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Risk factors of cancer

Unmodifiable factors, such as age and modifiable lifestyle factors impact the forming of cancers. Some factors increase the risk of developing cancer, and some decrease it.

Key points

  •  Most cancers are associated with aging. The longer a person lives, the more likely it is that cancer causing lesions accumulate in their cells.
  • It is estimated that more than 40 percent of all new cancer cases could be avoided by changing the risk factors which individuals can influence.
  • The single biggest risk factor is smoking, which explains even up to 20% of all new cancer cases.

The developing of cancer is a series of events over a period of many years, during which originally healthy genetic cell material is damaged and the cells change through a number of intermediate stages of the body into tissue independent of the body’s regulatory systems. As it grows, the malignant tissue eventually causes symptoms.See an animation of the initiation of the cancer process.
In the majority of cancer cases the specific cause of the disease cannot be identified. Cancers are a diverse group of diseases, and their causes, progression, symptoms and treatment can differ a great deal from each other.

Human factors related to behavior and living habitat are relevant in the development of most cancers. Although individual susceptibility might be a factor associated with some cancers, external factors are needed almost always for a cancer to develop. For the sake of cancer prevention and the cancer burden of the entire population, it is vital to know the factors that impact the development of cancer probability in the Finnish population specifically.

Cancer risk factors can be roughly divided into the following categories:

  • internal factors, such as age, sex, metabolism of substances foreign to the body, inherited genetic defects and non-inherited gene disorders, as well as the type of skin,
  • lifestyle related factors,
  • occupational exposures, e.g. many chemicals, radioactive materials and asbestos,
  • environmental exposure, e.g. radon and UV radiation, as well as small particles.

Attributable proportions of risk factors

Attempts have been made to relate different risk factors associated with cancer with each other. It is estimated that by changing the risk factors for cancer, which individuals can influence with their own actions, an estimated 43% of all new cancer cases could be avoided. The biggest single factor is smoking, which accounts for up to 20% of all new cancer cases. [1, 2] Table 1 lists some of the most common, modifiable risk factors of the incidence proportions of cancers. It should be noted, that the importance of the various factors on the population level will vary according to regional conditions, and the health and socio-economic behavior of the population. [3]


Most cancers are associated with aging. The longer a person lives, the more likely it is that cancer causing lesions accumulate in their cells. The ability of cells to prevent and recover from these defects weakens with age.


There are clear differences in the prevalence of also other cancers than those related only to gender (such as ovarian cancer and prostate cancer) among men and women. For example, the age-adjusted morbidity of laryngeal cancer in men is nearly ten-fold compared to women. The difference in lung and lip cancers is now less than three-fold, while it was 15-fold until the 1960s. These changes can be explained largely by the fact that the smoking habits of men and women have evolved in different ways in the past decades.


The tumor or cancer cell is neither contagious nor hereditary. Instead, susceptibility to an increased risk of developing cancer can be inherited. In this case, a change in the inheritance factor in cancer development is already in place in all human cells, and it can be passed on to offspring along with the gamete. In addition, environmental factors are most often needed to cause other required changes necessary for the development of a malignant tumor in most cases.

Regarding cancer heritability see “Cancer in the family

Living habits

 Tobacco. The use of tobacco products is the single most important factor in increasing cancer risk. The hazards of tobacco are due to a large amount of carcinogenic compounds: those which are already in the tobacco product and those that form during smoking.

The impact that smoking has on lung cancer development is best known. The probability of developing lung cancer is the greater the younger people start smoking, the more they smoke on a daily basis, and the longer they continue smoking. [4, 5] If a person has smoked 20 cigarettes a day for 50 years, his chances of developing lung cancer is almost 50-fold compared to non-smokers. After quitting smoking, the risk of lung cancer rather quickly approaches those of non-smokers the same age, but it does not drop to the same level. People who have smoked the longest, benefit the most from quitting.  Smoking is a major cause of cancer of the larynx, and it also has impact on the development of oral, pharyngeal, kidney, pancreatic, esophageal, cervical and bladder cancer. Smoking might slightly increase the risk of breast cancer, too. [6]

In recent years, clear evidence on carcinogenic potential of the use of snus has accumulated in research. For those using snus the risk of developing oral and pharyngeal cancer, pancreatic and gastric cancer and esophageal cancer is much higher than those who do not use tobacco products. [7-9] Electronic smoking has increased significantly during recent years. Its impact on health is being studied.

