Malignant melanoma and cervical cancer highly prevalent among pregnancy-associated cancers

In a recent study, malignant melanoma, breast and cervical cancer constitute 50% of PAC. The malignant melanoma incidence rate is higher during pregnancy, and hospital-based studies may miss a substantial proportion of cases. Researchers in this study also found that PACs are lower during pregnancy, particularly during the first and second trimesters, compared with the first year post-delivery. The team highlighted higher maternal age as the strongest PAC risk factor. Nulliparity and non-immigrant background have an association with higher PAC risk.

This study, "Risk factors for the increasing incidence of pregnancy-associated cancer in Sweden - a population-based study" by Lundberg, is published in Acta Obstetricia et Gynecologica Scandinavica.

PAC incidence is increasing in many countries, and there is little data about these trends' risk factors. In the present study, a team of researchers quantified the incidence of PAC by trimesters and post-delivery periods. It assessed the role of maternal age, parity, immigrant status, education, smoking and body mass index for PAC risk and incidence trends. They used data from Sweden's national birth and cancer registers from 1973-2017.

The key results of the study are:

• Out of 4 557 284 deliveries, a total of 1274 (during pregnancy) and 3355 (within one year post-delivery) cases of PAC were diagnosed, with around 50 cases/year diagnosed during pregnancy and 110 cases/year during the first year post-delivery in the latest period 2015-2017.
• Malignant melanoma, breast and cervical cancer were common during pregnancy and accounted for 57 % of cases during pregnancy and 53% during the first year post-delivery.
• There were lower numbers of PAC during pregnancy than during post-delivery for all tumour types, with the lowest numbers during the first trimester.
• The incidence rates of PAC increased over calendar time.
• There was an association between high maternal age at diagnosis, smoking, nulliparity non-immigrant background and higher risks of PAC.

They said we found high maternal age to be the strongest risk factor for PAC. Smoking, nulliparity and non-immigrant background are contributing risk factors for PAC.

Team reported increased rates of cervical cancer 3–6 months after delivery. Risk factors influence the incidence of PAC. This includes skin type, lifestyle, childbearing patterns, pregnancy termination legislation, and screening.

The study's strength includes population-based data from the cancer and birth registers. Limitations include a lack of information on miscarriages and terminated pregnancies, causing a larger underestimation of PAC incidence for less favourable cancers, where treatment cannot be given during pregnancy or has to be postponed until after delivery.

Radiumhemmet Research Foundations, The Swedish Breast Cancer Association, Karolinska Institutet Foundations and the Swedish Research Council funded the study.

Further reading:

https://obgyn.onlinelibrary.wiley.com/doi/10.1111/aogs.14677