 positive (33.3%), HR-BRCA negative (30.8%), low-risk HBOC (0%) and the general population (30.9%; p = 0.007, OR = 7.8; 95% CI = 1.7 to 55.7).
The stage at diagnose of BC tumors was significantly more advanced (p = 0.043) in BRCA1/2 patients than in sporadic tumors. Over 55% of tumors were at regional/advanced stage among BRCA carriers compared to 40.4% and 43% in the low risk HBOC and the general population, respectively. The same trend was observed for OC among BRCA1 carriers, although numbers were too small to reach statistical significance.
Mean age at diagnose of BC and OC was lower in all four groups of the HBOC study than in the general population (Table 5, Figure 3).. BRCA1/2 carriers were diagnosed of BC 16.6 years earlier (44.2 vs 60.8 years), while for OC the time difference was 11.7 years (53.9 vs 65.6).
Survival over the course of 15 years was also studied. For BC, 5- 10- and 15-year OS did not show significant differences among risk groups (Table 6).. More than 64% of BRCA carriers lived 15 or more years after diagnosis, a percentage similar to that observed in sporadic BC. However, mean age at death differed between groups. BRCA1/2 mutation carriers died 20 years earlier than BC patients from the general population, indicating that age at diagnosis could be a co-variant of prognosis (HR = 1.08; 95% CI = 1.07 to 1.08; p<0.0001). Further analysis, adjusting by age at diagnosis, showed that BRCA1 and BRCA2 carriers had a significant worse prognosis than individuals of the other groups (Figure 4A),, with HR of 3.2 (95% CI = 1.5 to 6.7; p = 0.002) and 2.6 (95%CI = 1.5 to 4.7; p = 0.001) respectively, when compared with BC of sporadic origin.
For OC, the general population showed worst 5-year OS rate (41%), becoming, however, similar in all risk groups at 15 years after diagnosis, with OS rates of 20% in BRCA1 mutation carriers and 28% in the general population (Table 6, Figure 4B).. Mean age at death differed notoriously, but sample size was not sufficient to use the modelling approach as for BC analysis. Nevertheless, when we analysed OS only in patients diagnosed before the age of 65 years, no significant differences were observed among risk groups (data not shown).