Comedy queen Catherine O’Hara, who most recently starred in Schitt’s Creek, The Studio and Beetlejuice Beetlejuice, died unexpectedly January 30 at age 71. The release of her death certificate this week by TMZ reveals that the beloved Home Alone mom died of a pulmonary embolism caused by rectal cancer. In other words, her cancer led to the formation of a blood clot that traveled up her body and became lodged in a pulmonary artery in the lung, blocking blood flow and oxygen.

It was not revealed how long O’Hara had been living with rectal cancer or what treatment she was undergoing, though an oncologist who signed off on the death certificat said he had been treating her since March 2025, according to MedPage Today. But it is well established that cancer and its treatments can give rise to the formation of exaggerated blood clots, a tendency known as hypercoagulability.

As MD Anderson Cancer Center explains, cancer and its therapies can change the flow of blood, result in a blood vessel injury and alter the composition of the blood—for example, by making it thicker. Inflammation from cancer can also result in blood clotting. Tumors and microscopic damage to the body as a result of radiation and surgeries can also lead to blockages.

Notably, cancer patients are at an elevated risk for a deep vein thrombosis (DVT), a blood clot that forms in a deep vein. This most commonly occurs in the legs where, thanks to gravity, blood is likely to pool. DVTs can break off and travel up the body and cause a pulmonary embolism.

People are at an elevated risk for DVTs if they have gastrointestinal (GI) cancers—such as colon and rectal cancers—and if they have tumors in the pelvis, including the pancreas, uterus and ovaries.

“This, unfortunately, is a major cause of complications and morbidity and even mortality for patients with all cancers—but particularly GI cancers,” David Rivadeneira, MD, MBA, of the Northwell Health Cancer Institute at Huntington Hospital in Huntington, New York, told MedPage Today in a separate article.

Many specialists and advocates hope that the details of O’Hara death will raise awareness of the link between cancer and blood clots and also shine a spotlight on rectal cancer, a type of the malignancy that is often overlooked.

“On some level, there is a stigma associated with this cancer,” John Marshall, MD, chief medical consultant for the Colorectal Cancer Alliance, told MedPage. “There are a whole lot of people out there with this problem, and they don’t feel like they have a club that they can be a part of or share tips with, and so I think it’s yet another example of where we need to use this event to improve awareness for this.”

About 50,000 people will be diagnosed with rectal cancer this year (28,750 in men and 21,240 in women), according to estimates by the American Cancer Society. About 109,000 new cases of colon cancer will be diagnosed (55,410 in men and 53,450 in women). The organization further explains:

“The rate of people being diagnosed with colon or rectal cancer has dropped overall since the mid-1980s, mainly because more people are getting screened and changing their lifestyle-related risk factors. From 2013 to 2022, incidence rates dropped by about 1% each year. But this downward trend is mostly in older adults. In people younger than 50 years of age, rates have increased by 2.9% per year from 2013 to 2022. In adults aged 50–64, the rate has increased by 0.4% per year during this time.”

Colon and rectal cancers are often lumped together as colorectal cancers, but the two malignancies are often treated differently (the rectum is the last several inches of the colon, or large intestine). For example, rectal cancers are often first treated with chemotherapy and radiation to shrink the tumor, with the goal of sparing the sphincter from surgical procedures. Tumors in the colon, by contrast, can often be surgically removed with minimal intrusion.

Another celebrity obituary this week is highlighting these cancers. For more, see “James Van Der Beek of Hit TV Series ‘Dawson’s Creek’ Dies at 48 of Colorectal Cancer.”

In related news, “Colorectal Cancer Is Now the Top Cancer Killer Among Younger Adults,” according to recent data from the American Cancer Society, although overall cancer death rates in people under 50 dropped 44% since 1990. For a collection of articles on this type of illness, click #Colon Cancer, and for more background, read the Cancer Health Basics “Colon Cancer 101.”