78. The science behind radiotherapy

Let me tell you about the science behind the radiotherapy decision, or rather, the lack of science.

This is a rather technical blogpost, so do feel free to sign off if you don't feel the need to understand all the medical ins and outs.

And before you start asking: yes, I've made it to Glasgow. Hurray. I managed the train journey, chaired a two hour meeting (I haven't attended, let alone chaired, a meeting since March) and had dinner with colleagues from across the UK. It is completely wonderful to be with these passionate and compassionate people who have become friends over the years, who share and understand the work I do, and who have been so supportive of me whilst I've been ill.

I've woken up early, so before I embark on the busy conference day, let me finish what I started writing on the train yesterday.

The doctors would be quite happy not to treat me with radiotherapy, so why go through it?

Women with my diagnosis and lab results are routinely given chemotherapy. Young ones, that is (and it seems that whilst I may be old in the eyes of my children or fellow bus passengers, cancer doctors invariably describe me as young). It's to do with the cancer having spread to the lymph nodes. If it has started journeying beyond the original lump, who knows where else it has journeyed to? Better be on the safe side, if your body is strong enough to cope with the poison.

Still, it's a guessing game. They base their guess on the size of the tumour (mine was small, although if you count the pre-cancerous cells that surrounded it, you're looking at something quite big) and the number of positive lymph nodes. In this context, positive means cancerous: not quite so positive, really.

I had three, and that's where the problem lies. Because in the absence of a machine that reliably lights up every single cancer cell in your body, doctors like to base their treatment decisions on likelihoods and probabilities that have been tested in research. Such research tends to divide women into three groups, depending on how many of their lymph nodes tested positive: none at all; between one and three; four or more. Then they look to see how many women in each group have a recurrence of their cancer within five, ten, twenty years. Does the treatment make a difference?

The case for chemotherapy is strong.

If your cancer hasn't spread, you don't need to attack your entire body. But if it has spread to your lymph nodes, it's best to get the poison out. The studies will have shown (I'm told) that whilst there are plenty of women with between one and three positive lymph nodes who will survive without chemotherapy, there are also enough women who don't. And because you simply don't know which way the dice will roll, it's worth treating everyone.

But radiotherapy? The research evidence simply isn't available yet.

Four or more positive lymph nodes? Yes, definitely. Blasting you with radiotherapy after the chemo can save lives. If your cancer has been merrily taking up residence in the nearby nodes, they are clearly fans of travel, and there may have been some cancer cells left behind on the chest wall (even after a mastectomy) or in the lymph nodes near your collar bone.

But one to three nodes? It hasn't been demonstrated that radiotherapy makes any difference. But the problem is that if you lump these women together in your study, and you find that there is a bit of a difference between survivors and non-survivors, whether you treat them or not, you don't know whether the few non-survivors tend to be the ones with the three lymph nodes rather than just the one.

There is a study going on right now that is looking at exactly this question. Do women with one positive lymph node survive longer with radiotherapy? How about two? Or three? But the results of this important study are not out until next year.

I hope you are keeping up. It isn't easy, this stuff, because you are hoping for answers and they simply aren't there.

The doctor who explained all this was rather pleased about my background, because it can be quite hard for patients to grasp that doctors make treatment decisions based on such evidence. If the evidence isn't there, it's down to the doctor's own best guess, which is based on their own opinion and experience. If the patient can be involved in the decision, so much the better.

My Chemo Consultant had already hinted at the dilemma. I was given a choice between two cancer hospitals. The radiotherapy consultant in one of them, she knew, is keen on treating women like me. She didn't know about the Radio Consultant in the other hospital, which I chose (it's easier to get to). 

I was seen, not by my own Radio Consulant, but by someone from her team.

"We don't tend to treat women like you routinely," she said. "But we are happy for you to have radiotherapy if you want it."

So it was down to costs and benefits. The benefits, as you've seen, are uncertain. I wouldn't have chosen it if the cost was great. If there was a significant risk of long term side effects, for example.

But it sounds as if the cost is short term, the side effects only temporary. Tiredness, skin burning, that kind of thing. It might damage a bit of my lung, but it's only a small part. It would have been more risky if it had been my left breast, as that would run the risk of some heart damage.

"Let me see if I got this right," my husband said. He was doing a good job, keeping up with all this medical talk. "You could see the radiotherapy as an insurance policy, which you buy even though you know the chances that you'll ever need it are very slim. I understand that we don't know if she needs the policy, and we may find out next year that this study shows there was actually no need. What is the price she will have paid? It sounds like it's not particularly high."

The doctor agreed. I agreed. I can do tiredness, if I know it will get better. Which it will. I am happy to take the one-in-a-few-thousand risk that in twenty years time, I develop a different kind of cancer caused by the radiation itself. ("It's such a small chance," the doctor explained, "that I don't even tell most of my patients about it. But it seems that you can weigh it all up properly.")

So there it is. I'll have radiotherapy to my chest wall and to the collar bone. The collar bone was another decision: often, radiotherapy is only given to the chest wall. I based my decision on the fact that the radiotherapy consultant in the other hospital tends to include the collar bone, because of the lymph nodes that are there.

I'll leave it there for now. I'd better get ready for my conference. Have a good day everyone.