New research suggests that popular weight-loss injections, such as Ozempic and Mounjaro, while potentially offering protection against various tumours, may also be linked to an increased risk of kidney cancer. This comes from the largest study to date, which tracked nearly 44,000 overweight and obese individuals for up to ten years.

The study found that patients using these slimming injections experienced a 17 per cent lower risk of cancer overall, with significant reductions observed in ovarian and womb tumours. However, a concerning signal emerged for kidney cancer. Patients on the jabs were approximately a third more likely to develop kidney cancer compared to those who did not take them, with this risk being highest among individuals under 65 and those who were overweight.

Kidney cancer is a rapidly increasing cancer in both Britain and the US, frequently referred to as a 'silent killer' due to its tendency to remain asymptomatic until advanced stages. Symptoms like blood in the urine, persistent back pain, or a lump under the ribs often indicate late-stage disease, when successful treatment becomes challenging. Annually, nearly 14,000 Britons are diagnosed, resulting in 4,700 deaths, while the US sees around 80,000 new cases. Early detection dramatically improves the five-year survival rate to three-quarters, but this drops sharply to 18 per cent once the cancer has metastasized.

Alarmingly, kidney cancer cases are also rising sharply in younger adults, with those born in 1990 up to three times more likely to develop the disease than individuals born in the 1950s. This trend is partially attributed by doctors to increasing rates of obesity and high blood pressure.

The study, published in JAMA Oncology, compared 43,317 individuals prescribed the injections with 43,315 who were not. Overall, 891 cancers were diagnosed in jab users versus 1,022 in non-users. However, for kidney cancer specifically, there were 83 cases among users compared to 58 among non-users. Dr. Hao Dai, the lead researcher from Indiana University, expressed concern about this uptick, stating, 'We need to do another observational study to confirm that these drugs increase the risk. But from my point of view, it might be that the drugs raise the risk of some types of kidney cancer. We don't know, however, and need to do more research.'

Several theories attempt to explain this potential link. One hypothesis suggests that common side effects of the drugs, such as severe nausea, vomiting, and dehydration, could lead to recurrent acute kidney injury. Over time, this stress might damage kidney tissue and increase the risk of cancerous mutations. Another area of concern is the presence of GLP-1 receptors in the kidneys, which are the same receptors targeted by Ozempic to regulate blood sugar and promote satiety. Some scientists speculate that constant stimulation of these receptors could cause kidney cells to grow uncontrollably, though this remains unproven in humans. Rapid weight loss and significant metabolic shifts induced by the drugs might also contribute by altering the body's immune response or exacerbating pre-existing kidney conditions.

Despite these findings, experts urge caution in interpretation. Professor Paul Pharoah, a cancer specialist at Cedars-Sinai Medical Center, advised, 'While these results suggest that GLP1 receptor agonist have an effect on cancer risk the presence of an association does not mean that the association is a causal one.' Dr. Stephen Lawrence, an associate clinical professor at the University of Warwick, highlighted the relatively small increase: 'There was a slight uptick among users—two cases per 1,000 patients per year compared with 1.3 per 1,000 for non-users. That's about six extra cases for every 10,000 patients treated over a year. Not ideal, but still a drop in the ocean against other health benefits.' He emphasized the need for further research before drawing firm conclusions.

Concurrently, the study found that users of these jabs were significantly less likely to be diagnosed with other cancers. Rates of ovarian cancer nearly halved, and cases of womb cancer and certain brain tumours (meningiomas) also decreased. Overall, patients on the injections had a 17 per cent lower chance of developing any type of cancer compared to non-users. These findings were presented at the American Clinical Society of Oncology's annual conference. Experts remain cautious, noting that the overall reduction in cancer risk might be a consequence of weight loss itself rather than a direct drug effect.

Weight-loss jabs have already been credited with reducing the risk of heart attacks, strokes, and kidney failure, in addition to their pronounced weight-loss benefits. Experts conclude that while these medications may offer protection against some cancers, continued vigilance regarding the warning signs of kidney disease is essential.