Epidemiology of breast carcinoma II: Factors related to the predominance of left-sided disease

Abstract

A study of the laterality of 980 patients with unilateral breast carcinoma revealed a leftiright ratio of 1.26. Detailed analysis disclosed a significant association between left predominance and the following clinico-pathologic features: menarche after age 13, age at diagnosis, parity especially among those between ages 40 and 54, and all histologic types except medullary tumors. When asynchronous bilateral carcinoma was documented, the disease first occurred more often in the left breast. Patients with simultaneous bilateral disease usually had a larger tumor on the left. Because differences in breast size were considered a contributing factor, relative breast volumes were computed from the mammograms of 174 healthy women; 55% were found to have a larger left breast. These data and other observations cited in the literature suggest that the asymmetry of breast carcinoma reflects differences in the sensitivity of the mam-mary glands to hormonal stimulation, resulting in unequal volumes of tissue at risk to develop carcinoma. Cancer 46:1705-1713, 1980. SMALL BUT CONSISTENT predominance of left-A sided breast cancer has been known for decades. Interest in the laterality of carcinoma in women was expressed almost 40 years ago by Fellenbergs who found a greater frequency of involvement of the left breast following a review of 986 cases identified by the Swiss Cancer Census for the years 1933-35. Although the left predominance has since been repeatedly noted, no satisfactory explanation has been found. The pur-The authors are indebted to the women who responded to the extensive interview during a very stressful period of hospitalization. Without their cooperation and the assistance of the members of the Breast Service, this prospective study would not have been possible. The authors also appreciate the help of Margaret McVicar, RN, with patient interviewing, Jean Foster and Catherine Clements for typing the manuscript, and the many volunteers who have assisted with computer data entry.

Lower Incidence but More Aggressive Behavior of Right Sided Breast Cancer in Pakistani Women: Does Right Deserve More Respect?

“…The reason of increased risk in left breast is unclear (Weiss et al, 1996) but few studies have shown a possible correlation with relatively larger left breast size (Ing et al, 1997), unilateral lactation (Ing et al, 1997), detection biased due to predominant right handedness (Perkins et al, 2004) or more denser left breast (American Cancer Society, 2011-12). This study also revealed that women having right breast cancer were younger than those having left sided disease and this concurs with various published studies showing left sided laterality is more pronounced at higher ages (Busk, 1947;Garfinkel et al, 1959;Senie et al, 1980). Interestingly in this study, patients with right sided disease had smaller primary tumor size and were more prone to have triple negative as well as isolated ER, PR and Her2-Neu negativity.…”

Cell turnover in the “resting” human breast: influence of parity, contraceptive pill, age and laterality

“…Such changes could take place more readily over a prolonged "resting" period, as in the breasts of the perpetual nullipara. We have no explanation for the difference of response according to laterality, but emphasize that this is the first objective evidence that the breasts may differ in their parenchymal behaviour, despite previous exhaustive comparisons for such a distribution on other grounds (Senie et al, 1980).…”

Positional Variations in Mammary Gland Development and Cancer

“…Although modest with a ~1.10 left/right incidence ratio, such laterality was consistently found in several epidemiological studies [30–36] regardless of gender and stage of disease. Even in bilateral breast cancer cases, the left breast is more frequently affected first, or with a larger tumor [37]. …”

“…A variety of epidemiological correlates have been investigated, including age, race, ethnicity, sex, breast size, stage of disease at diagnosis, histological tumor type, and even left- versus right-handedness. None of these factors emerged as a consistently significant variable for the increased left-sided incidence [30–32, 37]. By contrast, laterality in outcome may in part be explained by laterality of axillary lymph node metastasis.…”