Unfortunately we have to rely on American studies for this statistic. However it is reasonable to assume that we would see a similar distribution among Canadian veterans.

Gender Differences

The most frequently diagnosed cancer among Veteran men was prostate cancer, accounting for about 33% (12,543/38,513) of male cancer diagnoses. Among women Veterans, breast cancer was the most commonly diagnosed, accounting for about 30% (292/989) of female cancers. For both sexes, cancers of the lung and bronchus, and colon and rectum, occur second and third most frequently, respectively. Urinary bladder is fourth in ranking for men both nationally and within VA (1,397/38,513), comprising 4% of VA male cancer diagnoses. For women in the VA, the fourth ranked cancer is corpus uteri (49/989), accounting for 5% of female cancers.     source: Cancer Incidence Among American Veterans

Racial Differences

There are moderate differences between White and Black Veterans are apparent, such as for lung and bronchus (19.7% vs. 15.5%) and melanoma (4.2% vs. 0.1%). The most striking difference is in prostate cancer, which accounted for 28.9% of cancers in White Veterans but 42.7% of cancers in Black Veterans.    source: Cancer Incidence Among American Veterans

According to the American organization Mesothelioma VETS the five (5) most common cancers among veterans are: