Increase in lobular breast cancer incidence in Switzerland.

Abstract

We read with interest the report by Verkooijen et al.1 from the Geneva Cancer Registry showing a rise from 85.2 to 110.1/100,000 (age-standardized, European standard) in the incidence of ductal breast carcinoma, and from 2.9 to 20.5/100,000 of lobular carcinoma between 1976–99. The absolute rise was greater for ductal (+24.9/100,000 vs. 17.6/100,000 for lobular), but the proportional rise was greater for lobular (+14.4%/year) than for ductal carcinomas (+2.2%/year). In 9 registries from the Surveillance, Epidemiology, and End Results (SEER) program dataset including 190,458 breast cancer cases over the period 1987–99, invasive ductal carcinomas increased by 3% (from 153.8 to 155.3/100,000), lobular by 52% (from 12.9 to 19.1/100,000), and mixed ductal-lobular by 96% (from 6.9 to 14.3/100,000).2 We conducted similar analyses on the Vaud Cancer Registry data file. The data was abstracted from the Vaud Cancer registry file, which includes data concerning incident cases of malignant neoplasms in the Canton of Vaud (whose population according to the 1990 Census, was about 602,000 inhabitants). Information collected by the registry includes general demographic characteristics of the patient (age, gender, municipality of residence), site and histological type of the tumour according to the standard International classification of Diseases for Oncology (ICD-O-9),3 and time of diagnostic confirmation.4 The series comprises 8,196 women diagnosed with an invasive breast cancer (ICD code 174) between 1976 and 1999. The series was classified into the following 3 morphologic categories: ductal carcinoma (ICD-O 8500-3, 8521; n = 6,278, 76.6%), lobular carcinoma (ICD-O code 8520, including tumours with association of ductal and lobular carcinoma; n = 871, 10.6%), and other (all other neoplasms, including those with no microscopic confirmation; n = 1,047, 12.8%). Age-adjusted (in 5-year age groups, using the European standard population) incidence rates from 1976–99 for 5 subsequent calendar periods, and 5 age groups (<35, 35–44, 45–54, 55–74, >75 years), plus all age incidence rates, were calculated. Absolute and average percent yearly chance in rates across the 24-year period considered was calculated by log-linear regression models. The main findings are given in Table I in terms of age-standardized and age-specific rates. Overall, ductal breast carcinoma incidence increased from 71.1/100,000 to 85.9 (+14.8/100,000, 0.9%/year), and lobular breast carcinoma incidence from 2.1/100,000 to 16.8/100,000 (+14.7/100,000, +10.0%/year). The percentage increase, however, was substantially greater in the period 1976–87 (+16.7%) than in 1988–99 (+3.8%). Overall incidence rates for the category “other neoplasms” increased from 9.4 to 14.6/100,000 (+5.2/100,000, +2.6%/year). The rises for all morphological categories considered were observed in all subsequent age groups, but were larger in middle age, particularly at age 50–70, which have been covered by an organized screening program since the early 1990s.5 These findings, from another French-speaking Swiss population, confirm that breast cancer incidence increased over the last 2 decades.1, 6 The rise was greater in absolute terms for ductal, but in proportional terms for lobular breast carcinomas. The interpretation of these findings include a role of screening and ascertainment, and another, though difficult to quantify, of changed criteria of pathological classification of lobular and ductal (as well as mixed ductal-lobular) carcinomas. Use of combined oestrogen/progestin hormone replacement therapy (HRT) has been associated to greater risk of lobular than ductal breast carcinomas in at least 5 studies.7, 8, 9, 10, 11 Whether changes in risk factor exposure, including HRT,12 contributed to the changes in histotype distribution in this population remains however difficult to quantify, given also the observation that the rise was greater in the 1970s and early 1980s than in more recent calendar years. Yours sincerely, Fabio LEVI, Van-Cong TE, Lalao RANDIMBISON and Carlo LA VECCHIA The contribution of the Vaud Cancer Registry's staff is gratefully acknowledged. Fabio Levi*, Van-Cong Te*, Lalao Randimbison*, Carlo La Vecchia* , * Cancer Epidemiology Unit and Cancer Registries of Vaud and Neuchâtel, Institut Universitaire de Médecine Sociale et Préventive, Lausanne, Switzerland, Laboratory of Epidemiology, Istituto di Ricerche Farmacologiche ‘Mario Negri’, Milan, Italy, Istituto di Statistica Medica e Biometria, Università degli Studi di Milano, Milan, Italy.