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It comes from Newsweek, and has to do with a predicted shortage of oncologists in the years to come. It's not that the absolute numbers of these specialists is decreasing (although the article does talk about "a slowing growth in the supply"). The bigger issue is that the demand for their services is going up.
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As the doctor shortage worsens, it will become harder to get an appointment with an oncologist in the future. Some oncologists may begin referring patients back to their primary-care physicians for some aspects of their care, with the oncologist consulting from a distance – although the continuing trend toward highly-specialized cancer treatments makes this move problematic.
The Newsweek article also reports on a troubling personal characteristic of many younger doctors entering the oncology field today: they evidently don't have as strong a work ethic as their elders. Younger oncologists see significantly fewer patients per week, on the average. Some are intending to retire early, and others are seeking to work part-time during certain phases of their careers.
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A year ago, slogging though chemotherapy side effects, I was wondering whether my treatments would succeed in putting me into remission. The fact that I now have the luxury of worrying whether, years into the future, I'll still be able to get in to see my oncologist speaks volumes about how far I've come. Yet, it's a worry, all the same.