The risk of cancer often increases significantly with the combination of smoking and other factors. Together, smoking and outdoor work, e.g., multiply the risk of lip cancer by as much as 15-fold, even though outdoor work or smoking on their own only double the risk of lip cancer. [10] Smoking increases the impact of asbestos and many substances used in the working environment, which are not notably dangerous on their own.

Alcohol. There is a clear causal relationship between the use of alcoholic beverages and several types of cancer. There is convincing evidence that heavy use of alcohol increases risk of oral, pharynx, larynx, esophagus, liver, bowel and breast cancers. [11] (

Four daily doses of alcohol (50 grams of ethanol), for example, approximately doubles the risk of oral and pharyngeal cancer. Other factors may increase the effect of alcohol. For example, drinking alcohol and smoking together increase the risk of oral, pharynx and larynx cancers very strongly.

Regarding breast cancer there is no safe amount of alcohol use, but the risk of cancer is increased in direct proportion to the amount of alcohol consumed on a regular basis. The most important risk factor is the amount of ethanol consumed. Heavy alcohol use increases the risk of cancer and causes other clear health problems. The type of alcoholic beverages consumed does not significantly impact the risk of cancer risk.

Nutrition. Diet is a complex mix of components, which have joint and contrary effects that are difficult to reliably estimate. Nutrition is considered to have the most effect on gastric, lung and breast cancer of the esophagus, colon, rectum, bladder, prostate and endometrial cancer risk. These are common cancers in Finland and other Western countries.

Dietary fat increases, according to a number of animal tests, the risk of breast, colon and pancreatic cancer. Information on people however, is not yet convincing enough to enable definite judgment on fat’s effects on cancer risk. Cancer tissue needs energy and minerals, so nutrition can impact not only on the development of cancer, but also its growth.

Dietary fibers are likely to protect against colorectal cancer. [12] Root vegetables and rye bread, included in traditional Finnish diet, are also healthy in this respect. In addition, fruit and vegetable rich diets reduce the risk of many cancers.

The effect of red and processed meat on the incidence of some types of cancer has been studied extensively. Heavy consumption of processed meat is associated with an increased risk of colorectal and gastric cancer. Red meat is also a likely risk factor of colorectal as well as pancreatic and prostate cancer. [13]

The main interest regarding the connection of vitamins and cancer has been in carotenoids, vitamins A, E, C, and D and folate. Vitamin products have also been studied for the prevention of cancer, but none of them have yet been shown to prevent cancer alone or in any combination. [14] Therefore, it seems that the deciding factor in terms of cancer prevention is balanced overall nutrition, not individual dietary factors.

Some food preparation processes cause chemical changes which result in cancer-causing substances forming in the food. Smoking and grilling fatty food over an open fire or other high temperature generates small amounts of polycyclic aromatic hydrocarbons (PAHs) on the surface of the food, which increase the risk of cancer. The high consumption of salt and of foods conserved in salt increase the risk of gastric cancer.

 Exercise and weight control. The link between physical activity and the risk of cancer has been found in numerous studies. Scientific evidence has accumulated indicating that physical activity protects in particular from breast, colon, endometrial and prostate cancer (

Moderate physical activity changes the metabolism of certain hormones and enhances the body’s general defense mechanisms. Exercise reduces the amount of fat tissue, and the situation of various growth factors in the body becomes more balanced. People who exercise more often also often have more cancer protective ingredients in their diet.

According to recent studies, a total amount of about one hour of daily physical activity in form of everyday or beneficial activity, such as walking or biking to work or to the store, climbing the stairs or working the yard is adequate. Especially, people doing sedentary work should exercise regularly in order to prevent overweight. Swift exercise several days a week can increase the cancer protective effect of physical activity. [15]

Reproduction and hormones. Female genital cancers and breast cancer are clearly linked to sexual and reproductive behavior. If a woman has had multiple sexual partners, she is more likely to get cervical cancer. The number of sexual partners of their male partner also has an impact on women’s risk of developing cervical cancer. This can be explained by the fact that infectious viruses by sexual contact are important in the pathogenesis of cervical cancer (see below: Infections.)

Giving birth at young age and having many children protects against breast cancer. The protective effect is emphasized if the woman has a very large number of children. [16] Infertility is a risk factor also in ovarian and endometrial cancer. Early sexual maturity and late menopause increase the number of menstrual cycles and the risk of the aforementioned cancers.

