'I have to be careful now," he says, wary of the sparks loose words might toss towards any besieged mind.
Every patient must figure out cancer's grammar for themselves. Dr Liam Hennessy is ten years down this road now, but pushing no parables. He's been through the alternating phases of faith and anguish; days when this illness feels a wilderness; others when exultation comes from the most humdrum of things.
He mentions Bob Tisdall's line about sleep being "nature's workshop". Such a simple, profound wisdom.
In the decade since this illness forced Hennessy to step away from his post as a game-changing Director of Fitness with the IRFU, his methodical, physiologist's brain hasn't - maybe - always been an ally.
He is 62 now and in what feels the second act. Immunotherapy isn't just about rebuilding the body, it's about reprogramming the mind too. Hennessy has resolved that the wise thing to do is roll with this. He understands that now.
But it wasn't always entirely obvious.
"The worst thing that happened me with this cancer wasn't the disease," he explains, picking his words carefully. "The cancer was in the prostate and the radiation did its job, but the hormone therapy nearly killed me.
"You're taking female hormones on board basically, being clinically manipulated through those hormones, which has an effect on your head. And soon as that started, I knew I couldn't do my job with the IRFU.
"It had been a great ten years with huge development, but I understood the energy you had to put into all of that too.
"The role is Full Metal Jacket stuff. And one month into the hormones, sure I didn't know myself.
"Eddie Wigglesworth was my boss ostensibly, a great guy. We were just coming into the 2011 season and I said, 'I know I can't do this!' Eddie suggested doing maybe just a couple of days a month. But I knew I couldn't.
"You see, that initial, two-year period was the toughest bit. Not the disease. Not the radiation. Not the subsequent chemo. I've never been upset for one day at having this disease. I was only upset because the hormones were playing havoc with my brain."
They also did their work, mind.
From a starting Prostate Specific Antigen (PSA) reading of 39, he registered a figure of "less than one" two years later. His routines today focus, predominantly, on wellness and a resistance of struggle.
A regimen for which the language of sport, he admits, isn't especially helpful.
Actually, the idea that you "fight" an illness as you would an opponent is entirely counter-intuitive to him now. Because fighting isn't the answer here.
* * * * *
ON some level, he sees his past self as a ghost now. On another, he knows that only circumstance changes, people broadly don't.
He was once an athlete fighting an impossible fight and the principles that told him to walk away still anchor him today. On a scholarship in America, his ambition to represent Ireland as a pole-vaulter at the 1980 Olympics in Moscow fell victim, eventually, to cold realism.
Hennessy thought he'd registered a 'B' qualifying height in a '79 summer meet at Abilene Christian University, Texas only to discover the field referee hadn't signed off on his jump. So, with his father ill at home, he came back and ended up chasing the height on one long, frazzled night at Belfield.
Clearing 17-and-a-half feet in the warm-up, he could not repeat it in the event itself.
"I was so depressed," he remembers now.
Partly, that depression sprang from an understanding that, without drugs, he could never be the athlete he so desperately yearned to be. At his best, Hennessy was still probably 18 inches behind the big dogs of the sport, the habitual medal contenders.
At New Mexico Junior College, he was coached by Larry Heidebrecht, a man maybe best known today as Ben Johnson's agent at the '88 Olympics in Seoul.
Back then, Larry was a warm, supportive figure in Hennessy's life as well as that of his fellow Irish athlete on campus, Kevin Currid. But they didn't have to look far to see the widening gulf between glory and honour in Track and Field.
"I'm on the college team in New Mexico for about six months and one of the athletes I was comfortably beating is suddenly jumping nine inches higher than I am," Hennessy remembers now. "So I'm in the gym one day, doing my lifts and I remember seeing he has this bad acne on his chest.
"And, of course, one of the side-effects of water-based steroids is acne.
"I didn't know he was on them at that point, but we were coming back from a track meet one day and he said to me, 'You could really do very well if you were taking the right stuff!' I knew straight away what he was talking about. Because I'd been reading.
"In fairness to him, the change that he went through was seismic. He became bigger, stronger. He could accelerate harder, apply more force. I was technically better, but I couldn't increase the force enough.
"He was very open about it, but I just shrugged my shoulders that night. I knew now that this was it, I was going home.
"I mean you'd be down in El Paso and you'd see an awful lot on the runway. The pole-vaulters would all come out with their bags in which you'd have stuff for your hands, your spikes, your towel. And a lot of the bags I looked into didn't just have spikes or stuff to rub into the hands.
"They had needles, they had vials. So you'd see it happening. One of the pole-vaulters actually became a mule, bringing drugs across the border into Southern California."
