Larger doses of chemotherapy drugs do result in more cancer cells being killed. But a balance has to be struck between improved therapeutic effects and unacceptable toxic effects.
    It may not be a kind act for your doctor to limit the dosage to avoid toxic effects. For those tumors that can potentially be cured with chemotherapy or have a good chance of going into remission , reducing the dosage to minimize toxicity will also reduce the possibility of cure or remission. The kindest act is to provide the maximum safe dose for cure, even at the cost of some toxicity. When the risks are weighed against the benefits, it doesn't make sense to take all the risks yet fail to get the benefits because the dosage was too low.

When Therapy May Be Stopped Because of Side Effects  There is no reason to stop therapy when the drugs produce few problems and the control of the tumor is very satisfactory or even barely satisfactory. But major or objectionable side effects or complications can only be justified by a very significant and pronounced antitumor response.
    The decision to stop therapy really depends on how you and your doctor define "objectionable" and what you are willing to put up with. Most men with metastatic testis cancer, for example, can be cured with less than six months of chemotherapy. Naturally, both doctors and patients are usually willing to put up with more discomforting side effects in that case because of the improved chance of cure. The alternative would be fatal.