Cancer was a class of diseases among humans and other species. It was characterised by uncontrolled division of cells and the ability of these cells to invade other tissues. This unregulated growth was caused by damage to DNA, resulting in mutations to genes that controlled cell division. If untreated, cancers could kill its host.

Cancer could respond to chemotherapy, or other treatments, and go into remission. (TV: The Woman Who Fell to Earth)

Cancer cells were even sometimes considered to be immortal. As a result, there was a rumour spreading during Miracle Day that, since everything mortal became immortal, cancer cells became mortal, which Allen Shapiro took as a good enough excuse to start smoking again. (TV: End of the Road)

Smoking tobacco was a major cause of lung cancer, a fact that the Brigadier was aware of, and as a result he discouraged his subordinates from smoking. (PROSE: Doctor Who and the Green Death)

By studying alien artefacts, Henry van Statten discovered the cure for cancer, though he declined to release it as there was no financial incentive to. (TV: Dalek ^[+]Robert Shearman, adapted from Jubilee (Robert Shearman), Doctor Who series 1 (BBC One, 2005).) By one account, he bartered the cure to Hiram Duchesne for ownership of the Metaltron. (PROSE: Dalek ^[+]Robert Shearman, adapted from Dalek (Robert Shearman), Target novelisations (Target Books, 2021).)

Jamie Burton had cancer and done Chemotherapy and it didn't work so he did it again. (TV: Dead Man Walking ^[+]Matt Jones, Torchwood series 2 (BBC Three, 2008).)

References[]

The First Doctor met the elderly Christian leader Hebron, who was dying from cancer. This revelation humbled him, since until then he had been immersed in self-pity over the loss of the TARDIS and separation from his companions. (PROSE: Byzantium!)

While a Coordinator within the Kaled Scientific Elite, Davros developed a device capable of curing cancer among the Kaled population. (AUDIO: Corruption)

One of Lord Nicholas Carnon's prisoners, Dr Donald Morton, was a scientist who hoped to find a cure for cancer until Death took him. (PROSE: The Eternity Contract)

In 1972, the war criminal Oskar Steinmann died of spine cancer. (PROSE: Just War)

In 1976, Carolyn McConnell had dreams of finding a cure for cancer when she started out as a pre-med student in San Francisco. Some of her passion was diverted to an interest in vampires after the Eighth Doctor and Sam Jones rescued her from one of them. (PROSE: Vampire Science)

Charlie Reynish had cancer. Paul Reynish was told by the Ministry of Defence that Charlie had died, when in actuality he had survived the cancer. (HOMEVID: When to Die)

Tegan Jovanka's father William died of cancer. (PROSE: Divided Loyalties)

In 1991, George Smithers' wife died of lung cancer. (PROSE: Invasion of the Cat-People)

Marjorie Hopkins had cancer but went into remission. On 31 December 1999, the little girl informed Alex that her cancer would again become a problem again in three months. (AUDIO: The Torchwood Archive)

By 2006, Tegan herself had cancer, a brain tumour. (AUDIO: The Gathering)

Brad Travers developed lung cancer fifty years after exposure to deadly gas while a guard at Alcatraz. (PROSE: Inmate 280)

In 2011, during the Miracle Day phenomenon, the switch from mortal to immortal had rendered cancer cells mortal, allowing people to smoke freely, although the government kept this information quiet. (TV: End of the Road, WC: Web of Lies)

In the early 21st century, cancer was more common due to high pollution levels. Maria Chavez died from cancer brought on by years of exposure to toxic cleaning fluids. Stephanie had lung transplant surgery done to treat her lung cancer. (PROSE: Cat's Cradle: Warhead)

The Head of the House of Delahaye on Arcadia was dying from cancer; he wrote his memoirs using burnt sticks for pencils and old sheets for parchment. (PROSE: Prelude Deceit)

When Ace was attending the Time Lord Academy on Gallifrey, she discovered that her mother Audrey Dudman had died of cancer. She was warned by her tutor not to try to go back in time and prevent that from happening. While trapped in its halls, Bernice Summerfield compared the Dalek City to a cancer on Skaro's surface. (AUDIO: The Lights of Skaro)

Davros sneered at compassion, comparing it to cancer as it grows and will kill the host. He contemptuously voiced this belief to the Twelfth Doctor who proudly claimed that he "wouldn't die of anything else". (TV: The Witch's Familiar)

Graham O'Brien suffered from cancer, and it was through his chemo treatment that he met and fell in love with Grace. He was still in remission three years later. (TV: The Woman Who Fell to Earth) Graham later went for a checkup in 2020, where he learned that all of his test results were "as they should be". (TV: Spyfall) Despite this, he remained afraid that his cancer could return. In a nightmare induced by Zellin, he learned that his cancer had come back and that he only had hours to live. He later confided in the Thirteenth Doctor about this fear, who was unable to find the right words in response. (TV: Can You Hear Me?)