There isn't a single type of cancer, and even within cancer types there is the potential for each and every cancer to be unique in a significant way.
That's why there hasn't been some magic cure - however huge progress has been made in the past 20 years and the last 5-10 in particular - though it's difficult to disentangle the effects of new treatments from earlier diagnosis - the bottom line for many cancers now the 5 year survival rate is > 90 %.
Note such indicators are lagging - ie you have to wait 5 years to see 5 year survival data etc.
"there is the potential for each and every cancer to be unique in a significant way."
True, but that does not mean that cancer doesn't have some common root cause. I think that everybody who claims that there cannot be any common cure for cancers should be able to explain two things (you can attack them as well, I will be glad to hear your responses):
A. Incidence of most cancers increases with age in a very uniform way. Like, the slopes of the curves are basically identical for very different cancers. It at least seems that "being young" translates into "being very resistant (though not immune) to many cancers at once, and "growing old" is the magic anti-cure which makes you susceptible for all sorts of cancers at the same time.
If all those diseases were genuinely different, you would expect to see more variation in their mathematical properties. There aren't such close correlations between, say, dental caries and tuberculosis. And if "growing old" acts as a "magic anti-cure", maybe there can be the opposite, too. I get that "growing young" is probably complicated, but I am not that certain if it is categorically impossible in the future.
B. Cancer is not just a human disease, but generally a mammalian disease, but some mammalian species are much less prone to cancer than others: whales, elephants, bats. And what is again interesting, is the fact that the species less prone to cancer are less prone to all types of cancer again, not just a single type or two.
Also, birds don't get nearly as many cancers as mammals do - and again, they get less cancer overall, not just one or two types.
For me, this epidemiological uniformity indicates a possible common root cause, something like "a failure of the immune system to hold bad cells in check", regardless of the vast diversity of the symptoms.
For a rough analogy: people dying of AIDS will succumb to a wild variety of deadly infections, but that does not mean that AIDS is a family of very different diseases. It just means that their immune system stopped being able to hold multiple different foes in check. And once you can stop HIV from ravaging the immune system of the patients, all of these diverse deadly infections are prevented at once.
A. Incidence of most cancers increases with age in a very uniform way.
Cancer is caused by random(ish) mutations creating cellular variants that have uncontrolled growth - typically you need multiple mutations. It's related to age mostly because you accumulate mutations over time - it's a game of chance.
So the underlying cause is the same - mutations - however there are lots and lots of different ways to mutate a cell into a dangerous state ( that's not to say there are not common mutations found across lots of cancers in key regulatory targets ).
Different species effects
I don't think this is well understood, but some of that is to do differentials in effective DNA repair or detection of cancer cells by the immune system ( you body can detect and kill cancer cells as if they were foreign invaders ).
The other thing is perhaps less exposure to mutation causing agents ( humans are probablyt exposured to lots of mutagenic things at a low level we don't really know about yet - scandals of the future ) - and birds not getting cancer is probably mostly they don't live long enough.
And finally if your cancer get's to a later stage - typically it just hasn't picked up mutations to grow faster it's probably picked up mutations allow it to evolve faster ( ie a higher mutation rate ) - they means a single cancer that started from a single cell can evolve into a tree of related cells with different sets of mutations. ) And it's those different mutations that allow cells to survive in parts of the body they weren't originally from ).
In terms of treatment of cancer you need to try and target a difference between normal and cancer cells - so you tend to go after those differences driven by the mutations - often making the treatments sub-type specific. ie this particular cancer is different from normal in this way - so we target that difference, others might be different in another.
There are some treatments that are more generic - chemo basically targets fast growing cells ( for whatever underlying reasons ) - however these don't differentiate between normal fast growing cells and cancer so they have quite nasty side effects.
Comments
There isn't a single type of cancer, and even within cancer types there is the potential for each and every cancer to be unique in a significant way.
That's why there hasn't been some magic cure - however huge progress has been made in the past 20 years and the last 5-10 in particular - though it's difficult to disentangle the effects of new treatments from earlier diagnosis - the bottom line for many cancers now the 5 year survival rate is > 90 %.
Note such indicators are lagging - ie you have to wait 5 years to see 5 year survival data etc.
"there is the potential for each and every cancer to be unique in a significant way."
True, but that does not mean that cancer doesn't have some common root cause. I think that everybody who claims that there cannot be any common cure for cancers should be able to explain two things (you can attack them as well, I will be glad to hear your responses):
A. Incidence of most cancers increases with age in a very uniform way. Like, the slopes of the curves are basically identical for very different cancers. It at least seems that "being young" translates into "being very resistant (though not immune) to many cancers at once, and "growing old" is the magic anti-cure which makes you susceptible for all sorts of cancers at the same time.
If all those diseases were genuinely different, you would expect to see more variation in their mathematical properties. There aren't such close correlations between, say, dental caries and tuberculosis. And if "growing old" acts as a "magic anti-cure", maybe there can be the opposite, too. I get that "growing young" is probably complicated, but I am not that certain if it is categorically impossible in the future.
B. Cancer is not just a human disease, but generally a mammalian disease, but some mammalian species are much less prone to cancer than others: whales, elephants, bats. And what is again interesting, is the fact that the species less prone to cancer are less prone to all types of cancer again, not just a single type or two.
Also, birds don't get nearly as many cancers as mammals do - and again, they get less cancer overall, not just one or two types.
For me, this epidemiological uniformity indicates a possible common root cause, something like "a failure of the immune system to hold bad cells in check", regardless of the vast diversity of the symptoms.
For a rough analogy: people dying of AIDS will succumb to a wild variety of deadly infections, but that does not mean that AIDS is a family of very different diseases. It just means that their immune system stopped being able to hold multiple different foes in check. And once you can stop HIV from ravaging the immune system of the patients, all of these diverse deadly infections are prevented at once.
Cancer is caused by random(ish) mutations creating cellular variants that have uncontrolled growth - typically you need multiple mutations. It's related to age mostly because you accumulate mutations over time - it's a game of chance. So the underlying cause is the same - mutations - however there are lots and lots of different ways to mutate a cell into a dangerous state ( that's not to say there are not common mutations found across lots of cancers in key regulatory targets ).
I don't think this is well understood, but some of that is to do differentials in effective DNA repair or detection of cancer cells by the immune system ( you body can detect and kill cancer cells as if they were foreign invaders ). The other thing is perhaps less exposure to mutation causing agents ( humans are probablyt exposured to lots of mutagenic things at a low level we don't really know about yet - scandals of the future ) - and birds not getting cancer is probably mostly they don't live long enough.
And finally if your cancer get's to a later stage - typically it just hasn't picked up mutations to grow faster it's probably picked up mutations allow it to evolve faster ( ie a higher mutation rate ) - they means a single cancer that started from a single cell can evolve into a tree of related cells with different sets of mutations. ) And it's those different mutations that allow cells to survive in parts of the body they weren't originally from ).
In terms of treatment of cancer you need to try and target a difference between normal and cancer cells - so you tend to go after those differences driven by the mutations - often making the treatments sub-type specific. ie this particular cancer is different from normal in this way - so we target that difference, others might be different in another.
There are some treatments that are more generic - chemo basically targets fast growing cells ( for whatever underlying reasons ) - however these don't differentiate between normal fast growing cells and cancer so they have quite nasty side effects.