Breast, endometrial and ovarian cancers are diagnosed more often in women using long-term hormone therapy during menopause. [17-19] Progesterone, associated with estrogen replacement therapy increases the risk of breast cancer, but, in turn, protects from endometrial cancer. [17, 18, 20] The benefits of estrogen replacement therapy in treating menopause should therefore be weighed individually, in relation to the risk of cancer, among other things.

Concerning men, high male hormone i.e. androgen level is likely to be associated with a higher risk of prostate cancer.

Cosmetics. We are exposed, intentionally or unintentionally, to a wide range of chemicals in everyday life. Among other things, links with the use deodorants and hair dyes to cancer risk has been researched in several studies. Some studies have found that the use of hair dyes slightly increase the incidence of, e.g., bladder and breast cancer, but there is not sufficient evidence on their definite role as a potential cancer risk factor. [21-24]

 Infections. Some viral infections increase the risk of cancer. Also infections caused by the bacteria may increase the risk of certain cancers. The most studied virus family causing cancer risk are papillomaviruses (HPV, human papilloma virus), some of which result in chronic inflammation and thus cervical cancer. [25] Papilloma viruses may also cause other cancers, such as pharyngeal cancer. [26] Vaccines for the prevention of infections caused by the papilloma virus have been available for a few years, and for girls, HPV vaccination is part of the national vaccination program in Finland. Ongoing long-term follow-up studies are set to find out to what extent HPV vaccines also prevent cancer. [27]

The bacteria Helicobacter pylori increases the risk of gastric cancer. [28] Chronic liver inflammation (hepatitis B and C virus infections) is associated with an increased risk of liver cancer. A hepatitis B virus (HBV) vaccination campaign, started in 1984 in Taiwan, first led to a decline in the prevalence of HBV and, subsequently, to a significant reduction in the incidence of liver cancer in the vaccinated age groups. [29]

Table 1. Percentages of incident cancer cases attributable to different modifiable risk factors (all cancers).

The impact of work-related exposures, such as chemicals, on cancer risk has been studied in hundreds of separate studies. On the Finnish Institute of Occupational Health’s web site you can find good information about dangerous exposures to cancer in the work environment and on their measurement.

Cancer risk related to various professional groups is systematically examined in a large Nordic NOCCA study. The NOCCA study confirms already known links between certain professions and cancer hazards, as well as provides an indication of the importance of choices associated with occupational exposures and lifestyle. More detailed information on profession-related cancer risks can be found in a joint Nordic NOCCA project’s site .

The increase of sedentary work reduces physical activity, which has protective properties against cancer. The lack of physical activity and abundant sitting is harmful to health in many ways. [30] Shift work is currently also considered to increase the risk of cancer. [31]. Also, mine workers and seamen are diagnosed with 20-30% more cancers than Finnish men on average (Table 2).

The sun’s ultraviolet radiation plays a role in cancer risk for certain professions. For example, lip cancer is found most often in fishermen and farmers, while the risk of cutaneous melanoma is the largest in indoor workers whose unaccustomed skin burns easily during holiday periods.

Finnish women’s risk of cancer is the highest in safety work, which includes, for example, police and security work. Next on the list are dentists and doctors. Cancer risk is in turn significantly lower than the average for example in farmers and gardeners.


Table 2. Occupations with the lowest and highest cancer morbidity in Finland in 1971-2005: The numbers of cancers (N) and the difference in cancer risk (%) compared to the population average (46). All shown percentages are statistically significant.

Environmental exposures

 Pollutions of the living environment. Air pollution, mainly emissions from industry and traffic, increase the risk of lung cancer to some extent. However, men’s lung cancer is most often found in those parts of Finland where the air is cleanest. Air pollution is a negligible risk factor compared to tobacco. Yet studies are currently ongoing among other things, on what connection wood-heated houses and small particle emissions have with cancer. [32]

The production of drinking water by surface water chlorination generates mutation-causing compounds which may slightly increase the risk of, for example, genitourinary cancer. [33] The arsenic in drilled well water appears to have a similar effect. [34]

Measurement results describing the state of the environment have been produced increasingly in recent years, and they can be utilized to better assess the causes of cancer risk. An example of such is an environmental health study of people who once lived in houses built–and later demolished–on top of a former landfill in Myllypuro, Helsinki. According to the first survey some more cancer and asthma was discovered in the residents of these houses, compared to reference residents [35], but according to the latest studies, those who lived in the Myllypuro area were not diagnosed with cancer more often than people living in any other area in Helsinki in the 2000s. [36]

Ionizing radiation occurs everywhere, because radiation can be found e.g. in the earth crust’s natural radioactive substances, which are transported into the human body via nutrition. The main source of radiation for the Finnish population is indoor air radon, which provides an average amount of 2 mSv per year, i.e., about half of the total radiation dosage. Inhalation of radon causes a radiation dosage primarily only in the lungs. The only clearly established health effect of radon is the increased risk of lung cancer. The risk of lung cancer caused by radon is higher in smokers than non-smokers. It is estimated that radon in the indoor air, in conjunction with smoking, causes approximately 300 lung cancers every year. [37]

X-ray radiation is used in radiology and various forms of radiation are used in radiation treatments. In health care, it should therefore always be assessed carefully, if the benefit achieved with the use of radiation is greater than the risk caused by it. Cancer patients undergoing radiation treatment receive very high radiation dosages, and in addition to the tumor, other tissues may be exposed to radiation as well. Patients treated with radiation therapy are at increased risk of developing leukemia and some other cancers [38-43], but the benefits of treatment are far greater than the disadvantages.


Ionizing radiation has been estimated to cause 1-3% of all cancers. Radiation increases particularly strongly the risk of leukemia, as well as thyroid, breast, lung and bladder cancer.

 Non-ionizing radiation includes ultraviolet radiation, as well as the magnetic and electric fields. Ultraviolet radiation is obtained primarily from sunlight and sunbeds, and it causes skin cancers. The main cause of cutaneous melanoma is repeated burning of the skin due to excessive UV radiation, especially in childhood and youth. Particularly at risk are fair-skinned, blue-eyed people with easily burning and poorly tanning skin.

Power cords and electrical equipment create very low frequency magnetic fields (50-60 Hz) around them. Their effect on the risk of cancer and, above all, the risk of childhood leukemia has been studied on several occasions, but the results have been inconsistent. According to Finnish comprehensive series of studies on the entire population, the risk of cancer in children or adults is not increased in the vicinity of power lines. [44, 45]

The frequency of radio frequency magnetic fields is millions of hertz. They are created by, among others, radar, radio transmitters, mobile phones and base stations. Radio frequency radiation does not cause mutation and has not increased cancers in animal tests. In epidemiological studies, mobile phone use has not been shown to increase the cancer risk in human, either (Interphone Study Group 2010), but the problem with the studies has been the relatively short ten-year follow-up period, and the unreliability of the questionnaire-based use of information. New large-scale, ongoing follow-up studies in different countries are hoped to provide more information.


