Marijuana isn't chemically addictive like cigarettes are. And can you provide a good link that shows marijuana smoking can cause cancer?
American Lung Association
Smoke is harmful to lung health. Whether from burning wood, tobacco or marijuana, toxins and carcinogens are released from the combustion of materials. Smoke from marijuana combustion has been shown to contain many of the same toxins, irritants and carcinogens as tobacco smoke.4-7
Sources they list from that section
Effects of Marijuana Smoking on the Lung
Regular smoking of marijuana by itself causes visible and
microscopic injury to the large airways that is consistently
associated with an increased likelihood of symptoms of chronic
bronchitis that subside after cessation of use.
This concern is heightened by the finding that the
smoke contents of marijuana and
a comparable quantity of tobacco (unfiltered
Kentucky reference cigarette) include roughly
similar amounts of volatile constituents
(including ammonia, hydrocyanic acid, and
nitrosamines) and qualitatively similar tar
components (including phenols, naphthalene,
and the procarcinogenic benzopyrene and
benzanthracene) with the major exceptions of
nicotine (found only in tobacco) and D9
-tetrahydrocannabinol (THC)
Another source referenced
Recently, a short-term test on mouse skin showed that a particulate matter of marijuana smoke induced dose-related sebaceous aland destruction and epidermal hyperplasia with acenthosis
Marijuana smoke has been reported to increase abnormal cell proliferation in epithelial cells of lung explants from mice