Recently several papers have been published about kidney cancer that are relevant to Birt-Hogg-Dubé syndrome (BHD). In this blog, we summarise the papers and share what we can learn from them.
Is surgery or active surveillance better?
There are many different types of kidney cancer. The most common types seen in BHD are chromophobe, oncocytoma or a mixture of the two. These cancers are often slow growing, and they rarely spread. A recent paper described a case of oncocytoma and discussed whether it should be managed with active surveillance (regular scans to monitor tumour growth) or surgery.
The case described a 66-year-old man who was admitted to hospital with back pain. A CT scan showed he had tumours on both kidneys. The biggest was 3.3 cm. Due to its large size, they were concerned it may spread to other parts of the body. This is because larger tumours are more at risk of spreading. Therefore, he had a partial nephrectomy (a type of kidney surgery) to have it removed. Samples of the tumour were then analysed, which revealed a slow-growing oncocytoma. At this point, as the cancer was shown to be an oncocytoma, the patient was given options for the smaller tumours. Either he could have them removed or have active surveillance. He opted for the surgery.
The researchers reviewing this case agreed that surgery was the best treatment option for the large tumour. However, they suggest that active surveillance may be the best option for smaller oncocytomas. This is because tumours under 3 cm are very unlikely to spread so the benefit of surgically removing them does not outweigh potential complications caused by surgery.
Although this paper is not about BHD it does comment on a type of kidney cancer seen in BHD. It explains that oncocytomas are very unlikely to spread and that active monitoring is often the best option. This is in line with current BHD recommendations that suggest active kidney surveillance until tumours research 3 cm and then surgery.
Is active surveillance cost-effective?
The next study explored whether active surveillance of the kidneys, in conditions that predispose to kidney cancer, is cost-effective. They focused on a condition called HLRCC. Like BHD, HLRCC can cause kidney cancer. However, in HLRCC the tumours tend to grow more quickly and appear in younger people. The team assessed the cost-effectiveness of doing a yearly MRI scan in HLRCC compared with doing no MRI scans. They looked at a range of different age groups from 11 to 60. To determine if the scans were cost-effective, they assessed the effect of the scans on quality and length of life in addition to the monetary cost. They found that active surveillance was cost-effective across all age groups. Although this paper did not look at BHD, BHD does share similarities to HLRCC. Therefore, it suggests that active surveillance in people with BHD may not only positively impact their lives but be cost-effective. Before a study can be done looking at the cost-effectiveness of active surveillance in BHD, further research is needed to determine how often people with BHD should be screened.
Are there alternatives to surgery?
Lastly, we looked at a review of another type of kidney cancer called renal angiomyolipoma (rAML). rAML is a rare type of kidney cancer that is sometimes seen in BHD. Similar to the other types of cancer seen in BHD it is normally slow growing and active surveillance is recommended. Once it reaches a certain size it is then often removed by surgery.
rAML is also seen in tuberous sclerosis complex (TSC). TSC is a rare genetic condition that shares many similarities to BHD (read our recent blog post where we discuss what TSC can teach us about BHD). In addition to active surveillance, people with TSC-associated rAML can be offered a drug called an mTOR inhibitor. mTOR signalling is involved in cell growth and survival and is often overactive in cancer. mTOR inhibitors block this activity and are used to treat cancers. They are used in TSC-associated rAML to reduce the size of tumours and delay the need for surgery. Research into mTOR signalling and BHD is still ongoing so the benefit of mTOR inhibitors in BHD is unknown. However, this paper demonstrates that treatments are being developed for rare cancer types and that further research into BHD may one day find an alternative treatment to surgery.
The one stark similarity between all these papers is how there are no clear guidelines on when slow-growing kidney cancers, such as those seen in BHD, should be removed. Current research into BHD suggests it should be when they reach 3 cm. At the BHD Foundation, we want a clear answer to this question. We have launched the BHD syndrome International Registry (BIRT) to help us collect as much information about BHD as possible and drive forward research. Take part in the registry now.