Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling

We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1° × 1° spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.

Contralateral Breast Cancer in BRCA1/2 Mutation Carriers: Risk Assessment by Age at Diagnosis of the First Primary Breast Cancer

Purpose Age at diagnosis of the first breast cancer is a known predictive factor of the risk of contralateral breast cancer (CBC) in BRCA1/2 mutation carriers. However, accurate risk estimates for different age subgroups are scarce.Methods We studied the risk of CBC in 560 women with a primary breast cancer (PBC) from families with a proven BRCA1 or BRCA2 mutation in relation to the age at diagnosis of the first PBC, taking into account history of oophorectomy. Time at risk was the period between diagnosis of the first PBC and date of contralateral breast cancer, contralateral mastectomy, metastatic disease, death or last follow-up. Oophorectomy was treated as a time-dependent covariate. Patients with bilateral breast cancer diagnosed before the first visit at the family cancer clinic were excluded.Results We observed 96 CBCs in 423 BRCA1 mutation carriers and 21 cases in 137 BRCA2 mutation carriers. Actuarial risk of CBC at 5, 10 and 15 years was 14%, 34% and 39%, respectively, for BRCA1-, and 13%, 22% and 27%, respectively, for BRCA2 mutation carriers. For BRCA1 carriers 10-year actuarial risk of CBC was 54% for women with a PBC ≤ 30 years, 39% for the group with PBC between 31-40 years, 26% for the 41-50 group and 17% for those with PBC > 50 years. In BRCA2 carriers 10-year risk of CBC was 28% for women with a PBC ≤ 40 years, 19% for the 41-50 group and 10% for those with PBC > 50 years. For BRCA1 carriers who had an oophorectomy, 10-year risk of CBC was 33% and 26%, respectively, for those with PBC younger and older than 40 years, against 44% and 24% in women who had no such treatment. In BRCA2 carriers with a history of oophorectomy 10-year risk of CBC was 21% and 14%, respectively, for those with PBC younger and older than 40 years, while the risk was 29% and 17%, respectively, in women without oophorectomy. Effect of adjuvant therapy is being analyzed and will be presented at the meeting.Conclusions The availability of risk estimates of CBC by more detailed age groups at PBC is a helpful tool in the counselling process concerning screening and/or preventive surgery for breast cancer patients with a BRCA1 or BRCA2 mutation.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 903.

Breast cancer after prophylactic bilateral mastectomy in women with a BRCA1 or BRCA2 mutation

BACKGROUND

Women with a BRCA1 or BRCA2 mutation have a high risk of breast cancer and may choose to undergo prophylactic bilateral total mastectomy. We investigated the efficacy of this procedure in such women.

METHODS

We conducted a prospective study of 139 women with a pathogenic BRCA1 or BRCA2 mutation who were enrolled in a breast-cancer surveillance program at the Rotterdam Family Cancer Clinic. At the time of enrollment, none of the women had a history of breast cancer. Seventy-six of these women eventually underwent prophylactic mastectomy, and the other 63 remained under regular surveillance. The effect of mastectomy on the incidence of breast cancer was analyzed by the Cox proportional-hazards method in which mastectomy was modeled as a time-dependent covariate.

RESULTS

No cases of breast cancer were observed after prophylactic mastectomy after a mean (+/-SE) follow-up of 2.9+/-1.4 years, whereas eight breast cancers developed in women under regular surveillance after a mean follow-up of 3.0+/-1.5 years (P=0.003; hazard ratio, 0; 95 percent confidence interval, 0 to 0.36). The actuarial mean five-year incidence of breast cancer among all women in the surveillance group was 17+/-7 percent. On the basis of an exponential model, the yearly incidence of breast cancer in this group was 2.5 percent. The observed number of breast cancers in the surveillance group was consistent with the expected number (ratio of observed to expected cases, 1.2; 95 percent confidence interval, 0.4 to 3.7; P=0.80).

CONCLUSIONS

In women with a BRCA1 or BRCA2 mutation, prophylactic bilateral total mastectomy reduces the incidence of breast cancer at three years of follow-up.

The relation between pharmacokinetics and endocrine effects of buserelin implants in patients with mastalgia

Six patients with mastalgia were treated with polylactide/glycolide 50:50 implants containing 6.6 mg buserelin once every 4 weeks, to study the relationship between buserelin pharmacokinetics and suppression of pituitary-ovarian function. On the first treatment day there was an initial rise in plasma and urinary buserelin levels followed by a rapid fall during the next 2 days. After a plateau phase (60-80 micrograms/g creatinine) urinary buserelin/creatinine ratios decreased slowly to a mean value of 25 micrograms/g creatinine 4 weeks after implantation. Plasma oestradiol concentrations dropped to castrate values within 2 weeks of treatment reaching a mean concentration of 17 pmol/l compared to 27 pmol/l (P less than 0.01) determined in 680 postmenopausal control women. After the last implant injection urinary buserelin/creatinine ratios remained relatively high (greater than 5 micrograms/g creatinine) during more than 8 weeks followed by an exponential decrease (half-life of buserelin release: 15 days) to undetectable buserelin levels at 16-22 weeks after the last implantation. A rise of suppressed plasma oestradiol concentrations to above castrate levels was found 15-20 weeks after the last buserelin implantation, at a time when urinary buserelin excretion had decreased below 0.2 micrograms/g creatinine. It is concluded that after initial suppression of pituitary-ovarian function only very low concentrations of buserelin are needed to maintain suppression of ovarian activity by using slow release preparations.