I looked at a website, but I wasn't sure. It says that it can suffer from cancer. I just want to make sure if that is correct. Also, does it have any other issues?
It is true that labrador retrievers are affected by certain types of cancer - lymphoma (also known as lymphosarcoma) to be precise - more often than other breeds (source).
While this information doesn't mean that a labrador retriever is guaranteed to get this type of cancer sooner or later in life, labrador retrievers are indeed one of the breeds with the higher than average cancer occurrence. But it turns out to not be really that bad.
I have found a study about Breed-Predispositions to Cancer in Pedigree Dogs* and it states that basing on the collected data, on average, 27.0% of all dogs' deaths were related to cancer. On comparison, somewhere between 27.4% to 35.0% of labrador retrievers' deaths were cancer-related.
Actually, 574 labrador retrievers were considered in this study, which is quite a well sized and reliable sample, but the percentage interval isn't super accurate. And even if we pretend it was, still I don't think labrador retrievers are at significantly higher risk of cancer enough to worry about if you want to get one. Ultimately and sadly, all dogs could possibly suffer from cancer at some point.
Labrador retrievers are known for their above-average chance of, among other diseases, developing liver problems, bleeding disorders (hemophilia), diabetes, eye problems, bone and joint problems or gastric bloat.
But I'd say that it's not just about retrievers, because generally all purebred dogs are more prone to diseases. Reason for this is their genetic burden - selective breeding and keeping it "pure" actually decreases the diversity of their gene pool, and thus their vitality and resistance to diseases.
If you were to choose other breed that lab retriever, there could be let's say much lower risk of cancer but instead significantly increased occurrence of breathing problems or eyes prone to popping out of their sockets on daily basis. In this regard I'd say that all pure breeds in this context have their sad health-related quirks.
I recall, based on your other question, that you are recently doing some research about possibly getting a dog in the future. I'd say in either case that, in my subjective opinion, if you care about the vitality and health of your dog, the best bet is a mongrel (mixed-breed) one from the shelter. In general, I think mixed-breeds are more vivid, brighter, more cheerful, more intelligent and able to from more satisfying bonds with their owners. Wikipedia says:
Studies that have been done in the area of health show that mixed-breeds on average are both healthier and longer-lived than their purebred relations. This is because current accepted breeding practices within the pedigreed community results in a reduction in genetic diversity, and can result in physical characteristics that lead to health issues.
Studies have shown that cross-bred dogs have a number of desirable reproductive traits. Scott and Fuller found that cross-bred dogs were superior mothers compared to purebred mothers, producing more milk and giving better care. These advantages led to a decreased mortality in the offspring of cross-bred dogs.
*Little, short, oversimplified guide note, if someone wants to read this article I linked but happens to hate mathematics as much as I do: please consider that this is concluded based on limited number of dogs (samples) and thus these percentage values are not exact. If one wanted to get the exact spot-on percentages, one would have to include the data about all the dogs that have ever lived, which is impossible so the result would always be skewed a bit on either side.
A figure under label "all deaths" indicates how many dogs' deaths were considered in the article for a given breed. A big letter 'N' tells how many of these deaths were related to cancer. Then, an interval labeled '95% CI', which means 95% confidence interval, shows somewhat of an error margin, telling you that the researchers are almost sure (namely 95% sure) that the true value - for all the "dogs that ever lived" is contained within this interval. In this whole context, one might notice that the more dogs were considered, the narrower, more reliable and spot-on the mentioned interval is.
For that reason, if you want to check other breeds please don't be tricked by that peculiar detail. Namely, if the number of considered dogs is too small, the concluded data is horribly unreliable and please don't even look at it. Let's say you wanted to check Nova Scotia duck tolling retriever and you learn that 33% of them died because of cancer, but then you notice there were only 9 of these dogs considered and the relevant confidence interval is 2.5 – 64.1%. What it means is that "researchers are almost sure that the cancer mortality of these dogs is somewhere between 2.5% and 64.1%", which in fact tells you absolutely nothing! For comparison, an extreme end example is that one could always tell that the mortality is certainly between 0 and 100% and absolutely no data is needed for that.
Please note that I am not criticizing the relevant study - quite the opposite is true, I actually praise it. Some dog breeds are just unpopular or rare enough that despite best efforts, collecting enough data could turn out to be impossible. And in that instance one couldn't really do anything to narrow the confidence intervals and make the results of the study more accurate.
The biggest single congenital issue for labradors is joint problems, particularly hip and elbow dysplacia. The puppy vendor should have reports of joint scores for both parents, and you need to insist on seeing the physical certificate for the bitch and either the physical certificate or a photocopy for the dog. (For non-professional breeders, it is relatively common for the dog to belong to a friend.) Do not buy from a vendor who does not provide this, or who simply says that they're OK without providing proof.
Labradors can also suffer from eye problems. Again, you should ask to see test results for both parents.
Other tests also exist. Non-professional breeders may not routinely carry out further testing, because they aren't doing this as seriously. Professional breeders should though. Prices of a puppy from a professional breeder are usually somewhat higher, and part of the reason is that they carry out more thorough checks on their breeding animals. For more information, this link provides a good summary of the issues and tests.
All this said though, there is one elephant (or elephant-sized dog) in the room here. By far the biggest issue with labradors is obesity and the myriad health problems which are caused by this. Vastly more dogs suffer from obesity-related conditions than suffer from congenital diseases. Labradors are notoriously greedy, and as working animals their metabolism is geared up for a level of exercise which most people do not give them. It is critical to control the amount of food they eat and to monitor their weight. If they do start to get fatter, either restrict the amount of food you give them, or switch to low-calorie kibble. Of course this doesn't prevent other health issues, but as with obesity in humans, it dramatically reduces the risks.
One of the best things you can do is look at the lineage of the dog. Looking through it’s lines at its family history can provide an insight into what the dog could potentially be vulnerable to.
You can do this on things like The Kennel Club or MyKC (if it is UK registered, any other country you could try the equivalent).
This would be the most accurate way of predicting what your specific Labrador will get. The other way would be to research the most common illnesses of the breed but this wouldn’t be as accurate.
Any breeder worth their salt will know this information.
You can also get swob tests that can be done through the mail that can give you results on any thing the dog carries but you’d need to own the dog by then to get them.