Younger women have totally different breast cancers than older women. Breast cancer in older women is slower growing. Many older women who may have had breast cancer, die "with" their cancer, rather than from it (or better yet, from the side effects of treatment).
The effects of aging on bodily functions and physiology cannot be ignored when making treatment and referral decisions. Pharmacokinetic processes such as the absorption, metabolism, and excretion of drugs appear to be different in older patients, and in general, a person's physiologic tolerance or reserve diminishes with increasing age.
The process of aging reduces your organ capacitance. You may have a functioning kidney, functioning lungs, and a functioning brain, but you have less capacitance at age 70 or 80 than you did 20 years ago.
Complications of cytotoxic chemotherapy are more common in older patients (65 years of age and older) with cancer than in younger patients, and the occurrence of myelosuppression, mucositis, cardiodepression, peripheral neuropathy, and central neurotoxicity can complicate treatment.
Age-related physiologic changes that can increase the toxicity of chemotherapy are decreased stem-cell reserves, decreased ability to repair cell damage, progressive loss of body protein, and accumulation of body fat. A decline in organ function can alter the pharmacokinetics of many of the commonly used chemotherapeutic agents in some elderly patients, making toxicity less predictable.
Comorbidities increase the risk of toxicity through their effects on the body. Furthermore, the drugs used to treat comorbidities may interact with chemotherapeutic drugs, potentially increasing toxicity in elderly patients. Prospective trials in older patients with solid tumors have found that age is a risk factor for chemotherapy-induced neutropenia and its complications.
And published clinical trials enroll the "best" patients. What really happens when less than the "best" patients are enrolled? Both with respect to toxicity and "efficacy," most studies purporting to show a benefit of one form of chemotherapy versus another show really minuscule benefits. The "real world" side effects are markedly greater than reported in clinical trials.
It could well be that, in the "real world" the putatively improved chemotherapy is actually worse than the "old fashioned" chemotherapy, if the putatively improved chemotherapy is more toxic (increased toxicity would be magnified in the "real world," more than canceling out the putative benefits seen in the non-real world setting.