What I am seeing is that this is because Evenity might activate breast cancer cells which have migrated to the bone not because it might cause breast cancer.

"There is concern regarding the use of Evenity (romosozumab) in patients with a history of breast cancer primarily due to theoretical risks that it could promote the growth of bone metastases or dormant cancer cells already in the bone, rather than evidence that it causes new breast cancer.

Bone Metastases and Theoretical Risks
The caution regarding Evenity in breast cancer survivors stems from its mechanism of action as a sclerostin inhibitor:

Promoting Growth in Bone: Some studies suggest that blocking sclerostin may activate signaling pathways (Wnt/β-catenin) in breast cancer cells that have already colonized the bone, potentially increasing bone metastases by enhancing the stem cell-like properties of those cancer cells.

Occult Cells: There is a theoretical risk that anabolic (bone-building) agents like Evenity could promote the growth of "occult" or hidden breast cancer cells that are already disseminated in the bone, even years after primary treatment.

Contrast with Other Meds: Unlike older bone-building drugs (Forteo or Tymlos) which are specifically contraindicated in patients with a history of bone cancer or metastases, Evenity is sometimes considered a more attractive theoretical option because it also helps decrease bone resorption.

Carcinogenicity and New Cancers
Current evidence does not suggest that Evenity causes breast cancer:
Not Carcinogenic: A carcinogenicity risk assessment, including lifetime studies in animals, concluded that romosozumab is not likely to pose a carcinogenic risk to humans.

Mechanism: As a monoclonal antibody, romosozumab does not directly interfere with cellular DNA and has no known genotoxic activity, making an intrinsic oncogenic (cancer-causing) risk theoretically low.

Clinical Observations: In small observational studies of cancer survivors (including breast cancer) treated with Evenity for osteoporosis, no cases of disease progression or recurrence were documented in the short term.

Other Risks for Cancer Patients
Beyond the concerns related to metastasis, patients with a history of cancer may face higher risks for specific side effects:
Osteonecrosis of the Jaw (ONJ): Evenity can rarely cause severe jawbone damage. This risk is notably higher in people with cancer, especially those who have received chemotherapy, radiation, or other bone-active drugs like bisphosphonates.
Primary Safety Warnings: It is important to note that the most serious "boxed warning" for Evenity is actually for cardiovascular risks, specifically an increased risk of heart attack, stroke, and cardiovascular death."

Prolia seems to be the drug most often used with breast cancer survivors who wish a pharma drug to treat osteoporosis:
Prolia (Denosumab):
Mechanism: Slows bone breakdown (resorption).
Cancer History: Widely used and often preferred for cancer patients because it is effective at preventing "skeletal-related events" (like fractures) in those with bone metastases.
Safety: It does not carry the same cardiovascular boxed warning as Evenity.

Strontium Citrate as a treatment for osteoporosis is not bound to any breast or bone cancer concerns. Indeed, strontium occupies a unique space between medical drugs and over-the-counter supplements. For breast cancer survivors, it offers a non-hormonal path of treatment.