So Belfield was the last gasp of a dream.
And Hennessy had little interest in putting his life on hold for another four-year cycle in a domain where you're not jumping simply against technique or talent, but against power, chemical power.
If something in him withered with his failure to make Moscow then, any fading faith Liam Hennessy had in the Olympic ideal would finally perish in Atlanta 16 years later. He travelled to those Games as the Irish team's Exercise Physiologist, the experience broadly demorialising.
Watching Michelle de Bruin stockpile medals in the Olympic pool, the Cappawhite man felt only quiet dismay.
"Nothing was a surprise before or after," he says now of the disgraced champion. "In '96, we had I think 148 athletes that we use to monitor through the clinic and 147 turned up. The 148th didn't.
"I had a very strong view at the time, because the writing was on the wall. So what happened wasn't a surprise and that was a kind of landmark for me. I think it's fair to say that so many who have stepped on Olympic podiums over so many years can't put their hands up with much conviction and say that they were clean.
"I'm not saying all, but quite a few.
"Sonia O'Sullivan was a victim of it. She never really got to stand where she should have stood because she was trying to compete against those who were doped and the gains they were making as a result of that. Sonia, maybe the greatest female athlete of all, victimised by others who had taken drugs.
"I lost any great interest in the Olympics from '96 on. But ask me anything about the old Games … I'll tell you all about Tisdall in '32, August 1, between 3-4 in the afternoon. I'll go back to Pat O'Callaghan four years beforehand. I'll tell you who won what in Paris in '24.
"There was a time, I loved the Olympics. I could rattle off the various champions.
"Like Wolfgang Nordwig won the pole-vault in Munich '72. Tadeusz Slusarski and Antti Kalliomaki took gold and silver in Montreal '76.
"That was the year I went to Thomond College. All I wanted to do was sport. But then the deeper I got into it, the more you realised how widespread the cheating was. Drugs were so widely accessible. There's a simple way of summarising it.
"East was systematic; West was arbitrary/random. My dream was to go to Moscow, but when you look at so many of the medal winners from those Games … there was no such thing as a drug test then.
"And when I didn't make it, I was never going to go back to the States. Because I kind of knew the only way forward was taking drugs. And I'd made the decision, 'Nah, that's not for me!'"
* * * * *
Hennessy's visibility as a physiologist to elite athletes can be traced back to an unlikely alliance with 'Babs' Keating formed at the tail-end of 1990.
Deep into a thesis on inter-county Gaelic games players, he sought permission to collect data on the Tipperary senior hurling team. Access was granted on a winter's night in the Tipperary Town sports centre, 'Babs' observing the sports scientist at work with a more than inquisitive eye.
The fashion at the time was for former track and field athletes to train inter-county Gaelic games teams, the likes of Mick O'Flynn, Tim Crowe and Dave Mahedy all making their mark. And, having just lost a physical trainer of his own with the departure of '72 Olympian, Phil Conway, Babs - typically - was now plotting a new dawn.
As Hennessy was leaving Tipp Town that evening, Keating wondered if, maybe, he might return to do a second assessment of his players.
"I will," replied Hennessy, imagining something like six weeks as a respectable gap.
"Will you come in on Tuesday night?"
There was, then, no formal agreement. No announcement. No fanfare. Almost unwittingly, Hennessy became trainer to the Tipp hurling team, embarking on an unforgettable journey with men who became friends for life.
Conway, coaching them to All-Ireland success in '89, had begun a revolution of individualised training and Hennessy now took it to the next level. Believing that GAA teams were trapped in a soggy ritual of over-training through winter, he pared down Tipp's collective sessions in '91 to skeleton figures.
"We had 59 collective sessions in total to win an All-Ireland in '91," he recalls now. "That's from the previous November, right through to September. Nobody else was that low. But, behind that, there was a whole load of individual sessions.
"You see Babs gave me a mission. There were six guys that I had to mind and look after. Then six others that I had to get to work on. Babs had a phenomenal intuition on the individual condition.
"But I found this older awareness generally back then, this understanding that fellas needed freshness for hurling. So it actually was a very easy sell. Like Babs's selectors, Donie Nealon and John O'Donoghue, had no doubt that the right thing was being done.
"So someone like Pat Fox, say, couldn't really train collectively because his knees were never right. So we did all his training in the pitch behind his house in Annacarty. His strength work was lifting engines out of cars.
"Declan Ryan's session was, basically, a calorie-controlled diet. So he'd alternate between a 1,500 and a 1,200 calorie diet, which was pretty low for a big man. As long as he stuck to that and did the collective training, Declan was fine.
