Can you get cancer from fertility treatments?
This is a common fear based on some reports that women receiving fertility treatment have higher rates of cancer (e.g. breast, endometrial, and ovarian).
Many debates have played out about the relationship between fertility medication and cancer, which can be confusing to navigate when you're already facing huge medical decisions to make.
Here's what you need to know:
No causal link with cancer and fertility treatments has been identified.
An extensive study involving 25,000 women who had taken fertility medications found no increase in cases of breast cancer in women. 
Additionally, a 2019 review of studies found no relationship between fertility medications and breast, ovary, endometrial, uterus, colon, thyroid, skin, cervical, and non-Hodgkin's lymphoma. 
No causal link
In studies, no causal link has been identified between fertility treatments and higher rates of cancer.
What this means is that although some studies show that women who take fertility medications can have higher reported rates of cancer than other women, it's likely not actually the fertility medications themselves causing this pattern in the data.
Instead, scientists think that doctors might just be more likely to detect cancers in women who take fertility medications, given the many blood tests, scans and close medical attention they receive. They call this a "surveillance bias." 
Another explanation is that patients who take fertility treatments may end up more likely to have cancer than those that don't thanks to their pre-existing health profiles. Women who need fertility treatment are already more at-risk to develop cancer as a group thanks to higher rates of "co-morbidities" such as obesity.   In essence, women who are obese, as an example, are more likely to develop cancer and more likely to need fertility treatment - and this is the case with other health metrics and lifestyle choices, too, such as smoking.
Fertility Doctor Insight:
Studies are ongoing
With that said, overall, the exact relationship between infertility treatment and cancer incidence remains an open question that is still being investigated by scientists with the aim of gathering enough evidence to definitively explain the relationship.
What is useful to know right now if you're facing treatment is that while some studies suggest an increased risk of cancer, most do not.       
Also, studies have shown that women who already had breast cancer are not more likely to have a recurrence if they undergo ovarian stimulation.
In general, although doctors advise women not to worry about fertility medications causing cancer, there are caveats to this.
If someone has a genetic disposition to cancer (for instance, the BRCA gene) or already has particular kinds of cancer (such as estrogen-receptor-positive breast cancer, in which the cancer cells may receive signals from estrogen that could promote their growth) then different treatment pathways may be necessary.
Fertility Doctor Insight:
Always talk to your own doctor about concerns so she or he can best advise you based on your personal medical history.