Optimizing cancer treatment delivery could cut down greenhouse gas emissions and save lives

A recent study published by researchers at the University of Michigan Health Rogel Cancer Center found that reducing the frequency of administering pembrolizumab, a widely used immunotherapy, could significantly decrease greenhouse gas emissions without impacting patients’ health outcomes.

The high levels of energy used by the healthcare industry contributes to increased levels of pollution. In response, the Department of Health and Human Services has created a climate pledge requiring participating healthcare organizations to have net-zero emissions by 2050 to motivate sustainable practices. A significant factor in reducing carbon emissions is limiting transportation required for appointments; however, for patients with cancer, where telemedicine isn’t an option, this can be achieved by instead optimizing the dosage and frequency of their treatments.

In an email to The Michigan Daily, Dr. Mark Fendrick, professor of medicine and public health and one of the study’s contributors, said quantifying the environmental impact of healthcare delivery is necessary to help reduce the environmental impact of the U.S. healthcare system.   

“The U.S. healthcare system contributes to nearly 9% of domestic carbon emissions, exacerbating climate change and threatening human health,” Fendrick wrote. “It is increasingly important that we quantify emissions related to our current medical practices and identify more sustainable options to reduce this burden on population health.”

The drug the researchers considered in the study is pembrolizumab, a popular immunotherapy used for treating 20 different cancers. Its current dosage for all patients is 200 milligrams every three weeks. However, the study discussed how there is minimal evidence that this dosage amount and frequency needs to be the standard dosing strategy over others. Researchers of this study aimed to quantify the environmental benefits of switching the pembrolizumab dosage to 400 milligrams every six weeks. 

The study retrospectively examined anonymized data from 7,813 Veterans Health Administration patients who received at least one dose of pembrolizumab between May and September 2022. 

To simulate this cohort of patients’ data, pembrolizumab was instead delivered at 400 milligrams every six weeks. The study extrapolated the number of people receiving pembrolizumab treatment in the U.S. annually to 266,310 patients. Study authors found that the current pembrolizumab dosing generates 67,000 tons of CO2 annually. Implementing the new dosing strategy would decrease these emissions to 52,000 tons annually. 

Medical School alum Jacqueline Lewy, a study contributor, told The Daily in an interview reduced transportation was the main factor lowering emissions.

“It might seem like just a drop in the bucket compared to other things that we know are certainly affecting climate change and global warming like huge industries having to do with oil, but individual transportation really does add up a lot,” Lewy said.

Dr. Garth Strohbehn, an assistant professor of medicine in the University’s Division of Hematology & Oncology, was the study’s primary investigator. In an interview with The Daily, Strohbehn said his work as a medical oncologist contributed to his motivation to research immunotherapy dosage and the potential benefits for the environment, in addition to his patients.

“A lot of my patients have to travel a very long distance to come get their care,” Strohbehn said. “That’s not uncommon in the United States; care can be a really long distance for people to travel and that has a cost for them. Financially, in terms of the cost of gas and time, there’s a time toxicity to it. Spending all that time in a car may not be the best use of one’s time if you have an advanced cancer. It’s less time at home, less time with family, less time doing the things you’d otherwise love to do.”

The study also estimated the number of deaths that could be prevented by optimizing pembrolizumab’s administration using data on the mortality cost of carbon. The mortality cost of carbon is the projected number of deaths due to excessive heat from CO2 tonnage between the year when greenhouse gasses are emitted from a source and the year 2100. 

Lewy explained how the mortality cost of carbon is able to be estimated and connected to the study.

“For every metric tonne of carbon that’s going out into the atmosphere, even though we can’t necessarily pinpoint exactly who suffers because of that statistically around the world, is there a certain number of lives we can estimate will be lost because this tonne of carbon was emitted?” Lewy said. “We can estimate, conversely, how many lives could be saved if we could not emit that tonne of carbon.”

Storhbehn said the study estimated that an additional three deaths would occur in this time period for every year the drug is administered more than necessary. 

“We estimate a mortality cost of about three additional lives lost between now and the year 2100 for every year that prescribers choose to administer the drug more frequently than they otherwise need,” Storhbehn said. “So it means that the choices that we make as prescribers ultimately impact not just our patients, but probably impact bystanders.” 

The next step would be continuing these research efforts, including considering whether other treatments, such as radiation therapies and multimodal cancer care, are properly optimized. 

In its conclusion, the study discussed how clinical guidelines should be environmentally conscious so as to reduce harm to their patients. Lewy explained how implementing smaller changes on a systemic level into these guidelines is a significant part of this work so the healthcare industry can be more sustainable. 

“I think it takes a lot of moral fiber on a leadership level and a lot of resources to be able to make whole-system changes because it might be more expensive at first to buy a more environmentally friendly fuel source, for instance,” Lewy said. “But making those types of changes on a bigger level, even if they’re small changes, I think that’s going to be the biggest thing.”

Daily Staff Reporter Sophia Jayasekera can be reached at [email protected].

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