Cancer was once a defining challenge for humanity. "Cure for cancer" was a magical solution which would herald riches and fame to whoever produced it. The jump to transhuman technologies has largely solved this problem. While Flats may still sometimes suffer from genetic predispositions, genefix procedures eliminate most of these tendencies in morphs. Implants like Radiation Tolerance (p. 189 Rimward) greatly increase the amount of potentially toxic radiation a morph can endure, which can cause cancers and other diseases as a long-term symptom. And modern nanomedicine procedures, along with more conventional medicines can easily eliminate cancerous cells which arise from carcinogenic exposure. If all else fails, resleeving or rapid organ cloning can avoid the possibility of harm from cancer.
In many places, this has skewed transhumanity's perception of what was once a great killer. Scum and even Ultimates may consume products or enjoy activities which could lead to cancer for thrills and to prove the superior endurance of their morphs. In the Inner System, in the heart of the Planetary Consortium like Progress activities like smoking are a sign of wealth - because long term organ damage and cancer is no problem for anyone rich enough to buy a new set of lungs. In the Outer System habs, these sorts of activities tend to be frowned upon as it "wastes" community resources, but rarely to individuals who engage in entertainments or hobbies which have side effects feel excessive pressure from the community - only the habitually wasteful.
But, there are some ways to market this sort of activity. A common item seen on Extropia and in certain similar cultures is Cancer Sticks. A parody of classic marketing for cigarettes and other tobacco products, the "Cancer Stick" is literally a carcinogenic stick. They can be sucked, smoked, chewed or sometimes dissolved in drink depending on the particular brand and configuration. Even the components can depend on who makes and sells them - but usually their composition is similar to candy or other "treats" which have some attractive taste or smell to them, possibly some additional components to calm, numb pain or even stimulate (meaning they be mixed with other drugs) to give a pleasant experience while also containing various carcinogenic compounds or elements, such as arsenic, asbestos, cadmium, nickel and radon. Lung, mouth, throat and stomach cancers are the most common effects of the Sticks, but depending on the substances a variety of areas can develop symptoms. A common variant on this style is "Radium Gum", a chewing gum made with radioactive elements or isotopes or other carcinogens mixed in.
Both iterations of this idea are often reserved for the fairly well-off, because their use of certain radioactive or heavy metallic elements and compounds is a draw on limited resources - which also happen to be rarer in the Outer System. The inherent medical costs also tend to bracket the users of Sticks to higher incomes. This means that the habit is usually seen among the middle and upper class in the Main Belt and Inner System, a "conspicuous consumption" which can be genuinely habit forming (especially for those with oral fixations), though the Scum "shits and giggles" trade in Cancer Sticks across the system is high - and their components can be recycled into useful materials which often makes them an interesting - if hazardous trade good. The Jovian Republic and many other individual Bioconservative habs heavily restrict or ban Cancer Sticks also, making them an interesting black market and sometimes politically-minded good; boxes of Cancer Sticks tend to show up at the offices and doorsteps of notorious bioconservative politicians as a sign of protest.