"Bobby Ryan was farming, pulling cattle and all of that. There was no point in having him do all the physical work.
"Like you could have two brothers like Cormac and Conal Bonnar. Cormac's engine was huge. He got extraordinarily fit from doing high loads.
"You couldn't do that with Conal. He'd break down. So even within one family, you had these two entirely different beasts. So you're training them like athletes essentially. Phil Conway had started it. All I was doing was extending it out into lifestyle."
There were the sceptics, of course. Some more hostile than others.
A first-ever gym had been installed under the Kinnane Stand in Thurles, with basketballs, American footballs, rugby balls and soccer balls provided. Yet one night Hennessy arrived in to discover a knife had been taken to every ball in the building, bar sliotars.
He knew who was responsible, but there was never a confession.
He remembers a moment too when even Babs's faith began to waver.
The week of Tipp's opening Munster Championship game with Limerick, someone told the manager that their opponents' collective sessions already ran into triple figures. "Babs flared up on me when he heard that!" remembers Hennessy now.
"And I was, 'Babs, trust me. But don't just trust me, trust your instinct. You've been saying it yourself that some of them do too much, others not enough'. I knew the work had been done all through winter. Huge work.
"Then it was tapered and the concept of the taper came from Eastern Bloc, weight-lifting periodisation models. That meant sessions were much shorter, collective and individual. We held ourselves back then for three weeks leading into the game. I knew they'd be flying because all their figures were way up.
"To be fair, Babs's understanding of the principle was fabulous. He was way ahead of his time, but just had that little wobble the week of the Limerick game."
A wobble never to be repeated once he'd witnessed a game that ended with the scoreline: TIPPERARY 2-18; LIMERICK 0-10.
* * * * *
It was in 2000 that the IRFU came calling or, more specifically, Noel Murphy and Eddie Coleman.
They met Hennessy one evening at Dublin Airport, looking for him - essentially - to draft a coach-education system in Irish rugby that he was already doing with some of Europe's biggest football clubs.
For a time, he'd even based himself in Manchester, such was the amount of traveling required while helping revitalise academies at clubs like Liverpool, Lazio and Bayern Munich.
Through that work, Hennessy became close to Carmelo Bosco, renowned physiologist to the great Italian athlete Pietro Mennea who still holds the European 200 metres record today, a record set in 1972.
Murphy and Coleman instantly read his reluctance to get involved in what was still - at the time - a "very amateurish" system. But, assuring him that he'd be "pushing an open door", they finally persuaded Hennessy to begin rewriting the DNA of Irish rugby.
"Murphy and Coleman wanted to produce a generation of our own coaches, right across the support staff," he remembers now. "They were like Babs. Ahead of their time."
Hennessy was, by now, already into a working relationship with golfer Pádraig Harrington too that survives to this day. And he would, in time (2007), set up the distance-learning institution, Setanta College.
Of all the athletes he has worked with, it's clear Harrington holds a special place.
"The greatest athlete that I've been involved with," he says categorically. "His longevity is just phenomenal. In most sports, you might have a ten-year window to produce the goods, but Pádraig is extending that to 30 years at this stage.
"Why? Because I haven't seen anybody else with his capacity for work. It's the physical and mental combined. Put it this way, Pádraig was squatting more and hang-cleaning more than any professional Irish rugby player during the period '03 to '09. He could lift more than any of them.
"When I started working with him back in the '90s, I quickly realised this guy's tolerance for work was far greater than any of the rugby players I was dealing with at the time. Or any footballer's.
"I mean I've a photo of him up in Stackstown in the late '90s, wearing what I call 'the monkey suit', connected to all these reflectors that are doing a 3D analysis of his swing. This lady came over from Texas to show us how to use it.
"He was the first athlete in Western Europe to use a vibration platform, the first athlete in Western Europe to use a whole body cryotherapy chamber. Pádraig's understanding of the golf swing is informed by 25 years of using technology and growing with it.
"He's used everything in the book. Not the book of golf. The book of anything."
As he speaks, Hennessy - suddenly - is up from the table, rolling off the balls of his feet, mimicking some mechanical revelation.
It is as if he, the physiologist, takes energy from simply bearing witness to Harrington's otherworldly capacity for work.
Just talking about Harrington, something shifts inside of him.
"You know something?" he says, smiling now.
"Pádraig bridges the gap between the art and the science. Some sports people are just art, without any real structure. Others are too scientific. But he has this great filter system.
"He's as good as any sports scientist. And he's as good as any coach who relies on instinct. I've never seen anyone else like him."