  1. Parkin DM, Boyd L, Walker LC. The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Br J Cancer. 2011 Dec 6;105:S77–81.
  2. Olsen JH, Andersen A, Dreyer L, Pukkala E, Tryggvadottir L, Gerhardsson de Verdier M, et al. Summary of avoidable cancers in the Nordic countries. APMIS Suppl. 1997;76:141–6.
  3. Doll R, Peto R. The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today. J Natl Cancer Inst. 1981 Jun;66(6):1191–308.
  4. Hakulinen T, Pukkala E. Vaihtoehtoisten tupakointimuutosten vaikutus miesten keuhkosyöpäsairastuvuuteen Suomessa 2000-luvulle siirryttäessä. Lääket Aik. 1980(17):223–33.
  5. Lee PN, Forey BA, Coombs KJ. Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer. BMC Cancer. 2012;12:385.
  6. Xue F, Willett WC, Rosner BA, Hankinson SE, Michels KB. Cigarette smoking and the incidence of breast cancer. Arch Intern Med. 2011 Jan 24;171(2):125–33.
  7. Luo J, Ye W, Zendehdel K, Adami J, Adami H-O, Boffetta P, et al. Oral use of Swedish moist snuff (snus) and risk for cancer of the mouth, lung, and pancreas in male construction workers: a retrospective cohort study. Lancet Lond Engl. 2007 Jun 16;369(9578):2015–20.
  8. Roosaar A, Johansson ALV, Sandborgh-Englund G, Axéll T, Nyrén O. Cancer and mortality among users and nonusers of snus. Int J Cancer J Int Cancer. 2008 Jul 1;123(1):168–73.
  9. Zendehdel K, Nyrén O, Luo J, Dickman PW, Boffetta P, Englund A, et al. Risk of gastroesophageal cancer among smokers and users of Scandinavian moist snuff. Int J Cancer J Int Cancer. 2008 Mar 1;122(5):1095–9.
  10. Lindqvist C. Risk factors in lip cancer – an epidemiological study. Proc Finn Dent Soc Suom Hammaslääkäriseuran Edit. 1979;75 Suppl 1-2:1–43.
  11. Baan R, Straif K, Grosse Y, Secretan B, El Ghissassi F, Bouvard V, et al. Carcinogenicity of alcoholic beverages. Lancet Oncol. 2007 Apr;8(4):292–3.
  12. Bingham SA, Day NE, Luben R, Ferrari P, Slimani N, Norat T, et al. Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study. Lancet Lond Engl. 2003 May 3;361(9368):1496–501.
  13. Bouvard V, Loomis D, Guyton KZ, Grosse Y, Ghissassi FE, Benbrahim-Tallaa L, et al. Carcinogenicity of consumption of red and processed meat. Lancet Oncol. 2015 Dec;16(16):1599–600.
  14. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. N Engl J Med. 1994 Apr 14;330(15):1029–35.
  15. Latikka P, Pukkala E, Vihko V. Relationship between the risk of breast cancer and physical activity. An epidemiological perspective. Sports Med Auckl NZ. 1998 Sep;26(3):133–43.
  16. Högnäs E, Kauppila A, Hinkula M, Tapanainen JS, Pukkala E. Incidence of cancer among grand multiparous women in Finland with special focus on non-gynaecological cancers: A population-based cohort study. Acta Oncol Stockh Swed. 2016 Mar;55(3):370–6.
  17. Jaakkola S, Lyytinen H, Pukkala E, Ylikorkala O. Endometrial cancer in postmenopausal women using estradiol-progestin therapy. Obstet Gynecol. 2009 Dec;114(6):1197–204.
  18. Lyytinen HK, Dyba T, Ylikorkala O, Pukkala EI. A case-control study on hormone therapy as a risk factor for breast cancer in Finland: Intrauterine system carries a risk as well. Int J Cancer J Int Cancer. 2010 Jan 15;126(2):483–9.
  19. Koskela-Niska V, Lyytinen H, Riska A, Pukkala E, Ylikorkala O. Ovarian cancer risk in postmenopausal women using estradiol-progestin therapy – a nationwide study. Climacteric J Int Menopause Soc. 2013 Feb;16(1):48–53.
  20. Heikkinen S, Koskenvuo M, Malila N, Sarkeala T, Pukkala E, Pitkäniemi J. Use of exogenous hormones and the risk of breast cancer: results from self-reported survey data with validity assessment. Cancer Causes Control. 2016 Feb;27(2):249–58.
  21. Huncharek M, Kupelnick B. Personal use of hair dyes and the risk of bladder cancer: results of a meta-analysis. Public Health Rep Wash DC 1974. 2005 Feb;120(1):31–8.
  22. Turati F, Pelucchi C, Galeone C, Decarli A, La Vecchia C. Personal hair dye use and bladder cancer: a meta-analysis. Ann Epidemiol. 2014 Feb;24(2):151–9.
  23. Heikkinen S, Pitkäniemi J, Sarkeala T, Malila N, Koskenvuo M. Does Hair Dye Use Increase the Risk of Breast Cancer? A Population-Based Case-Control Study of Finnish Women. PloS One. 2015;10(8):e0135190.
  24. Takkouche B, Etminan M, Montes-Martínez A. Personal use of hair dyes and risk of cancer: a meta-analysis. JAMA. 2005 May 25;293(20):2516–25.
