One interesting study on breast cancer patients receiving radiotherapy, found that local control was obtained but more women were eventually dying from heart failure from being in the radiation field. This essentially offset the gain. This couldn't be seen with 5 year survival rates. Now physicians are focused on protecting the heart and hopefully, eliminating cardiac toxicities.
That vignette just shows that 5y survival is a difficult metric and only shows a small piece of the picture. Others have rightly pointed out, stratification of data based on stage would be helpful. Improvement in 5 year survival of stage 4 patients, could be very meaningful.
Unfortunately, new treatments are adding months (on average) not years.
The best thing we (as a country) did, was wake up to the dangers of smoking. When per capita cancer diagnoses decline and survival rates remain steady (or improve), then we know more people are living longer.
My mother in law lived with breast cancer for ten years, and dropped dead of a heart attack in a dentist's waiting room. Radiation effect on coronary arteries may well have contributed.
I am sorry for your loss. It may very well may have been due to the radiotherapy. Left Breast cancer patients were at greatest risk. The Left Anterior Descending (LAD) has been identified as the "Organ At Risk."
We used to treat the heart as a parallel organ, like the lungs; damage a piece with no significant harm to the overall function. We've discovered that it may be a serial organ, like the spine; damage a piece and you impair the entire organ. Or in this case the LAD is a critical element.
The mechanism of action is believed to be accelerated atherosclerosis; hardening of the artery leading to blockage:
We now use breath hold techniques and completely spare the heart, but mistakes were made -- that only a long retrospective review of the data was able to reveal:
There’s no such thing as “cured” with cancer, only remission.
In general the goal with Oncology is to help people live longer, and improve quality of life for people with cancer. 5 year survival rates are one broad metric which probably broadly indicates they’re getting better at fighting the disease on those fronts.
Do people survive longer with cancer before eventually dying, or are more people cured?