Despite being around for more than 40 years and with a plethora of newer therapies to take their place, platinum drugs are still being used in about half of treatments for cancer patients.

A retrospective study based on oncology dispensing records at Concord Repatriation General Hospital in Sydney found 46% of patients were dispensed at least one platinum during their cancer treatment.

They included patients with gastrointestinal, lung and gynaecological cancers.

“In this study cohort patients treated with a chemotherapy regimen that did not include a platinum drug were more likely to be diagnosed with either breast (48%) or colorectal (27%) cancer,” the study said.

In almost all (93%) patients receiving platinum drugs – mostly cisplatin and carboplatin – the treatment was dispensed as a first-line treatment.

The chemotherapy protocols depended on the cancer types. For example, there was a clear preference for the carboplatin/gemcitabine regimen over other combinations for lung cancer; or in combination with either paclitaxel or doxorubicin for gynaecological cancers.

Of the 1,592 chemotherapy doses given, 322 dose reductions were documented in the clinical noes. It was frequently a 25% reduction initially but ranged in size from 10 to 60% of the protocol recommended dose.

Associate Professor Nial Wheate, from the University of Sydney’s Pharmacy School told the limbic reasons for dose reduction included neutropenia, myelosuppression and pancytopenia.

“We only looked at dispensing notes so it wasn’t always clear, but we are relatively certain that 99% of dose reductions were due to side effects.”

They found patients were also more likely to receive a dose reduction in a non-platinum chemotherapy drug if they were currently taking, or had a history of receiving a platinum drug.

Associate Professor Wheate said platinum drugs were clearly still very important for a lot of patients.

“My assumption was these drugs were on the out. But the surprising thing from our study is that the new drugs aren’t replacing the platinums, they are being used side by side.”

He said the findings justified the ongoing research to try and make them better drugs.

“Platinums can be used in a wide range of cancers and a lot of doctors will use them as a last resort as well as in first line therapy.”

He said one line of research was whether any drug-drug interactions with polypharmacy in older patients might make the platinum treatment less effective.