  25. Lehtinen M, Dillner J, Knekt P, Luostarinen T, Aromaa A, Kirnbauer R, et al. Serologically diagnosed infection with human papillomavirus type 16 and risk for subsequent development of cervical carcinoma: nested case-control study. BMJ. 1996 Mar 2;312(7030):537–9.
  26. Mork J, Lie AK, Glattre E, Hallmans G, Jellum E, Koskela P, et al. Human papillomavirus infection as a risk factor for squamous-cell carcinoma of the head and neck. N Engl J Med. 2001 Apr 12;344(15):1125–31.
  27. Lehtinen M, Herrero R, Mayaud P, Barnabas R, Dillner J, Paavonen J, et al. Chapter 28: Studies to assess the long-term efficacy and effectiveness of HPV vaccination in developed and developing countries. Vaccine. 2006 Aug 31;24 Suppl 3:S3/233–41.
  28. Rehnberg-Laiho L, Rautelin H, Koskela P, Sarna S, Pukkala E, Aromaa A, et al. Decreasing prevalence of helicobacter antibodies in Finland, with reference to the decreasing incidence of gastric cancer. Epidemiol Infect. 2001 Feb;126(1):37–42.
  29. Chang M-H. Hepatitis B virus and cancer prevention. Recent Results Cancer Res Fortschritte Krebsforsch Prog Dans Rech Sur Cancer. 2011;188:75–84.
  30. World Health Organization, editor. Global health risks: mortality and burden of disease attributable to selected major risks. Geneva, Switzerland: World Health Organization; 2009. 62 p.
  31. Straif K, Baan R, Grosse Y, Secretan B, El Ghissassi F, Bouvard V, et al. Carcinogenicity of shift-work, painting, and fire-fighting. Lancet Oncol. 2007 Dec;8(12):1065–6.
  32. Salonen R, Pasanen K, Pulkkinen A-M, Pennanen A, Sokura M, Pärjälä E, et al. Puun pienpolton savut. Uutta tietoa altistumisesta ja terveyshaitoista. Ympäristö ja Terveys. 2015(46):4–11.
  33. Koivusalo M, Pukkala E, Vartiainen T, Jaakkola JJ, Hakulinen T. Drinking water chlorination and cancer-a historical cohort study in Finland. Cancer Causes Control CCC. 1997 Mar;8(2):192–200.
  34. Kurttio P, Pukkala E, Kahelin H, Auvinen A, Pekkanen J. Arsenic concentrations in well water and risk of bladder and kidney cancer in Finland. Environ Health Perspect. 1999 Sep;107(9):705–10.
  35. Pukkala E, Pönkä A. Increased incidence of cancer and asthma in houses built on a former dump area. Environ Health Perspect. 2001 Nov;109(11):1121–5.
  36. Pukkala E. A follow-up of cancer incidence among former Finnish dump site residents: 1999-2011. Int J Occup Environ Health. 2014 Oct;20(4):313–7.
  37. Mäkeläinen, I. Kuka saa syövän radonista? Ympäristö ja terveys. 2010(3):60–3.
  38. Travis LB, Andersson M, Gospodarowicz M, van Leeuwen FE, Bergfeldt K, Lynch CF, et al. Treatment-associated leukemia following testicular cancer. J Natl Cancer Inst. 2000 Jul 19;92(14):1165–71.
  39. Worrillow LJ, Travis LB, Smith AG, Rollinson S, Smith AJ, Wild CP, et al. An intron splice acceptor polymorphism in hMSH2 and risk of leukemia after treatment with chemotherapeutic alkylating agents. Clin Cancer Res Off J Am Assoc Cancer Res. 2003 Aug 1;9(8):3012–20.
  40. Virtanen A, Pukkala E, Auvinen A. Angiosarcoma after radiotherapy: a cohort study of 332,163 Finnish cancer patients. Br J Cancer. 2007 Jul 2;97(1):115–7.
  41. Virtanen A, Pukkala E, Auvinen A. Incidence of bone and soft tissue sarcoma after radiotherapy: a cohort study of 295,712 Finnish cancer patients. Int J Cancer J Int Cancer. 2006 Feb 15;118(4):1017–21.
  42. Hill DA, Gilbert E, Dores GM, Gospodarowicz M, van Leeuwen FE, Holowaty E, et al. Breast cancer risk following radiotherapy for Hodgkin lymphoma: modification by other risk factors. Blood. 2005 Nov 15;106(10):3358–65.
  43. Salminen EK, Pukkala E, Kiel KD, Hakulinen TT. Impact of radiotherapy in the risk of esophageal cancer as subsequent primary cancer after breast cancer. Int J Radiat Oncol Biol Phys. 2006 Jul 1;65(3):699–704.
  44. Verkasalo PK, Pukkala E, Hongisto MY, Valjus JE, Järvinen PJ, Heikkilä KV, et al. Risk of cancer in Finnish children living close to power lines. BMJ. 1993 Oct 9;307(6909):895–9.
  45. Verkasalo PK, Pukkala E, Kaprio J, Heikkilä KV, Koskenvuo M. Magnetic fields of high voltage power lines and risk of cancer in Finnish adults: nationwide cohort study. BMJ. 1996 Oct 26;313(7064):1047–51.
  46. Pukkala E, Martinsen JI, Lynge E, Gunnarsdottir HK, Sparén P, Tryggvadottir L, et al. Occupation and cancer – follow-up of 15 million people in five Nordic countries. Acta Oncol Stockh Swed. 2009;48(5):646–790.